Merge #7234 'built-in expression parser'

23 files changed, 5191 insertions, 608 deletions

diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index a166ee6c02..d3e07326bf 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -86,6 +86,8 @@ foreach(subdir
         event
         eval
         lua
+        viml
+        viml/parser
        )
   if(${subdir} MATCHES "tui" AND NOT FEAT_TUI)
     continue()
diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index f4ccf07bec..416e7d22d2 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -33,6 +33,8 @@
 #include "nvim/syntax.h"
 #include "nvim/getchar.h"
 #include "nvim/os/input.h"
+#include "nvim/viml/parser/expressions.h"
+#include "nvim/viml/parser/parser.h"
 
 #define LINE_BUFFER_SIZE 4096
 
@@ -889,6 +891,458 @@ theend:
   return rv;
 }
 
+typedef struct {
+  ExprASTNode **node_p;
+  Object *ret_node_p;
+} ExprASTConvStackItem;
+
+typedef kvec_withinit_t(ExprASTConvStackItem, 16) ExprASTConvStack;
+
+/// Parse a VimL expression
+///
+/// @param[in]  expr  Expression to parse. Is always treated as a single line.
+/// @param[in]  flags  Flags:
+///
+///                    - "m" if multiple expressions in a row are allowed (only
+///                      the first one will be parsed),
+///                    - "E" if EOC tokens are not allowed (determines whether
+///                      they will stop parsing process or be recognized as an
+///                      operator/space, though also yielding an error).
+///                    - "l" when needing to start parsing with lvalues for
+///                      ":let" or ":for".
+///
+///                    Common flag sets:
+///                    - "m" to parse like for ":echo".
+///                    - "E" to parse like for "<C-r>=".
+///                    - empty string for ":call".
+///                    - "lm" to parse for ":let".
+/// @param[in]  highlight  If true, return value will also include "highlight"
+///                        key containing array of 4-tuples (arrays) (Integer,
+///                        Integer, Integer, String), where first three numbers
+///                        define the highlighted region and represent line,
+///                        starting column and ending column (latter exclusive:
+///                        one should highlight region [start_col, end_col)).
+///
+/// @return AST: top-level dictionary holds keys
+///
+///         "error": Dictionary with error, present only if parser saw some
+///                  error. Contains the following keys:
+///
+///           "message": String, error message in printf format, translated.
+///                      Must contain exactly one "%.*s".
+///           "arg": String, error message argument.
+///
+///         "len": Amount of bytes successfully parsed. With flags equal to ""
+///                that should be equal to the length of expr string.
+///
+///                @note: “Sucessfully parsed” here means “participated in AST
+///                       creation”, not “till the first error”.
+///
+///         "ast": AST, either nil or a dictionary with these keys:
+///
+///           "type": node type, one of the value names from ExprASTNodeType
+///                   stringified without "kExprNode" prefix.
+///           "start": a pair [line, column] describing where node is “started”
+///                    where "line" is always 0 (will not be 0 if you will be
+///                    using nvim_parse_viml() on e.g. ":let", but that is not
+///                    present yet). Both elements are Integers.
+///           "len": “length” of the node. This and "start" are there for
+///                  debugging purposes primary (debugging parser and providing
+///                  debug information).
+///           "children": a list of nodes described in top/"ast". There always
+///                       is zero, one or two children, key will not be present
+///                       if node has no children. Maximum number of children
+///                       may be found in node_maxchildren array.
+///
+///           Local values (present only for certain nodes):
+///
+///           "scope": a single Integer, specifies scope for "Option" and
+///                    "PlainIdentifier" nodes. For "Option" it is one of
+///                    ExprOptScope values, for "PlainIdentifier" it is one of
+///                    ExprVarScope values.
+///           "ident": identifier (without scope, if any), present for "Option",
+///                    "PlainIdentifier", "PlainKey" and "Environment" nodes.
+///           "name": Integer, register name (one character) or -1. Only present
+///                   for "Register" nodes.
+///           "cmp_type": String, comparison type, one of the value names from
+///                       ExprComparisonType, stringified without "kExprCmp"
+///                       prefix. Only present for "Comparison" nodes.
+///           "ccs_strategy": String, case comparison strategy, one of the
+///                           value names from ExprCaseCompareStrategy,
+///                           stringified without "kCCStrategy" prefix. Only
+///                           present for "Comparison" nodes.
+///           "augmentation": String, augmentation type for "Assignment" nodes.
+///                           Is either an empty string, "Add", "Subtract" or
+///                           "Concat" for "=", "+=", "-=" or ".=" respectively.
+///           "invert": Boolean, true if result of comparison needs to be
+///                     inverted. Only present for "Comparison" nodes.
+///           "ivalue": Integer, integer value for "Integer" nodes.
+///           "fvalue": Float, floating-point value for "Float" nodes.
+///           "svalue": String, value for "SingleQuotedString" and
+///                     "DoubleQuotedString" nodes.
+Dictionary nvim_parse_expression(String expr, String flags, Boolean highlight,
+                                 Error *err)
+  FUNC_API_SINCE(4) FUNC_API_ASYNC
+{
+  int pflags = 0;
+  for (size_t i = 0 ; i < flags.size ; i++) {
+    switch (flags.data[i]) {
+      case 'm': { pflags |= kExprFlagsMulti; break; }
+      case 'E': { pflags |= kExprFlagsDisallowEOC; break; }
+      case 'l': { pflags |= kExprFlagsParseLet; break; }
+      case NUL: {
+        api_set_error(err, kErrorTypeValidation, "Invalid flag: '\\0' (%u)",
+                      (unsigned)flags.data[i]);
+        return (Dictionary)ARRAY_DICT_INIT;
+      }
+      default: {
+        api_set_error(err, kErrorTypeValidation, "Invalid flag: '%c' (%u)",
+                      flags.data[i], (unsigned)flags.data[i]);
+        return (Dictionary)ARRAY_DICT_INIT;
+      }
+    }
+  }
+  ParserLine plines[] = {
+    {
+      .data = expr.data,
+      .size = expr.size,
+      .allocated = false,
+    },
+    { NULL, 0, false },
+  };
+  ParserLine *plines_p = plines;
+  ParserHighlight colors;
+  kvi_init(colors);
+  ParserHighlight *const colors_p = (highlight ? &colors : NULL);
+  ParserState pstate;
+  viml_parser_init(
+      &pstate, parser_simple_get_line, &plines_p, colors_p);
+  ExprAST east = viml_pexpr_parse(&pstate, pflags);
+
+  const size_t ret_size = (
+      2  // "ast", "len"
+      + (size_t)(east.err.msg != NULL)  // "error"
+      + (size_t)highlight  // "highlight"
+      + 0);
+  Dictionary ret = {
+    .items = xmalloc(ret_size * sizeof(ret.items[0])),
+    .size = 0,
+    .capacity = ret_size,
+  };
+  ret.items[ret.size++] = (KeyValuePair) {
+    .key = STATIC_CSTR_TO_STRING("ast"),
+    .value = NIL,
+  };
+  ret.items[ret.size++] = (KeyValuePair) {
+    .key = STATIC_CSTR_TO_STRING("len"),
+    .value = INTEGER_OBJ((Integer)(pstate.pos.line == 1
+                                   ? plines[0].size
+                                   : pstate.pos.col)),
+  };
+  if (east.err.msg != NULL) {
+    Dictionary err_dict = {
+      .items = xmalloc(2 * sizeof(err_dict.items[0])),
+      .size = 2,
+      .capacity = 2,
+    };
+    err_dict.items[0] = (KeyValuePair) {
+      .key = STATIC_CSTR_TO_STRING("message"),
+      .value = STRING_OBJ(cstr_to_string(east.err.msg)),
+    };
+    if (east.err.arg == NULL) {
+      err_dict.items[1] = (KeyValuePair) {
+        .key = STATIC_CSTR_TO_STRING("arg"),
+        .value = STRING_OBJ(STRING_INIT),
+      };
+    } else {
+      err_dict.items[1] = (KeyValuePair) {
+        .key = STATIC_CSTR_TO_STRING("arg"),
+        .value = STRING_OBJ(((String) {
+          .data = xmemdupz(east.err.arg, (size_t)east.err.arg_len),
+          .size = (size_t)east.err.arg_len,
+        })),
+      };
+    }
+    ret.items[ret.size++] = (KeyValuePair) {
+      .key = STATIC_CSTR_TO_STRING("error"),
+      .value = DICTIONARY_OBJ(err_dict),
+    };
+  }
+  if (highlight) {
+    Array hl = (Array) {
+      .items = xmalloc(kv_size(colors) * sizeof(hl.items[0])),
+      .capacity = kv_size(colors),
+      .size = kv_size(colors),
+    };
+    for (size_t i = 0 ; i < kv_size(colors) ; i++) {
+      const ParserHighlightChunk chunk = kv_A(colors, i);
+      Array chunk_arr = (Array) {
+        .items = xmalloc(4 * sizeof(chunk_arr.items[0])),
+        .capacity = 4,
+        .size = 4,
+      };
+      chunk_arr.items[0] = INTEGER_OBJ((Integer)chunk.start.line);
+      chunk_arr.items[1] = INTEGER_OBJ((Integer)chunk.start.col);
+      chunk_arr.items[2] = INTEGER_OBJ((Integer)chunk.end_col);
+      chunk_arr.items[3] = STRING_OBJ(cstr_to_string(chunk.group));
+      hl.items[i] = ARRAY_OBJ(chunk_arr);
+    }
+    ret.items[ret.size++] = (KeyValuePair) {
+      .key = STATIC_CSTR_TO_STRING("highlight"),
+      .value = ARRAY_OBJ(hl),
+    };
+  }
+  kvi_destroy(colors);
+
+  // Walk over the AST, freeing nodes in process.
+  ExprASTConvStack ast_conv_stack;
+  kvi_init(ast_conv_stack);
+  kvi_push(ast_conv_stack, ((ExprASTConvStackItem) {
+    .node_p = &east.root,
+    .ret_node_p = &ret.items[0].value,
+  }));
+  while (kv_size(ast_conv_stack)) {
+    ExprASTConvStackItem cur_item = kv_last(ast_conv_stack);
+    ExprASTNode *const node = *cur_item.node_p;
+    if (node == NULL) {
+      assert(kv_size(ast_conv_stack) == 1);
+      kv_drop(ast_conv_stack, 1);
+    } else {
+      if (cur_item.ret_node_p->type == kObjectTypeNil) {
+        const size_t ret_node_items_size = (size_t)(
+            3  // "type", "start" and "len"
+            + (node->children != NULL)  // "children"
+            + (node->type == kExprNodeOption
+               || node->type == kExprNodePlainIdentifier)  // "scope"
+            + (node->type == kExprNodeOption
+               || node->type == kExprNodePlainIdentifier
+               || node->type == kExprNodePlainKey
+               || node->type == kExprNodeEnvironment)  // "ident"
+            + (node->type == kExprNodeRegister)  // "name"
+            + (3  // "cmp_type", "ccs_strategy", "invert"
+               * (node->type == kExprNodeComparison))
+            + (node->type == kExprNodeInteger)  // "ivalue"
+            + (node->type == kExprNodeFloat)  // "fvalue"
+            + (node->type == kExprNodeDoubleQuotedString
+               || node->type == kExprNodeSingleQuotedString)  // "svalue"
+            + (node->type == kExprNodeAssignment)  // "augmentation"
+            + 0);
+        Dictionary ret_node = {
+          .items = xmalloc(ret_node_items_size * sizeof(ret_node.items[0])),
+          .capacity = ret_node_items_size,
+          .size = 0,
+        };
+        *cur_item.ret_node_p = DICTIONARY_OBJ(ret_node);
+      }
+      Dictionary *ret_node = &cur_item.ret_node_p->data.dictionary;
+      if (node->children != NULL) {
+        const size_t num_children = 1 + (node->children->next != NULL);
+        Array children_array = {
+          .items = xmalloc(num_children * sizeof(children_array.items[0])),
+          .capacity = num_children,
+          .size = num_children,
+        };
+        for (size_t i = 0; i < num_children; i++) {
+          children_array.items[i] = NIL;
+        }
+        ret_node->items[ret_node->size++] = (KeyValuePair) {
+          .key = STATIC_CSTR_TO_STRING("children"),
+          .value = ARRAY_OBJ(children_array),
+        };
+        kvi_push(ast_conv_stack, ((ExprASTConvStackItem) {
+          .node_p = &node->children,
+          .ret_node_p = &children_array.items[0],
+        }));
+      } else if (node->next != NULL) {
+        kvi_push(ast_conv_stack, ((ExprASTConvStackItem) {
+          .node_p = &node->next,
+          .ret_node_p = cur_item.ret_node_p + 1,
+        }));
+      } else if (node != NULL) {
+        kv_drop(ast_conv_stack, 1);
+        ret_node->items[ret_node->size++] = (KeyValuePair) {
+          .key = STATIC_CSTR_TO_STRING("type"),
+          .value = STRING_OBJ(cstr_to_string(east_node_type_tab[node->type])),
+        };
+        Array start_array = {
+          .items = xmalloc(2 * sizeof(start_array.items[0])),
+          .capacity = 2,
+          .size = 2,
+        };
+        start_array.items[0] = INTEGER_OBJ((Integer)node->start.line);
+        start_array.items[1] = INTEGER_OBJ((Integer)node->start.col);
+        ret_node->items[ret_node->size++] = (KeyValuePair) {
+          .key = STATIC_CSTR_TO_STRING("start"),
+          .value = ARRAY_OBJ(start_array),
+        };
+        ret_node->items[ret_node->size++] = (KeyValuePair) {
+          .key = STATIC_CSTR_TO_STRING("len"),
+          .value = INTEGER_OBJ((Integer)node->len),
+        };
+        switch (node->type) {
+          case kExprNodeDoubleQuotedString:
+          case kExprNodeSingleQuotedString: {
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("svalue"),
+              .value = STRING_OBJ(((String) {
+                .data = node->data.str.value,
+                .size = node->data.str.size,
+              })),
+            };
+            break;
+          }
+          case kExprNodeOption: {
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("scope"),
+              .value = INTEGER_OBJ(node->data.opt.scope),
+            };
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("ident"),
+              .value = STRING_OBJ(((String) {
+                .data = xmemdupz(node->data.opt.ident,
+                                 node->data.opt.ident_len),
+                .size = node->data.opt.ident_len,
+              })),
+            };
+            break;
+          }
+          case kExprNodePlainIdentifier: {
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("scope"),
+              .value = INTEGER_OBJ(node->data.var.scope),
+            };
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("ident"),
+              .value = STRING_OBJ(((String) {
+                .data = xmemdupz(node->data.var.ident,
+                                 node->data.var.ident_len),
+                .size = node->data.var.ident_len,
+              })),
+            };
+            break;
+          }
+          case kExprNodePlainKey: {
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("ident"),
+              .value = STRING_OBJ(((String) {
+                .data = xmemdupz(node->data.var.ident,
+                                 node->data.var.ident_len),
+                .size = node->data.var.ident_len,
+              })),
+            };
+            break;
+          }
+          case kExprNodeEnvironment: {
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("ident"),
+              .value = STRING_OBJ(((String) {
+                .data = xmemdupz(node->data.env.ident,
+                                 node->data.env.ident_len),
+                .size = node->data.env.ident_len,
+              })),
+            };
+            break;
+          }
+          case kExprNodeRegister: {
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("name"),
+              .value = INTEGER_OBJ(node->data.reg.name),
+            };
+            break;
+          }
+          case kExprNodeComparison: {
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("cmp_type"),
+              .value = STRING_OBJ(cstr_to_string(
+                  eltkn_cmp_type_tab[node->data.cmp.type])),
+            };
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("ccs_strategy"),
+              .value = STRING_OBJ(cstr_to_string(
+                  ccs_tab[node->data.cmp.ccs])),
+            };
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("invert"),
+              .value = BOOLEAN_OBJ(node->data.cmp.inv),
+            };
+            break;
+          }
+          case kExprNodeFloat: {
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("fvalue"),
+              .value = FLOAT_OBJ(node->data.flt.value),
+            };
+            break;
+          }
+          case kExprNodeInteger: {
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("ivalue"),
+              .value = INTEGER_OBJ((Integer)(
+                  node->data.num.value > API_INTEGER_MAX
+                  ? API_INTEGER_MAX
+                  : (Integer)node->data.num.value)),
+            };
+            break;
+          }
+          case kExprNodeAssignment: {
+            const ExprAssignmentType asgn_type = node->data.ass.type;
+            ret_node->items[ret_node->size++] = (KeyValuePair) {
+              .key = STATIC_CSTR_TO_STRING("augmentation"),
+              .value = STRING_OBJ(
+                  asgn_type == kExprAsgnPlain
+                  ? (String)STRING_INIT
+                  : cstr_to_string(expr_asgn_type_tab[asgn_type])),
+            };
+            break;
+          }
+          case kExprNodeMissing:
+          case kExprNodeOpMissing:
+          case kExprNodeTernary:
+          case kExprNodeTernaryValue:
+          case kExprNodeSubscript:
+          case kExprNodeListLiteral:
+          case kExprNodeUnaryPlus:
+          case kExprNodeBinaryPlus:
+          case kExprNodeNested:
+          case kExprNodeCall:
+          case kExprNodeComplexIdentifier:
+          case kExprNodeUnknownFigure:
+          case kExprNodeLambda:
+          case kExprNodeDictLiteral:
+          case kExprNodeCurlyBracesIdentifier:
+          case kExprNodeComma:
+          case kExprNodeColon:
+          case kExprNodeArrow:
+          case kExprNodeConcat:
+          case kExprNodeConcatOrSubscript:
+          case kExprNodeOr:
+          case kExprNodeAnd:
+          case kExprNodeUnaryMinus:
+          case kExprNodeBinaryMinus:
+          case kExprNodeNot:
+          case kExprNodeMultiplication:
+          case kExprNodeDivision:
+          case kExprNodeMod: {
+            break;
+          }
+        }
+        assert(cur_item.ret_node_p->data.dictionary.size
+               == cur_item.ret_node_p->data.dictionary.capacity);
+        xfree(*cur_item.node_p);
+        *cur_item.node_p = NULL;
+      }
+    }
+  }
+  kvi_destroy(ast_conv_stack);
+
+  assert(ret.size == ret.capacity);
+  // Should be a no-op actually, leaving it in case non-nodes will need to be
+  // freed later.
+  viml_pexpr_free_ast(east);
+  viml_parser_destroy(&pstate);
+  return ret;
+}
+
 
 /// Writes a message to vim output or error buffer. The string is split
 /// and flushed after each newline. Incomplete lines are kept for writing
diff --git a/src/nvim/ascii.h b/src/nvim/ascii.h
index adde91f9ec..9ccb70764d 100644
--- a/src/nvim/ascii.h
+++ b/src/nvim/ascii.h
@@ -3,6 +3,7 @@
 
 #include <stdbool.h>
 
+#include "nvim/macros.h"
 #include "nvim/func_attr.h"
 #include "nvim/os/os_defs.h"
 
@@ -98,6 +99,10 @@ static inline bool ascii_isxdigit(int)
   REAL_FATTR_CONST
   REAL_FATTR_ALWAYS_INLINE;
 
+static inline bool ascii_isident(int)
+  REAL_FATTR_CONST
+  REAL_FATTR_ALWAYS_INLINE;
+
 static inline bool ascii_isbdigit(int)
   REAL_FATTR_CONST
   REAL_FATTR_ALWAYS_INLINE;
@@ -138,6 +143,14 @@ static inline bool ascii_isxdigit(int c)
          || (c >= 'A' && c <= 'F');
 }
 
+/// Checks if `c` is an “identifier” character
+///
+/// That is, whether it is alphanumeric character or underscore.
+static inline bool ascii_isident(const int c)
+{
+  return ASCII_ISALNUM(c) || c == '_';
+}
+
 /// Checks if `c` is a binary digit, that is, 0-1.
 ///
 /// @see {ascii_isdigit}
diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index 577fc13a31..980b4ed426 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -1611,141 +1611,145 @@ bool vim_isblankline(char_u *lbuf)
 /// If maxlen > 0, check at a maximum maxlen chars.
 ///
 /// @param start
-/// @param prep Returns type of number 0 = decimal, 'x' or 'X' is hex,
-///        '0' = octal, 'b' or 'B' is bin
+/// @param prep Returns guessed type of number 0 = decimal, 'x' or 'X' is
+///             hexadecimal, '0' = octal, 'b' or 'B' is binary. When using
+///             STR2NR_FORCE is always zero.
 /// @param len Returns the detected length of number.
-/// @param what Recognizes what number passed.
+/// @param what Recognizes what number passed, @see ChStr2NrFlags.
 /// @param nptr Returns the signed result.
 /// @param unptr Returns the unsigned result.
 /// @param maxlen Max length of string to check.
 void vim_str2nr(const char_u *const start, int *const prep, int *const len,
                 const int what, varnumber_T *const nptr,
                 uvarnumber_T *const unptr, const int maxlen)
+  FUNC_ATTR_NONNULL_ARG(1)
 {
-  const char_u *ptr = start;
+  const char *ptr = (const char *)start;
+#define STRING_ENDED(ptr) \
+    (!(maxlen == 0 || (int)((ptr) - (const char *)start) < maxlen))
   int pre = 0;  // default is decimal
-  bool negative = false;
+  const bool negative = (ptr[0] == '-');
   uvarnumber_T un = 0;
 
-  if (ptr[0] == '-') {
-    negative = true;
+  if (negative) {
     ptr++;
   }
 
-  // Recognize hex, octal and bin.
-  if ((ptr[0] == '0') && (ptr[1] != '8') && (ptr[1] != '9')
-      && (maxlen == 0 || maxlen > 1)) {
+  if (what & STR2NR_FORCE) {
+    // When forcing main consideration is skipping the prefix. Octal and decimal
+    // numbers have no prefixes to skip. pre is not set.
+    switch ((unsigned)what & (~(unsigned)STR2NR_FORCE)) {
+      case STR2NR_HEX: {
+        if (!STRING_ENDED(ptr + 2)
+            && ptr[0] == '0'
+            && (ptr[1] == 'x' || ptr[1] == 'X')
+            && ascii_isxdigit(ptr[2])) {
+          ptr += 2;
+        }
+        goto vim_str2nr_hex;
+      }
+      case STR2NR_BIN: {
+        if (!STRING_ENDED(ptr + 2)
+            && ptr[0] == '0'
+            && (ptr[1] == 'b' || ptr[1] == 'B')
+            && ascii_isbdigit(ptr[2])) {
+          ptr += 2;
+        }
+        goto vim_str2nr_bin;
+      }
+      case STR2NR_OCT: {
+        goto vim_str2nr_oct;
+      }
+      case 0: {
+        goto vim_str2nr_dec;
+      }
+      default: {
+        assert(false);
+      }
+    }
+  } else if ((what & (STR2NR_HEX|STR2NR_OCT|STR2NR_BIN))
+             && !STRING_ENDED(ptr + 1)
+             && ptr[0] == '0' && ptr[1] != '8' && ptr[1] != '9') {
     pre = ptr[1];
-
+    // Detect hexadecimal: 0x or 0X follwed by hex digit
     if ((what & STR2NR_HEX)
-        && ((pre == 'X') || (pre == 'x'))
-        && ascii_isxdigit(ptr[2])
-        && (maxlen == 0 || maxlen > 2)) {
-      // hexadecimal
+        && !STRING_ENDED(ptr + 2)
+        && (pre == 'X' || pre == 'x')
+        && ascii_isxdigit(ptr[2])) {
       ptr += 2;
-    } else if ((what & STR2NR_BIN)
-               && ((pre == 'B') || (pre == 'b'))
-               && ascii_isbdigit(ptr[2])
-               && (maxlen == 0 || maxlen > 2)) {
-      // binary
+      goto vim_str2nr_hex;
+    }
+    // Detect binary: 0b or 0B follwed by 0 or 1
+    if ((what & STR2NR_BIN)
+        && !STRING_ENDED(ptr + 2)
+        && (pre == 'B' || pre == 'b')
+        && ascii_isbdigit(ptr[2])) {
       ptr += 2;
-    } else {
-      // decimal or octal, default is decimal
-      pre = 0;
-
-      if (what & STR2NR_OCT) {
-        // Don't interpret "0", "08" or "0129" as octal.
-        for (int n = 1; ascii_isdigit(ptr[n]); ++n) {
-          if (ptr[n] > '7') {
-            // can't be octal
-            pre = 0;
-            break;
-          }
-          if (ptr[n] >= '0') {
-            // assume octal
-            pre = '0';
-          }
-          if (n == maxlen) {
-            break;
-          }
-        }
+      goto vim_str2nr_bin;
+    }
+    // Detect octal number: zero followed by octal digits without '8' or '9'
+    pre = 0;
+    if (!(what & STR2NR_OCT)
+        || !('0' <= ptr[1] && ptr[1] <= '7')) {
+      goto vim_str2nr_dec;
+    }
+    for (int i = 2; !STRING_ENDED(ptr + i) && ascii_isdigit(ptr[i]); i++) {
+      if (ptr[i] > '7') {
+        goto vim_str2nr_dec;
       }
     }
+    pre = '0';
+    goto vim_str2nr_oct;
+  } else {
+    goto vim_str2nr_dec;
   }
 
   // Do the string-to-numeric conversion "manually" to avoid sscanf quirks.
-  int n = 1;
-  if ((pre == 'B') || (pre == 'b') || what == STR2NR_BIN + STR2NR_FORCE) {
-    // bin
-    if (pre != 0) {
-      n += 2;  // skip over "0b"
+  assert(false);  // Should’ve used goto earlier.
+#define PARSE_NUMBER(base, cond, conv) \
+  do { \
+    while (!STRING_ENDED(ptr) && (cond)) { \
+      /* avoid ubsan error for overflow */ \
+      if (un < UVARNUMBER_MAX / base) { \
+        un = base * un + (uvarnumber_T)(conv); \
+      } else { \
+        un = UVARNUMBER_MAX; \
+      } \
+      ptr++; \
+    } \
+  } while (0)
+  switch (pre) {
+    case 'b':
+    case 'B': {
+vim_str2nr_bin:
+      PARSE_NUMBER(2, (*ptr == '0' || *ptr == '1'), (*ptr - '0'));
+      break;
     }
-    while ('0' <= *ptr && *ptr <= '1') {
-      // avoid ubsan error for overflow
-      if (un < UVARNUMBER_MAX / 2) {
-        un = 2 * un + (uvarnumber_T)(*ptr - '0');
-      } else {
-        un = UVARNUMBER_MAX;
-      }
-      ptr++;
-      if (n++ == maxlen) {
-        break;
-      }
-    }
-  } else if ((pre == '0') || what == STR2NR_OCT + STR2NR_FORCE) {
-    // octal
-    while ('0' <= *ptr && *ptr <= '7') {
-      // avoid ubsan error for overflow
-      if (un < UVARNUMBER_MAX / 8) {
-        un = 8 * un + (uvarnumber_T)(*ptr - '0');
-      } else {
-        un = UVARNUMBER_MAX;
-      }
-      ptr++;
-      if (n++ == maxlen) {
-        break;
-      }
+    case '0': {
+vim_str2nr_oct:
+      PARSE_NUMBER(8, ('0' <= *ptr && *ptr <= '7'), (*ptr - '0'));
+      break;
     }
-  } else if ((pre == 'X') || (pre == 'x')
-             || what == STR2NR_HEX + STR2NR_FORCE) {
-    // hex
-    if (pre != 0) {
-      n += 2;  // skip over "0x"
-    }
-    while (ascii_isxdigit(*ptr)) {
-      // avoid ubsan error for overflow
-      if (un < UVARNUMBER_MAX / 16) {
-        un = 16 * un + (uvarnumber_T)hex2nr(*ptr);
-      } else {
-        un = UVARNUMBER_MAX;
-      }
-      ptr++;
-      if (n++ == maxlen) {
-        break;
-      }
+    case 0: {
+vim_str2nr_dec:
+      PARSE_NUMBER(10, (ascii_isdigit(*ptr)), (*ptr - '0'));
+      break;
     }
-  } else {
-    // decimal
-    while (ascii_isdigit(*ptr)) {
-      // avoid ubsan error for overflow
-      if (un < UVARNUMBER_MAX / 10) {
-        un = 10 * un + (uvarnumber_T)(*ptr - '0');
-      } else {
-        un = UVARNUMBER_MAX;
-      }
-      ptr++;
-      if (n++ == maxlen) {
-        break;
-      }
+    case 'x':
+    case 'X': {
+vim_str2nr_hex:
+      PARSE_NUMBER(16, (ascii_isxdigit(*ptr)), (hex2nr(*ptr)));
+      break;
     }
   }
+#undef PARSE_NUMBER
 
   if (prep != NULL) {
     *prep = pre;
   }
 
   if (len != NULL) {
-    *len = (int)(ptr - start);
+    *len = (int)(ptr - (const char *)start);
   }
 
   if (nptr != NULL) {
@@ -1767,6 +1771,7 @@ void vim_str2nr(const char_u *const start, int *const prep, int *const len,
   if (unptr != NULL) {
     *unptr = un;
   }
+#undef STRING_ENDED
 }
 
 /// Return the value of a single hex character.
diff --git a/src/nvim/charset.h b/src/nvim/charset.h
index c69582c4c6..eb64b6128a 100644
--- a/src/nvim/charset.h
+++ b/src/nvim/charset.h
@@ -4,6 +4,7 @@
 #include "nvim/types.h"
 #include "nvim/pos.h"
 #include "nvim/buffer_defs.h"
+#include "nvim/eval/typval.h"
 
 /// Return the folded-case equivalent of the given character
 ///
@@ -15,6 +16,21 @@
              ?((int)(uint8_t)(c)) \
              :((int)(c)))
 
+/// Flags for vim_str2nr()
+typedef enum {
+  STR2NR_DEC = 0,
+  STR2NR_BIN = (1 << 0),  ///< Allow binary numbers.
+  STR2NR_OCT = (1 << 1),  ///< Allow octal numbers.
+  STR2NR_HEX = (1 << 2),  ///< Allow hexadecimal numbers.
+  /// Force one of the above variants.
+  ///
+  /// STR2NR_FORCE|STR2NR_DEC is actually not different from supplying zero
+  /// as flags, but still present for completeness.
+  STR2NR_FORCE = (1 << 3),
+  /// Recognize all formats vim_str2nr() can recognize.
+  STR2NR_ALL = STR2NR_BIN | STR2NR_OCT | STR2NR_HEX,
+} ChStr2NrFlags;
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "charset.h.generated.h"
 #endif
diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index 2bafb77fef..859f98d2ad 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -6066,27 +6066,30 @@ void free_last_insert(void)
 
 #endif
 
-/*
- * Add character "c" to buffer "s".  Escape the special meaning of K_SPECIAL
- * and CSI.  Handle multi-byte characters.
- * Returns a pointer to after the added bytes.
- */
+/// Add character "c" to buffer "s"
+///
+/// Escapes the special meaning of K_SPECIAL and CSI, handles multi-byte
+/// characters.
+///
+/// @param[in]  c  Character to add.
+/// @param[out]  s  Buffer to add to. Must have at least MB_MAXBYTES + 1 bytes.
+///
+/// @return Pointer to after the added bytes.
 char_u *add_char2buf(int c, char_u *s)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
 {
   char_u temp[MB_MAXBYTES + 1];
-  int i;
-  int len;
-
-  len = (*mb_char2bytes)(c, temp);
-  for (i = 0; i < len; ++i) {
+  const int len = utf_char2bytes(c, temp);
+  for (int i = 0; i < len; i++) {
     c = temp[i];
-    /* Need to escape K_SPECIAL and CSI like in the typeahead buffer. */
+    // Need to escape K_SPECIAL and CSI like in the typeahead buffer.
     if (c == K_SPECIAL) {
       *s++ = K_SPECIAL;
       *s++ = KS_SPECIAL;
       *s++ = KE_FILLER;
-    } else
+    } else {
       *s++ = c;
+    }
   }
   return s;
 }
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index e11788531b..f6a5f59676 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -5925,9 +5925,10 @@ static void ex_colorscheme(exarg_T *eap)
 
 static void ex_highlight(exarg_T *eap)
 {
-  if (*eap->arg == NUL && eap->cmd[2] == '!')
+  if (*eap->arg == NUL && eap->cmd[2] == '!') {
     MSG(_("Greetings, Vim user!"));
-  do_highlight(eap->arg, eap->forceit, FALSE);
+  }
+  do_highlight((const char *)eap->arg, eap->forceit, false);
 }
 
 
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 99330c177c..1adc8325f8 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -66,6 +66,8 @@
 #include "nvim/lib/kvec.h"
 #include "nvim/api/private/helpers.h"
 #include "nvim/highlight_defs.h"
+#include "nvim/viml/parser/parser.h"
+#include "nvim/viml/parser/expressions.h"
 
 /// Command-line colors: one chunk
 ///
@@ -2428,6 +2430,63 @@ void free_cmdline_buf(void)
 
 enum { MAX_CB_ERRORS = 1 };
 
+/// Color expression cmdline using built-in expressions parser
+///
+/// @param[in]  colored_ccline  Command-line to color.
+/// @param[out]  ret_ccline_colors  What should be colored.
+///
+/// Always colors the whole cmdline.
+static void color_expr_cmdline(const CmdlineInfo *const colored_ccline,
+                               ColoredCmdline *const ret_ccline_colors)
+  FUNC_ATTR_NONNULL_ALL
+{
+  ParserLine plines[] = {
+    {
+      .data = (const char *)colored_ccline->cmdbuff,
+      .size = STRLEN(colored_ccline->cmdbuff),
+      .allocated = false,
+    },
+    { NULL, 0, false },
+  };
+  ParserLine *plines_p = plines;
+  ParserHighlight colors;
+  kvi_init(colors);
+  ParserState pstate;
+  viml_parser_init(
+      &pstate, parser_simple_get_line, &plines_p, &colors);
+  ExprAST east = viml_pexpr_parse(&pstate, kExprFlagsDisallowEOC);
+  viml_pexpr_free_ast(east);
+  viml_parser_destroy(&pstate);
+  kv_resize(ret_ccline_colors->colors, kv_size(colors));
+  size_t prev_end = 0;
+  for (size_t i = 0 ; i < kv_size(colors) ; i++) {
+    const ParserHighlightChunk chunk = kv_A(colors, i);
+    if (chunk.start.col != prev_end) {
+      kv_push(ret_ccline_colors->colors, ((CmdlineColorChunk) {
+        .start = prev_end,
+        .end = chunk.start.col,
+        .attr = 0,
+      }));
+    }
+    const int id = syn_name2id((const char_u *)chunk.group);
+    const int attr = (id == 0 ? 0 : syn_id2attr(id));
+    kv_push(ret_ccline_colors->colors, ((CmdlineColorChunk) {
+        .start = chunk.start.col,
+        .end = chunk.end_col,
+        .attr = attr,
+    }));
+    prev_end = chunk.end_col;
+  }
+  if (prev_end < (size_t)colored_ccline->cmdlen) {
+    kv_push(ret_ccline_colors->colors, ((CmdlineColorChunk) {
+      .start = prev_end,
+      .end = (size_t)colored_ccline->cmdlen,
+      .attr = 0,
+    }));
+  }
+  kvi_destroy(colors);
+}
+
 /// Color command-line
 ///
 /// Should use built-in command parser or user-specified one. Currently only the
@@ -2510,13 +2569,7 @@ static bool color_cmdline(CmdlineInfo *colored_ccline)
     tl_ret = try_leave(&tstate, &err);
     can_free_cb = true;
   } else if (colored_ccline->cmdfirstc == '=') {
-    try_enter(&tstate);
-    err_errmsg = N_(
-        "E5409: Unable to get g:Nvim_color_expr callback: %s");
-    dgc_ret = tv_dict_get_callback(&globvardict, S_LEN("Nvim_color_expr"),
-                                   &color_cb);
-    tl_ret = try_leave(&tstate, &err);
-    can_free_cb = true;
+    color_expr_cmdline(colored_ccline, ccline_colors);
   }
   if (!tl_ret || !dgc_ret) {
     goto color_cmdline_error;
diff --git a/src/nvim/generators/gen_declarations.lua b/src/nvim/generators/gen_declarations.lua
index e999e53e4a..065c043557 100755
--- a/src/nvim/generators/gen_declarations.lua
+++ b/src/nvim/generators/gen_declarations.lua
@@ -164,9 +164,40 @@ local pattern = concat(
 )
 
 if fname == '--help' then
-  print'Usage:'
-  print()
-  print'  gendeclarations.lua definitions.c static.h non-static.h preprocessor.i'
+  print([[
+Usage:
+
+    gendeclarations.lua definitions.c static.h non-static.h definitions.i
+
+Generates declarations for a C file definitions.c, putting declarations for
+static functions into static.h and declarations for non-static functions into
+non-static.h. File `definitions.i' should contain an already preprocessed
+version of definitions.c and it is the only one which is actually parsed,
+definitions.c is needed only to determine functions from which file out of all
+functions found in definitions.i are needed.
+
+Additionally uses the following environment variables:
+
+    NVIM_GEN_DECLARATIONS_LINE_NUMBERS:
+        If set to 1 then all generated declarations receive a comment with file
+        name and line number after the declaration. This may be useful for
+        debugging gen_declarations script, but not much beyond that with
+        configured development environment (i.e. with ctags/cscope/finding
+        definitions with clang/etc).
+
+        WARNING: setting this to 1 will cause extensive rebuilds: declarations
+                 generator script will not regenerate non-static.h file if its
+                 contents did not change, but including line numbers will make
+                 contents actually change.
+
+                 With contents changed timestamp of the file is regenerated even
+                 when no real changes were made (e.g. a few lines were added to
+                 a function which is not at the bottom of the file).
+
+                 With changed timestamp build system will assume that header
+                 changed, triggering rebuilds of all C files which depend on the
+                 "changed" header.
+]])
   os.exit()
 end
 
@@ -249,8 +280,10 @@ while init ~= nil do
       declaration = declaration:gsub(' $', '')
       declaration = declaration:gsub('^ ', '')
       declaration = declaration .. ';'
-      declaration = declaration .. ('  // %s/%s:%u'):format(
-          curdir, curfile, declline)
+      if os.getenv('NVIM_GEN_DECLARATIONS_LINE_NUMBERS') == '1' then
+        declaration = declaration .. ('  // %s/%s:%u'):format(
+            curdir, curfile, declline)
+      end
       declaration = declaration .. '\n'
       if declaration:sub(1, 6) == 'static' then
         static = static .. declaration
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index dcb8b40973..ef56954aa0 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -729,29 +729,6 @@ EXTERN int vr_lines_changed INIT(= 0);      /* #Lines changed by "gR" so far */
 /// Encoding used when 'fencs' is set to "default"
 EXTERN char_u *fenc_default INIT(= NULL);
 
-// To speed up BYTELEN(); keep a lookup table to quickly get the length in
-// bytes of a UTF-8 character from the first byte of a UTF-8 string.  Bytes
-// which are illegal when used as the first byte have a 1.  The NUL byte has
-// length 1.
-EXTERN char utf8len_tab[256] INIT(= {
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
-  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
-  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
-  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
-  4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 1, 1,
-});
-
 # if defined(USE_ICONV) && defined(DYNAMIC_ICONV)
 /* Pointers to functions and variables to be loaded at runtime */
 EXTERN size_t (*iconv)(iconv_t cd, const char **inbuf, size_t *inbytesleft,
diff --git a/src/nvim/keymap.c b/src/nvim/keymap.c
index a75fe793ac..0eb5a41b1e 100644
--- a/src/nvim/keymap.c
+++ b/src/nvim/keymap.c
@@ -24,23 +24,22 @@
  * Some useful tables.
  */
 
-static struct modmasktable {
-  short mod_mask;               /* Bit-mask for particular key modifier */
-  short mod_flag;               /* Bit(s) for particular key modifier */
-  char_u name;                  /* Single letter name of modifier */
-} mod_mask_table[] =
-{
-  {MOD_MASK_ALT,              MOD_MASK_ALT,           (char_u)'M'},
-  {MOD_MASK_META,             MOD_MASK_META,          (char_u)'T'},
-  {MOD_MASK_CTRL,             MOD_MASK_CTRL,          (char_u)'C'},
-  {MOD_MASK_SHIFT,            MOD_MASK_SHIFT,         (char_u)'S'},
-  {MOD_MASK_MULTI_CLICK,      MOD_MASK_2CLICK,        (char_u)'2'},
-  {MOD_MASK_MULTI_CLICK,      MOD_MASK_3CLICK,        (char_u)'3'},
-  {MOD_MASK_MULTI_CLICK,      MOD_MASK_4CLICK,        (char_u)'4'},
-  {MOD_MASK_CMD,              MOD_MASK_CMD,           (char_u)'D'},
+static const struct modmasktable {
+  uint16_t mod_mask;  ///< Bit-mask for particular key modifier.
+  uint16_t mod_flag;  ///< Bit(s) for particular key modifier.
+  char_u name;  ///< Single letter name of modifier.
+} mod_mask_table[] = {
+  { MOD_MASK_ALT,              MOD_MASK_ALT,           (char_u)'M' },
+  { MOD_MASK_META,             MOD_MASK_META,          (char_u)'T' },
+  { MOD_MASK_CTRL,             MOD_MASK_CTRL,          (char_u)'C' },
+  { MOD_MASK_SHIFT,            MOD_MASK_SHIFT,         (char_u)'S' },
+  { MOD_MASK_MULTI_CLICK,      MOD_MASK_2CLICK,        (char_u)'2' },
+  { MOD_MASK_MULTI_CLICK,      MOD_MASK_3CLICK,        (char_u)'3' },
+  { MOD_MASK_MULTI_CLICK,      MOD_MASK_4CLICK,        (char_u)'4' },
+  { MOD_MASK_CMD,              MOD_MASK_CMD,           (char_u)'D' },
   // 'A' must be the last one
-  {MOD_MASK_ALT,              MOD_MASK_ALT,           (char_u)'A'},
-  {0, 0, NUL}
+  { MOD_MASK_ALT,              MOD_MASK_ALT,           (char_u)'A' },
+  { 0, 0, NUL }
 };
 
 /*
@@ -139,11 +138,10 @@ static char_u modifier_keys_table[] =
   NUL
 };
 
-static struct key_name_entry {
+static const struct key_name_entry {
   int key;              // Special key code or ascii value
-  char *name;           // Name of key
-} key_names_table[] =
-{
+  const char *name;           // Name of key
+} key_names_table[] = {
   { ' ',               "Space" },
   { TAB,               "Tab" },
   { K_TAB,             "Tab" },
@@ -318,73 +316,73 @@ static struct mousetable {
   {0,                         0,              0,      0},
 };
 
-/*
- * Return the modifier mask bit (MOD_MASK_*) which corresponds to the given
- * modifier name ('S' for Shift, 'C' for Ctrl etc).
- */
+/// Return the modifier mask bit (#MOD_MASK_*) corresponding to mod name
+///
+/// E.g. 'S' for shift, 'C' for ctrl.
 int name_to_mod_mask(int c)
+  FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  int i;
-
   c = TOUPPER_ASC(c);
-  for (i = 0; mod_mask_table[i].mod_mask != 0; i++)
-    if (c == mod_mask_table[i].name)
+  for (size_t i = 0; mod_mask_table[i].mod_mask != 0; i++) {
+    if (c == mod_mask_table[i].name) {
       return mod_mask_table[i].mod_flag;
+    }
+  }
   return 0;
 }
 
-/*
- * Check if if there is a special key code for "key" that includes the
- * modifiers specified.
- */
-int simplify_key(int key, int *modifiers)
+/// Check if there is a special key code for "key" with specified modifiers
+///
+/// @param[in]  key  Initial key code.
+/// @param[in,out]  modifiers  Initial modifiers, is adjusted to have simplified
+///                            modifiers.
+///
+/// @return Simplified key code.
+int simplify_key(const int key, int *modifiers)
+  FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
 {
-  int i;
-  int key0;
-  int key1;
-
   if (*modifiers & (MOD_MASK_SHIFT | MOD_MASK_CTRL | MOD_MASK_ALT)) {
-    /* TAB is a special case */
+    // TAB is a special case.
     if (key == TAB && (*modifiers & MOD_MASK_SHIFT)) {
       *modifiers &= ~MOD_MASK_SHIFT;
       return K_S_TAB;
     }
-    key0 = KEY2TERMCAP0(key);
-    key1 = KEY2TERMCAP1(key);
-    for (i = 0; modifier_keys_table[i] != NUL; i += MOD_KEYS_ENTRY_SIZE)
+    const int key0 = KEY2TERMCAP0(key);
+    const int key1 = KEY2TERMCAP1(key);
+    for (int i = 0; modifier_keys_table[i] != NUL; i += MOD_KEYS_ENTRY_SIZE) {
       if (key0 == modifier_keys_table[i + 3]
           && key1 == modifier_keys_table[i + 4]
           && (*modifiers & modifier_keys_table[i])) {
         *modifiers &= ~modifier_keys_table[i];
         return TERMCAP2KEY(modifier_keys_table[i + 1],
-            modifier_keys_table[i + 2]);
+                           modifier_keys_table[i + 2]);
       }
+    }
   }
   return key;
 }
 
-/*
- * Change <xHome> to <Home>, <xUp> to <Up>, etc.
- */
-int handle_x_keys(int key)
+/// Change <xKey> to <Key>
+int handle_x_keys(const int key)
+  FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
 {
   switch (key) {
-  case K_XUP:     return K_UP;
-  case K_XDOWN:   return K_DOWN;
-  case K_XLEFT:   return K_LEFT;
-  case K_XRIGHT:  return K_RIGHT;
-  case K_XHOME:   return K_HOME;
-  case K_ZHOME:   return K_HOME;
-  case K_XEND:    return K_END;
-  case K_ZEND:    return K_END;
-  case K_XF1:     return K_F1;
-  case K_XF2:     return K_F2;
-  case K_XF3:     return K_F3;
-  case K_XF4:     return K_F4;
-  case K_S_XF1:   return K_S_F1;
-  case K_S_XF2:   return K_S_F2;
-  case K_S_XF3:   return K_S_F3;
-  case K_S_XF4:   return K_S_F4;
+    case K_XUP:     return K_UP;
+    case K_XDOWN:   return K_DOWN;
+    case K_XLEFT:   return K_LEFT;
+    case K_XRIGHT:  return K_RIGHT;
+    case K_XHOME:   return K_HOME;
+    case K_ZHOME:   return K_HOME;
+    case K_XEND:    return K_END;
+    case K_ZEND:    return K_END;
+    case K_XF1:     return K_F1;
+    case K_XF2:     return K_F2;
+    case K_XF3:     return K_F3;
+    case K_XF4:     return K_F4;
+    case K_S_XF1:   return K_S_F1;
+    case K_S_XF2:   return K_S_F2;
+    case K_S_XF3:   return K_S_F3;
+    case K_S_XF4:   return K_S_F4;
   }
   return key;
 }
@@ -508,7 +506,7 @@ unsigned int trans_special(const char_u **srcp, const size_t src_len,
     return 0;
   }
 
-  /* Put the appropriate modifier in a string */
+  // Put the appropriate modifier in a string.
   if (modifiers != 0) {
     dst[dlen++] = K_SPECIAL;
     dst[dlen++] = KS_MODIFIER;
@@ -569,15 +567,11 @@ int find_special_key(const char_u **srcp, const size_t src_len, int *const modp,
 
   // Find end of modifier list
   last_dash = src;
-  for (bp = src + 1; bp <= end && (*bp == '-' || vim_isIDc(*bp)); bp++) {
+  for (bp = src + 1; bp <= end && (*bp == '-' || ascii_isident(*bp)); bp++) {
     if (*bp == '-') {
       last_dash = bp;
       if (bp + 1 <= end) {
-        if (has_mbyte) {
-          l = mb_ptr2len_len(bp + 1, (int) (end - bp) + 1);
-        } else {
-          l = 1;
-        }
+        l = utfc_ptr2len_len(bp + 1, (int)(end - bp) + 1);
         // Anything accepted, like <C-?>.
         // <C-"> or <M-"> are not special in strings as " is
         // the string delimiter. With a backslash it works: <M-\">
@@ -702,33 +696,39 @@ int find_special_key_in_table(int c)
 {
   int i;
 
-  for (i = 0; key_names_table[i].name != NULL; i++)
-    if (c == key_names_table[i].key)
+  for (i = 0; key_names_table[i].name != NULL; i++) {
+    if (c == key_names_table[i].key) {
       break;
-  if (key_names_table[i].name == NULL)
+    }
+  }
+  if (key_names_table[i].name == NULL) {
     i = -1;
+  }
   return i;
 }
 
-/*
- * Find the special key with the given name (the given string does not have to
- * end with NUL, the name is assumed to end before the first non-idchar).
- * If the name starts with "t_" the next two characters are interpreted as a
- * termcap name.
- * Return the key code, or 0 if not found.
- */
+/// Find the special key with the given name
+///
+/// @param[in]  name  Name of the special. Does not have to end with NUL, it is
+///                   assumed to end before the first non-idchar. If name starts
+///                   with "t_" the next two characters are interpreted as
+///                   a termcap name.
+///
+/// @return Key code or 0 if not found.
 int get_special_key_code(const char_u *name)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  char *table_name;
-  int i, j;
-
-  for (i = 0; key_names_table[i].name != NULL; i++) {
-    table_name = key_names_table[i].name;
-    for (j = 0; vim_isIDc(name[j]) && table_name[j] != NUL; j++)
-      if (TOLOWER_ASC(table_name[j]) != TOLOWER_ASC(name[j]))
+  for (int i = 0; key_names_table[i].name != NULL; i++) {
+    const char *const table_name = key_names_table[i].name;
+    int j;
+    for (j = 0; ascii_isident(name[j]) && table_name[j] != NUL; j++) {
+      if (TOLOWER_ASC(table_name[j]) != TOLOWER_ASC(name[j])) {
         break;
-    if (!vim_isIDc(name[j]) && table_name[j] == NUL)
+      }
+    }
+    if (!ascii_isident(name[j]) && table_name[j] == NUL) {
       return key_names_table[i].key;
+    }
   }
 
   return 0;
diff --git a/src/nvim/lib/kvec.h b/src/nvim/lib/kvec.h
index 584282d773..ee1b890cb9 100644
--- a/src/nvim/lib/kvec.h
+++ b/src/nvim/lib/kvec.h
@@ -62,7 +62,16 @@
 #define kv_pop(v) ((v).items[--(v).size])
 #define kv_size(v) ((v).size)
 #define kv_max(v) ((v).capacity)
-#define kv_last(v) kv_A(v, kv_size(v) - 1)
+#define kv_Z(v, i) kv_A(v, kv_size(v) - (i) - 1)
+#define kv_last(v) kv_Z(v, 0)
+
+/// Drop last n items from kvec without resizing
+///
+/// Previously spelled as `(void)kv_pop(v)`, repeated n times.
+///
+/// @param[out]  v  Kvec to drop items from.
+/// @param[in]  n  Number of elements to drop.
+#define kv_drop(v, n) ((v).size -= (n))
 
 #define kv_resize(v, s) \
     ((v).capacity = (s), \
diff --git a/src/nvim/lib/ringbuf.h b/src/nvim/lib/ringbuf.h
index 12b75ec65a..e63eae70b0 100644
--- a/src/nvim/lib/ringbuf.h
+++ b/src/nvim/lib/ringbuf.h
@@ -15,6 +15,7 @@
 #ifndef NVIM_LIB_RINGBUF_H
 #define NVIM_LIB_RINGBUF_H
 
+#include <stddef.h>
 #include <string.h>
 #include <assert.h>
 #include <stdint.h>
@@ -73,6 +74,32 @@ typedef struct { \
   RBType *buf_end; \
 } TypeName##RingBuffer;
 
+/// Dummy item free macros, for use in RINGBUF_INIT
+///
+/// This macros actually does nothing.
+///
+/// @param[in]  item  Item to be freed.
+#define RINGBUF_DUMMY_FREE(item)
+
+/// Static ring buffer
+///
+/// @warning Ring buffers created with this macros must neither be freed nor
+///          deallocated.
+///
+/// @param  scope  Ring buffer scope.
+/// @param  TypeName  Ring buffer type name.
+/// @param  RBType  Type of the single ring buffer element.
+/// @param  varname  Variable name.
+/// @param  rbsize  Ring buffer size.
+#define RINGBUF_STATIC(scope, TypeName, RBType, varname, rbsize) \
+static RBType _##varname##_buf[rbsize]; \
+scope TypeName##RingBuffer varname = { \
+  .buf = _##varname##_buf, \
+  .next = _##varname##_buf, \
+  .first = NULL, \
+  .buf_end = _##varname##_buf + rbsize - 1, \
+};
+
 /// Initialize a new ring buffer
 ///
 /// @param TypeName    Ring buffer type name. Actual type name will be
diff --git a/src/nvim/mbyte.c b/src/nvim/mbyte.c
index b24770a409..008bce6df6 100644
--- a/src/nvim/mbyte.c
+++ b/src/nvim/mbyte.c
@@ -72,19 +72,49 @@ struct interval {
 # include "unicode_tables.generated.h"
 #endif
 
-/*
- * Like utf8len_tab above, but using a zero for illegal lead bytes.
- */
-const uint8_t utf8len_tab_zero[256] =
-{
-  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
-  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
-  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
-  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
-  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
-  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
-  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
-  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,5,5,5,5,6,6,0,0,
+// To speed up BYTELEN(); keep a lookup table to quickly get the length in
+// bytes of a UTF-8 character from the first byte of a UTF-8 string.  Bytes
+// which are illegal when used as the first byte have a 1.  The NUL byte has
+// length 1.
+const uint8_t utf8len_tab[] = {
+  // ?1 ?2 ?3 ?4 ?5 ?6 ?7 ?8 ?9 ?A ?B ?C ?D ?E ?F
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 0?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 1?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 2?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 3?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 4?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 5?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 6?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 7?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 8?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 9?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // A?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // B?
+  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // C?
+  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // D?
+  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,  // E?
+  4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 1, 1,  // F?
+};
+
+// Like utf8len_tab above, but using a zero for illegal lead bytes.
+const uint8_t utf8len_tab_zero[] = {
+  // ?1 ?2 ?3 ?4 ?5 ?6 ?7 ?8 ?9 ?A ?B ?C ?D ?E ?F
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 0?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 1?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 2?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 3?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 4?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 5?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 6?
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,  // 7?
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 8?
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // 9?
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // A?
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  // B?
+  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // C?
+  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,  // D?
+  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,  // E?
+  4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 0, 0,  // F?
 };
 
 /*
@@ -528,45 +558,52 @@ int utf_off2cells(unsigned off, unsigned max_off)
   return (off + 1 < max_off && ScreenLines[off + 1] == 0) ? 2 : 1;
 }
 
-/*
- * Convert a UTF-8 byte sequence to a wide character.
- * If the sequence is illegal or truncated by a NUL the first byte is
- * returned.
- * Does not include composing characters, of course.
- */
-int utf_ptr2char(const char_u *p)
+/// Convert a UTF-8 byte sequence to a wide character
+///
+/// If the sequence is illegal or truncated by a NUL then the first byte is
+/// returned. Does not include composing characters for obvious reasons.
+///
+/// @param[in]  p  String to convert.
+///
+/// @return Unicode codepoint or byte value.
+int utf_ptr2char(const char_u *const p)
+  FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  uint8_t len;
-
-  if (p[0] < 0x80)      /* be quick for ASCII */
+  if (p[0] < 0x80) {  // Be quick for ASCII.
     return p[0];
+  }
 
-  len = utf8len_tab_zero[p[0]];
+  const uint8_t len = utf8len_tab_zero[p[0]];
   if (len > 1 && (p[1] & 0xc0) == 0x80) {
-    if (len == 2)
+    if (len == 2) {
       return ((p[0] & 0x1f) << 6) + (p[1] & 0x3f);
+    }
     if ((p[2] & 0xc0) == 0x80) {
-      if (len == 3)
-        return ((p[0] & 0x0f) << 12) + ((p[1] & 0x3f) << 6)
-          + (p[2] & 0x3f);
+      if (len == 3) {
+        return (((p[0] & 0x0f) << 12) + ((p[1] & 0x3f) << 6)
+                + (p[2] & 0x3f));
+      }
       if ((p[3] & 0xc0) == 0x80) {
-        if (len == 4)
-          return ((p[0] & 0x07) << 18) + ((p[1] & 0x3f) << 12)
-            + ((p[2] & 0x3f) << 6) + (p[3] & 0x3f);
+        if (len == 4) {
+          return (((p[0] & 0x07) << 18) + ((p[1] & 0x3f) << 12)
+                  + ((p[2] & 0x3f) << 6) + (p[3] & 0x3f));
+        }
         if ((p[4] & 0xc0) == 0x80) {
-          if (len == 5)
-            return ((p[0] & 0x03) << 24) + ((p[1] & 0x3f) << 18)
-              + ((p[2] & 0x3f) << 12) + ((p[3] & 0x3f) << 6)
-              + (p[4] & 0x3f);
-          if ((p[5] & 0xc0) == 0x80 && len == 6)
-            return ((p[0] & 0x01) << 30) + ((p[1] & 0x3f) << 24)
-              + ((p[2] & 0x3f) << 18) + ((p[3] & 0x3f) << 12)
-              + ((p[4] & 0x3f) << 6) + (p[5] & 0x3f);
+          if (len == 5) {
+            return (((p[0] & 0x03) << 24) + ((p[1] & 0x3f) << 18)
+                    + ((p[2] & 0x3f) << 12) + ((p[3] & 0x3f) << 6)
+                    + (p[4] & 0x3f));
+          }
+          if ((p[5] & 0xc0) == 0x80 && len == 6) {
+            return (((p[0] & 0x01) << 30) + ((p[1] & 0x3f) << 24)
+                    + ((p[2] & 0x3f) << 18) + ((p[3] & 0x3f) << 12)
+                    + ((p[4] & 0x3f) << 6) + (p[5] & 0x3f));
+          }
         }
       }
     }
   }
-  /* Illegal value, just return the first byte */
+  // Illegal value: just return the first byte.
   return p[0];
 }
 
@@ -767,23 +804,24 @@ int utfc_char2bytes(int off, char_u *buf)
   return len;
 }
 
-/*
- * Get the length of a UTF-8 byte sequence, not including any following
- * composing characters.
- * Returns 0 for "".
- * Returns 1 for an illegal byte sequence.
- */
-int utf_ptr2len(const char_u *p)
+/// Get the length of a UTF-8 byte sequence representing a single codepoint
+///
+/// @param[in]  p  UTF-8 string.
+///
+/// @return Sequence length, 0 for empty string and 1 for non-UTF-8 byte
+///         sequence.
+int utf_ptr2len(const char_u *const p)
+  FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
 {
-  int len;
-  int i;
-
-  if (*p == NUL)
+  if (*p == NUL) {
     return 0;
-  len = utf8len_tab[*p];
-  for (i = 1; i < len; ++i)
-    if ((p[i] & 0xc0) != 0x80)
+  }
+  const int len = utf8len_tab[*p];
+  for (int i = 1; i < len; i++) {
+    if ((p[i] & 0xc0) != 0x80) {
       return 1;
+    }
+  }
   return len;
 }
 
@@ -824,38 +862,38 @@ int utf_ptr2len_len(const char_u *p, int size)
   return len;
 }
 
-/*
- * Return the number of bytes the UTF-8 encoding of the character at "p" takes.
- * This includes following composing characters.
- */
-int utfc_ptr2len(const char_u *p)
+/// Return the number of bytes occupied by a UTF-8 character in a string
+///
+/// This includes following composing characters.
+int utfc_ptr2len(const char_u *const p)
+  FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
 {
-  int len;
-  int b0 = *p;
-  int prevlen;
+  uint8_t b0 = (uint8_t)(*p);
 
-  if (b0 == NUL)
+  if (b0 == NUL) {
     return 0;
-  if (b0 < 0x80 && p[1] < 0x80)         /* be quick for ASCII */
+  }
+  if (b0 < 0x80 && p[1] < 0x80) {  // be quick for ASCII
     return 1;
+  }
 
-  /* Skip over first UTF-8 char, stopping at a NUL byte. */
-  len = utf_ptr2len(p);
+  // Skip over first UTF-8 char, stopping at a NUL byte.
+  int len = utf_ptr2len(p);
 
-  /* Check for illegal byte. */
-  if (len == 1 && b0 >= 0x80)
+  // Check for illegal byte.
+  if (len == 1 && b0 >= 0x80) {
     return 1;
+  }
 
-  /*
-   * Check for composing characters.  We can handle only the first six, but
-   * skip all of them (otherwise the cursor would get stuck).
-   */
-  prevlen = 0;
-  for (;; ) {
-    if (p[len] < 0x80 || !UTF_COMPOSINGLIKE(p + prevlen, p + len))
+  // Check for composing characters.  We can handle only the first six, but
+  // skip all of them (otherwise the cursor would get stuck).
+  int prevlen = 0;
+  for (;;) {
+    if (p[len] < 0x80 || !UTF_COMPOSINGLIKE(p + prevlen, p + len)) {
       return len;
+    }
 
-    /* Skip over composing char */
+    // Skip over composing char.
     prevlen = len;
     len += utf_ptr2len(p + len);
   }
@@ -913,23 +951,22 @@ int utfc_ptr2len_len(const char_u *p, int size)
   return len;
 }
 
-/*
- * Return the number of bytes the UTF-8 encoding of character "c" takes.
- * This does not include composing characters.
- */
-int utf_char2len(int c)
+/// Determine how many bytes certain unicode codepoint will occupy
+int utf_char2len(const int c)
 {
-  if (c < 0x80)
+  if (c < 0x80) {
     return 1;
-  if (c < 0x800)
+  } else if (c < 0x800) {
     return 2;
-  if (c < 0x10000)
+  } else if (c < 0x10000) {
     return 3;
-  if (c < 0x200000)
+  } else if (c < 0x200000) {
     return 4;
-  if (c < 0x4000000)
+  } else if (c < 0x4000000) {
     return 5;
-  return 6;
+  } else {
+    return 6;
+  }
 }
 
 /// Convert Unicode character to UTF-8 string
@@ -937,46 +974,42 @@ int utf_char2len(int c)
 /// @param c character to convert to \p buf
 /// @param[out] buf UTF-8 string generated from \p c, does not add \0
 /// @return Number of bytes (1-6). Does not include composing characters.
-int utf_char2bytes(int c, char_u *const buf)
+int utf_char2bytes(const int c, char_u *const buf)
 {
-  if (c < 0x80) {               /* 7 bits */
+  if (c < 0x80) {  // 7 bits
     buf[0] = c;
     return 1;
-  }
-  if (c < 0x800) {              /* 11 bits */
+  } else if (c < 0x800) {  // 11 bits
     buf[0] = 0xc0 + ((unsigned)c >> 6);
     buf[1] = 0x80 + (c & 0x3f);
     return 2;
-  }
-  if (c < 0x10000) {            /* 16 bits */
+  } else if (c < 0x10000) {  // 16 bits
     buf[0] = 0xe0 + ((unsigned)c >> 12);
     buf[1] = 0x80 + (((unsigned)c >> 6) & 0x3f);
     buf[2] = 0x80 + (c & 0x3f);
     return 3;
-  }
-  if (c < 0x200000) {           /* 21 bits */
+  } else if (c < 0x200000) {  // 21 bits
     buf[0] = 0xf0 + ((unsigned)c >> 18);
     buf[1] = 0x80 + (((unsigned)c >> 12) & 0x3f);
     buf[2] = 0x80 + (((unsigned)c >> 6) & 0x3f);
     buf[3] = 0x80 + (c & 0x3f);
     return 4;
-  }
-  if (c < 0x4000000) {          /* 26 bits */
+  } else if (c < 0x4000000) {  // 26 bits
     buf[0] = 0xf8 + ((unsigned)c >> 24);
     buf[1] = 0x80 + (((unsigned)c >> 18) & 0x3f);
     buf[2] = 0x80 + (((unsigned)c >> 12) & 0x3f);
     buf[3] = 0x80 + (((unsigned)c >> 6) & 0x3f);
     buf[4] = 0x80 + (c & 0x3f);
     return 5;
+  } else {  // 31 bits
+    buf[0] = 0xfc + ((unsigned)c >> 30);
+    buf[1] = 0x80 + (((unsigned)c >> 24) & 0x3f);
+    buf[2] = 0x80 + (((unsigned)c >> 18) & 0x3f);
+    buf[3] = 0x80 + (((unsigned)c >> 12) & 0x3f);
+    buf[4] = 0x80 + (((unsigned)c >> 6) & 0x3f);
+    buf[5] = 0x80 + (c & 0x3f);
+    return 6;
   }
-  /* 31 bits */
-  buf[0] = 0xfc + ((unsigned)c >> 30);
-  buf[1] = 0x80 + (((unsigned)c >> 24) & 0x3f);
-  buf[2] = 0x80 + (((unsigned)c >> 18) & 0x3f);
-  buf[3] = 0x80 + (((unsigned)c >> 12) & 0x3f);
-  buf[4] = 0x80 + (((unsigned)c >> 6) & 0x3f);
-  buf[5] = 0x80 + (c & 0x3f);
-  return 6;
 }
 
 /*
@@ -1513,14 +1546,15 @@ int utf_head_off(const char_u *base, const char_u *p)
   return (int)(p - q);
 }
 
-/*
- * Copy a character from "*fp" to "*tp" and advance the pointers.
- */
-void mb_copy_char(const char_u **fp, char_u **tp)
+/// Copy a character, advancing the pointers
+///
+/// @param[in,out]  fp  Source of the character to copy.
+/// @param[in,out]  tp  Destination to copy to.
+void mb_copy_char(const char_u **const fp, char_u **const tp)
 {
-  int l = (*mb_ptr2len)(*fp);
+  const size_t l = (size_t)utfc_ptr2len(*fp);
 
-  memmove(*tp, *fp, (size_t)l);
+  memmove(*tp, *fp, l);
   *tp += l;
   *fp += l;
 }
@@ -2262,9 +2296,7 @@ int convert_setup_ext(vimconv_T *vcp, char_u *from, bool from_unicode_is_utf8,
   if (vcp->vc_type == CONV_ICONV && vcp->vc_fd != (iconv_t)-1)
     iconv_close(vcp->vc_fd);
 # endif
-  vcp->vc_type = CONV_NONE;
-  vcp->vc_factor = 1;
-  vcp->vc_fail = false;
+  *vcp = (vimconv_T)MBYTE_NONE_CONV;
 
   /* No conversion when one of the names is empty or they are equal. */
   if (from == NULL || *from == NUL || to == NULL || *to == NUL
diff --git a/src/nvim/mbyte.h b/src/nvim/mbyte.h
index bf6ccb13a5..a5ce1b0a15 100644
--- a/src/nvim/mbyte.h
+++ b/src/nvim/mbyte.h
@@ -60,6 +60,12 @@ typedef enum {
   CONV_ICONV     = 5,
 } ConvFlags;
 
+#define MBYTE_NONE_CONV { \
+  .vc_type = CONV_NONE, \
+  .vc_factor = 1, \
+  .vc_fail = false, \
+}
+
 /// Structure used for string conversions
 typedef struct {
   int vc_type;  ///< Zero or more ConvFlags.
@@ -73,6 +79,8 @@ typedef struct {
 
 extern const uint8_t utf8len_tab_zero[256];
 
+extern const uint8_t utf8len_tab[256];
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "mbyte.h.generated.h"
 #endif
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index bc7362af72..d1a5f0bd1c 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -5930,9 +5930,9 @@ static void syntime_report(void)
 //
 // When making changes here, also change runtime/colors/default.vim!
 
-static char *highlight_init_both[] =
-{
-  "Conceal      ctermbg=DarkGrey ctermfg=LightGrey guibg=DarkGrey guifg=LightGrey",
+static const char *highlight_init_both[] = {
+  "Conceal "
+      "ctermbg=DarkGrey ctermfg=LightGrey guibg=DarkGrey guifg=LightGrey",
   "Cursor       guibg=fg guifg=bg",
   "lCursor      guibg=fg guifg=bg",
   "DiffText     cterm=bold ctermbg=Red gui=bold guibg=Red",
@@ -5955,8 +5955,7 @@ static char *highlight_init_both[] =
   NULL
 };
 
-static char *highlight_init_light[] =
-{
+static const char *highlight_init_light[] = {
   "ColorColumn  ctermbg=LightRed guibg=LightRed",
   "CursorColumn ctermbg=LightGrey guibg=Grey90",
   "CursorLine   cterm=underline guibg=Grey90",
@@ -5989,8 +5988,7 @@ static char *highlight_init_light[] =
   NULL
 };
 
-static char *highlight_init_dark[] =
-{
+static const char *highlight_init_dark[] = {
   "ColorColumn  ctermbg=DarkRed guibg=DarkRed",
   "CursorColumn ctermbg=DarkGrey guibg=Grey40",
   "CursorLine   cterm=underline guibg=Grey40",
@@ -6023,18 +6021,223 @@ static char *highlight_init_dark[] =
   NULL
 };
 
+const char *const highlight_init_cmdline[] = {
+  // XXX When modifying a list modify it in both valid and invalid halfs.
+  // TODO(ZyX-I): merge valid and invalid groups via a macros.
+
+  // NvimInternalError should appear only when highlighter has a bug.
+  "NvimInternalError ctermfg=Red ctermbg=Red guifg=Red guibg=Red",
+
+  // Highlight groups (links) used by parser:
+
+  "default link NvimAssignment Operator",
+  "default link NvimPlainAssignment NvimAssignment",
+  "default link NvimAugmentedAssignment NvimAssignment",
+  "default link NvimAssignmentWithAddition NvimAugmentedAssignment",
+  "default link NvimAssignmentWithSubtraction NvimAugmentedAssignment",
+  "default link NvimAssignmentWithConcatenation NvimAugmentedAssignment",
+
+  "default link NvimOperator Operator",
+
+  "default link NvimUnaryOperator NvimOperator",
+  "default link NvimUnaryPlus NvimUnaryOperator",
+  "default link NvimUnaryMinus NvimUnaryOperator",
+  "default link NvimNot NvimUnaryOperator",
+
+  "default link NvimBinaryOperator NvimOperator",
+  "default link NvimComparison NvimBinaryOperator",
+  "default link NvimComparisonModifier NvimComparison",
+  "default link NvimBinaryPlus NvimBinaryOperator",
+  "default link NvimBinaryMinus NvimBinaryOperator",
+  "default link NvimConcat NvimBinaryOperator",
+  "default link NvimConcatOrSubscript NvimConcat",
+  "default link NvimOr NvimBinaryOperator",
+  "default link NvimAnd NvimBinaryOperator",
+  "default link NvimMultiplication NvimBinaryOperator",
+  "default link NvimDivision NvimBinaryOperator",
+  "default link NvimMod NvimBinaryOperator",
+
+  "default link NvimTernary NvimOperator",
+  "default link NvimTernaryColon NvimTernary",
+
+  "default link NvimParenthesis Delimiter",
+  "default link NvimLambda NvimParenthesis",
+  "default link NvimNestingParenthesis NvimParenthesis",
+  "default link NvimCallingParenthesis NvimParenthesis",
+
+  "default link NvimSubscript NvimParenthesis",
+  "default link NvimSubscriptBracket NvimSubscript",
+  "default link NvimSubscriptColon NvimSubscript",
+  "default link NvimCurly NvimSubscript",
+
+  "default link NvimContainer NvimParenthesis",
+  "default link NvimDict NvimContainer",
+  "default link NvimList NvimContainer",
+
+  "default link NvimIdentifier Identifier",
+  "default link NvimIdentifierScope NvimIdentifier",
+  "default link NvimIdentifierScopeDelimiter NvimIdentifier",
+  "default link NvimIdentifierName NvimIdentifier",
+  "default link NvimIdentifierKey NvimIdentifier",
+
+  "default link NvimColon Delimiter",
+  "default link NvimComma Delimiter",
+  "default link NvimArrow Delimiter",
+
+  "default link NvimRegister SpecialChar",
+  "default link NvimNumber Number",
+  "default link NvimFloat NvimNumber",
+  "default link NvimNumberPrefix Type",
+
+  "default link NvimOptionSigil Type",
+  "default link NvimOptionName NvimIdentifier",
+  "default link NvimOptionScope NvimIdentifierScope",
+  "default link NvimOptionScopeDelimiter NvimIdentifierScopeDelimiter",
+
+  "default link NvimEnvironmentSigil NvimOptionSigil",
+  "default link NvimEnvironmentName NvimIdentifier",
+
+  "default link NvimString String",
+  "default link NvimStringBody NvimString",
+  "default link NvimStringQuote NvimString",
+  "default link NvimStringSpecial SpecialChar",
+
+  "default link NvimSingleQuote NvimStringQuote",
+  "default link NvimSingleQuotedBody NvimStringBody",
+  "default link NvimSingleQuotedQuote NvimStringSpecial",
+
+  "default link NvimDoubleQuote NvimStringQuote",
+  "default link NvimDoubleQuotedBody NvimStringBody",
+  "default link NvimDoubleQuotedEscape NvimStringSpecial",
+
+  "default link NvimFigureBrace NvimInternalError",
+  "default link NvimSingleQuotedUnknownEscape NvimInternalError",
+
+  "default link NvimSpacing Normal",
+
+  // NvimInvalid groups:
+
+  "default link NvimInvalidSingleQuotedUnknownEscape NvimInternalError",
+
+  "default link NvimInvalid Error",
+
+  "default link NvimInvalidAssignment NvimInvalid",
+  "default link NvimInvalidPlainAssignment NvimInvalidAssignment",
+  "default link NvimInvalidAugmentedAssignment NvimInvalidAssignment",
+  "default link NvimInvalidAssignmentWithAddition "
+      "NvimInvalidAugmentedAssignment",
+  "default link NvimInvalidAssignmentWithSubtraction "
+      "NvimInvalidAugmentedAssignment",
+  "default link NvimInvalidAssignmentWithConcatenation "
+      "NvimInvalidAugmentedAssignment",
+
+  "default link NvimInvalidOperator NvimInvalid",
+
+  "default link NvimInvalidUnaryOperator NvimInvalidOperator",
+  "default link NvimInvalidUnaryPlus NvimInvalidUnaryOperator",
+  "default link NvimInvalidUnaryMinus NvimInvalidUnaryOperator",
+  "default link NvimInvalidNot NvimInvalidUnaryOperator",
+
+  "default link NvimInvalidBinaryOperator NvimInvalidOperator",
+  "default link NvimInvalidComparison NvimInvalidBinaryOperator",
+  "default link NvimInvalidComparisonModifier NvimInvalidComparison",
+  "default link NvimInvalidBinaryPlus NvimInvalidBinaryOperator",
+  "default link NvimInvalidBinaryMinus NvimInvalidBinaryOperator",
+  "default link NvimInvalidConcat NvimInvalidBinaryOperator",
+  "default link NvimInvalidConcatOrSubscript NvimInvalidConcat",
+  "default link NvimInvalidOr NvimInvalidBinaryOperator",
+  "default link NvimInvalidAnd NvimInvalidBinaryOperator",
+  "default link NvimInvalidMultiplication NvimInvalidBinaryOperator",
+  "default link NvimInvalidDivision NvimInvalidBinaryOperator",
+  "default link NvimInvalidMod NvimInvalidBinaryOperator",
+
+  "default link NvimInvalidTernary NvimInvalidOperator",
+  "default link NvimInvalidTernaryColon NvimInvalidTernary",
+
+  "default link NvimInvalidDelimiter NvimInvalid",
+
+  "default link NvimInvalidParenthesis NvimInvalidDelimiter",
+  "default link NvimInvalidLambda NvimInvalidParenthesis",
+  "default link NvimInvalidNestingParenthesis NvimInvalidParenthesis",
+  "default link NvimInvalidCallingParenthesis NvimInvalidParenthesis",
+
+  "default link NvimInvalidSubscript NvimInvalidParenthesis",
+  "default link NvimInvalidSubscriptBracket NvimInvalidSubscript",
+  "default link NvimInvalidSubscriptColon NvimInvalidSubscript",
+  "default link NvimInvalidCurly NvimInvalidSubscript",
+
+  "default link NvimInvalidContainer NvimInvalidParenthesis",
+  "default link NvimInvalidDict NvimInvalidContainer",
+  "default link NvimInvalidList NvimInvalidContainer",
+
+  "default link NvimInvalidValue NvimInvalid",
+
+  "default link NvimInvalidIdentifier NvimInvalidValue",
+  "default link NvimInvalidIdentifierScope NvimInvalidIdentifier",
+  "default link NvimInvalidIdentifierScopeDelimiter NvimInvalidIdentifier",
+  "default link NvimInvalidIdentifierName NvimInvalidIdentifier",
+  "default link NvimInvalidIdentifierKey NvimInvalidIdentifier",
+
+  "default link NvimInvalidColon NvimInvalidDelimiter",
+  "default link NvimInvalidComma NvimInvalidDelimiter",
+  "default link NvimInvalidArrow NvimInvalidDelimiter",
+
+  "default link NvimInvalidRegister NvimInvalidValue",
+  "default link NvimInvalidNumber NvimInvalidValue",
+  "default link NvimInvalidFloat NvimInvalidNumber",
+  "default link NvimInvalidNumberPrefix NvimInvalidNumber",
+
+  "default link NvimInvalidOptionSigil NvimInvalidIdentifier",
+  "default link NvimInvalidOptionName NvimInvalidIdentifier",
+  "default link NvimInvalidOptionScope NvimInvalidIdentifierScope",
+  "default link NvimInvalidOptionScopeDelimiter "
+      "NvimInvalidIdentifierScopeDelimiter",
+
+  "default link NvimInvalidEnvironmentSigil NvimInvalidOptionSigil",
+  "default link NvimInvalidEnvironmentName NvimInvalidIdentifier",
+
+  // Invalid string bodies and specials are still highlighted as valid ones to
+  // minimize the red area.
+  "default link NvimInvalidString NvimInvalidValue",
+  "default link NvimInvalidStringBody NvimStringBody",
+  "default link NvimInvalidStringQuote NvimInvalidString",
+  "default link NvimInvalidStringSpecial NvimStringSpecial",
+
+  "default link NvimInvalidSingleQuote NvimInvalidStringQuote",
+  "default link NvimInvalidSingleQuotedBody NvimInvalidStringBody",
+  "default link NvimInvalidSingleQuotedQuote NvimInvalidStringSpecial",
+
+  "default link NvimInvalidDoubleQuote NvimInvalidStringQuote",
+  "default link NvimInvalidDoubleQuotedBody NvimInvalidStringBody",
+  "default link NvimInvalidDoubleQuotedEscape NvimInvalidStringSpecial",
+  "default link NvimInvalidDoubleQuotedUnknownEscape NvimInvalidValue",
+
+  "default link NvimInvalidFigureBrace NvimInvalidDelimiter",
+
+  "default link NvimInvalidSpacing ErrorMsg",
+
+  // Not actually invalid, but we highlight user that he is doing something
+  // wrong.
+  "default link NvimDoubleQuotedUnknownEscape NvimInvalidValue",
+  NULL,
+};
+
+/// Create default links for Nvim* highlight groups used for cmdline coloring
+void syn_init_cmdline_highlight(bool reset, bool init)
+{
+  for (size_t i = 0 ; highlight_init_cmdline[i] != NULL ; i++) {
+    do_highlight(highlight_init_cmdline[i], reset, init);
+  }
+}
 
 /// Load colors from a file if "g:colors_name" is set, otherwise load builtin
 /// colors
 ///
 /// @param both include groups where 'bg' doesn't matter
 /// @param reset clear groups first
-void
-init_highlight(int both, int reset)
+void init_highlight(bool both, bool reset)
 {
-  int i;
-  char        **pp;
-  static int had_both = FALSE;
+  static int had_both = false;
 
   // Try finding the color scheme file.  Used when a color file was loaded
   // and 'background' or 't_Co' is changed.
@@ -6054,10 +6257,10 @@ init_highlight(int both, int reset)
    * Didn't use a color file, use the compiled-in colors.
    */
   if (both) {
-    had_both = TRUE;
-    pp = highlight_init_both;
-    for (i = 0; pp[i] != NULL; i++) {
-      do_highlight((char_u *)pp[i], reset, true);
+    had_both = true;
+    const char *const *const pp = highlight_init_both;
+    for (size_t i = 0; pp[i] != NULL; i++) {
+      do_highlight(pp[i], reset, true);
     }
   } else if (!had_both) {
     // Don't do anything before the call with both == TRUE from main().
@@ -6066,10 +6269,11 @@ init_highlight(int both, int reset)
     return;
   }
 
-  pp = (*p_bg == 'l') ?  highlight_init_light : highlight_init_dark;
-
-  for (i = 0; pp[i] != NULL; i++) {
-    do_highlight((char_u *)pp[i], reset, true);
+  const char *const *const pp = ((*p_bg == 'l')
+                                 ? highlight_init_light
+                                 : highlight_init_dark);
+  for (size_t i = 0; pp[i] != NULL; i++) {
+    do_highlight(pp[i], reset, true);
   }
 
   /* Reverse looks ugly, but grey may not work for 8 colors.  Thus let it
@@ -6079,15 +6283,14 @@ init_highlight(int both, int reset)
    * Clear the attributes, needed when changing the t_Co value. */
   if (t_colors > 8) {
     do_highlight(
-        (char_u *)(*p_bg == 'l'
-                   ? "Visual cterm=NONE ctermbg=LightGrey"
-                   : "Visual cterm=NONE ctermbg=DarkGrey"), false,
-        true);
+        (*p_bg == 'l'
+         ? "Visual cterm=NONE ctermbg=LightGrey"
+         : "Visual cterm=NONE ctermbg=DarkGrey"), false, true);
   } else {
-    do_highlight((char_u *)"Visual cterm=reverse ctermbg=NONE",
-        FALSE, TRUE);
-    if (*p_bg == 'l')
-      do_highlight((char_u *)"Search ctermfg=black", FALSE, TRUE);
+    do_highlight("Visual cterm=reverse ctermbg=NONE", false, true);
+    if (*p_bg == 'l') {
+      do_highlight("Search ctermfg=black", false, true);
+    }
   }
 
   /*
@@ -6104,6 +6307,7 @@ init_highlight(int both, int reset)
       recursive--;
     }
   }
+  syn_init_cmdline_highlight(false, false);
 }
 
 /*
@@ -6138,17 +6342,22 @@ int load_colors(char_u *name)
 }
 
 
-/// Handle the ":highlight .." command.
-/// When using ":hi clear" this is called recursively for each group with
-/// "forceit" and "init" both TRUE.
-/// @param init TRUE when called for initializing
-void
-do_highlight(char_u *line, int forceit, int init) {
-  char_u      *name_end;
-  char_u      *linep;
-  char_u      *key_start;
-  char_u      *arg_start;
-  char_u      *key = NULL, *arg = NULL;
+/// Handle ":highlight" command
+///
+/// When using ":highlight clear" this is called recursively for each group with
+/// forceit and init being both true.
+///
+/// @param[in]  line  Command arguments.
+/// @param[in]  forceit  True when bang is given, allows to link group even if
+///                      it has its own settings.
+/// @param[in]  init  True when initializing.
+void do_highlight(const char *line, const bool forceit, const bool init)
+  FUNC_ATTR_NONNULL_ALL
+{
+  const char *name_end;
+  const char *linep;
+  const char *key_start;
+  const char *arg_start;
   long i;
   int off;
   int len;
@@ -6162,94 +6371,87 @@ do_highlight(char_u *line, int forceit, int init) {
   int color;
   bool is_normal_group = false;   // "Normal" group
 
-  /*
-   * If no argument, list current highlighting.
-   */
-  if (ends_excmd(*line)) {
+  // If no argument, list current highlighting.
+  if (ends_excmd((uint8_t)(*line))) {
     for (int i = 1; i <= highlight_ga.ga_len && !got_int; i++) {
-      // todo(vim): only call when the group has attributes set
+      // TODO(brammool): only call when the group has attributes set
       highlight_list_one(i);
     }
     return;
   }
 
-  /*
-   * Isolate the name.
-   */
-  name_end = skiptowhite(line);
-  linep = skipwhite(name_end);
+  // Isolate the name.
+  name_end = (const char *)skiptowhite((const char_u *)line);
+  linep = (const char *)skipwhite((const char_u *)name_end);
 
-  /*
-   * Check for "default" argument.
-   */
-  if (STRNCMP(line, "default", name_end - line) == 0) {
-    dodefault = TRUE;
+  // Check for "default" argument.
+  if (strncmp(line, "default", name_end - line) == 0) {
+    dodefault = true;
     line = linep;
-    name_end = skiptowhite(line);
-    linep = skipwhite(name_end);
+    name_end = (const char *)skiptowhite((const char_u *)line);
+    linep = (const char *)skipwhite((const char_u *)name_end);
   }
 
-  /*
-   * Check for "clear" or "link" argument.
-   */
-  if (STRNCMP(line, "clear", name_end - line) == 0)
-    doclear = TRUE;
-  if (STRNCMP(line, "link", name_end - line) == 0)
-    dolink = TRUE;
+  // Check for "clear" or "link" argument.
+  if (strncmp(line, "clear", name_end - line) == 0) {
+    doclear = true;
+  } else if (strncmp(line, "link", name_end - line) == 0) {
+    dolink = true;
+  }
 
-  /*
-   * ":highlight {group-name}": list highlighting for one group.
-   */
-  if (!doclear && !dolink && ends_excmd(*linep)) {
-    id = syn_namen2id(line, (int)(name_end - line));
-    if (id == 0)
-      EMSG2(_("E411: highlight group not found: %s"), line);
-    else
+  // ":highlight {group-name}": list highlighting for one group.
+  if (!doclear && !dolink && ends_excmd((uint8_t)(*linep))) {
+    id = syn_namen2id((const char_u *)line, (int)(name_end - line));
+    if (id == 0) {
+      emsgf(_("E411: highlight group not found: %s"), line);
+    } else {
       highlight_list_one(id);
+    }
     return;
   }
 
-  /*
-   * Handle ":highlight link {from} {to}" command.
-   */
+  // Handle ":highlight link {from} {to}" command.
   if (dolink) {
-    char_u      *from_start = linep;
-    char_u      *from_end;
-    char_u      *to_start;
-    char_u      *to_end;
+    const char *from_start = linep;
+    const char *from_end;
+    const char *to_start;
+    const char *to_end;
     int from_id;
     int to_id;
 
-    from_end = skiptowhite(from_start);
-    to_start = skipwhite(from_end);
-    to_end   = skiptowhite(to_start);
+    from_end = (const char *)skiptowhite((const char_u *)from_start);
+    to_start = (const char *)skipwhite((const char_u *)from_end);
+    to_end   = (const char *)skiptowhite((const char_u *)to_start);
 
-    if (ends_excmd(*from_start) || ends_excmd(*to_start)) {
-      EMSG2(_("E412: Not enough arguments: \":highlight link %s\""),
-          from_start);
+    if (ends_excmd((uint8_t)(*from_start))
+        || ends_excmd((uint8_t)(*to_start))) {
+      emsgf(_("E412: Not enough arguments: \":highlight link %s\""),
+            from_start);
       return;
     }
 
-    if (!ends_excmd(*skipwhite(to_end))) {
-      EMSG2(_("E413: Too many arguments: \":highlight link %s\""), from_start);
+    if (!ends_excmd(*skipwhite((const char_u *)to_end))) {
+      emsgf(_("E413: Too many arguments: \":highlight link %s\""), from_start);
       return;
     }
 
-    from_id = syn_check_group(from_start, (int)(from_end - from_start));
-    if (STRNCMP(to_start, "NONE", 4) == 0)
+    from_id = syn_check_group((const char_u *)from_start,
+                              (int)(from_end - from_start));
+    if (strncmp(to_start, "NONE", 4) == 0) {
       to_id = 0;
-    else
-      to_id = syn_check_group(to_start, (int)(to_end - to_start));
+    } else {
+      to_id = syn_check_group((const char_u *)to_start,
+                              (int)(to_end - to_start));
+    }
 
     if (from_id > 0 && (!init || HL_TABLE()[from_id - 1].sg_set == 0)) {
-      /*
-       * Don't allow a link when there already is some highlighting
-       * for the group, unless '!' is used
-       */
+      // Don't allow a link when there already is some highlighting
+      // for the group, unless '!' is used
       if (to_id > 0 && !forceit && !init
           && hl_has_settings(from_id - 1, dodefault)) {
-        if (sourcing_name == NULL && !dodefault)
+        if (sourcing_name == NULL && !dodefault) {
           EMSG(_("E414: group has settings, highlight link ignored"));
+        }
       } else {
         if (!init)
           HL_TABLE()[from_id - 1].sg_set |= SG_LINK;
@@ -6259,43 +6461,38 @@ do_highlight(char_u *line, int forceit, int init) {
       }
     }
 
-    /* Only call highlight_changed() once, after sourcing a syntax file */
-    need_highlight_changed = TRUE;
+    // Only call highlight_changed() once, after sourcing a syntax file.
+    need_highlight_changed = true;
 
     return;
   }
 
   if (doclear) {
-    /*
-     * ":highlight clear [group]" command.
-     */
+    // ":highlight clear [group]" command.
     line = linep;
-    if (ends_excmd(*line)) {
+    if (ends_excmd((uint8_t)(*line))) {
       do_unlet(S_LEN("colors_name"), true);
       restore_cterm_colors();
 
-      /*
-       * Clear all default highlight groups and load the defaults.
-       */
-      for (int idx = 0; idx < highlight_ga.ga_len; ++idx) {
+      // Clear all default highlight groups and load the defaults.
+      for (int idx = 0; idx < highlight_ga.ga_len; idx++) {
         highlight_clear(idx);
       }
-      init_highlight(TRUE, TRUE);
+      init_highlight(true, true);
       highlight_changed();
       redraw_later_clear();
       return;
     }
-    name_end = skiptowhite(line);
-    linep = skipwhite(name_end);
+    name_end = (const char *)skiptowhite((const char_u *)line);
+    linep = (const char *)skipwhite((const char_u *)name_end);
   }
 
-  /*
-   * Find the group name in the table.  If it does not exist yet, add it.
-   */
-  id = syn_check_group(line, (int)(name_end - line));
-  if (id == 0)                          /* failed (out of memory) */
+  // Find the group name in the table.  If it does not exist yet, add it.
+  id = syn_check_group((const char_u *)line, (int)(name_end - line));
+  if (id == 0) {  // Failed (out of memory).
     return;
-  idx = id - 1;                         /* index is ID minus one */
+  }
+  idx = id - 1;  // Index is ID minus one.
 
   // Return if "default" was used and the group already has settings
   if (dodefault && hl_has_settings(idx, true)) {
@@ -6304,19 +6501,21 @@ do_highlight(char_u *line, int forceit, int init) {
 
   is_normal_group = (STRCMP(HL_TABLE()[idx].sg_name_u, "NORMAL") == 0);
 
-  /* Clear the highlighting for ":hi clear {group}" and ":hi clear". */
+  // Clear the highlighting for ":hi clear {group}" and ":hi clear".
   if (doclear || (forceit && init)) {
     highlight_clear(idx);
     if (!doclear)
       HL_TABLE()[idx].sg_set = 0;
   }
 
+  char *key = NULL;
+  char *arg = NULL;
   if (!doclear) {
-    while (!ends_excmd(*linep)) {
+    while (!ends_excmd((uint8_t)(*linep))) {
       key_start = linep;
       if (*linep == '=') {
-        EMSG2(_("E415: unexpected equal sign: %s"), key_start);
-        error = TRUE;
+        emsgf(_("E415: unexpected equal sign: %s"), key_start);
+        error = true;
         break;
       }
 
@@ -6326,61 +6525,58 @@ do_highlight(char_u *line, int forceit, int init) {
         linep++;
       }
       xfree(key);
-      key = vim_strnsave_up(key_start, (int)(linep - key_start));
-      linep = skipwhite(linep);
+      key = (char *)vim_strnsave_up((const char_u *)key_start,
+                                    (int)(linep - key_start));
+      linep = (const char *)skipwhite((const char_u *)linep);
 
-      if (STRCMP(key, "NONE") == 0) {
+      if (strcmp(key, "NONE") == 0) {
         if (!init || HL_TABLE()[idx].sg_set == 0) {
-          if (!init)
+          if (!init) {
             HL_TABLE()[idx].sg_set |= SG_CTERM+SG_GUI;
+          }
           highlight_clear(idx);
         }
         continue;
       }
 
-      /*
-       * Check for the equal sign.
-       */
+      // Check for the equal sign.
       if (*linep != '=') {
-        EMSG2(_("E416: missing equal sign: %s"), key_start);
-        error = TRUE;
+        emsgf(_("E416: missing equal sign: %s"), key_start);
+        error = true;
         break;
       }
-      ++linep;
+      linep++;
 
-      /*
-       * Isolate the argument.
-       */
-      linep = skipwhite(linep);
-      if (*linep == '\'') {             /* guifg='color name' */
+      // Isolate the argument.
+      linep = (const char *)skipwhite((const char_u *)linep);
+      if (*linep == '\'') {  // guifg='color name'
         arg_start = ++linep;
-        linep = vim_strchr(linep, '\'');
+        linep = strchr(linep, '\'');
         if (linep == NULL) {
-          EMSG2(_(e_invarg2), key_start);
-          error = TRUE;
+          emsgf(_(e_invarg2), key_start);
+          error = true;
           break;
         }
       } else {
         arg_start = linep;
-        linep = skiptowhite(linep);
+        linep = (const char *)skiptowhite((const char_u *)linep);
       }
       if (linep == arg_start) {
-        EMSG2(_("E417: missing argument: %s"), key_start);
-        error = TRUE;
+        emsgf(_("E417: missing argument: %s"), key_start);
+        error = true;
         break;
       }
       xfree(arg);
-      arg = vim_strnsave(arg_start, (int)(linep - arg_start));
+      arg = xstrndup(arg_start, (size_t)(linep - arg_start));
 
-      if (*linep == '\'')
-        ++linep;
+      if (*linep == '\'') {
+        linep++;
+      }
 
-      /*
-       * Store the argument.
-       */
-      if (  STRCMP(key, "TERM") == 0
-            || STRCMP(key, "CTERM") == 0
-            || STRCMP(key, "GUI") == 0) {
+      // Store the argument.
+      if (strcmp(key, "TERM") == 0
+          || strcmp(key, "CTERM") == 0
+          || strcmp(key, "GUI") == 0) {
         attr = 0;
         off = 0;
         while (arg[off] != NUL) {
@@ -6393,26 +6589,30 @@ do_highlight(char_u *line, int forceit, int init) {
             }
           }
           if (i < 0) {
-            EMSG2(_("E418: Illegal value: %s"), arg);
-            error = TRUE;
+            emsgf(_("E418: Illegal value: %s"), arg);
+            error = true;
             break;
           }
-          if (arg[off] == ',')                  /* another one follows */
-            ++off;
+          if (arg[off] == ',') {  // Another one follows.
+            off++;
+          }
         }
-        if (error)
+        if (error) {
           break;
+        }
         if (*key == 'C')   {
           if (!init || !(HL_TABLE()[idx].sg_set & SG_CTERM)) {
-            if (!init)
+            if (!init) {
               HL_TABLE()[idx].sg_set |= SG_CTERM;
+            }
             HL_TABLE()[idx].sg_cterm = attr;
             HL_TABLE()[idx].sg_cterm_bold = FALSE;
           }
         } else if (*key == 'G') {
           if (!init || !(HL_TABLE()[idx].sg_set & SG_GUI)) {
-            if (!init)
+            if (!init) {
               HL_TABLE()[idx].sg_set |= SG_GUI;
+            }
             HL_TABLE()[idx].sg_gui = attr;
           }
         }
@@ -6431,14 +6631,14 @@ do_highlight(char_u *line, int forceit, int init) {
             HL_TABLE()[idx].sg_cterm_bold = FALSE;
           }
 
-          if (ascii_isdigit(*arg))
+          if (ascii_isdigit(*arg)) {
             color = atoi((char *)arg);
-          else if (STRICMP(arg, "fg") == 0) {
-            if (cterm_normal_fg_color)
+          } else if (STRICMP(arg, "fg") == 0) {
+            if (cterm_normal_fg_color) {
               color = cterm_normal_fg_color - 1;
-            else {
+            } else {
               EMSG(_("E419: FG color unknown"));
-              error = TRUE;
+              error = true;
               break;
             }
           } else if (STRICMP(arg, "bg") == 0)   {
@@ -6446,70 +6646,84 @@ do_highlight(char_u *line, int forceit, int init) {
               color = cterm_normal_bg_color - 1;
             else {
               EMSG(_("E420: BG color unknown"));
-              error = TRUE;
+              error = true;
               break;
             }
           } else {
-            static char *(color_names[28]) = {
+            static const char *color_names[] = {
               "Black", "DarkBlue", "DarkGreen", "DarkCyan",
               "DarkRed", "DarkMagenta", "Brown", "DarkYellow",
               "Gray", "Grey",
               "LightGray", "LightGrey", "DarkGray", "DarkGrey",
               "Blue", "LightBlue", "Green", "LightGreen",
               "Cyan", "LightCyan", "Red", "LightRed", "Magenta",
-              "LightMagenta", "Yellow", "LightYellow", "White", "NONE"
+              "LightMagenta", "Yellow", "LightYellow", "White",
+              "NONE"
+            };
+            static const int color_numbers_16[] = {
+              0, 1, 2, 3,
+              4, 5, 6, 6,
+              7, 7,
+              7, 7, 8, 8,
+              9, 9, 10, 10,
+              11, 11, 12, 12, 13,
+              13, 14, 14, 15,
+              -1
+            };
+            // For xterm with 88 colors:
+            static int color_numbers_88[] = {
+              0, 4, 2, 6,
+              1, 5, 32, 72,
+              84, 84,
+              7, 7, 82, 82,
+              12, 43, 10, 61,
+              14, 63, 9, 74, 13,
+              75, 11, 78, 15,
+              -1
             };
-            static int color_numbers_16[28] = {0, 1, 2, 3,
-                                               4, 5, 6, 6,
-                                               7, 7,
-                                               7, 7, 8, 8,
-                                               9, 9, 10, 10,
-                                               11, 11, 12, 12, 13,
-                                               13, 14, 14, 15, -1};
-            /* for xterm with 88 colors... */
-            static int color_numbers_88[28] = {0, 4, 2, 6,
-                                               1, 5, 32, 72,
-                                               84, 84,
-                                               7, 7, 82, 82,
-                                               12, 43, 10, 61,
-                                               14, 63, 9, 74, 13,
-                                               75, 11, 78, 15, -1};
-            /* for xterm with 256 colors... */
-            static int color_numbers_256[28] = {0, 4, 2, 6,
-                                                1, 5, 130, 130,
-                                                248, 248,
-                                                7, 7, 242, 242,
-                                                12, 81, 10, 121,
-                                                14, 159, 9, 224, 13,
-                                                225, 11, 229, 15, -1};
-            /* for terminals with less than 16 colors... */
-            static int color_numbers_8[28] = {0, 4, 2, 6,
-                                              1, 5, 3, 3,
-                                              7, 7,
-                                              7, 7, 0+8, 0+8,
-                                              4+8, 4+8, 2+8, 2+8,
-                                              6+8, 6+8, 1+8, 1+8, 5+8,
-                                              5+8, 3+8, 3+8, 7+8, -1};
-
-            /* reduce calls to STRICMP a bit, it can be slow */
+            // For xterm with 256 colors:
+            static int color_numbers_256[] = {
+              0, 4, 2, 6,
+              1, 5, 130, 130,
+              248, 248,
+              7, 7, 242, 242,
+              12, 81, 10, 121,
+              14, 159, 9, 224, 13,
+              225, 11, 229, 15,
+              -1
+            };
+            // For terminals with less than 16 colors:
+            static int color_numbers_8[28] = {
+              0, 4, 2, 6,
+              1, 5, 3, 3,
+              7, 7,
+              7, 7, 0+8, 0+8,
+              4+8, 4+8, 2+8, 2+8,
+              6+8, 6+8, 1+8, 1+8, 5+8,
+              5+8, 3+8, 3+8, 7+8,
+              -1
+            };
+
+            // Reduce calls to STRICMP a bit, it can be slow.
             off = TOUPPER_ASC(*arg);
-            for (i = ARRAY_SIZE(color_names); --i >= 0; )
+            for (i = ARRAY_SIZE(color_names); --i >= 0; ) {
               if (off == color_names[i][0]
-                  && STRICMP(arg + 1, color_names[i] + 1) == 0)
+                  && STRICMP(arg + 1, color_names[i] + 1) == 0) {
                 break;
+              }
+            }
             if (i < 0) {
-              EMSG2(_(
-                      "E421: Color name or number not recognized: %s"),
-                  key_start);
-              error = TRUE;
+              emsgf(_("E421: Color name or number not recognized: %s"),
+                    key_start);
+              error = true;
               break;
             }
 
-            /* Use the _16 table to check if its a valid color name. */
+            // Use the _16 table to check if its a valid color name.
             color = color_numbers_16[i];
             if (color >= 0) {
               if (t_colors == 8) {
-                /* t_Co is 8: use the 8 colors table */
+                // t_Co is 8: use the 8 colors table.
                 color = color_numbers_8[i];
                 if (key[5] == 'F') {
                   /* set/reset bold attribute to get light foreground
@@ -6533,16 +6747,14 @@ do_highlight(char_u *line, int forceit, int init) {
               }
             }
           }
-          /* Add one to the argument, to avoid zero.  Zero is used for
-           * "NONE", then "color" is -1. */
+          // Add one to the argument, to avoid zero.  Zero is used for
+          // "NONE", then "color" is -1.
           if (key[5] == 'F') {
             HL_TABLE()[idx].sg_cterm_fg = color + 1;
             if (is_normal_group) {
               cterm_normal_fg_color = color + 1;
               cterm_normal_fg_bold = (HL_TABLE()[idx].sg_cterm & HL_BOLD);
-              {
-                must_redraw = CLEAR;
-              }
+              must_redraw = CLEAR;
             }
           } else {
             HL_TABLE()[idx].sg_cterm_bg = color + 1;
@@ -6566,15 +6778,15 @@ do_highlight(char_u *line, int forceit, int init) {
             }
           }
         }
-      } else if (STRCMP(key, "GUIFG") == 0)   {
+      } else if (strcmp(key, "GUIFG") == 0)   {
         if (!init || !(HL_TABLE()[idx].sg_set & SG_GUI)) {
           if (!init)
             HL_TABLE()[idx].sg_set |= SG_GUI;
 
           xfree(HL_TABLE()[idx].sg_rgb_fg_name);
-          if (STRCMP(arg, "NONE")) {
-            HL_TABLE()[idx].sg_rgb_fg_name = (uint8_t *)xstrdup((char *)arg);
-            HL_TABLE()[idx].sg_rgb_fg = name_to_color(arg);
+          if (strcmp(arg, "NONE")) {
+            HL_TABLE()[idx].sg_rgb_fg_name = (char_u *)xstrdup((char *)arg);
+            HL_TABLE()[idx].sg_rgb_fg = name_to_color((const char_u *)arg);
           } else {
             HL_TABLE()[idx].sg_rgb_fg_name = NULL;
             HL_TABLE()[idx].sg_rgb_fg = -1;
@@ -6591,8 +6803,8 @@ do_highlight(char_u *line, int forceit, int init) {
 
           xfree(HL_TABLE()[idx].sg_rgb_bg_name);
           if (STRCMP(arg, "NONE") != 0) {
-            HL_TABLE()[idx].sg_rgb_bg_name = (uint8_t *)xstrdup((char *)arg);
-            HL_TABLE()[idx].sg_rgb_bg = name_to_color(arg);
+            HL_TABLE()[idx].sg_rgb_bg_name = (char_u *)xstrdup((char *)arg);
+            HL_TABLE()[idx].sg_rgb_bg = name_to_color((const char_u *)arg);
           } else {
             HL_TABLE()[idx].sg_rgb_bg_name = NULL;
             HL_TABLE()[idx].sg_rgb_bg = -1;
@@ -6602,15 +6814,15 @@ do_highlight(char_u *line, int forceit, int init) {
         if (is_normal_group) {
           normal_bg = HL_TABLE()[idx].sg_rgb_bg;
         }
-      } else if (STRCMP(key, "GUISP") == 0)   {
+      } else if (strcmp(key, "GUISP") == 0)   {
         if (!init || !(HL_TABLE()[idx].sg_set & SG_GUI)) {
           if (!init)
             HL_TABLE()[idx].sg_set |= SG_GUI;
 
           xfree(HL_TABLE()[idx].sg_rgb_sp_name);
-          if (STRCMP(arg, "NONE") != 0) {
-            HL_TABLE()[idx].sg_rgb_sp_name = (uint8_t *)xstrdup((char *)arg);
-            HL_TABLE()[idx].sg_rgb_sp = name_to_color(arg);
+          if (strcmp(arg, "NONE") != 0) {
+            HL_TABLE()[idx].sg_rgb_sp_name = (char_u *)xstrdup((char *)arg);
+            HL_TABLE()[idx].sg_rgb_sp = name_to_color((const char_u *)arg);
           } else {
             HL_TABLE()[idx].sg_rgb_sp_name = NULL;
             HL_TABLE()[idx].sg_rgb_sp = -1;
@@ -6620,31 +6832,25 @@ do_highlight(char_u *line, int forceit, int init) {
         if (is_normal_group) {
           normal_sp = HL_TABLE()[idx].sg_rgb_sp;
         }
-      } else if (STRCMP(key, "START") == 0 || STRCMP(key, "STOP") == 0)   {
+      } else if (strcmp(key, "START") == 0 || strcmp(key, "STOP") == 0)   {
         // Ignored for now
       } else {
-        EMSG2(_("E423: Illegal argument: %s"), key_start);
-        error = TRUE;
+        emsgf(_("E423: Illegal argument: %s"), key_start);
+        error = true;
         break;
       }
 
-      /*
-       * When highlighting has been given for a group, don't link it.
-       */
+      // When highlighting has been given for a group, don't link it.
       if (!init || !(HL_TABLE()[idx].sg_set & SG_LINK)) {
         HL_TABLE()[idx].sg_link = 0;
       }
 
-      /*
-       * Continue with next argument.
-       */
-      linep = skipwhite(linep);
+      // Continue with next argument.
+      linep = (const char *)skipwhite((const char_u *)linep);
     }
   }
 
-  /*
-   * If there is an error, and it's a new entry, remove it from the table.
-   */
+  // If there is an error, and it's a new entry, remove it from the table.
   if (error && idx == highlight_ga.ga_len) {
     syn_unadd_group();
   } else {
@@ -7202,7 +7408,7 @@ char_u *syn_id2name(int id)
 /*
  * Like syn_name2id(), but take a pointer + length argument.
  */
-int syn_namen2id(char_u *linep, int len)
+int syn_namen2id(const char_u *linep, int len)
 {
   char_u *name = vim_strnsave(linep, len);
   int id = syn_name2id(name);
@@ -7218,7 +7424,7 @@ int syn_namen2id(char_u *linep, int len)
 /// @param len length of \p pp
 ///
 /// @return 0 for failure else the id of the group
-int syn_check_group(char_u *pp, int len)
+int syn_check_group(const char_u *pp, int len)
 {
   char_u  *name = vim_strnsave(pp, len);
   int id = syn_name2id(name);
@@ -8221,7 +8427,7 @@ color_name_table_T color_name_table[] = {
 ///
 /// @param[in] name string value to convert to RGB
 /// return the hex value or -1 if could not find a correct value
-RgbValue name_to_color(const uint8_t *name)
+RgbValue name_to_color(const char_u *name)
 {
 
   if (name[0] == '#' && isxdigit(name[1]) && isxdigit(name[2])
diff --git a/src/nvim/syntax.h b/src/nvim/syntax.h
index bb733ead30..c9b0665ec8 100644
--- a/src/nvim/syntax.h
+++ b/src/nvim/syntax.h
@@ -45,6 +45,9 @@ typedef struct {
 } color_name_table_T;
 extern color_name_table_T color_name_table[];
 
+/// Array of highlight definitions, used for unit testing
+extern const char *const highlight_init_cmdline[];
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "syntax.h.generated.h"
 #endif
diff --git a/src/nvim/version.c b/src/nvim/version.c
index 8d85855c6e..1a9c9d73e5 100644
--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -30,8 +30,8 @@
 // for ":version", ":intro", and "nvim --version"
 #ifndef NVIM_VERSION_MEDIUM
 #define NVIM_VERSION_MEDIUM "v" STR(NVIM_VERSION_MAJOR)\
-  "." STR(NVIM_VERSION_MINOR) "." STR(NVIM_VERSION_PATCH)\
-  NVIM_VERSION_PRERELEASE
+"." STR(NVIM_VERSION_MINOR) "." STR(NVIM_VERSION_PATCH)\
+NVIM_VERSION_PRERELEASE
 #endif
 #define NVIM_VERSION_LONG "NVIM " NVIM_VERSION_MEDIUM
 
@@ -47,33 +47,33 @@ char *version_cflags = "Compilation: " NVIM_VERSION_CFLAGS;
 
 static char *features[] = {
 #ifdef HAVE_ACL
-  "+acl",
+"+acl",
 #else
-  "-acl",
+"-acl",
 #endif
 
 #if (defined(HAVE_ICONV_H) && defined(USE_ICONV)) || defined(DYNAMIC_ICONV)
 # ifdef DYNAMIC_ICONV
-  "+iconv/dyn",
+"+iconv/dyn",
 # else
-  "+iconv",
+"+iconv",
 # endif
 #else
-  "-iconv",
+"-iconv",
 #endif
 
 #ifdef HAVE_JEMALLOC
-  "+jemalloc",
+"+jemalloc",
 #else
-  "-jemalloc",
+"-jemalloc",
 #endif
 
 #ifdef FEAT_TUI
-  "+tui",
+"+tui",
 #else
-  "-tui",
+"-tui",
 #endif
-  NULL
+NULL
 };
 
 // clang-format off
@@ -205,8 +205,8 @@ static const int included_patches[] = {
   // 1233,
   // 1232,
   // 1231,
-  // 1230,
-  // 1229,
+  1230,
+  1229,
   // 1228,
   // 1227,
   // 1226,
diff --git a/src/nvim/vim.h b/src/nvim/vim.h
index 7da3c8246f..b535e380d1 100644
--- a/src/nvim/vim.h
+++ b/src/nvim/vim.h
@@ -26,13 +26,6 @@
 /// length of a buffer to store a number in ASCII (64 bits binary + NUL)
 enum { NUMBUFLEN = 65 };
 
-// flags for vim_str2nr()
-#define STR2NR_BIN 1
-#define STR2NR_OCT 2
-#define STR2NR_HEX 4
-#define STR2NR_ALL (STR2NR_BIN + STR2NR_OCT + STR2NR_HEX)
-#define STR2NR_FORCE 8  // only when ONE of the above is used
-
 #define MAX_TYPENR 65535
 
 #define ROOT_UID 0
diff --git a/src/nvim/viml/parser/expressions.c b/src/nvim/viml/parser/expressions.c
new file mode 100644
index 0000000000..4196ecb9d2
--- /dev/null
+++ b/src/nvim/viml/parser/expressions.c
@@ -0,0 +1,3102 @@
+// This is an open source non-commercial project. Dear PVS-Studio, please check
+// it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+
+/// VimL expression parser
+
+// Planned incompatibilities (to be included into vim_diff.txt when this parser
+// will be an actual part of VimL evaluation process):
+//
+// 1. Expressions are first fully parsed and only then executed.  This means
+//    that while ":echo [system('touch abc')" will create file "abc" in Vim and
+//    only then raise syntax error regarding missing comma in list in Neovim
+//    trying to execute that will immediately raise syntax error regarding
+//    missing list end without actually executing anything.
+// 2. Expressions are first fully parsed, without considering any runtime
+//    information.  This means things like that "d.a" does not change its
+//    meaning depending on type of "d" (or whether Vim is currently executing or
+//    skipping).  For compatibility reasons the dot thus may either be “concat
+//    or subscript” operator or just “concat” operator.
+// 3. Expressions parser is aware whether it is called for :echo or <C-r>=.
+//    This means that while "<C-r>=1 | 2<CR>" is equivalent to "<C-r>=1<CR>"
+//    because "| 2" part is left to be treated as a command separator and then
+//    ignored in Neovim it is an error.
+// 4. Expressions parser has generally better error reporting.  But for
+//    compatibility reasons most errors have error code E15 while error messages
+//    are significantly different from Vim’s E15.  Also some error codes were
+//    retired because of being harder to emulate or because of them being
+//    a result of differences in parsing process: e.g. with ":echo {a, b}" Vim
+//    will attempt to parse expression as lambda, fail, check whether it is
+//    a curly-braces-name, fail again, and evaluate that as a dictionary, giving
+//    error regarding undefined variable "a" (or about missing colon).  Neovim
+//    will not try to evaluate anything here: comma right after an argument name
+//    means that expression may not be anything, but lambda, so the resulting
+//    error message will never be about missing variable or colon: it will be
+//    about missing arrow (or a continuation of argument list).
+// 5. Failing to parse expression always gives exactly one error message: no
+//    more stack of error messages like >
+//
+//        :echo [1,
+//        E697: Missing end of List ']':
+//        E15: Invalid expression: [1,
+//
+// <  , just exactly one E697 message.
+// 6. Some expressions involving calling parenthesis which are treated
+//    separately by Vim even when not separated by spaces are treated as one
+//    expression by Neovim: e.g. ":echo (1)(1)" will yield runtime error after
+//    failing to call "1", while Vim will echo "1 1". Reasoning is the same:
+//    type of what is in the first expression is generally not known when
+//    parsing, so to have separate expressions like this separate them with
+//    spaces.
+// 7. 'isident' no longer applies to environment variables, they always include
+//    ASCII alphanumeric characters and underscore and nothing except this.
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <assert.h>
+#include <string.h>
+
+#include "nvim/vim.h"
+#include "nvim/memory.h"
+#include "nvim/types.h"
+#include "nvim/charset.h"
+#include "nvim/ascii.h"
+#include "nvim/assert.h"
+#include "nvim/lib/kvec.h"
+#include "nvim/eval/typval.h"
+
+#include "nvim/viml/parser/expressions.h"
+#include "nvim/viml/parser/parser.h"
+
+#define vim_str2nr(s, ...) vim_str2nr((const char_u *)(s), __VA_ARGS__)
+
+typedef kvec_withinit_t(ExprASTNode **, 16) ExprASTStack;
+
+/// Which nodes may be wanted
+typedef enum {
+  /// Operators: function call, subscripts, binary operators, …
+  ///
+  /// For unrestricted expressions.
+  kENodeOperator,
+  /// Values: literals, variables, nested expressions, unary operators.
+  ///
+  /// For unrestricted expressions as well, implies that top item in AST stack
+  /// points to NULL.
+  kENodeValue,
+} ExprASTWantedNode;
+
+/// Parse type: what is being parsed currently
+typedef enum {
+  /// Parsing regular VimL expression
+  kEPTExpr = 0,
+  /// Parsing lambda arguments
+  ///
+  /// Just like parsing function arguments, but it is valid to be ended with an
+  /// arrow only.
+  kEPTLambdaArguments,
+  /// Assignment: parsing for :let
+  kEPTAssignment,
+  /// Single assignment: used when lists are not allowed (i.e. when nesting)
+  kEPTSingleAssignment,
+} ExprASTParseType;
+
+typedef kvec_withinit_t(ExprASTParseType, 4) ExprASTParseTypeStack;
+
+/// Operator priority level
+typedef enum {
+  kEOpLvlInvalid = 0,
+  kEOpLvlComplexIdentifier,
+  kEOpLvlParens,
+  kEOpLvlAssignment,
+  kEOpLvlArrow,
+  kEOpLvlComma,
+  kEOpLvlColon,
+  kEOpLvlTernaryValue,
+  kEOpLvlTernary,
+  kEOpLvlOr,
+  kEOpLvlAnd,
+  kEOpLvlComparison,
+  kEOpLvlAddition,  ///< Addition, subtraction and concatenation.
+  kEOpLvlMultiplication,  ///< Multiplication, division and modulo.
+  kEOpLvlUnary,  ///< Unary operations: not, minus, plus.
+  kEOpLvlSubscript,  ///< Subscripts.
+  kEOpLvlValue,  ///< Values: literals, variables, nested expressions, …
+} ExprOpLvl;
+
+/// Operator associativity
+typedef enum {
+  kEOpAssNo= 'n',  ///< Not associative / not applicable.
+  kEOpAssLeft = 'l',  ///< Left associativity.
+  kEOpAssRight = 'r',  ///< Right associativity.
+} ExprOpAssociativity;
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "viml/parser/expressions.c.generated.h"
+#endif
+
+/// Character used as a separator in autoload function/variable names.
+#define AUTOLOAD_CHAR '#'
+
+/// Scale number by a given factor
+///
+/// Used to apply exponent to a number. Idea taken from uClibc.
+///
+/// @param[in]  num  Number to scale. Does not bother doing anything if it is
+///                  zero.
+/// @param[in]  base  Base, should be 10 since non-decimal floating-point
+///                   numbers are not supported.
+/// @param[in]  exponent  Exponent to scale by.
+/// @param[in]  exponent_negative  True if exponent is negative.
+static inline float_T scale_number(const float_T num,
+                                   const uint8_t base,
+                                   const uvarnumber_T exponent,
+                                   const bool exponent_negative)
+  FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_CONST
+{
+  if (num == 0 || exponent == 0) {
+    return num;
+  }
+  assert(base);
+  uvarnumber_T exp = exponent;
+  float_T p_base = (float_T)base;
+  float_T ret = num;
+  while (exp) {
+    if (exp & 1) {
+      if (exponent_negative) {
+        ret /= p_base;
+      } else {
+        ret *= p_base;
+      }
+    }
+    exp >>= 1;
+    p_base *= p_base;
+  }
+  return ret;
+}
+
+/// Get next token for the VimL expression input
+///
+/// @param  pstate  Parser state.
+/// @param[in]  flags  Flags, @see LexExprFlags.
+///
+/// @return Next token.
+LexExprToken viml_pexpr_next_token(ParserState *const pstate, const int flags)
+  FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
+{
+  LexExprToken ret = {
+    .type = kExprLexInvalid,
+    .start = pstate->pos,
+  };
+  ParserLine pline;
+  if (!viml_parser_get_remaining_line(pstate, &pline)) {
+    ret.type = kExprLexEOC;
+    return ret;
+  }
+  if (pline.size <= 0) {
+    ret.len = 0;
+    ret.type = kExprLexEOC;
+    goto viml_pexpr_next_token_adv_return;
+  }
+  ret.len = 1;
+  const uint8_t schar = (uint8_t)pline.data[0];
+#define GET_CCS(ret, pline) \
+  do { \
+    if (ret.len < pline.size \
+        && strchr("?#", pline.data[ret.len]) != NULL) { \
+      ret.data.cmp.ccs = \
+          (ExprCaseCompareStrategy)pline.data[ret.len]; \
+      ret.len++; \
+    } else { \
+      ret.data.cmp.ccs = kCCStrategyUseOption; \
+    } \
+  } while (0)
+  switch (schar) {
+    // Paired brackets.
+#define BRACKET(typ, opning, clsing) \
+    case opning: \
+    case clsing: { \
+      ret.type = typ; \
+      ret.data.brc.closing = (schar == clsing); \
+      break; \
+    }
+    BRACKET(kExprLexParenthesis, '(', ')')
+    BRACKET(kExprLexBracket, '[', ']')
+    BRACKET(kExprLexFigureBrace, '{', '}')
+#undef BRACKET
+
+    // Single character tokens without data.
+#define CHAR(typ, ch) \
+    case ch: { \
+      ret.type = typ; \
+      break; \
+    }
+    CHAR(kExprLexQuestion, '?')
+    CHAR(kExprLexColon, ':')
+    CHAR(kExprLexComma, ',')
+#undef CHAR
+
+    // Multiplication/division/modulo.
+#define MUL(mul_type, ch) \
+    case ch: { \
+      ret.type = kExprLexMultiplication; \
+      ret.data.mul.type = mul_type; \
+      break; \
+    }
+    MUL(kExprLexMulMul, '*')
+    MUL(kExprLexMulDiv, '/')
+    MUL(kExprLexMulMod, '%')
+#undef MUL
+
+#define CHARREG(typ, cond) \
+    do { \
+      ret.type = typ; \
+      for (; (ret.len < pline.size \
+              && cond(pline.data[ret.len])) \
+           ; ret.len++) { \
+      } \
+    } while (0)
+
+    // Whitespace.
+    case ' ':
+    case TAB: {
+      CHARREG(kExprLexSpacing, ascii_iswhite);
+      break;
+    }
+
+    // Control character, except for NUL, NL and TAB.
+    case Ctrl_A: case Ctrl_B: case Ctrl_C: case Ctrl_D: case Ctrl_E:
+    case Ctrl_F: case Ctrl_G: case Ctrl_H:
+
+    case Ctrl_K: case Ctrl_L: case Ctrl_M: case Ctrl_N: case Ctrl_O:
+    case Ctrl_P: case Ctrl_Q: case Ctrl_R: case Ctrl_S: case Ctrl_T:
+    case Ctrl_U: case Ctrl_V: case Ctrl_W: case Ctrl_X: case Ctrl_Y:
+    case Ctrl_Z: {
+#define ISCTRL(schar) (schar < ' ')
+      CHARREG(kExprLexInvalid, ISCTRL);
+      ret.data.err.type = kExprLexSpacing;
+      ret.data.err.msg =
+          _("E15: Invalid control character present in input: %.*s");
+      break;
+#undef ISCTRL
+    }
+
+    // Number.
+    case '0': case '1': case '2': case '3': case '4': case '5': case '6':
+    case '7': case '8': case '9': {
+      ret.data.num.is_float = false;
+      ret.data.num.base = 10;
+      size_t frac_start = 0;
+      size_t exp_start = 0;
+      size_t frac_end = 0;
+      bool exp_negative = false;
+      CHARREG(kExprLexNumber, ascii_isdigit);
+      if (flags & kELFlagAllowFloat) {
+        const LexExprToken non_float_ret = ret;
+        if (pline.size > ret.len + 1
+            && pline.data[ret.len] == '.'
+            && ascii_isdigit(pline.data[ret.len + 1])) {
+          ret.len++;
+          frac_start = ret.len;
+          frac_end = ret.len;
+          ret.data.num.is_float = true;
+          for (; ret.len < pline.size && ascii_isdigit(pline.data[ret.len])
+               ; ret.len++) {
+            // A small optimization: trailing zeroes in fractional part do not
+            // add anything to significand, so it is useless to include them in
+            // frac_end.
+            if (pline.data[ret.len] != '0') {
+              frac_end = ret.len + 1;
+            }
+          }
+          if (pline.size > ret.len + 1
+              && (pline.data[ret.len] == 'e'
+                  || pline.data[ret.len] == 'E')
+              && ((pline.size > ret.len + 2
+                   && (pline.data[ret.len + 1] == '+'
+                       || pline.data[ret.len + 1] == '-')
+                   && ascii_isdigit(pline.data[ret.len + 2]))
+                  || ascii_isdigit(pline.data[ret.len + 1]))) {
+            ret.len++;
+            if (pline.data[ret.len] == '+'
+                || (exp_negative = (pline.data[ret.len] == '-'))) {
+              ret.len++;
+            }
+            exp_start = ret.len;
+            CHARREG(kExprLexNumber, ascii_isdigit);
+          }
+        }
+        if (pline.size > ret.len
+            && (pline.data[ret.len] == '.'
+                || ASCII_ISALPHA(pline.data[ret.len]))) {
+          ret = non_float_ret;
+        }
+      }
+      // TODO(ZyX-I): detect overflows
+      if (ret.data.num.is_float) {
+        // Vim used to use string2float here which in turn uses strtod(). There
+        // are two problems with this approach:
+        // 1. strtod() is locale-dependent. Not sure how it is worked around so
+        //    that I do not see relevant bugs, but it still does not look like
+        //    a good idea.
+        // 2. strtod() does not accept length argument.
+        //
+        // The below variant of parsing floats was recognized as acceptable
+        // because it is basically how uClibc does the thing: it generates
+        // a number ignoring decimal point (but recording its position), then
+        // uses recorded position to scale number down when processing exponent.
+        float_T significand_part = 0;
+        uvarnumber_T exp_part = 0;
+        const size_t frac_size = (size_t)(frac_end - frac_start);
+        for (size_t i = 0; i < frac_end; i++) {
+          if (i == frac_start - 1) {
+            continue;
+          }
+          significand_part = significand_part * 10 + (pline.data[i] - '0');
+        }
+        if (exp_start) {
+          vim_str2nr(pline.data + exp_start, NULL, NULL, 0, NULL, &exp_part,
+                     (int)(ret.len - exp_start));
+        }
+        if (exp_negative) {
+          exp_part += frac_size;
+        } else {
+          if (exp_part < frac_size) {
+            exp_negative = true;
+            exp_part = frac_size - exp_part;
+          } else {
+            exp_part -= frac_size;
+          }
+        }
+        ret.data.num.val.floating = scale_number(significand_part, 10, exp_part,
+                                                 exp_negative);
+      } else {
+        int len;
+        int prep;
+        vim_str2nr(pline.data, &prep, &len, STR2NR_ALL, NULL,
+                   &ret.data.num.val.integer, (int)pline.size);
+        ret.len = (size_t)len;
+        const uint8_t bases[] = {
+          [0] = 10,
+          ['0'] = 8,
+          ['x'] = 16, ['X'] = 16,
+          ['b'] = 2, ['B'] = 2,
+        };
+        ret.data.num.base = bases[prep];
+      }
+      break;
+    }
+
+#define ISWORD_OR_AUTOLOAD(x) \
+      (ascii_isident(x) || (x) == AUTOLOAD_CHAR)
+
+    // Environment variable.
+    case '$': {
+      CHARREG(kExprLexEnv, ascii_isident);
+      break;
+    }
+
+    // Normal variable/function name.
+    case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g':
+    case 'h': case 'i': case 'j': case 'k': case 'l': case 'm': case 'n':
+    case 'o': case 'p': case 'q': case 'r': case 's': case 't': case 'u':
+    case 'v': case 'w': case 'x': case 'y': case 'z':
+    case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G':
+    case 'H': case 'I': case 'J': case 'K': case 'L': case 'M': case 'N':
+    case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U':
+    case 'V': case 'W': case 'X': case 'Y': case 'Z':
+    case '_': {
+      ret.data.var.scope = 0;
+      ret.data.var.autoload = false;
+      CHARREG(kExprLexPlainIdentifier, ascii_isident);
+      // "is" and "isnot" operators.
+      if (!(flags & kELFlagIsNotCmp)
+          && ((ret.len == 2 && memcmp(pline.data, "is", 2) == 0)
+              || (ret.len == 5 && memcmp(pline.data, "isnot", 5) == 0))) {
+        ret.type = kExprLexComparison;
+        ret.data.cmp.type = kExprCmpIdentical;
+        ret.data.cmp.inv = (ret.len == 5);
+        GET_CCS(ret, pline);
+      // Scope: `s:`, etc.
+      } else if (ret.len == 1
+                 && pline.size > 1
+                 && memchr(EXPR_VAR_SCOPE_LIST, schar,
+                           sizeof(EXPR_VAR_SCOPE_LIST)) != NULL
+                 && pline.data[ret.len] == ':'
+                 && !(flags & kELFlagForbidScope)) {
+        ret.len++;
+        ret.data.var.scope = (ExprVarScope)schar;
+        CHARREG(kExprLexPlainIdentifier, ISWORD_OR_AUTOLOAD);
+        ret.data.var.autoload = (
+            memchr(pline.data + 2, AUTOLOAD_CHAR, ret.len - 2)
+            != NULL);
+      // Previous CHARREG stopped at autoload character in order to make it
+      // possible to detect `is#`. Continue now with autoload characters
+      // included.
+      //
+      // Warning: there is ambiguity for the lexer: `is#Foo(1)` is a call of
+      // function `is#Foo()`, `1is#Foo(1)` is a comparison `1 is# Foo(1)`. This
+      // needs to be resolved on the higher level where context is available.
+      } else if (pline.size > ret.len
+                 && pline.data[ret.len] == AUTOLOAD_CHAR) {
+        ret.data.var.autoload = true;
+        CHARREG(kExprLexPlainIdentifier, ISWORD_OR_AUTOLOAD);
+      }
+      break;
+    }
+
+#undef ISWORD_OR_AUTOLOAD
+#undef CHARREG
+
+    // Option.
+    case '&': {
+#define OPTNAMEMISS(ret) \
+        do { \
+          ret.type = kExprLexInvalid; \
+          ret.data.err.type = kExprLexOption; \
+          ret.data.err.msg = _("E112: Option name missing: %.*s"); \
+        } while (0)
+      if (pline.size > 1 && pline.data[1] == '&') {
+        ret.type = kExprLexAnd;
+        ret.len++;
+        break;
+      }
+      if (pline.size == 1 || !ASCII_ISALPHA(pline.data[1])) {
+        OPTNAMEMISS(ret);
+        break;
+      }
+      ret.type = kExprLexOption;
+      if (pline.size > 2
+          && pline.data[2] == ':'
+          && memchr(EXPR_OPT_SCOPE_LIST, pline.data[1],
+                    sizeof(EXPR_OPT_SCOPE_LIST)) != NULL) {
+        ret.len += 2;
+        ret.data.opt.scope = (ExprOptScope)pline.data[1];
+        ret.data.opt.name = pline.data + 3;
+      } else {
+        ret.data.opt.scope = kExprOptScopeUnspecified;
+        ret.data.opt.name = pline.data + 1;
+      }
+      const char *p = ret.data.opt.name;
+      const char *const e = pline.data + pline.size;
+      if (e - p >= 4 && p[0] == 't' && p[1] == '_') {
+        ret.data.opt.len = 4;
+        ret.len += 4;
+      } else {
+        for (; p < e && ASCII_ISALPHA(*p); p++) {
+        }
+        ret.data.opt.len = (size_t)(p - ret.data.opt.name);
+        if (ret.data.opt.len == 0) {
+          OPTNAMEMISS(ret);
+        } else {
+          ret.len += ret.data.opt.len;
+        }
+      }
+      break;
+#undef OPTNAMEMISS
+    }
+
+    // Register.
+    case '@': {
+      ret.type = kExprLexRegister;
+      if (pline.size > 1) {
+        ret.len++;
+        ret.data.reg.name = (uint8_t)pline.data[1];
+      } else {
+        ret.data.reg.name = -1;
+      }
+      break;
+    }
+
+    // Single quoted string.
+    case '\'': {
+      ret.type = kExprLexSingleQuotedString;
+      ret.data.str.closed = false;
+      for (; ret.len < pline.size && !ret.data.str.closed; ret.len++) {
+        if (pline.data[ret.len] == '\'') {
+          if (ret.len + 1 < pline.size && pline.data[ret.len + 1] == '\'') {
+            ret.len++;
+          } else {
+            ret.data.str.closed = true;
+          }
+        }
+      }
+      break;
+    }
+
+    // Double quoted string.
+    case '"': {
+      ret.type = kExprLexDoubleQuotedString;
+      ret.data.str.closed = false;
+      for (; ret.len < pline.size && !ret.data.str.closed; ret.len++) {
+        if (pline.data[ret.len] == '\\') {
+          if (ret.len + 1 < pline.size) {
+            ret.len++;
+          }
+        } else if (pline.data[ret.len] == '"') {
+          ret.data.str.closed = true;
+        }
+      }
+      break;
+    }
+
+    // Unary not, (un)equality and regex (not) match comparison operators.
+    case '!':
+    case '=': {
+      if (pline.size == 1) {
+        ret.type = (schar == '!' ? kExprLexNot : kExprLexAssignment);
+        ret.data.ass.type = kExprAsgnPlain;
+        break;
+      }
+      ret.type = kExprLexComparison;
+      ret.data.cmp.inv = (schar == '!');
+      if (pline.data[1] == '=') {
+        ret.data.cmp.type = kExprCmpEqual;
+        ret.len++;
+      } else if (pline.data[1] == '~') {
+        ret.data.cmp.type = kExprCmpMatches;
+        ret.len++;
+      } else if (schar == '!') {
+        ret.type = kExprLexNot;
+      } else {
+        ret.type = kExprLexAssignment;
+        ret.data.ass.type = kExprAsgnPlain;
+      }
+      GET_CCS(ret, pline);
+      break;
+    }
+
+    // Less/greater [or equal to] comparison operators.
+    case '>':
+    case '<': {
+      ret.type = kExprLexComparison;
+      const bool haseqsign = (pline.size > 1 && pline.data[1] == '=');
+      if (haseqsign) {
+        ret.len++;
+      }
+      GET_CCS(ret, pline);
+      ret.data.cmp.inv = (schar == '<');
+      ret.data.cmp.type = ((ret.data.cmp.inv ^ haseqsign)
+                           ? kExprCmpGreaterOrEqual
+                           : kExprCmpGreater);
+      break;
+    }
+
+    // Minus sign, arrow from lambdas or augmented assignment.
+    case '-': {
+      if (pline.size > 1 && pline.data[1] == '>') {
+        ret.len++;
+        ret.type = kExprLexArrow;
+      } else if (pline.size > 1 && pline.data[1] == '=') {
+        ret.len++;
+        ret.type = kExprLexAssignment;
+        ret.data.ass.type = kExprAsgnSubtract;
+      } else {
+        ret.type = kExprLexMinus;
+      }
+      break;
+    }
+
+    // Sign or augmented assignment.
+#define CHAR_OR_ASSIGN(ch, ch_type, ass_type) \
+    case ch: { \
+      if (pline.size > 1 && pline.data[1] == '=') { \
+        ret.len++; \
+        ret.type = kExprLexAssignment; \
+        ret.data.ass.type = ass_type; \
+      } else { \
+        ret.type = ch_type; \
+      } \
+      break; \
+    }
+    CHAR_OR_ASSIGN('+', kExprLexPlus, kExprAsgnAdd)
+    CHAR_OR_ASSIGN('.', kExprLexDot, kExprAsgnConcat)
+#undef CHAR_OR_ASSIGN
+
+    // Expression end because Ex command ended.
+    case NUL:
+    case NL: {
+      if (flags & kELFlagForbidEOC) {
+        ret.type = kExprLexInvalid;
+        ret.data.err.msg = _("E15: Unexpected EOC character: %.*s");
+        ret.data.err.type = kExprLexSpacing;
+      } else {
+        ret.type = kExprLexEOC;
+      }
+      break;
+    }
+
+    case '|': {
+      if (pline.size >= 2 && pline.data[ret.len] == '|') {
+        // "||" is or.
+        ret.len++;
+        ret.type = kExprLexOr;
+      } else if (flags & kELFlagForbidEOC) {
+        // Note: `<C-r>=1 | 2<CR>` actually yields 1 in Vim without any
+        //       errors. This will be changed here.
+        ret.type = kExprLexInvalid;
+        ret.data.err.msg = _("E15: Unexpected EOC character: %.*s");
+        ret.data.err.type = kExprLexOr;
+      } else {
+        ret.type = kExprLexEOC;
+      }
+      break;
+    }
+
+    // Everything else is not valid.
+    default: {
+      ret.len = (size_t)utfc_ptr2len_len((const char_u *)pline.data,
+                                         (int)pline.size);
+      ret.type = kExprLexInvalid;
+      ret.data.err.type = kExprLexPlainIdentifier;
+      ret.data.err.msg = _("E15: Unidentified character: %.*s");
+      break;
+    }
+  }
+#undef GET_CCS
+viml_pexpr_next_token_adv_return:
+  if (!(flags & kELFlagPeek)) {
+    viml_parser_advance(pstate, ret.len);
+  }
+  return ret;
+}
+
+static const char *const eltkn_type_tab[] = {
+  [kExprLexInvalid] = "Invalid",
+  [kExprLexMissing] = "Missing",
+  [kExprLexSpacing] = "Spacing",
+  [kExprLexEOC] = "EOC",
+
+  [kExprLexQuestion] = "Question",
+  [kExprLexColon] = "Colon",
+  [kExprLexOr] = "Or",
+  [kExprLexAnd] = "And",
+  [kExprLexComparison] = "Comparison",
+  [kExprLexPlus] = "Plus",
+  [kExprLexMinus] = "Minus",
+  [kExprLexDot] = "Dot",
+  [kExprLexMultiplication] = "Multiplication",
+
+  [kExprLexNot] = "Not",
+
+  [kExprLexNumber] = "Number",
+  [kExprLexSingleQuotedString] = "SingleQuotedString",
+  [kExprLexDoubleQuotedString] = "DoubleQuotedString",
+  [kExprLexOption] = "Option",
+  [kExprLexRegister] = "Register",
+  [kExprLexEnv] = "Env",
+  [kExprLexPlainIdentifier] = "PlainIdentifier",
+
+  [kExprLexBracket] = "Bracket",
+  [kExprLexFigureBrace] = "FigureBrace",
+  [kExprLexParenthesis] = "Parenthesis",
+  [kExprLexComma] = "Comma",
+  [kExprLexArrow] = "Arrow",
+  [kExprLexAssignment] = "Assignment",
+};
+
+const char *const eltkn_cmp_type_tab[] = {
+  [kExprCmpEqual] = "Equal",
+  [kExprCmpMatches] = "Matches",
+  [kExprCmpGreater] = "Greater",
+  [kExprCmpGreaterOrEqual] = "GreaterOrEqual",
+  [kExprCmpIdentical] = "Identical",
+};
+
+const char *const expr_asgn_type_tab[] = {
+  [kExprAsgnPlain] = "Plain",
+  [kExprAsgnAdd] = "Add",
+  [kExprAsgnSubtract] = "Subtract",
+  [kExprAsgnConcat] = "Concat",
+};
+
+const char *const ccs_tab[] = {
+  [kCCStrategyUseOption] = "UseOption",
+  [kCCStrategyMatchCase] = "MatchCase",
+  [kCCStrategyIgnoreCase] = "IgnoreCase",
+};
+
+static const char *const eltkn_mul_type_tab[] = {
+  [kExprLexMulMul] = "Mul",
+  [kExprLexMulDiv] = "Div",
+  [kExprLexMulMod] = "Mod",
+};
+
+static const char *const eltkn_opt_scope_tab[] = {
+  [kExprOptScopeUnspecified] = "Unspecified",
+  [kExprOptScopeGlobal] = "Global",
+  [kExprOptScopeLocal] = "Local",
+};
+
+/// Represent token as a string
+///
+/// Intended for testing and debugging purposes.
+///
+/// @param[in]  pstate  Parser state, needed to get token string from it. May be
+///                     NULL, in which case in place of obtaining part of the
+///                     string represented by token only token length is
+///                     returned.
+/// @param[in]  token  Token to represent.
+/// @param[out]  ret_size  Return string size, for cases like NULs inside
+///                        a string. May be NULL.
+///
+/// @return Token represented in a string form, in a static buffer (overwritten
+///         on each call).
+const char *viml_pexpr_repr_token(const ParserState *const pstate,
+                                  const LexExprToken token,
+                                  size_t *const ret_size)
+  FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  static char ret[1024];
+  char *p = ret;
+  const char *const e = &ret[1024] - 1;
+#define ADDSTR(...) \
+  do { \
+    p += snprintf(p, (size_t)(sizeof(ret) - (size_t)(p - ret)), __VA_ARGS__); \
+    if (p >= e) { \
+      goto viml_pexpr_repr_token_end; \
+    } \
+  } while (0)
+  ADDSTR("%zu:%zu:%s", token.start.line, token.start.col,
+         eltkn_type_tab[token.type]);
+  switch (token.type) {
+#define TKNARGS(tkn_type, ...) \
+    case tkn_type: { \
+      ADDSTR(__VA_ARGS__); \
+      break; \
+    }
+    TKNARGS(kExprLexComparison, "(type=%s,ccs=%s,inv=%i)",
+            eltkn_cmp_type_tab[token.data.cmp.type],
+            ccs_tab[token.data.cmp.ccs],
+            (int)token.data.cmp.inv)
+    TKNARGS(kExprLexMultiplication, "(type=%s)",
+            eltkn_mul_type_tab[token.data.mul.type])
+    TKNARGS(kExprLexAssignment, "(type=%s)",
+            expr_asgn_type_tab[token.data.ass.type])
+    TKNARGS(kExprLexRegister, "(name=%s)", intchar2str(token.data.reg.name))
+    case kExprLexDoubleQuotedString:
+    TKNARGS(kExprLexSingleQuotedString, "(closed=%i)",
+            (int)token.data.str.closed)
+    TKNARGS(kExprLexOption, "(scope=%s,name=%.*s)",
+            eltkn_opt_scope_tab[token.data.opt.scope],
+            (int)token.data.opt.len, token.data.opt.name)
+    TKNARGS(kExprLexPlainIdentifier, "(scope=%s,autoload=%i)",
+            intchar2str(token.data.var.scope), (int)token.data.var.autoload)
+    TKNARGS(kExprLexNumber, "(is_float=%i,base=%i,val=%lg)",
+            (int)token.data.num.is_float,
+            (int)token.data.num.base,
+            (double)(token.data.num.is_float
+                     ? (double)token.data.num.val.floating
+                     : (double)token.data.num.val.integer))
+    TKNARGS(kExprLexInvalid, "(msg=%s)", token.data.err.msg)
+    default: {
+      // No additional arguments.
+      break;
+    }
+#undef TKNARGS
+  }
+  if (pstate == NULL) {
+    ADDSTR("::%zu", token.len);
+  } else {
+    *p++ = ':';
+    memmove(
+        p, &pstate->reader.lines.items[token.start.line].data[token.start.col],
+        token.len);
+    p += token.len;
+    *p = NUL;
+  }
+#undef ADDSTR
+viml_pexpr_repr_token_end:
+  if (ret_size != NULL) {
+    *ret_size = (size_t)(p - ret);
+  }
+  return ret;
+}
+
+const char *const east_node_type_tab[] = {
+  [kExprNodeMissing] = "Missing",
+  [kExprNodeOpMissing] = "OpMissing",
+  [kExprNodeTernary] = "Ternary",
+  [kExprNodeTernaryValue] = "TernaryValue",
+  [kExprNodeRegister] = "Register",
+  [kExprNodeSubscript] = "Subscript",
+  [kExprNodeListLiteral] = "ListLiteral",
+  [kExprNodeUnaryPlus] = "UnaryPlus",
+  [kExprNodeBinaryPlus] = "BinaryPlus",
+  [kExprNodeNested] = "Nested",
+  [kExprNodeCall] = "Call",
+  [kExprNodePlainIdentifier] = "PlainIdentifier",
+  [kExprNodePlainKey] = "PlainKey",
+  [kExprNodeComplexIdentifier] = "ComplexIdentifier",
+  [kExprNodeUnknownFigure] = "UnknownFigure",
+  [kExprNodeLambda] = "Lambda",
+  [kExprNodeDictLiteral] = "DictLiteral",
+  [kExprNodeCurlyBracesIdentifier] = "CurlyBracesIdentifier",
+  [kExprNodeComma] = "Comma",
+  [kExprNodeColon] = "Colon",
+  [kExprNodeArrow] = "Arrow",
+  [kExprNodeComparison] = "Comparison",
+  [kExprNodeConcat] = "Concat",
+  [kExprNodeConcatOrSubscript] = "ConcatOrSubscript",
+  [kExprNodeInteger] = "Integer",
+  [kExprNodeFloat] = "Float",
+  [kExprNodeSingleQuotedString] = "SingleQuotedString",
+  [kExprNodeDoubleQuotedString] = "DoubleQuotedString",
+  [kExprNodeOr] = "Or",
+  [kExprNodeAnd] = "And",
+  [kExprNodeUnaryMinus] = "UnaryMinus",
+  [kExprNodeBinaryMinus] = "BinaryMinus",
+  [kExprNodeNot] = "Not",
+  [kExprNodeMultiplication] = "Multiplication",
+  [kExprNodeDivision] = "Division",
+  [kExprNodeMod] = "Mod",
+  [kExprNodeOption] = "Option",
+  [kExprNodeEnvironment] = "Environment",
+  [kExprNodeAssignment] = "Assignment",
+};
+
+/// Represent `int` character as a string
+///
+/// Converts
+/// - ASCII digits into '{digit}'
+/// - ASCII printable characters into a single-character strings
+/// - everything else to numbers.
+///
+/// @param[in]  ch  Character to convert.
+///
+/// @return Converted string, stored in a static buffer (overriden after each
+///         call).
+static const char *intchar2str(const int ch)
+  FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  static char buf[sizeof(int) * 3 + 1];
+  if (' ' <= ch && ch < 0x7f) {
+    if (ascii_isdigit(ch)) {
+      buf[0] = '\'';
+      buf[1] = (char)ch;
+      buf[2] = '\'';
+      buf[3] = NUL;
+    } else {
+      buf[0] = (char)ch;
+      buf[1] = NUL;
+    }
+  } else {
+    snprintf(buf, sizeof(buf), "%i", ch);
+  }
+  return buf;
+}
+
+#ifdef UNIT_TESTING
+#include <stdio.h>
+
+REAL_FATTR_UNUSED
+static inline void viml_pexpr_debug_print_ast_node(
+    const ExprASTNode *const *const eastnode_p,
+    const char *const prefix)
+{
+  if (*eastnode_p == NULL) {
+    fprintf(stderr, "%s %p : NULL\n", prefix, (void *)eastnode_p);
+  } else {
+    fprintf(stderr, "%s %p : %p : %s : %zu:%zu:%zu\n",
+            prefix, (void *)eastnode_p, (void *)(*eastnode_p),
+            east_node_type_tab[(*eastnode_p)->type], (*eastnode_p)->start.line,
+            (*eastnode_p)->start.col, (*eastnode_p)->len);
+  }
+}
+
+REAL_FATTR_UNUSED
+static inline void viml_pexpr_debug_print_ast_stack(
+    const ExprASTStack *const ast_stack,
+    const char *const msg)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_ALWAYS_INLINE
+{
+  fprintf(stderr, "\n%sstack: %zu:\n", msg, kv_size(*ast_stack));
+  for (size_t i = 0; i < kv_size(*ast_stack); i++) {
+    viml_pexpr_debug_print_ast_node(
+        (const ExprASTNode *const *)kv_A(*ast_stack, i),
+        "-");
+  }
+}
+
+REAL_FATTR_UNUSED
+static inline void viml_pexpr_debug_print_token(
+    const ParserState *const pstate, const LexExprToken token)
+  FUNC_ATTR_ALWAYS_INLINE
+{
+  fprintf(stderr, "\ntkn: %s\n", viml_pexpr_repr_token(pstate, token, NULL));
+}
+#define PSTACK(msg) \
+    viml_pexpr_debug_print_ast_stack(&ast_stack, #msg)
+#define PSTACK_P(msg) \
+    viml_pexpr_debug_print_ast_stack(ast_stack, #msg)
+#define PNODE_P(eastnode_p, msg) \
+    viml_pexpr_debug_print_ast_node((const ExprASTNode *const *)eastnode_p, \
+                                    (#msg))
+#define PTOKEN(tkn) \
+    viml_pexpr_debug_print_token(pstate, tkn)
+#endif
+
+const uint8_t node_maxchildren[] = {
+  [kExprNodeMissing] = 0,
+  [kExprNodeOpMissing] = 2,
+  [kExprNodeTernary] = 2,
+  [kExprNodeTernaryValue] = 2,
+  [kExprNodeRegister] = 0,
+  [kExprNodeSubscript] = 2,
+  [kExprNodeListLiteral] = 1,
+  [kExprNodeUnaryPlus] = 1,
+  [kExprNodeBinaryPlus] = 2,
+  [kExprNodeNested] = 1,
+  [kExprNodeCall] = 2,
+  [kExprNodePlainIdentifier] = 0,
+  [kExprNodePlainKey] = 0,
+  [kExprNodeComplexIdentifier] = 2,
+  [kExprNodeUnknownFigure] = 1,
+  [kExprNodeLambda] = 2,
+  [kExprNodeDictLiteral] = 1,
+  [kExprNodeCurlyBracesIdentifier] = 1,
+  [kExprNodeComma] = 2,
+  [kExprNodeColon] = 2,
+  [kExprNodeArrow] = 2,
+  [kExprNodeComparison] = 2,
+  [kExprNodeConcat] = 2,
+  [kExprNodeConcatOrSubscript] = 2,
+  [kExprNodeInteger] = 0,
+  [kExprNodeFloat] = 0,
+  [kExprNodeSingleQuotedString] = 0,
+  [kExprNodeDoubleQuotedString] = 0,
+  [kExprNodeOr] = 2,
+  [kExprNodeAnd] = 2,
+  [kExprNodeUnaryMinus] = 1,
+  [kExprNodeBinaryMinus] = 2,
+  [kExprNodeNot] = 1,
+  [kExprNodeMultiplication] = 2,
+  [kExprNodeDivision] = 2,
+  [kExprNodeMod] = 2,
+  [kExprNodeOption] = 0,
+  [kExprNodeEnvironment] = 0,
+  [kExprNodeAssignment] = 2,
+};
+
+/// Free memory occupied by AST
+///
+/// @param  ast  AST stack to free.
+void viml_pexpr_free_ast(ExprAST ast)
+{
+  ExprASTStack ast_stack;
+  kvi_init(ast_stack);
+  kvi_push(ast_stack, &ast.root);
+  while (kv_size(ast_stack)) {
+    ExprASTNode **const cur_node = kv_last(ast_stack);
+#ifndef NDEBUG
+    // Explicitly check for AST recursiveness.
+    for (size_t i = 0 ; i < kv_size(ast_stack) - 1 ; i++) {
+      assert(*kv_A(ast_stack, i) != *cur_node);
+    }
+#endif
+    if (*cur_node == NULL) {
+      assert(kv_size(ast_stack) == 1);
+      kv_drop(ast_stack, 1);
+    } else if ((*cur_node)->children != NULL) {
+#ifndef NDEBUG
+      const uint8_t maxchildren = node_maxchildren[(*cur_node)->type];
+      assert(maxchildren > 0);
+      assert(maxchildren <= 2);
+      assert(maxchildren == 1
+             ? (*cur_node)->children->next == NULL
+             : ((*cur_node)->children->next == NULL
+                || (*cur_node)->children->next->next == NULL));
+#endif
+      kvi_push(ast_stack, &(*cur_node)->children);
+    } else if ((*cur_node)->next != NULL) {
+      kvi_push(ast_stack, &(*cur_node)->next);
+    } else if (*cur_node != NULL) {
+      kv_drop(ast_stack, 1);
+      switch ((*cur_node)->type) {
+        case kExprNodeDoubleQuotedString:
+        case kExprNodeSingleQuotedString: {
+          xfree((*cur_node)->data.str.value);
+          break;
+        }
+        case kExprNodeMissing:
+        case kExprNodeOpMissing:
+        case kExprNodeTernary:
+        case kExprNodeTernaryValue:
+        case kExprNodeRegister:
+        case kExprNodeSubscript:
+        case kExprNodeListLiteral:
+        case kExprNodeUnaryPlus:
+        case kExprNodeBinaryPlus:
+        case kExprNodeNested:
+        case kExprNodeCall:
+        case kExprNodePlainIdentifier:
+        case kExprNodePlainKey:
+        case kExprNodeComplexIdentifier:
+        case kExprNodeUnknownFigure:
+        case kExprNodeLambda:
+        case kExprNodeDictLiteral:
+        case kExprNodeCurlyBracesIdentifier:
+        case kExprNodeAssignment:
+        case kExprNodeComma:
+        case kExprNodeColon:
+        case kExprNodeArrow:
+        case kExprNodeComparison:
+        case kExprNodeConcat:
+        case kExprNodeConcatOrSubscript:
+        case kExprNodeInteger:
+        case kExprNodeFloat:
+        case kExprNodeOr:
+        case kExprNodeAnd:
+        case kExprNodeUnaryMinus:
+        case kExprNodeBinaryMinus:
+        case kExprNodeNot:
+        case kExprNodeMultiplication:
+        case kExprNodeDivision:
+        case kExprNodeMod:
+        case kExprNodeOption:
+        case kExprNodeEnvironment: {
+          break;
+        }
+      }
+      xfree(*cur_node);
+      *cur_node = NULL;
+    }
+  }
+  kvi_destroy(ast_stack);
+}
+
+// Binary operator precedence and associativity:
+//
+// Operator | Precedence | Associativity
+// ---------+------------+-----------------
+// ||       | 2          | left
+// &&       | 3          | left
+// cmp*     | 4          | not associative
+// + - .    | 5          | left
+// * / %    | 6          | left
+//
+// * comparison operators:
+//
+// == ==# ==?  != !=# !=?
+// =~ =~# =~?  !~ !~# !~?
+//  >  >#  >?  <= <=# <=?
+//  <  <#  <?  >= >=# >=?
+// is is# is?  isnot isnot# isnot?
+
+/// Allocate a new node and set some of the values
+///
+/// @param[in]  type  Node type to allocate.
+/// @param[in]  level  Node level to allocate
+static inline ExprASTNode *viml_pexpr_new_node(const ExprASTNodeType type)
+  FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_MALLOC
+{
+  ExprASTNode *ret = xmalloc(sizeof(*ret));
+  ret->type = type;
+  ret->children = NULL;
+  ret->next = NULL;
+  return ret;
+}
+
+static struct {
+  ExprOpLvl lvl;
+  ExprOpAssociativity ass;
+} node_type_to_node_props[] = {
+  [kExprNodeMissing] = { kEOpLvlInvalid, kEOpAssNo, },
+  [kExprNodeOpMissing] = { kEOpLvlMultiplication, kEOpAssNo },
+
+  [kExprNodeNested] = { kEOpLvlParens, kEOpAssNo },
+  // Note: below nodes are kEOpLvlSubscript for “binary operator” itself, but
+  //       kEOpLvlParens when it comes to inside the parenthesis.
+  [kExprNodeCall] = { kEOpLvlParens, kEOpAssNo },
+  [kExprNodeSubscript] = { kEOpLvlParens, kEOpAssNo },
+
+  [kExprNodeUnknownFigure] = { kEOpLvlParens, kEOpAssLeft },
+  [kExprNodeLambda] = { kEOpLvlParens, kEOpAssNo },
+  [kExprNodeDictLiteral] = { kEOpLvlParens, kEOpAssNo },
+  [kExprNodeListLiteral] = { kEOpLvlParens, kEOpAssNo },
+
+  [kExprNodeArrow] = { kEOpLvlArrow, kEOpAssNo },
+
+  // Right associativity for comma because this means easier access to arguments
+  // list, etc: for "[a, b, c, d]" you can access "a" in one step if it is
+  // represented as "list(comma(a, comma(b, comma(c, d))))" then if it is
+  // "list(comma(comma(comma(a, b), c), d))" in which case you will need to
+  // traverse all three comma() structures. And with comma operator (including
+  // actual comma operator from C which is not present in VimL) nobody cares
+  // about associativity, only about order of execution.
+  [kExprNodeComma] = { kEOpLvlComma, kEOpAssRight },
+
+  // Colons are not eligible for chaining, so nobody cares about associativity.
+  [kExprNodeColon] = { kEOpLvlColon, kEOpAssNo },
+
+  [kExprNodeTernary] = { kEOpLvlTernary, kEOpAssRight },
+
+  [kExprNodeOr] = { kEOpLvlOr, kEOpAssLeft },
+
+  [kExprNodeAnd] = { kEOpLvlAnd, kEOpAssLeft },
+
+  [kExprNodeTernaryValue] = { kEOpLvlTernaryValue, kEOpAssRight },
+
+  [kExprNodeComparison] = { kEOpLvlComparison, kEOpAssRight },
+
+  [kExprNodeBinaryPlus] = { kEOpLvlAddition, kEOpAssLeft },
+  [kExprNodeBinaryMinus] = { kEOpLvlAddition, kEOpAssLeft },
+  [kExprNodeConcat] = { kEOpLvlAddition, kEOpAssLeft },
+
+  [kExprNodeMultiplication] = { kEOpLvlMultiplication, kEOpAssLeft },
+  [kExprNodeDivision] = { kEOpLvlMultiplication, kEOpAssLeft },
+  [kExprNodeMod] = { kEOpLvlMultiplication, kEOpAssLeft },
+
+  [kExprNodeUnaryPlus] = { kEOpLvlUnary, kEOpAssNo },
+  [kExprNodeUnaryMinus] = { kEOpLvlUnary, kEOpAssNo },
+  [kExprNodeNot] = { kEOpLvlUnary, kEOpAssNo },
+
+  [kExprNodeConcatOrSubscript] = { kEOpLvlSubscript, kEOpAssLeft },
+
+  [kExprNodeCurlyBracesIdentifier] = { kEOpLvlComplexIdentifier, kEOpAssLeft },
+
+  [kExprNodeAssignment] = { kEOpLvlAssignment, kEOpAssLeft },
+
+  [kExprNodeComplexIdentifier] = { kEOpLvlValue, kEOpAssLeft },
+
+  [kExprNodePlainIdentifier] = { kEOpLvlValue, kEOpAssNo },
+  [kExprNodePlainKey] = { kEOpLvlValue, kEOpAssNo },
+  [kExprNodeRegister] = { kEOpLvlValue, kEOpAssNo },
+  [kExprNodeInteger] = { kEOpLvlValue, kEOpAssNo },
+  [kExprNodeFloat] = { kEOpLvlValue, kEOpAssNo },
+  [kExprNodeDoubleQuotedString] = { kEOpLvlValue, kEOpAssNo },
+  [kExprNodeSingleQuotedString] = { kEOpLvlValue, kEOpAssNo },
+  [kExprNodeOption] = { kEOpLvlValue, kEOpAssNo },
+  [kExprNodeEnvironment] = { kEOpLvlValue, kEOpAssNo },
+};
+
+/// Get AST node priority level
+///
+/// Used primary to reduce line length, so keep the name short.
+///
+/// @param[in]  node  Node to get priority for.
+///
+/// @return Node priority level.
+static inline ExprOpLvl node_lvl(const ExprASTNode node)
+  FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  return node_type_to_node_props[node.type].lvl;
+}
+
+/// Get AST node associativity, to be used for operator nodes primary
+///
+/// Used primary to reduce line length, so keep the name short.
+///
+/// @param[in]  node  Node to get priority for.
+///
+/// @return Node associativity.
+static inline ExprOpAssociativity node_ass(const ExprASTNode node)
+  FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  return node_type_to_node_props[node.type].ass;
+}
+
+/// Handle binary operator
+///
+/// This function is responsible for handling priority levels as well.
+///
+/// @param[in]  pstate  Parser state, used for error reporting.
+/// @param  ast_stack  AST stack. May be popped of some values and will
+///                    definitely receive new ones.
+/// @param  bop_node  New node to handle.
+/// @param[out]  want_node_p  New value of want_node.
+/// @param[out]  ast_err  Location where error is saved, if any.
+///
+/// @return True if no errors occurred, false otherwise.
+static bool viml_pexpr_handle_bop(const ParserState *const pstate,
+                                  ExprASTStack *const ast_stack,
+                                  ExprASTNode *const bop_node,
+                                  ExprASTWantedNode *const want_node_p,
+                                  ExprASTError *const ast_err)
+  FUNC_ATTR_NONNULL_ALL
+{
+  bool ret = true;
+  ExprASTNode **top_node_p = NULL;
+  ExprASTNode *top_node;
+  ExprOpLvl top_node_lvl;
+  ExprOpAssociativity top_node_ass;
+  assert(kv_size(*ast_stack));
+  const ExprOpLvl bop_node_lvl = ((bop_node->type == kExprNodeCall
+                                   || bop_node->type == kExprNodeSubscript)
+                                  ? kEOpLvlSubscript
+                                  : node_lvl(*bop_node));
+#ifndef NDEBUG
+  const ExprOpAssociativity bop_node_ass = (
+      (bop_node->type == kExprNodeCall
+       || bop_node->type == kExprNodeSubscript)
+      ? kEOpAssLeft
+      : node_ass(*bop_node));
+#endif
+  do {
+    ExprASTNode **new_top_node_p = kv_last(*ast_stack);
+    ExprASTNode *new_top_node = *new_top_node_p;
+    assert(new_top_node != NULL);
+    const ExprOpLvl new_top_node_lvl = node_lvl(*new_top_node);
+    const ExprOpAssociativity new_top_node_ass = node_ass(*new_top_node);
+    assert(bop_node_lvl != new_top_node_lvl
+           || bop_node_ass == new_top_node_ass);
+    if (top_node_p != NULL
+        && ((bop_node_lvl > new_top_node_lvl
+             || (bop_node_lvl == new_top_node_lvl
+                 && new_top_node_ass == kEOpAssNo)))) {
+      break;
+    }
+    kv_drop(*ast_stack, 1);
+    top_node_p = new_top_node_p;
+    top_node = new_top_node;
+    top_node_lvl = new_top_node_lvl;
+    top_node_ass = new_top_node_ass;
+    if (bop_node_lvl == top_node_lvl && top_node_ass == kEOpAssRight) {
+      break;
+    }
+  } while (kv_size(*ast_stack));
+  if (top_node_ass == kEOpAssLeft || top_node_lvl != bop_node_lvl) {
+    // outer(op(x,y)) -> outer(new_op(op(x,y),*))
+    //
+    // Before: top_node_p = outer(*), points to op(x,y)
+    //         Other stack elements unknown
+    //
+    // After: top_node_p = outer(*), points to new_op(op(x,y))
+    //        &bop_node->children->next = new_op(op(x,y),*), points to NULL
+    *top_node_p = bop_node;
+    bop_node->children = top_node;
+    assert(bop_node->children->next == NULL);
+    kvi_push(*ast_stack, top_node_p);
+    kvi_push(*ast_stack, &bop_node->children->next);
+  } else {
+    assert(top_node_lvl == bop_node_lvl && top_node_ass == kEOpAssRight);
+    assert(top_node->children != NULL && top_node->children->next != NULL);
+    // outer(op(x,y)) -> outer(op(x,new_op(y,*)))
+    //
+    // Before: top_node_p = outer(*), points to op(x,y)
+    //         Other stack elements unknown
+    //
+    // After: top_node_p = outer(*), points to op(x,new_op(y))
+    //        &top_node->children->next = op(x,*), points to new_op(y)
+    //        &bop_node->children->next = new_op(y,*), points to NULL
+    bop_node->children = top_node->children->next;
+    top_node->children->next = bop_node;
+    assert(bop_node->children->next == NULL);
+    kvi_push(*ast_stack, top_node_p);
+    kvi_push(*ast_stack, &top_node->children->next);
+    kvi_push(*ast_stack, &bop_node->children->next);
+    // TODO(ZyX-I): Make this not error, but treat like Python does
+    if (bop_node->type == kExprNodeComparison) {
+      east_set_error(pstate, ast_err,
+                     _("E15: Operator is not associative: %.*s"),
+                     bop_node->start);
+      ret = false;
+    }
+  }
+  *want_node_p = kENodeValue;
+  return ret;
+}
+
+/// ParserPosition literal based on ParserPosition pos with columns shifted
+///
+/// Function does not check whether resulting position is valid.
+///
+/// @param[in]  pos  Position to shift.
+/// @param[in]  shift  Number of bytes to shift.
+///
+/// @return Shifted position.
+static inline ParserPosition shifted_pos(const ParserPosition pos,
+                                         const size_t shift)
+  FUNC_ATTR_CONST FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  return (ParserPosition) { .line = pos.line, .col = pos.col + shift };
+}
+
+/// ParserPosition literal based on ParserPosition pos with specified column
+///
+/// Function does not check whether remaining position is valid.
+///
+/// @param[in]  pos  Position to adjust.
+/// @param[in]  new_col  New column.
+///
+/// @return Shifted position.
+static inline ParserPosition recol_pos(const ParserPosition pos,
+                                       const size_t new_col)
+  FUNC_ATTR_CONST FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  return (ParserPosition) { .line = pos.line, .col = new_col };
+}
+
+/// Get highlight group name
+#define HL(g) (is_invalid ? "NvimInvalid" #g : "Nvim" #g)
+
+/// Highlight current token with the given group
+#define HL_CUR_TOKEN(g) \
+        viml_parser_highlight(pstate, cur_token.start, cur_token.len, \
+                              HL(g))
+
+/// Allocate new node, saving some values
+#define NEW_NODE(type) \
+    viml_pexpr_new_node(type)
+
+/// Set position of the given node to position from the given token
+///
+/// @param  cur_node  Node to modify.
+/// @param  cur_token  Token to set position from.
+#define POS_FROM_TOKEN(cur_node, cur_token) \
+    do { \
+      (cur_node)->start = cur_token.start; \
+      (cur_node)->len = cur_token.len; \
+    } while (0)
+
+/// Allocate new node and set its position from the current token
+///
+/// If previous token happened to contain spacing then it will be included.
+///
+/// @param  cur_node  Variable to save allocated node to.
+/// @param  typ  Node type.
+#define NEW_NODE_WITH_CUR_POS(cur_node, typ) \
+    do { \
+      (cur_node) = NEW_NODE(typ); \
+      POS_FROM_TOKEN((cur_node), cur_token); \
+      if (prev_token.type == kExprLexSpacing) { \
+        (cur_node)->start = prev_token.start; \
+        (cur_node)->len += prev_token.len; \
+      } \
+    } while (0)
+
+/// Check whether it is possible to have next expression after current
+///
+/// For :echo: `:echo @a @a` is a valid expression. `:echo (@a @a)` is not.
+#define MAY_HAVE_NEXT_EXPR \
+    (kv_size(ast_stack) == 1)
+
+/// Add operator node
+///
+/// @param[in]  cur_node  Node to add.
+#define ADD_OP_NODE(cur_node) \
+    is_invalid |= !viml_pexpr_handle_bop(pstate, &ast_stack, cur_node, \
+                                         &want_node, &ast.err)
+
+/// Record missing operator: for things like
+///
+///     :echo @a @a
+///
+/// (allowed) or
+///
+///     :echo (@a @a)
+///
+/// (parsed as OpMissing(@a, @a)).
+#define OP_MISSING \
+    do { \
+      if (flags & kExprFlagsMulti && MAY_HAVE_NEXT_EXPR) { \
+        /* Multiple expressions allowed, return without calling */ \
+        /* viml_parser_advance(). */ \
+        goto viml_pexpr_parse_end; \
+      } else { \
+        assert(*top_node_p != NULL); \
+        ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Missing operator: %.*s")); \
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeOpMissing); \
+        cur_node->len = 0; \
+        ADD_OP_NODE(cur_node); \
+        goto viml_pexpr_parse_process_token; \
+      } \
+    } while (0)
+
+/// Record missing value: for things like "* 5"
+///
+/// @param[in]  msg  Error message.
+#define ADD_VALUE_IF_MISSING(msg) \
+        do { \
+          if (want_node == kENodeValue) { \
+            ERROR_FROM_TOKEN_AND_MSG(cur_token, (msg)); \
+            NEW_NODE_WITH_CUR_POS((*top_node_p), kExprNodeMissing); \
+            (*top_node_p)->len = 0; \
+            want_node = kENodeOperator; \
+          } \
+        } while (0)
+
+/// Set AST error, unless AST already is not correct
+///
+/// @param[out]  ret_ast  AST to set error in.
+/// @param[in]  pstate  Parser state, used to get error message argument.
+/// @param[in]  msg  Error message, assumed to be already translated and
+///                  containing a single %token "%.*s".
+/// @param[in]  start  Position at which error occurred.
+static inline void east_set_error(const ParserState *const pstate,
+                                  ExprASTError *const ret_ast_err,
+                                  const char *const msg,
+                                  const ParserPosition start)
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_ALWAYS_INLINE
+{
+  if (ret_ast_err->msg != NULL) {
+    return;
+  }
+  const ParserLine pline = pstate->reader.lines.items[start.line];
+  ret_ast_err->msg = msg;
+  ret_ast_err->arg_len = (int)(pline.size - start.col);
+  ret_ast_err->arg = pline.data + start.col;
+}
+
+/// Set error from the given token and given message
+#define ERROR_FROM_TOKEN_AND_MSG(cur_token, msg) \
+    do { \
+      is_invalid = true; \
+      east_set_error(pstate, &ast.err, msg, cur_token.start); \
+    } while (0)
+
+/// Like #ERROR_FROM_TOKEN_AND_MSG, but gets position from a node
+#define ERROR_FROM_NODE_AND_MSG(node, msg) \
+    do { \
+      is_invalid = true; \
+      east_set_error(pstate, &ast.err, msg, node->start); \
+    } while (0)
+
+/// Set error from the given kExprLexInvalid token
+#define ERROR_FROM_TOKEN(cur_token) \
+    ERROR_FROM_TOKEN_AND_MSG(cur_token, cur_token.data.err.msg)
+
+/// Select figure brace type, altering highlighting as well if needed
+///
+/// @param[out]  node  Node to modify type.
+/// @param[in]  new_type  New type, one of ExprASTNodeType values without
+///                       kExprNode prefix.
+/// @param[in]  hl  Corresponding highlighting, passed as an argument to #HL.
+#define SELECT_FIGURE_BRACE_TYPE(node, new_type, hl) \
+    do { \
+      ExprASTNode *const node_ = (node); \
+      assert(node_->type == kExprNodeUnknownFigure \
+             || node_->type == kExprNode##new_type); \
+      node_->type = kExprNode##new_type; \
+      if (pstate->colors) { \
+        kv_A(*pstate->colors, node_->data.fig.opening_hl_idx).group = \
+             HL(hl); \
+      } \
+    } while (0)
+
+/// Add identifier which should constitute complex identifier node
+///
+/// This one is to be called only in case want_node is kENodeOperator.
+///
+/// @param  new_ident_node_code  Code used to create a new identifier node and
+///                              update want_node and ast_stack, without
+///                              a trailing semicolon.
+/// @param  hl  Highlighting name to use, passed as an argument to #HL.
+#define ADD_IDENT(new_ident_node_code, hl) \
+    do { \
+      assert(want_node == kENodeOperator); \
+      /* Operator: may only be curly braces name, but only under certain */ \
+      /* conditions. */ \
+\
+      /* First condition is that there is no space before a part of complex */ \
+      /* identifier. */ \
+      if (prev_token.type == kExprLexSpacing) { \
+        OP_MISSING; \
+      } \
+      switch ((*top_node_p)->type) { \
+        /* Second is that previous node is one of the identifiers: */ \
+        /* complex, plain, curly braces. */ \
+\
+        /* TODO(ZyX-I): Extend syntax to allow ${expr}. This is needed to */ \
+        /* handle environment variables like those bash uses for */ \
+        /* `export -f`: their names consist not only of alphanumeric */ \
+        /* characetrs. */ \
+        case kExprNodeComplexIdentifier: \
+        case kExprNodePlainIdentifier: \
+        case kExprNodeCurlyBracesIdentifier: { \
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeComplexIdentifier); \
+          cur_node->len = 0; \
+          cur_node->children = *top_node_p; \
+          *top_node_p = cur_node; \
+          kvi_push(ast_stack, &cur_node->children->next); \
+          ExprASTNode **const new_top_node_p = kv_last(ast_stack); \
+          assert(*new_top_node_p == NULL); \
+          new_ident_node_code; \
+          *new_top_node_p = cur_node; \
+          HL_CUR_TOKEN(hl); \
+          break; \
+        } \
+        default: { \
+          OP_MISSING; \
+          break; \
+        } \
+      } \
+    } while (0)
+
+/// Determine whether given parse type is an assignment
+///
+/// @param[in]  pt  Checked parse type.
+///
+/// @return true if parsing an assignment, false otherwise.
+static inline bool pt_is_assignment(const ExprASTParseType pt)
+  FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_CONST FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  return (pt == kEPTAssignment || pt == kEPTSingleAssignment);
+}
+
+/// Structure used to define “string shifts” necessary to map string
+/// highlighting to actual strings.
+typedef struct {
+  size_t start;  ///< Where special character starts in original string.
+  size_t orig_len;  ///< Length of orininal string (e.g. 4 for "\x80").
+  size_t act_len;  ///< Length of resulting character(s) (e.g. 1 for "\x80").
+  bool escape_not_known;  ///< True if escape sequence in original is not known.
+} StringShift;
+
+/// Parse and highlight single- or double-quoted string
+///
+/// Function is supposed to detect and highlight regular expressions (but does
+/// not do now).
+///
+/// @param[out]  pstate  Parser state which also contains a place where
+///                      highlighting is saved.
+/// @param[out]  node  Node where string parsing results are saved.
+/// @param[in]  token  Token to highlight.
+/// @param[in]  ast_stack  Parser AST stack, used to detect whether current
+///                        string is a regex.
+/// @param[in]  is_invalid  Whether currently processed token is not valid.
+static void parse_quoted_string(ParserState *const pstate,
+                                ExprASTNode *const node,
+                                const LexExprToken token,
+                                const ExprASTStack ast_stack,
+                                const bool is_invalid)
+  FUNC_ATTR_NONNULL_ALL
+{
+  const ParserLine pline = pstate->reader.lines.items[token.start.line];
+  const char *const s = pline.data + token.start.col;
+  const char *const e = s + token.len - token.data.str.closed;
+  const char *p = s + 1;
+  const bool is_double = (token.type == kExprLexDoubleQuotedString);
+  size_t size = token.len - token.data.str.closed - 1;
+  kvec_withinit_t(StringShift, 16) shifts;
+  kvi_init(shifts);
+  if (!is_double) {
+    viml_parser_highlight(pstate, token.start, 1, HL(SingleQuote));
+    while (p < e) {
+      const char *const chunk_e = memchr(p, '\'', (size_t)(e - p));
+      if (chunk_e == NULL) {
+        break;
+      }
+      size--;
+      p = chunk_e + 2;
+      if (pstate->colors) {
+        kvi_push(shifts, ((StringShift) {
+            .start = token.start.col + (size_t)(chunk_e - s),
+            .orig_len = 2,
+            .act_len = 1,
+            .escape_not_known = false,
+        }));
+      }
+    }
+    node->data.str.size = size;
+    if (size == 0) {
+      node->data.str.value = NULL;
+    } else {
+      char *v_p;
+      v_p = node->data.str.value = xmallocz(size);
+      p = s + 1;
+      while (p < e) {
+        const char *const chunk_e = memchr(p, '\'', (size_t)(e - p));
+        if (chunk_e == NULL) {
+          memcpy(v_p, p, (size_t)(e - p));
+          break;
+        }
+        memcpy(v_p, p, (size_t)(chunk_e - p));
+        v_p += (size_t)(chunk_e - p) + 1;
+        v_p[-1] = '\'';
+        p = chunk_e + 2;
+      }
+    }
+  } else {
+    viml_parser_highlight(pstate, token.start, 1, HL(DoubleQuote));
+    for (p = s + 1; p < e; p++) {
+      if (*p == '\\' && p + 1 < e) {
+        p++;
+        if (p + 1 == e) {
+          size--;
+          break;
+        }
+        switch (*p) {
+          // A "\<x>" form occupies at least 4 characters, and produces up to
+          // 6 characters: reserve space for 2 extra, but do not compute actual
+          // length just now, it would be costy.
+          case '<': {
+            size += 2;
+            break;
+          }
+          // Hexadecimal, always single byte, but at least three bytes each.
+          case 'x': case 'X': {
+            size--;
+            if (ascii_isxdigit(p[1])) {
+              size--;
+              if (p + 2 < e && ascii_isxdigit(p[2])) {
+                size--;
+              }
+            }
+            break;
+          }
+          // Unicode
+          //
+          // \uF takes 1 byte which is 2 bytes less then escape sequence.
+          // \uFF: 2 bytes, 2 bytes less.
+          // \uFFF: 3 bytes, 2 bytes less.
+          // \uFFFF: 3 bytes, 3 bytes less.
+          // \UFFFFF: 4 bytes, 3 bytes less.
+          // \UFFFFFF: 5 bytes, 3 bytes less.
+          // \UFFFFFFF: 6 bytes, 3 bytes less.
+          // \U7FFFFFFF: 6 bytes, 4 bytes less.
+          case 'u': case 'U': {
+            const char *const esc_start = p;
+            size_t n = (*p == 'u' ? 4 : 8);
+            int nr = 0;
+            p++;
+            while (p + 1 < e && n-- && ascii_isxdigit(p[1])) {
+              p++;
+              nr = (nr << 4) + hex2nr(*p);
+            }
+            // Escape length: (esc_start - 1) points to "\\", esc_start to "u"
+            // or "U", p to the byte after last byte. So escape sequence
+            // occupies p - (esc_start - 1), but it stands for a utf_char2len
+            // bytes.
+            size -= (size_t)((p - (esc_start - 1)) - utf_char2len(nr));
+            p--;
+            break;
+          }
+          // Octal, always single byte, but at least two bytes each.
+          case '0': case '1': case '2': case '3': case '4': case '5': case '6':
+          case '7': {
+            size--;
+            p++;
+            if (*p >= '0' && *p <= '7') {
+              size--;
+              p++;
+              if (p < e && *p >= '0' && *p <= '7') {
+                size--;
+                p++;
+              }
+            }
+            break;
+          }
+          default: {
+            size--;
+            break;
+          }
+        }
+      }
+    }
+    if (size == 0) {
+      node->data.str.value = NULL;
+      node->data.str.size = 0;
+    } else {
+      char *v_p;
+      v_p = node->data.str.value = xmalloc(size);
+      p = s + 1;
+      while (p < e) {
+        const char *const chunk_e = memchr(p, '\\', (size_t)(e - p));
+        if (chunk_e == NULL) {
+          memcpy(v_p, p, (size_t)(e - p));
+          v_p += e - p;
+          break;
+        }
+        memcpy(v_p, p, (size_t)(chunk_e - p));
+        v_p += (size_t)(chunk_e - p);
+        p = chunk_e + 1;
+        if (p == e) {
+          *v_p++ = '\\';
+          break;
+        }
+        bool is_unknown = false;
+        const char *const v_p_start = v_p;
+        switch (*p) {
+#define SINGLE_CHAR_ESC(ch, real_ch) \
+          case ch: { \
+            *v_p++ = real_ch; \
+            p++; \
+            break; \
+          }
+          SINGLE_CHAR_ESC('b', BS)
+          SINGLE_CHAR_ESC('e', ESC)
+          SINGLE_CHAR_ESC('f', FF)
+          SINGLE_CHAR_ESC('n', NL)
+          SINGLE_CHAR_ESC('r', CAR)
+          SINGLE_CHAR_ESC('t', TAB)
+          SINGLE_CHAR_ESC('"', '"')
+          SINGLE_CHAR_ESC('\\', '\\')
+#undef SINGLE_CHAR_ESC
+
+          // Hexadecimal or unicode.
+          case 'X': case 'x': case 'u': case 'U': {
+            if (p + 1 < e && ascii_isxdigit(p[1])) {
+              size_t n;
+              int nr;
+              bool is_hex = (*p == 'x' || *p == 'X');
+
+              if (is_hex) {
+                n = 2;
+              } else if (*p == 'u') {
+                n = 4;
+              } else {
+                n = 8;
+              }
+              nr = 0;
+              while (p + 1 < e && n-- && ascii_isxdigit(p[1])) {
+                p++;
+                nr = (nr << 4) + hex2nr(*p);
+              }
+              p++;
+              if (is_hex) {
+                *v_p++ = (char)nr;
+              } else {
+                v_p += utf_char2bytes(nr, (char_u *)v_p);
+              }
+            } else {
+              is_unknown = true;
+              *v_p++ = *p;
+              p++;
+            }
+            break;
+          }
+          // Octal: "\1", "\12", "\123".
+          case '0': case '1': case '2': case '3': case '4': case '5': case '6':
+          case '7': {
+            uint8_t ch = (uint8_t)(*p++ - '0');
+            if (p < e && *p >= '0' && *p <= '7') {
+              ch = (uint8_t)((ch << 3) + *p++ - '0');
+              if (p < e && *p >= '0' && *p <= '7') {
+                ch = (uint8_t)((ch << 3) + *p++ - '0');
+              }
+            }
+            *v_p++ = (char)ch;
+            break;
+          }
+          // Special key, e.g.: "\<C-W>"
+          case '<': {
+            const size_t special_len = (
+                trans_special((const char_u **)&p, (size_t)(e - p),
+                              (char_u *)v_p, true, true));
+            if (special_len != 0) {
+              v_p += special_len;
+            } else {
+              is_unknown = true;
+              mb_copy_char((const char_u **)&p, (char_u **)&v_p);
+            }
+            break;
+          }
+          default: {
+            is_unknown = true;
+            mb_copy_char((const char_u **)&p, (char_u **)&v_p);
+            break;
+          }
+        }
+        if (pstate->colors) {
+          kvi_push(shifts, ((StringShift) {
+              .start = token.start.col + (size_t)(chunk_e - s),
+              .orig_len = (size_t)(p - chunk_e),
+              .act_len = (size_t)(v_p - (char *)v_p_start),
+              .escape_not_known = is_unknown,
+          }));
+        }
+      }
+      node->data.str.size = (size_t)(v_p - node->data.str.value);
+    }
+  }
+  if (pstate->colors) {
+    // TODO(ZyX-I): use ast_stack to determine and highlight regular expressions
+    // TODO(ZyX-I): use ast_stack to determine and highlight printf format str
+    // TODO(ZyX-I): use ast_stack to determine and highlight expression strings
+    size_t next_col = token.start.col + 1;
+    const char *const body_str = (is_double
+                                  ? HL(DoubleQuotedBody)
+                                  : HL(SingleQuotedBody));
+    const char *const esc_str = (is_double
+                                 ? HL(DoubleQuotedEscape)
+                                 : HL(SingleQuotedQuote));
+    const char *const ukn_esc_str = (is_double
+                                     ? HL(DoubleQuotedUnknownEscape)
+                                     : HL(SingleQuotedUnknownEscape));
+    for (size_t i = 0; i < kv_size(shifts); i++) {
+      const StringShift cur_shift = kv_A(shifts, i);
+      if (cur_shift.start > next_col) {
+        viml_parser_highlight(pstate, recol_pos(token.start, next_col),
+                              cur_shift.start - next_col,
+                              body_str);
+      }
+      viml_parser_highlight(pstate, recol_pos(token.start, cur_shift.start),
+                            cur_shift.orig_len,
+                            (cur_shift.escape_not_known
+                             ? ukn_esc_str
+                             : esc_str));
+      next_col = cur_shift.start + cur_shift.orig_len;
+    }
+    if (next_col - token.start.col < token.len - token.data.str.closed) {
+      viml_parser_highlight(pstate, recol_pos(token.start, next_col),
+                            (token.start.col
+                             + token.len
+                             - token.data.str.closed
+                             - next_col),
+                            body_str);
+    }
+  }
+  if (token.data.str.closed) {
+    if (is_double) {
+      viml_parser_highlight(pstate, shifted_pos(token.start, token.len - 1),
+                            1, HL(DoubleQuote));
+    } else {
+      viml_parser_highlight(pstate, shifted_pos(token.start, token.len - 1),
+                            1, HL(SingleQuote));
+    }
+  }
+  kvi_destroy(shifts);
+}
+
+/// Additional flags to pass to lexer depending on want_node
+static const int want_node_to_lexer_flags[] = {
+  [kENodeValue] = kELFlagIsNotCmp,
+  [kENodeOperator] = kELFlagForbidScope,
+};
+
+/// Number of characters to highlight as NumberPrefix depending on the base
+static const uint8_t base_to_prefix_length[] = {
+  [2] = 2,
+  [8] = 1,
+  [10] = 0,
+  [16] = 2,
+};
+
+/// Parse one VimL expression
+///
+/// @param  pstate  Parser state.
+/// @param[in]  flags  Additional flags, see ExprParserFlags
+///
+/// @return Parsed AST.
+ExprAST viml_pexpr_parse(ParserState *const pstate, const int flags)
+  FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
+{
+  ExprAST ast = {
+    .err = {
+      .msg = NULL,
+      .arg_len = 0,
+      .arg = NULL,
+    },
+    .root = NULL,
+  };
+  // Expression stack contains current branch in AST tree: that is
+  // - Stack item 0 contains root of the tree, i.e. &ast->root.
+  // - Stack item i points to the previous stack items’ last child.
+  //
+  // When parser expects “value” node that is something like identifier or "["
+  // (list start) last stack item contains NULL. Otherwise last stack item is
+  // supposed to contain last “finished” value: e.g. "1" or "+(1, 1)" (node
+  // representing "1+1").
+  ExprASTStack ast_stack;
+  kvi_init(ast_stack);
+  kvi_push(ast_stack, &ast.root);
+  ExprASTWantedNode want_node = kENodeValue;
+  ExprASTParseTypeStack pt_stack;
+  kvi_init(pt_stack);
+  kvi_push(pt_stack, kEPTExpr);
+  if (flags & kExprFlagsParseLet) {
+    kvi_push(pt_stack, kEPTAssignment);
+  }
+  LexExprToken prev_token = { .type = kExprLexMissing };
+  bool highlighted_prev_spacing = false;
+  // Lambda node, valid when parsing lambda arguments only.
+  ExprASTNode *lambda_node = NULL;
+  size_t asgn_level = 0;
+  do {
+    const bool is_concat_or_subscript = (
+        want_node == kENodeValue
+        && kv_size(ast_stack) > 1
+        && (*kv_Z(ast_stack, 1))->type == kExprNodeConcatOrSubscript);
+    const int lexer_additional_flags = (
+        kELFlagPeek
+        | ((flags & kExprFlagsDisallowEOC) ? kELFlagForbidEOC : 0)
+        | ((want_node == kENodeValue
+            && (kv_size(ast_stack) == 1
+                || ((*kv_Z(ast_stack, 1))->type != kExprNodeConcat
+                    && ((*kv_Z(ast_stack, 1))->type
+                        != kExprNodeConcatOrSubscript))))
+           ? kELFlagAllowFloat
+           : 0));
+    LexExprToken cur_token = viml_pexpr_next_token(
+        pstate, want_node_to_lexer_flags[want_node] | lexer_additional_flags);
+    if (cur_token.type == kExprLexEOC) {
+      break;
+    }
+    LexExprTokenType tok_type = cur_token.type;
+    const bool token_invalid = (tok_type == kExprLexInvalid);
+    bool is_invalid = token_invalid;
+viml_pexpr_parse_process_token:
+    // May use different flags this time.
+    cur_token = viml_pexpr_next_token(
+        pstate, want_node_to_lexer_flags[want_node] | lexer_additional_flags);
+    if (tok_type == kExprLexSpacing) {
+      if (is_invalid) {
+        HL_CUR_TOKEN(Spacing);
+      } else {
+        // Do not do anything: let regular spacing be highlighted as normal.
+        // This also allows later to highlight spacing as invalid.
+      }
+      goto viml_pexpr_parse_cycle_end;
+    } else if (is_invalid && prev_token.type == kExprLexSpacing
+               && !highlighted_prev_spacing) {
+      viml_parser_highlight(pstate, prev_token.start, prev_token.len,
+                            HL(Spacing));
+      is_invalid = false;
+      highlighted_prev_spacing = true;
+    }
+    const ParserLine pline = pstate->reader.lines.items[cur_token.start.line];
+    ExprASTNode **const top_node_p = kv_last(ast_stack);
+    assert(kv_size(ast_stack) >= 1);
+    ExprASTNode *cur_node = NULL;
+#ifndef NDEBUG
+    const bool want_value = (want_node == kENodeValue);
+    assert(want_value == (*top_node_p == NULL));
+    assert(kv_A(ast_stack, 0) == &ast.root);
+    // Check that stack item i + 1 points to stack items’ i *last* child.
+    for (size_t i = 0; i + 1 < kv_size(ast_stack); i++) {
+      const bool item_null = (want_value && i + 2 == kv_size(ast_stack));
+      assert((&(*kv_A(ast_stack, i))->children == kv_A(ast_stack, i + 1)
+              && (item_null
+                  ? (*kv_A(ast_stack, i))->children == NULL
+                  : (*kv_A(ast_stack, i))->children->next == NULL))
+             || ((&(*kv_A(ast_stack, i))->children->next
+                  == kv_A(ast_stack, i + 1))
+                 && (item_null
+                     ? (*kv_A(ast_stack, i))->children->next == NULL
+                     : (*kv_A(ast_stack, i))->children->next->next == NULL)));
+    }
+#endif
+    // Note: in Vim whether expression "cond?d.a:2" is valid depends both on
+    // "cond" and whether "d" is a dictionary: expression is valid if condition
+    // is true and "d" is a dictionary (with "a" key or it will complain about
+    // missing one, but this is not relevant); if any of the requirements is
+    // broken then this thing is parsed as "d . a:2" yielding missing colon
+    // error. This parser does not allow such ambiguity, especially because it
+    // simply can’t: whether "d" is a dictionary is not known at the parsing
+    // time.
+    //
+    // Here example will always contain a concat with "a:2" sucking colon,
+    // making expression invalid both because there is no longer a spare colon
+    // for ternary and because concatenating dictionary with anything is not
+    // valid. There are more cases when this will make a difference though.
+    const bool node_is_key = (
+        is_concat_or_subscript
+        && (cur_token.type == kExprLexPlainIdentifier
+            ? (!cur_token.data.var.autoload
+               && cur_token.data.var.scope == kExprVarScopeMissing)
+            : (cur_token.type == kExprLexNumber))
+        && prev_token.type != kExprLexSpacing);
+    if (is_concat_or_subscript && !node_is_key) {
+      // Note: in Vim "d. a" (this is the reason behind `prev_token.type !=
+      // kExprLexSpacing` part of the condition) as well as any other "d.{expr}"
+      // where "{expr}" does not look like a key is invalid whenever "d" happens
+      // to be a dictionary. Since parser has no idea whether preceding
+      // expression is actually a dictionary it can’t outright reject anything,
+      // so it turns kExprNodeConcatOrSubscript into kExprNodeConcat instead,
+      // which will yield different errors then Vim does in a number of
+      // circumstances, and in any case runtime and not parse time errors.
+      (*kv_Z(ast_stack, 1))->type = kExprNodeConcat;
+    }
+    // Pop some stack pt_stack items in case of misplaced nodes.
+    const bool is_single_assignment = kv_last(pt_stack) == kEPTSingleAssignment;
+    switch (kv_last(pt_stack)) {
+      case kEPTExpr: {
+        break;
+      }
+      case kEPTLambdaArguments: {
+        if ((want_node == kENodeOperator
+             && tok_type != kExprLexComma
+             && tok_type != kExprLexArrow)
+            || (want_node == kENodeValue
+                && !(cur_token.type == kExprLexPlainIdentifier
+                     && cur_token.data.var.scope == kExprVarScopeMissing
+                     && !cur_token.data.var.autoload)
+                && tok_type != kExprLexArrow)) {
+          lambda_node->data.fig.type_guesses.allow_lambda = false;
+          if (lambda_node->children != NULL
+              && lambda_node->children->type == kExprNodeComma) {
+            // If lambda has comma child this means that parser has already seen
+            // at least "{arg1,", so node cannot possibly be anything, but
+            // lambda.
+
+            // Vim may give E121 or E720 in this case, but it does not look
+            // right to have either because both are results of reevaluation
+            // possibly-lambda node as a dictionary and here this is not going
+            // to happen.
+            ERROR_FROM_TOKEN_AND_MSG(
+                cur_token,
+                _("E15: Expected lambda arguments list or arrow: %.*s"));
+          } else {
+            // Else it may appear that possibly-lambda node is actually
+            // a dictionary or curly-braces-name identifier.
+            lambda_node = NULL;
+            kv_drop(pt_stack, 1);
+          }
+        }
+        break;
+      }
+      case kEPTSingleAssignment:
+      case kEPTAssignment: {
+        if (want_node == kENodeValue
+            && tok_type != kExprLexBracket
+            && tok_type != kExprLexPlainIdentifier
+            && (tok_type != kExprLexFigureBrace || cur_token.data.brc.closing)
+            && !(node_is_key && tok_type == kExprLexNumber)
+            && tok_type != kExprLexEnv
+            && tok_type != kExprLexOption
+            && tok_type != kExprLexRegister) {
+          ERROR_FROM_TOKEN_AND_MSG(
+              cur_token,
+              _("E15: Expected value part of assignment lvalue: %.*s"));
+          kv_drop(pt_stack, 1);
+        } else if (want_node == kENodeOperator
+                   && tok_type != kExprLexBracket
+                   && (tok_type != kExprLexFigureBrace
+                       || cur_token.data.brc.closing)
+                   && tok_type != kExprLexDot
+                   && (tok_type != kExprLexComma || !is_single_assignment)
+                   && tok_type != kExprLexAssignment
+                   // Curly brace identifiers: will contain plain identifier or
+                   // another curly brace in position where operator is wanted.
+                   && !((tok_type == kExprLexPlainIdentifier
+                         || (tok_type == kExprLexFigureBrace
+                             && !cur_token.data.brc.closing))
+                        && prev_token.type != kExprLexSpacing)) {
+          if (flags & kExprFlagsMulti && MAY_HAVE_NEXT_EXPR) {
+            goto viml_pexpr_parse_end;
+          }
+          ERROR_FROM_TOKEN_AND_MSG(
+              cur_token,
+              _("E15: Expected assignment operator or subscript: %.*s"));
+          kv_drop(pt_stack, 1);
+        }
+        assert(kv_size(pt_stack));
+        break;
+      }
+    }
+    assert(kv_size(pt_stack));
+    const ExprASTParseType cur_pt = kv_last(pt_stack);
+    assert(lambda_node == NULL || cur_pt == kEPTLambdaArguments);
+    switch (tok_type) {
+      case kExprLexMissing:
+      case kExprLexSpacing:
+      case kExprLexEOC: {
+        assert(false);
+      }
+      case kExprLexInvalid: {
+        ERROR_FROM_TOKEN(cur_token);
+        tok_type = cur_token.data.err.type;
+        goto viml_pexpr_parse_process_token;
+      }
+      case kExprLexRegister: {
+        if (want_node == kENodeOperator) {
+          // Register in operator position: e.g. @a @a
+          OP_MISSING;
+        }
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeRegister);
+        cur_node->data.reg.name = cur_token.data.reg.name;
+        *top_node_p = cur_node;
+        want_node = kENodeOperator;
+        HL_CUR_TOKEN(Register);
+        break;
+      }
+#define SIMPLE_UB_OP(op) \
+      case kExprLex##op: { \
+        if (want_node == kENodeValue) { \
+          /* Value level: assume unary operator. */ \
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeUnary##op); \
+          *top_node_p = cur_node; \
+          kvi_push(ast_stack, &cur_node->children); \
+          HL_CUR_TOKEN(Unary##op); \
+        } else { \
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeBinary##op); \
+          ADD_OP_NODE(cur_node); \
+          HL_CUR_TOKEN(Binary##op); \
+        } \
+        want_node = kENodeValue; \
+        break; \
+      }
+      SIMPLE_UB_OP(Plus)
+      SIMPLE_UB_OP(Minus)
+#undef SIMPLE_UB_OP
+#define SIMPLE_B_OP(op, msg) \
+      case kExprLex##op: { \
+        ADD_VALUE_IF_MISSING(_("E15: Unexpected " msg ": %.*s")); \
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNode##op); \
+        HL_CUR_TOKEN(op); \
+        ADD_OP_NODE(cur_node); \
+        break; \
+      }
+      SIMPLE_B_OP(Or, "or operator")
+      SIMPLE_B_OP(And, "and operator")
+#undef SIMPLE_B_OP
+      case kExprLexMultiplication: {
+        ADD_VALUE_IF_MISSING(
+            _("E15: Unexpected multiplication-like operator: %.*s"));
+        switch (cur_token.data.mul.type) {
+#define MUL_OP(lex_op_tail, node_op_tail) \
+          case kExprLexMul##lex_op_tail: { \
+            NEW_NODE_WITH_CUR_POS(cur_node, kExprNode##node_op_tail); \
+            HL_CUR_TOKEN(node_op_tail); \
+            break; \
+          }
+          MUL_OP(Mul, Multiplication)
+          MUL_OP(Div, Division)
+          MUL_OP(Mod, Mod)
+#undef MUL_OP
+        }
+        ADD_OP_NODE(cur_node);
+        break;
+      }
+      case kExprLexOption: {
+        if (want_node == kENodeOperator) {
+          OP_MISSING;
+        }
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeOption);
+        if (cur_token.type == kExprLexInvalid) {
+          assert(cur_token.len == 1
+                 || (cur_token.len == 3
+                     && pline.data[cur_token.start.col + 2] == ':'));
+          cur_node->data.opt.ident = (
+              pline.data + cur_token.start.col + cur_token.len);
+          cur_node->data.opt.ident_len = 0;
+          cur_node->data.opt.scope = (
+              cur_token.len == 3
+              ? (ExprOptScope)pline.data[cur_token.start.col + 1]
+              : kExprOptScopeUnspecified);
+        } else {
+          cur_node->data.opt.ident = cur_token.data.opt.name;
+          cur_node->data.opt.ident_len = cur_token.data.opt.len;
+          cur_node->data.opt.scope = cur_token.data.opt.scope;
+        }
+        *top_node_p = cur_node;
+        want_node = kENodeOperator;
+        viml_parser_highlight(pstate, cur_token.start, 1, HL(OptionSigil));
+        const size_t scope_shift = (
+            cur_token.data.opt.scope == kExprOptScopeUnspecified ? 0 : 2);
+        if (scope_shift) {
+          viml_parser_highlight(pstate, shifted_pos(cur_token.start, 1), 1,
+                                HL(OptionScope));
+          viml_parser_highlight(pstate, shifted_pos(cur_token.start, 2), 1,
+                                HL(OptionScopeDelimiter));
+        }
+        viml_parser_highlight(
+            pstate, shifted_pos(cur_token.start, scope_shift + 1),
+            cur_token.len - (scope_shift + 1), HL(OptionName));
+        break;
+      }
+      case kExprLexEnv: {
+        if (want_node == kENodeOperator) {
+          OP_MISSING;
+        }
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeEnvironment);
+        cur_node->data.env.ident = pline.data + cur_token.start.col + 1;
+        cur_node->data.env.ident_len = cur_token.len - 1;
+        if (cur_node->data.env.ident_len == 0) {
+          ERROR_FROM_TOKEN_AND_MSG(cur_token,
+                                   _("E15: Environment variable name missing"));
+        }
+        *top_node_p = cur_node;
+        want_node = kENodeOperator;
+        viml_parser_highlight(pstate, cur_token.start, 1, HL(EnvironmentSigil));
+        viml_parser_highlight(pstate, shifted_pos(cur_token.start, 1),
+                              cur_token.len - 1, HL(EnvironmentName));
+        break;
+      }
+      case kExprLexNot: {
+        if (want_node == kENodeOperator) {
+          OP_MISSING;
+        }
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeNot);
+        *top_node_p = cur_node;
+        kvi_push(ast_stack, &cur_node->children);
+        HL_CUR_TOKEN(Not);
+        break;
+      }
+      case kExprLexComparison: {
+        ADD_VALUE_IF_MISSING(
+            _("E15: Expected value, got comparison operator: %.*s"));
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeComparison);
+        if (cur_token.type == kExprLexInvalid) {
+          cur_node->data.cmp.ccs = kCCStrategyUseOption;
+          cur_node->data.cmp.type = kExprCmpEqual;
+          cur_node->data.cmp.inv = false;
+        } else {
+          cur_node->data.cmp.ccs = cur_token.data.cmp.ccs;
+          cur_node->data.cmp.type = cur_token.data.cmp.type;
+          cur_node->data.cmp.inv = cur_token.data.cmp.inv;
+        }
+        ADD_OP_NODE(cur_node);
+        if (cur_token.data.cmp.ccs != kCCStrategyUseOption) {
+          viml_parser_highlight(pstate, cur_token.start, cur_token.len - 1,
+                                HL(Comparison));
+          viml_parser_highlight(
+              pstate, shifted_pos(cur_token.start, cur_token.len - 1), 1,
+              HL(ComparisonModifier));
+        } else {
+          HL_CUR_TOKEN(Comparison);
+        }
+        want_node = kENodeValue;
+        break;
+      }
+      case kExprLexComma: {
+        assert(!(want_node == kENodeValue && cur_pt == kEPTLambdaArguments));
+        if (want_node == kENodeValue) {
+          // Value level: comma appearing here is not valid.
+          // Note: in Vim string(,x) will give E116, this is not the case here.
+          ERROR_FROM_TOKEN_AND_MSG(
+              cur_token, _("E15: Expected value, got comma: %.*s"));
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeMissing);
+          cur_node->len = 0;
+          *top_node_p = cur_node;
+          want_node = kENodeOperator;
+        }
+        if (cur_pt == kEPTLambdaArguments) {
+          assert(lambda_node != NULL);
+          assert(lambda_node->data.fig.type_guesses.allow_lambda);
+          SELECT_FIGURE_BRACE_TYPE(lambda_node, Lambda, Lambda);
+        }
+        if (kv_size(ast_stack) < 2) {
+          goto viml_pexpr_parse_invalid_comma;
+        }
+        for (size_t i = 1; i < kv_size(ast_stack); i++) {
+          ExprASTNode *const *const eastnode_p =
+              (ExprASTNode *const *)kv_Z(ast_stack, i);
+          const ExprASTNodeType eastnode_type = (*eastnode_p)->type;
+          const ExprOpLvl eastnode_lvl = node_lvl(**eastnode_p);
+          if (eastnode_type == kExprNodeLambda) {
+            assert(cur_pt == kEPTLambdaArguments
+                   && want_node == kENodeOperator);
+            break;
+          } else if (eastnode_type == kExprNodeDictLiteral
+                     || eastnode_type == kExprNodeListLiteral
+                     || eastnode_type == kExprNodeCall) {
+            break;
+          } else if (eastnode_type == kExprNodeComma
+                     || eastnode_type == kExprNodeColon
+                     || eastnode_lvl > kEOpLvlComma) {
+            // Do nothing
+          } else {
+viml_pexpr_parse_invalid_comma:
+            ERROR_FROM_TOKEN_AND_MSG(
+                cur_token,
+                _("E15: Comma outside of call, lambda or literal: %.*s"));
+            break;
+          }
+          if (i == kv_size(ast_stack) - 1) {
+            goto viml_pexpr_parse_invalid_comma;
+          }
+        }
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeComma);
+        ADD_OP_NODE(cur_node);
+        HL_CUR_TOKEN(Comma);
+        break;
+      }
+#define EXP_VAL_COLON "E15: Expected value, got colon: %.*s"
+      case kExprLexColon: {
+        bool is_ternary = false;
+        if (kv_size(ast_stack) < 2) {
+          goto viml_pexpr_parse_invalid_colon;
+        }
+        bool can_be_ternary = true;
+        bool is_subscript = false;
+        for (size_t i = 1; i < kv_size(ast_stack); i++) {
+          ExprASTNode *const *const eastnode_p =
+              (ExprASTNode *const *)kv_Z(ast_stack, i);
+          const ExprASTNodeType eastnode_type = (*eastnode_p)->type;
+          const ExprOpLvl eastnode_lvl = node_lvl(**eastnode_p);
+          STATIC_ASSERT(kEOpLvlTernary > kEOpLvlComma,
+                        "Unexpected operator priorities");
+          if (can_be_ternary && eastnode_type == kExprNodeTernaryValue
+              && !(*eastnode_p)->data.ter.got_colon) {
+            kv_drop(ast_stack, i);
+            (*eastnode_p)->start = cur_token.start;
+            (*eastnode_p)->len = cur_token.len;
+            if (prev_token.type == kExprLexSpacing) {
+              (*eastnode_p)->start = prev_token.start;
+              (*eastnode_p)->len += prev_token.len;
+            }
+            is_ternary = true;
+            (*eastnode_p)->data.ter.got_colon = true;
+            ADD_VALUE_IF_MISSING(_(EXP_VAL_COLON));
+            assert((*eastnode_p)->children != NULL);
+            assert((*eastnode_p)->children->next == NULL);
+            kvi_push(ast_stack, &(*eastnode_p)->children->next);
+            break;
+          } else if (eastnode_type == kExprNodeUnknownFigure) {
+            SELECT_FIGURE_BRACE_TYPE(*eastnode_p, DictLiteral, Dict);
+            break;
+          } else if (eastnode_type == kExprNodeDictLiteral) {
+            break;
+          } else if (eastnode_type == kExprNodeSubscript) {
+            is_subscript = true;
+            can_be_ternary = false;
+            assert(!is_ternary);
+            break;
+          } else if (eastnode_type == kExprNodeColon) {
+            goto viml_pexpr_parse_invalid_colon;
+          } else if (eastnode_lvl >= kEOpLvlTernaryValue) {
+            // Do nothing
+          } else if (eastnode_lvl >= kEOpLvlComma) {
+            can_be_ternary = false;
+          } else {
+            goto viml_pexpr_parse_invalid_colon;
+          }
+          if (i == kv_size(ast_stack) - 1) {
+            goto viml_pexpr_parse_invalid_colon;
+          }
+        }
+        if (is_subscript) {
+          assert(kv_size(ast_stack) > 1);
+          // Colon immediately following subscript start: it is empty subscript
+          // part like a[:2].
+          if (want_node == kENodeValue
+              && (*kv_Z(ast_stack, 1))->type == kExprNodeSubscript) {
+            NEW_NODE_WITH_CUR_POS(*top_node_p, kExprNodeMissing);
+            (*top_node_p)->len = 0;
+            want_node = kENodeOperator;
+          } else {
+            ADD_VALUE_IF_MISSING(_(EXP_VAL_COLON));
+          }
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeColon);
+          ADD_OP_NODE(cur_node);
+          HL_CUR_TOKEN(SubscriptColon);
+        } else {
+          goto viml_pexpr_parse_valid_colon;
+viml_pexpr_parse_invalid_colon:
+          ERROR_FROM_TOKEN_AND_MSG(
+              cur_token,
+              _("E15: Colon outside of dictionary or ternary operator: %.*s"));
+viml_pexpr_parse_valid_colon:
+          ADD_VALUE_IF_MISSING(_(EXP_VAL_COLON));
+          if (is_ternary) {
+            HL_CUR_TOKEN(TernaryColon);
+          } else {
+            NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeColon);
+            ADD_OP_NODE(cur_node);
+            HL_CUR_TOKEN(Colon);
+          }
+        }
+        want_node = kENodeValue;
+        break;
+      }
+#undef EXP_VAL_COLON
+      case kExprLexBracket: {
+        if (cur_token.data.brc.closing) {
+          ExprASTNode **new_top_node_p = NULL;
+          // Always drop the topmost value:
+          //
+          // 1. When want_node != kENodeValue topmost item on stack is
+          //    a *finished* left operand, which may as well be "{@a}" which
+          //    needs not be finished again.
+          // 2. Otherwise it is pointing to NULL what nobody wants.
+          kv_drop(ast_stack, 1);
+          if (!kv_size(ast_stack)) {
+            NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeListLiteral);
+            cur_node->len = 0;
+            if (want_node != kENodeValue) {
+              cur_node->children = *top_node_p;
+            }
+            *top_node_p = cur_node;
+            goto viml_pexpr_parse_bracket_closing_error;
+          }
+          if (want_node == kENodeValue) {
+            // It is OK to want value if
+            //
+            // 1. It is empty list literal, in which case top node will be
+            //    ListLiteral.
+            // 2. It is list literal with trailing comma, in which case top node
+            //    will be that comma.
+            // 3. It is subscript with colon, but without one of the values:
+            //    e.g. "a[:]", "a[1:]", top node will be colon in this case.
+            if ((*kv_last(ast_stack))->type != kExprNodeListLiteral
+                && (*kv_last(ast_stack))->type != kExprNodeComma
+                && (*kv_last(ast_stack))->type != kExprNodeColon) {
+              ERROR_FROM_TOKEN_AND_MSG(
+                  cur_token,
+                  _("E15: Expected value, got closing bracket: %.*s"));
+            }
+          } else {
+            if (!kv_size(ast_stack)) {
+              new_top_node_p = top_node_p;
+              goto viml_pexpr_parse_bracket_closing_error;
+            }
+          }
+          do {
+            new_top_node_p = kv_pop(ast_stack);
+          } while (kv_size(ast_stack)
+                   && (new_top_node_p == NULL
+                       || ((*new_top_node_p)->type != kExprNodeListLiteral
+                           && (*new_top_node_p)->type != kExprNodeSubscript)));
+          ExprASTNode *new_top_node = *new_top_node_p;
+          switch (new_top_node->type) {
+            case kExprNodeListLiteral: {
+              if (pt_is_assignment(cur_pt) && new_top_node->children == NULL) {
+                ERROR_FROM_TOKEN_AND_MSG(
+                    cur_token, _("E475: Unable to assign to empty list: %.*s"));
+              }
+              HL_CUR_TOKEN(List);
+              break;
+            }
+            case kExprNodeSubscript: {
+              HL_CUR_TOKEN(SubscriptBracket);
+              break;
+            }
+            default: {
+viml_pexpr_parse_bracket_closing_error:
+              assert(!kv_size(ast_stack));
+              ERROR_FROM_TOKEN_AND_MSG(
+                  cur_token, _("E15: Unexpected closing figure brace: %.*s"));
+              HL_CUR_TOKEN(List);
+              break;
+            }
+          }
+          kvi_push(ast_stack, new_top_node_p);
+          want_node = kENodeOperator;
+          if (kv_size(ast_stack) <= asgn_level) {
+            assert(kv_size(ast_stack) == asgn_level);
+            asgn_level = 0;
+            if (cur_pt == kEPTAssignment) {
+              assert(ast.err.msg);
+            } else if (cur_pt == kEPTExpr
+                       && kv_size(pt_stack) > 1
+                       && pt_is_assignment(kv_Z(pt_stack, 1))) {
+              kv_drop(pt_stack, 1);
+            }
+          }
+          if (cur_pt == kEPTSingleAssignment && kv_size(ast_stack) == 1) {
+            kv_drop(pt_stack, 1);
+          }
+        } else {
+          if (want_node == kENodeValue) {
+            // Value means list literal or list assignment.
+            NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeListLiteral);
+            *top_node_p = cur_node;
+            kvi_push(ast_stack, &cur_node->children);
+            want_node = kENodeValue;
+            if (cur_pt == kEPTAssignment) {
+              // Additional assignment parse type allows to easily forbid nested
+              // lists.
+              kvi_push(pt_stack, kEPTSingleAssignment);
+            } else if (cur_pt == kEPTSingleAssignment) {
+              ERROR_FROM_TOKEN_AND_MSG(
+                  cur_token,
+                  _("E475: Nested lists not allowed when assigning: %.*s"));
+            }
+            HL_CUR_TOKEN(List);
+          } else {
+            // Operator means subscript, also in assignment. But in assignment
+            // subscript may be pretty much any expression, so need to push
+            // kEPTExpr.
+            if (prev_token.type == kExprLexSpacing) {
+              OP_MISSING;
+            }
+            NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeSubscript);
+            ADD_OP_NODE(cur_node);
+            HL_CUR_TOKEN(SubscriptBracket);
+            if (pt_is_assignment(cur_pt)) {
+              assert(want_node == kENodeValue);  // Subtract 1 for NULL at top.
+              asgn_level = kv_size(ast_stack) - 1;
+              kvi_push(pt_stack, kEPTExpr);
+            }
+          }
+        }
+        break;
+      }
+      case kExprLexFigureBrace: {
+        if (cur_token.data.brc.closing) {
+          ExprASTNode **new_top_node_p = NULL;
+          // Always drop the topmost value:
+          //
+          // 1. When want_node != kENodeValue topmost item on stack is
+          //    a *finished* left operand, which may as well be "{@a}" which
+          //    needs not be finished again.
+          // 2. Otherwise it is pointing to NULL what nobody wants.
+          kv_drop(ast_stack, 1);
+          if (!kv_size(ast_stack)) {
+            NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeUnknownFigure);
+            cur_node->data.fig.type_guesses.allow_lambda = false;
+            cur_node->data.fig.type_guesses.allow_dict = false;
+            cur_node->data.fig.type_guesses.allow_ident = false;
+            cur_node->len = 0;
+            if (want_node != kENodeValue) {
+              cur_node->children = *top_node_p;
+            }
+            *top_node_p = cur_node;
+            new_top_node_p = top_node_p;
+            goto viml_pexpr_parse_figure_brace_closing_error;
+          }
+          if (want_node == kENodeValue) {
+            if ((*kv_last(ast_stack))->type != kExprNodeUnknownFigure
+                && (*kv_last(ast_stack))->type != kExprNodeComma) {
+              // kv_last being UnknownFigure may occur for empty dictionary
+              // literal, while Comma is expected in case of non-empty one.
+              ERROR_FROM_TOKEN_AND_MSG(
+                  cur_token,
+                  _("E15: Expected value, got closing figure brace: %.*s"));
+            }
+          } else {
+            if (!kv_size(ast_stack)) {
+              new_top_node_p = top_node_p;
+              goto viml_pexpr_parse_figure_brace_closing_error;
+            }
+          }
+          do {
+            new_top_node_p = kv_pop(ast_stack);
+          } while (kv_size(ast_stack)
+                   && (new_top_node_p == NULL
+                       || ((*new_top_node_p)->type != kExprNodeUnknownFigure
+                           && (*new_top_node_p)->type != kExprNodeDictLiteral
+                           && ((*new_top_node_p)->type
+                               != kExprNodeCurlyBracesIdentifier)
+                           && (*new_top_node_p)->type != kExprNodeLambda)));
+          ExprASTNode *new_top_node = *new_top_node_p;
+          switch (new_top_node->type) {
+            case kExprNodeUnknownFigure: {
+              if (new_top_node->children == NULL) {
+                // No children of curly braces node indicates empty dictionary.
+                assert(want_node == kENodeValue);
+                assert(new_top_node->data.fig.type_guesses.allow_dict);
+                SELECT_FIGURE_BRACE_TYPE(new_top_node, DictLiteral, Dict);
+                HL_CUR_TOKEN(Dict);
+              } else if (new_top_node->data.fig.type_guesses.allow_ident) {
+                SELECT_FIGURE_BRACE_TYPE(new_top_node, CurlyBracesIdentifier,
+                                         Curly);
+                HL_CUR_TOKEN(Curly);
+              } else {
+                // If by this time type of the node has not already been
+                // guessed, but it definitely is not a curly braces name then
+                // it is invalid for sure.
+                ERROR_FROM_NODE_AND_MSG(
+                    new_top_node,
+                    _("E15: Don't know what figure brace means: %.*s"));
+                if (pstate->colors) {
+                  // Will reset to NvimInvalidFigureBrace.
+                  kv_A(*pstate->colors,
+                       new_top_node->data.fig.opening_hl_idx).group = (
+                           HL(FigureBrace));
+                }
+                HL_CUR_TOKEN(FigureBrace);
+              }
+              break;
+            }
+            case kExprNodeDictLiteral: {
+              HL_CUR_TOKEN(Dict);
+              break;
+            }
+            case kExprNodeCurlyBracesIdentifier: {
+              HL_CUR_TOKEN(Curly);
+              break;
+            }
+            case kExprNodeLambda: {
+              HL_CUR_TOKEN(Lambda);
+              break;
+            }
+            default: {
+viml_pexpr_parse_figure_brace_closing_error:
+              assert(!kv_size(ast_stack));
+              ERROR_FROM_TOKEN_AND_MSG(
+                  cur_token, _("E15: Unexpected closing figure brace: %.*s"));
+              HL_CUR_TOKEN(FigureBrace);
+              break;
+            }
+          }
+          kvi_push(ast_stack, new_top_node_p);
+          want_node = kENodeOperator;
+          if (kv_size(ast_stack) <= asgn_level) {
+            assert(kv_size(ast_stack) == asgn_level);
+            if (cur_pt == kEPTExpr
+                && kv_size(pt_stack) > 1
+                && pt_is_assignment(kv_Z(pt_stack, 1))) {
+              kv_drop(pt_stack, 1);
+              asgn_level = 0;
+            }
+          }
+        } else {
+          if (want_node == kENodeValue) {
+            HL_CUR_TOKEN(FigureBrace);
+            // Value: may be any of lambda, dictionary literal and curly braces
+            // name.
+
+            // Though if we are in an assignment this may only be a curly braces
+            // name.
+            if (pt_is_assignment(cur_pt)) {
+              NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeCurlyBracesIdentifier);
+              cur_node->data.fig.type_guesses.allow_lambda = false;
+              cur_node->data.fig.type_guesses.allow_dict = false;
+              cur_node->data.fig.type_guesses.allow_ident = true;
+              kvi_push(pt_stack, kEPTExpr);
+            } else {
+              NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeUnknownFigure);
+              cur_node->data.fig.type_guesses.allow_lambda = true;
+              cur_node->data.fig.type_guesses.allow_dict = true;
+              cur_node->data.fig.type_guesses.allow_ident = true;
+            }
+            if (pstate->colors) {
+              cur_node->data.fig.opening_hl_idx = kv_size(*pstate->colors) - 1;
+            }
+            *top_node_p = cur_node;
+            kvi_push(ast_stack, &cur_node->children);
+            kvi_push(pt_stack, kEPTLambdaArguments);
+            lambda_node = cur_node;
+          } else {
+            ADD_IDENT(
+                do {
+                  NEW_NODE_WITH_CUR_POS(cur_node,
+                                        kExprNodeCurlyBracesIdentifier);
+                  cur_node->data.fig.opening_hl_idx = kv_size(*pstate->colors);
+                  cur_node->data.fig.type_guesses.allow_lambda = false;
+                  cur_node->data.fig.type_guesses.allow_dict = false;
+                  cur_node->data.fig.type_guesses.allow_ident = true;
+                  kvi_push(ast_stack, &cur_node->children);
+                  if (pt_is_assignment(cur_pt)) {
+                    kvi_push(pt_stack, kEPTExpr);
+                  }
+                  want_node = kENodeValue;
+                } while (0),
+                Curly);
+          }
+          if (pt_is_assignment(cur_pt)
+              && !pt_is_assignment(kv_last(pt_stack))) {
+            assert(want_node == kENodeValue);  // Subtract 1 for NULL at top.
+            asgn_level = kv_size(ast_stack) - 1;
+          }
+        }
+        break;
+      }
+      case kExprLexArrow: {
+        if (cur_pt == kEPTLambdaArguments) {
+          kv_drop(pt_stack, 1);
+          assert(kv_size(pt_stack));
+          if (want_node == kENodeValue) {
+            // Wanting value means trailing comma and NULL at the top of the
+            // stack.
+            kv_drop(ast_stack, 1);
+          }
+          assert(kv_size(ast_stack) >= 1);
+          while ((*kv_last(ast_stack))->type != kExprNodeLambda
+                 && (*kv_last(ast_stack))->type != kExprNodeUnknownFigure) {
+            kv_drop(ast_stack, 1);
+          }
+          assert((*kv_last(ast_stack)) == lambda_node);
+          SELECT_FIGURE_BRACE_TYPE(lambda_node, Lambda, Lambda);
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeArrow);
+          if (lambda_node->children == NULL) {
+            assert(want_node == kENodeValue);
+            lambda_node->children = cur_node;
+            kvi_push(ast_stack, &lambda_node->children);
+          } else {
+            assert(lambda_node->children->next == NULL);
+            lambda_node->children->next = cur_node;
+            kvi_push(ast_stack, &lambda_node->children->next);
+          }
+          kvi_push(ast_stack, &cur_node->children);
+          lambda_node = NULL;
+        } else {
+          // Only first branch is valid.
+          ADD_VALUE_IF_MISSING(_("E15: Unexpected arrow: %.*s"));
+          ERROR_FROM_TOKEN_AND_MSG(
+              cur_token, _("E15: Arrow outside of lambda: %.*s"));
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeArrow);
+          ADD_OP_NODE(cur_node);
+        }
+        want_node = kENodeValue;
+        HL_CUR_TOKEN(Arrow);
+        break;
+      }
+      case kExprLexPlainIdentifier: {
+        const ExprVarScope scope = (cur_token.type == kExprLexInvalid
+                                    ? kExprVarScopeMissing
+                                    : cur_token.data.var.scope);
+        if (want_node == kENodeValue) {
+          want_node = kENodeOperator;
+          NEW_NODE_WITH_CUR_POS(cur_node,
+                                (node_is_key
+                                 ? kExprNodePlainKey
+                                 : kExprNodePlainIdentifier));
+          cur_node->data.var.scope = scope;
+          const size_t scope_shift = (scope == kExprVarScopeMissing ? 0 : 2);
+          cur_node->data.var.ident = (pline.data + cur_token.start.col
+                                      + scope_shift);
+          cur_node->data.var.ident_len = cur_token.len - scope_shift;
+          *top_node_p = cur_node;
+          if (scope_shift) {
+            assert(!node_is_key);
+            viml_parser_highlight(pstate, cur_token.start, 1,
+                                  HL(IdentifierScope));
+            viml_parser_highlight(pstate, shifted_pos(cur_token.start, 1), 1,
+                                  HL(IdentifierScopeDelimiter));
+          }
+          viml_parser_highlight(pstate, shifted_pos(cur_token.start,
+                                                    scope_shift),
+                                cur_token.len - scope_shift,
+                                (node_is_key
+                                 ? HL(IdentifierKey)
+                                 : HL(IdentifierName)));
+        } else {
+          if (scope == kExprVarScopeMissing) {
+            ADD_IDENT(
+                do {
+                  NEW_NODE_WITH_CUR_POS(cur_node, kExprNodePlainIdentifier);
+                  cur_node->data.var.scope = scope;
+                  cur_node->data.var.ident = pline.data + cur_token.start.col;
+                  cur_node->data.var.ident_len = cur_token.len;
+                  want_node = kENodeOperator;
+                } while (0),
+                IdentifierName);
+          } else {
+            OP_MISSING;
+          }
+        }
+        break;
+      }
+      case kExprLexNumber: {
+        if (want_node != kENodeValue) {
+          OP_MISSING;
+        }
+        if (node_is_key) {
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodePlainKey);
+          cur_node->data.var.ident = pline.data + cur_token.start.col;
+          cur_node->data.var.ident_len = cur_token.len;
+          HL_CUR_TOKEN(IdentifierKey);
+        } else if (cur_token.data.num.is_float) {
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeFloat);
+          cur_node->data.flt.value = cur_token.data.num.val.floating;
+          HL_CUR_TOKEN(Float);
+        } else {
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeInteger);
+          cur_node->data.num.value = cur_token.data.num.val.integer;
+          const uint8_t prefix_length = base_to_prefix_length[
+              cur_token.data.num.base];
+          viml_parser_highlight(pstate, cur_token.start, prefix_length,
+                                HL(NumberPrefix));
+          viml_parser_highlight(
+              pstate, shifted_pos(cur_token.start, prefix_length),
+              cur_token.len - prefix_length, HL(Number));
+        }
+        want_node = kENodeOperator;
+        *top_node_p = cur_node;
+        break;
+      }
+      case kExprLexDot: {
+        ADD_VALUE_IF_MISSING(_("E15: Unexpected dot: %.*s"));
+        if (prev_token.type == kExprLexSpacing) {
+          if (cur_pt == kEPTAssignment) {
+            ERROR_FROM_TOKEN_AND_MSG(
+                cur_token, _("E15: Cannot concatenate in assignments: %.*s"));
+          }
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeConcat);
+          HL_CUR_TOKEN(Concat);
+        } else {
+          NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeConcatOrSubscript);
+          HL_CUR_TOKEN(ConcatOrSubscript);
+        }
+        ADD_OP_NODE(cur_node);
+        break;
+      }
+      case kExprLexParenthesis: {
+        if (cur_token.data.brc.closing) {
+          if (want_node == kENodeValue) {
+            if (kv_size(ast_stack) > 1) {
+              const ExprASTNode *const prev_top_node = *kv_Z(ast_stack, 1);
+              if (prev_top_node->type == kExprNodeCall) {
+                // Function call without arguments, this is not an error.
+                // But further code does not expect NULL nodes.
+                kv_drop(ast_stack, 1);
+                goto viml_pexpr_parse_no_paren_closing_error;
+              }
+            }
+            ERROR_FROM_TOKEN_AND_MSG(
+                cur_token, _("E15: Expected value, got parenthesis: %.*s"));
+            NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeMissing);
+            cur_node->len = 0;
+            *top_node_p = cur_node;
+          } else {
+            // Always drop the topmost value: when want_node != kENodeValue
+            // topmost item on stack is a *finished* left operand, which may as
+            // well be "(@a)" which needs not be finished again.
+            kv_drop(ast_stack, 1);
+          }
+viml_pexpr_parse_no_paren_closing_error: {}
+          ExprASTNode **new_top_node_p = NULL;
+          while (kv_size(ast_stack)
+                 && (new_top_node_p == NULL
+                     || ((*new_top_node_p)->type != kExprNodeNested
+                         && (*new_top_node_p)->type != kExprNodeCall))) {
+            new_top_node_p = kv_pop(ast_stack);
+          }
+          if (new_top_node_p != NULL
+              && ((*new_top_node_p)->type == kExprNodeNested
+                  || (*new_top_node_p)->type == kExprNodeCall)) {
+            if ((*new_top_node_p)->type == kExprNodeNested) {
+              HL_CUR_TOKEN(NestingParenthesis);
+            } else {
+              HL_CUR_TOKEN(CallingParenthesis);
+            }
+          } else {
+            // “Always drop the topmost value” branch has got rid of the single
+            // value stack had, so there is nothing known to enclose. Correct
+            // this.
+            if (new_top_node_p == NULL) {
+              new_top_node_p = top_node_p;
+            }
+            ERROR_FROM_TOKEN_AND_MSG(
+                cur_token, _("E15: Unexpected closing parenthesis: %.*s"));
+            HL_CUR_TOKEN(NestingParenthesis);
+            cur_node = NEW_NODE(kExprNodeNested);
+            cur_node->start = cur_token.start;
+            cur_node->len = 0;
+            // Unexpected closing parenthesis, assume that it was wanted to
+            // enclose everything in ().
+            cur_node->children = *new_top_node_p;
+            *new_top_node_p = cur_node;
+            assert(cur_node->next == NULL);
+          }
+          kvi_push(ast_stack, new_top_node_p);
+          want_node = kENodeOperator;
+        } else {
+          if (want_node == kENodeValue) {
+            NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeNested);
+            *top_node_p = cur_node;
+            kvi_push(ast_stack, &cur_node->children);
+            HL_CUR_TOKEN(NestingParenthesis);
+          } else if (want_node == kENodeOperator) {
+            if (prev_token.type == kExprLexSpacing) {
+              // For some reason "function (args)" is a function call, but
+              // "(funcref) (args)" is not. AFAIR this somehow involves
+              // compatibility and Bram was commenting that this is
+              // intentionally inconsistent and he is not very happy with the
+              // situation himself.
+              if ((*top_node_p)->type != kExprNodePlainIdentifier
+                  && (*top_node_p)->type != kExprNodeComplexIdentifier
+                  && (*top_node_p)->type != kExprNodeCurlyBracesIdentifier) {
+                OP_MISSING;
+              }
+            }
+            NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeCall);
+            ADD_OP_NODE(cur_node);
+            HL_CUR_TOKEN(CallingParenthesis);
+          } else {
+            // Currently it is impossible to reach this.
+            assert(false);
+          }
+          want_node = kENodeValue;
+        }
+        break;
+      }
+      case kExprLexQuestion: {
+        ADD_VALUE_IF_MISSING(_("E15: Expected value, got question mark: %.*s"));
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeTernary);
+        ADD_OP_NODE(cur_node);
+        HL_CUR_TOKEN(Ternary);
+        ExprASTNode *ter_val_node;
+        NEW_NODE_WITH_CUR_POS(ter_val_node, kExprNodeTernaryValue);
+        ter_val_node->data.ter.got_colon = false;
+        assert(cur_node->children != NULL);
+        assert(cur_node->children->next == NULL);
+        assert(kv_last(ast_stack) == &cur_node->children->next);
+        *kv_last(ast_stack) = ter_val_node;
+        kvi_push(ast_stack, &ter_val_node->children);
+        break;
+      }
+      case kExprLexDoubleQuotedString:
+      case kExprLexSingleQuotedString: {
+        const bool is_double = (tok_type == kExprLexDoubleQuotedString);
+        if (!cur_token.data.str.closed) {
+          // It is weird, but Vim has two identical errors messages with
+          // different error numbers: "E114: Missing quote" and
+          // "E115: Missing quote".
+          ERROR_FROM_TOKEN_AND_MSG(
+              cur_token, (is_double
+                          ? _("E114: Missing double quote: %.*s")
+                          : _("E115: Missing single quote: %.*s")));
+        }
+        if (want_node == kENodeOperator) {
+          OP_MISSING;
+        }
+        NEW_NODE_WITH_CUR_POS(
+            cur_node, (is_double
+                       ? kExprNodeDoubleQuotedString
+                       : kExprNodeSingleQuotedString));
+        *top_node_p = cur_node;
+        parse_quoted_string(pstate, cur_node, cur_token, ast_stack, is_invalid);
+        want_node = kENodeOperator;
+        break;
+      }
+      case kExprLexAssignment: {
+        if (cur_pt == kEPTAssignment) {
+          kv_drop(pt_stack, 1);
+        } else if (cur_pt == kEPTSingleAssignment) {
+          kv_drop(pt_stack, 2);
+          ERROR_FROM_TOKEN_AND_MSG(
+              cur_token,
+              _("E475: Expected closing bracket to end list assignment "
+                "lvalue: %.*s"));
+        } else {
+          ERROR_FROM_TOKEN_AND_MSG(
+              cur_token, _("E15: Misplaced assignment: %.*s"));
+        }
+        assert(kv_size(pt_stack));
+        assert(kv_last(pt_stack) == kEPTExpr);
+        ADD_VALUE_IF_MISSING(_("E15: Unexpected assignment: %.*s"));
+        NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeAssignment);
+        cur_node->data.ass.type = cur_token.data.ass.type;
+        switch (cur_token.data.ass.type) {
+#define HL_ASGN(asgn, hl) \
+          case kExprAsgn##asgn: { HL_CUR_TOKEN(hl); break; }
+          HL_ASGN(Plain, PlainAssignment)
+          HL_ASGN(Add, AssignmentWithAddition)
+          HL_ASGN(Subtract, AssignmentWithSubtraction)
+          HL_ASGN(Concat, AssignmentWithConcatenation)
+#undef HL_ASGN
+        }
+        ADD_OP_NODE(cur_node);
+        break;
+      }
+    }
+viml_pexpr_parse_cycle_end:
+    prev_token = cur_token;
+    highlighted_prev_spacing = false;
+    viml_parser_advance(pstate, cur_token.len);
+  } while (true);
+viml_pexpr_parse_end:
+  assert(kv_size(pt_stack));
+  assert(kv_size(ast_stack));
+  if (want_node == kENodeValue
+      // Blacklist some parse type entries as their presence means better error
+      // message in the other branch.
+      && kv_last(pt_stack) != kEPTLambdaArguments) {
+    east_set_error(pstate, &ast.err, _("E15: Expected value, got EOC: %.*s"),
+                   pstate->pos);
+  } else if (kv_size(ast_stack) != 1) {
+    // Something may be wrong, check whether it really is.
+
+    // Pointer to ast.root must never be dropped, so “!= 1” is expected to be
+    // the same as “> 1”.
+    assert(kv_size(ast_stack));
+    // Topmost stack item must be a *finished* value, so it must not be
+    // analyzed. E.g. it may contain an already finished nested expression.
+    kv_drop(ast_stack, 1);
+    while (ast.err.msg == NULL && kv_size(ast_stack)) {
+      const ExprASTNode *const cur_node = (*kv_pop(ast_stack));
+      // This should only happen when want_node == kENodeValue.
+      assert(cur_node != NULL);
+      // TODO(ZyX-I): Rehighlight as invalid?
+      switch (cur_node->type) {
+        case kExprNodeOpMissing:
+        case kExprNodeMissing: {
+          // Error should’ve been already reported.
+          break;
+        }
+        case kExprNodeCall: {
+          east_set_error(
+              pstate, &ast.err,
+              _("E116: Missing closing parenthesis for function call: %.*s"),
+              cur_node->start);
+          break;
+        }
+        case kExprNodeNested: {
+          east_set_error(
+              pstate, &ast.err,
+              _("E110: Missing closing parenthesis for nested expression"
+                ": %.*s"),
+              cur_node->start);
+          break;
+        }
+        case kExprNodeListLiteral: {
+          // For whatever reason "[1" yields "E696: Missing comma in list" error
+          // in Vim while "[1," yields E697.
+          east_set_error(
+              pstate, &ast.err,
+              _("E697: Missing end of List ']': %.*s"),
+              cur_node->start);
+          break;
+        }
+        case kExprNodeDictLiteral: {
+          // Same problem like with list literal with E722 (missing comma) vs
+          // E723, but additionally just "{" yields only E15.
+          east_set_error(
+              pstate, &ast.err,
+              _("E723: Missing end of Dictionary '}': %.*s"),
+              cur_node->start);
+          break;
+        }
+        case kExprNodeUnknownFigure: {
+          east_set_error(
+              pstate, &ast.err,
+              _("E15: Missing closing figure brace: %.*s"),
+              cur_node->start);
+          break;
+        }
+        case kExprNodeLambda: {
+          east_set_error(
+              pstate, &ast.err,
+              _("E15: Missing closing figure brace for lambda: %.*s"),
+              cur_node->start);
+          break;
+        }
+        case kExprNodeCurlyBracesIdentifier: {
+          // Until trailing "}" it is impossible to distinguish curly braces
+          // identifier and dictionary, so it must not appear in the stack like
+          // this.
+          assert(false);
+        }
+        case kExprNodeInteger:
+        case kExprNodeFloat:
+        case kExprNodeSingleQuotedString:
+        case kExprNodeDoubleQuotedString:
+        case kExprNodeOption:
+        case kExprNodeEnvironment:
+        case kExprNodeRegister:
+        case kExprNodePlainIdentifier:
+        case kExprNodePlainKey: {
+          // These are plain values and not containers, for them it should only
+          // be possible to show up in the topmost stack element, but it was
+          // unconditionally popped at the start.
+          assert(false);
+        }
+        case kExprNodeComma:
+        case kExprNodeColon:
+        case kExprNodeArrow: {
+          // It is actually only valid inside something else, but everything
+          // where one of the above is valid requires to be closed and thus is
+          // to be caught later.
+          break;
+        }
+        case kExprNodeSubscript:
+        case kExprNodeConcatOrSubscript:
+        case kExprNodeComplexIdentifier:
+        case kExprNodeAssignment:
+        case kExprNodeMod:
+        case kExprNodeDivision:
+        case kExprNodeMultiplication:
+        case kExprNodeNot:
+        case kExprNodeAnd:
+        case kExprNodeOr:
+        case kExprNodeConcat:
+        case kExprNodeComparison:
+        case kExprNodeUnaryMinus:
+        case kExprNodeUnaryPlus:
+        case kExprNodeBinaryMinus:
+        case kExprNodeTernary:
+        case kExprNodeBinaryPlus: {
+          // It is OK to see these in the stack.
+          break;
+        }
+        case kExprNodeTernaryValue: {
+          if (!cur_node->data.ter.got_colon) {
+            // Actually Vim throws E109 in more cases.
+            east_set_error(
+                pstate, &ast.err, _("E109: Missing ':' after '?': %.*s"),
+                cur_node->start);
+          }
+          break;
+        }
+      }
+    }
+  }
+  kvi_destroy(ast_stack);
+  return ast;
+}  // NOLINT(readability/fn_size)
+
+#undef NEW_NODE
+#undef HL
diff --git a/src/nvim/viml/parser/expressions.h b/src/nvim/viml/parser/expressions.h
new file mode 100644
index 0000000000..23e172da75
--- /dev/null
+++ b/src/nvim/viml/parser/expressions.h
@@ -0,0 +1,389 @@
+#ifndef NVIM_VIML_PARSER_EXPRESSIONS_H
+#define NVIM_VIML_PARSER_EXPRESSIONS_H
+
+#include <stddef.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+#include "nvim/types.h"
+#include "nvim/viml/parser/parser.h"
+#include "nvim/eval/typval.h"
+
+// Defines whether to ignore case:
+//    ==   kCCStrategyUseOption
+//    ==#  kCCStrategyMatchCase
+//    ==?  kCCStrategyIgnoreCase
+typedef enum {
+  kCCStrategyUseOption = 0,  // 0 for xcalloc
+  kCCStrategyMatchCase = '#',
+  kCCStrategyIgnoreCase = '?',
+} ExprCaseCompareStrategy;
+
+/// Lexer token type
+typedef enum {
+  kExprLexInvalid = 0,  ///< Invalid token, indicaten an error.
+  kExprLexMissing,  ///< Missing token, for use in parser.
+  kExprLexSpacing,  ///< Spaces, tabs, newlines, etc.
+  kExprLexEOC,  ///< End of command character: NL, |, just end of stream.
+
+  kExprLexQuestion,  ///< Question mark, for use in ternary.
+  kExprLexColon,  ///< Colon, for use in ternary.
+  kExprLexOr,  ///< Logical or operator.
+  kExprLexAnd,  ///< Logical and operator.
+  kExprLexComparison,  ///< One of the comparison operators.
+  kExprLexPlus,  ///< Plus sign.
+  kExprLexMinus,  ///< Minus sign.
+  kExprLexDot,  ///< Dot: either concat or subscript, also part of the float.
+  kExprLexMultiplication,  ///< Multiplication, division or modulo operator.
+
+  kExprLexNot,  ///< Not: !.
+
+  kExprLexNumber,  ///< Integer number literal, or part of a float.
+  kExprLexSingleQuotedString,  ///< Single quoted string literal.
+  kExprLexDoubleQuotedString,  ///< Double quoted string literal.
+  kExprLexOption,  ///< &optionname option value.
+  kExprLexRegister,  ///< @r register value.
+  kExprLexEnv,  ///< Environment $variable value.
+  kExprLexPlainIdentifier,  ///< Identifier without scope: `abc`, `foo#bar`.
+
+  kExprLexBracket,  ///< Bracket, either opening or closing.
+  kExprLexFigureBrace,  ///< Figure brace, either opening or closing.
+  kExprLexParenthesis,  ///< Parenthesis, either opening or closing.
+  kExprLexComma,  ///< Comma.
+  kExprLexArrow,  ///< Arrow, like from lambda expressions.
+  kExprLexAssignment,  ///< Assignment: `=` or `{op}=`.
+  // XXX When modifying this enum you need to also modify eltkn_type_tab in
+  //     expressions.c and tests and, possibly, viml_pexpr_repr_token.
+} LexExprTokenType;
+
+typedef enum {
+  kExprCmpEqual,  ///< Equality, unequality.
+  kExprCmpMatches,  ///< Matches regex, not matches regex.
+  kExprCmpGreater,  ///< `>` or `<=`
+  kExprCmpGreaterOrEqual,  ///< `>=` or `<`.
+  kExprCmpIdentical,  ///< `is` or `isnot`
+} ExprComparisonType;
+
+/// All possible option scopes
+typedef enum {
+  kExprOptScopeUnspecified = 0,
+  kExprOptScopeGlobal = 'g',
+  kExprOptScopeLocal = 'l',
+} ExprOptScope;
+
+/// All possible assignment types: `=` and `{op}=`.
+typedef enum {
+  kExprAsgnPlain = 0,  ///< Plain assignment: `=`.
+  kExprAsgnAdd,  ///< Assignment augmented with addition: `+=`.
+  kExprAsgnSubtract,  ///< Assignment augmented with subtraction: `-=`.
+  kExprAsgnConcat,  ///< Assignment augmented with concatenation: `.=`.
+} ExprAssignmentType;
+
+#define EXPR_OPT_SCOPE_LIST \
+    ((char[]){ kExprOptScopeGlobal, kExprOptScopeLocal })
+
+/// All possible variable scopes
+typedef enum {
+  kExprVarScopeMissing = 0,
+  kExprVarScopeScript = 's',
+  kExprVarScopeGlobal = 'g',
+  kExprVarScopeVim = 'v',
+  kExprVarScopeBuffer = 'b',
+  kExprVarScopeWindow = 'w',
+  kExprVarScopeTabpage = 't',
+  kExprVarScopeLocal = 'l',
+  kExprVarScopeArguments = 'a',
+} ExprVarScope;
+
+#define EXPR_VAR_SCOPE_LIST \
+    ((char[]) { \
+        kExprVarScopeScript, kExprVarScopeGlobal, kExprVarScopeVim, \
+        kExprVarScopeBuffer, kExprVarScopeWindow, kExprVarScopeTabpage, \
+        kExprVarScopeLocal, kExprVarScopeBuffer, kExprVarScopeArguments, \
+    })
+
+/// Lexer token
+typedef struct {
+  ParserPosition start;
+  size_t len;
+  LexExprTokenType type;
+  union {
+    struct {
+      ExprComparisonType type;  ///< Comparison type.
+      ExprCaseCompareStrategy ccs;  ///< Case comparison strategy.
+      bool inv;  ///< True if comparison is to be inverted.
+    } cmp;  ///< For kExprLexComparison.
+
+    struct {
+      enum {
+        kExprLexMulMul,  ///< Real multiplication.
+        kExprLexMulDiv,  ///< Division.
+        kExprLexMulMod,  ///< Modulo.
+      } type;  ///< Multiplication type.
+    } mul;  ///< For kExprLexMultiplication.
+
+    struct {
+      bool closing;  ///< True if bracket/etc is a closing one.
+    } brc;  ///< For brackets/braces/parenthesis.
+
+    struct {
+      int name;  ///< Register name, may be -1 if name not present.
+    } reg;  ///< For kExprLexRegister.
+
+    struct {
+      bool closed;  ///< True if quote was closed.
+    } str;  ///< For kExprLexSingleQuotedString and kExprLexDoubleQuotedString.
+
+    struct {
+      const char *name;  ///< Option name start.
+      size_t len;  ///< Option name length.
+      ExprOptScope scope;  ///< Option scope: &l:, &g: or not specified.
+    } opt;  ///< Option properties.
+
+    struct {
+      ExprVarScope scope;  ///< Scope character or 0 if not present.
+      bool autoload;  ///< Has autoload characters.
+    } var;  ///< For kExprLexPlainIdentifier
+
+    struct {
+      LexExprTokenType type;  ///< Suggested type for parsing incorrect code.
+      const char *msg;  ///< Error message.
+    } err;  ///< For kExprLexInvalid
+
+    struct {
+      union {
+        float_T floating;
+        uvarnumber_T integer;
+      } val;  ///< Number value.
+      uint8_t base;  ///< Base: 2, 8, 10 or 16.
+      bool is_float;  ///< True if number is a floating-point.
+    } num;  ///< For kExprLexNumber
+
+    struct {
+      ExprAssignmentType type;
+    } ass;  ///< For kExprLexAssignment
+  } data;  ///< Additional data, if needed.
+} LexExprToken;
+
+typedef enum {
+  /// If set, “pointer” to the current byte in pstate will not be shifted
+  kELFlagPeek = (1 << 0),
+  /// Determines whether scope is allowed to come before the identifier
+  kELFlagForbidScope = (1 << 1),
+  /// Determines whether floating-point numbers are allowed
+  ///
+  /// I.e. whether dot is a decimal point separator or is not a part of
+  /// a number at all.
+  kELFlagAllowFloat = (1 << 2),
+  /// Determines whether `is` and `isnot` are seen as comparison operators
+  ///
+  /// If set they are supposed to be just regular identifiers.
+  kELFlagIsNotCmp = (1 << 3),
+  /// Determines whether EOC tokens are allowed
+  ///
+  /// If set then it will yield Invalid token with E15 in place of EOC one if
+  /// “EOC” is something like "|". It is fine with emitting EOC at the end of
+  /// string still, with or without this flag set.
+  kELFlagForbidEOC = (1 << 4),
+  // XXX Whenever you add a new flag, alter klee_assume() statement in
+  //     viml_expressions_lexer.c.
+} LexExprFlags;
+
+/// Expression AST node type
+typedef enum {
+  kExprNodeMissing = 0,
+  kExprNodeOpMissing,
+  kExprNodeTernary,  ///< Ternary operator.
+  kExprNodeTernaryValue,  ///< Ternary operator, colon.
+  kExprNodeRegister,  ///< Register.
+  kExprNodeSubscript,  ///< Subscript.
+  kExprNodeListLiteral,  ///< List literal.
+  kExprNodeUnaryPlus,
+  kExprNodeBinaryPlus,
+  kExprNodeNested,  ///< Nested parenthesised expression.
+  kExprNodeCall,  ///< Function call.
+  /// Plain identifier: simple variable/function name
+  ///
+  /// Looks like "string", "g:Foo", etc: consists from a single
+  /// kExprLexPlainIdentifier token.
+  kExprNodePlainIdentifier,
+  /// Plain dictionary key, for use with kExprNodeConcatOrSubscript
+  kExprNodePlainKey,
+  /// Complex identifier: variable/function name with curly braces
+  kExprNodeComplexIdentifier,
+  /// Figure brace expression which is not yet known
+  ///
+  /// May resolve to any of kExprNodeDictLiteral, kExprNodeLambda or
+  /// kExprNodeCurlyBracesIdentifier.
+  kExprNodeUnknownFigure,
+  kExprNodeLambda,  ///< Lambda.
+  kExprNodeDictLiteral,  ///< Dictionary literal.
+  kExprNodeCurlyBracesIdentifier,  ///< Part of the curly braces name.
+  kExprNodeComma,  ///< Comma “operator”.
+  kExprNodeColon,  ///< Colon “operator”.
+  kExprNodeArrow,  ///< Arrow “operator”.
+  kExprNodeComparison,  ///< Various comparison operators.
+  /// Concat operator
+  ///
+  /// To be only used in cases when it is known for sure it is not a subscript.
+  kExprNodeConcat,
+  /// Concat or subscript operator
+  ///
+  /// For cases when it is not obvious whether expression is a concat or
+  /// a subscript. May only have either number or plain identifier as the second
+  /// child. To make it easier to avoid curly braces in place of
+  /// kExprNodePlainIdentifier node kExprNodePlainKey is used.
+  kExprNodeConcatOrSubscript,
+  kExprNodeInteger,  ///< Integral number.
+  kExprNodeFloat,  ///< Floating-point number.
+  kExprNodeSingleQuotedString,
+  kExprNodeDoubleQuotedString,
+  kExprNodeOr,
+  kExprNodeAnd,
+  kExprNodeUnaryMinus,
+  kExprNodeBinaryMinus,
+  kExprNodeNot,
+  kExprNodeMultiplication,
+  kExprNodeDivision,
+  kExprNodeMod,
+  kExprNodeOption,
+  kExprNodeEnvironment,
+  kExprNodeAssignment,
+  // XXX When modifying this list also modify east_node_type_tab both in parser
+  //     and in tests, and you most likely will also have to alter list of
+  //     highlight groups stored in highlight_init_cmdline variable.
+} ExprASTNodeType;
+
+typedef struct expr_ast_node ExprASTNode;
+
+/// Structure representing one AST node
+struct expr_ast_node {
+  ExprASTNodeType type;  ///< Node type.
+  /// Node children: e.g. for 1 + 2 nodes 1 and 2 will be children of +.
+  ExprASTNode *children;
+  /// Next node: e.g. for 1 + 2 child nodes 1 and 2 are put into a single-linked
+  /// list: `(+)->children` references only node 1, node 2 is in
+  /// `(+)->children->next`.
+  ExprASTNode *next;
+  ParserPosition start;
+  size_t len;
+  union {
+    struct {
+      int name;  ///< Register name, may be -1 if name not present.
+    } reg;  ///< For kExprNodeRegister.
+    struct {
+      /// Which nodes UnknownFigure can’t possibly represent.
+      struct {
+        /// True if UnknownFigure may actually represent dictionary literal.
+        bool allow_dict;
+        /// True if UnknownFigure may actually represent lambda.
+        bool allow_lambda;
+        /// True if UnknownFigure may actually be part of curly braces name.
+        bool allow_ident;
+      } type_guesses;
+      /// Highlight chunk index, used for rehighlighting if needed
+      size_t opening_hl_idx;
+    } fig;  ///< For kExprNodeUnknownFigure.
+    struct {
+      ExprVarScope scope;  ///< Scope character or 0 if not present.
+      /// Actual identifier without scope.
+      ///
+      /// Points to inside parser reader state.
+      const char *ident;
+      size_t ident_len;  ///< Actual identifier length.
+    } var;  ///< For kExprNodePlainIdentifier and kExprNodePlainKey.
+    struct {
+      bool got_colon;  ///< True if colon was seen.
+    } ter;  ///< For kExprNodeTernaryValue.
+    struct {
+      ExprComparisonType type;  ///< Comparison type.
+      ExprCaseCompareStrategy ccs;  ///< Case comparison strategy.
+      bool inv;  ///< True if comparison is to be inverted.
+    } cmp;  ///< For kExprNodeComparison.
+    struct {
+      uvarnumber_T value;
+    } num;  ///< For kExprNodeInteger.
+    struct {
+      float_T value;
+    } flt;  ///< For kExprNodeFloat.
+    struct {
+      char *value;
+      size_t size;
+    } str;  ///< For kExprNodeSingleQuotedString and
+            ///< kExprNodeDoubleQuotedString.
+    struct {
+      const char *ident;  ///< Option name start.
+      size_t ident_len;  ///< Option name length.
+      ExprOptScope scope;  ///< Option scope: &l:, &g: or not specified.
+    } opt;  ///< For kExprNodeOption.
+    struct {
+      const char *ident;  ///< Environment variable name start.
+      size_t ident_len;  ///< Environment variable name length.
+    } env;  ///< For kExprNodeEnvironment.
+    struct {
+      ExprAssignmentType type;
+    } ass;  ///< For kExprNodeAssignment
+  } data;
+};
+
+enum {
+  /// Allow multiple expressions in a row: e.g. for :echo
+  ///
+  /// Parser will still parse only one of them though.
+  kExprFlagsMulti = (1 << 0),
+  /// Allow NL, NUL and bar to be EOC
+  ///
+  /// When parsing expressions input by user bar is assumed to be a binary
+  /// operator and other two are spacings.
+  kExprFlagsDisallowEOC = (1 << 1),
+  /// Parse :let argument
+  ///
+  /// That mean that top level node must be an assignment and first nodes
+  /// belong to lvalues.
+  kExprFlagsParseLet = (1 << 2),
+  // XXX whenever you add a new flag, alter klee_assume() statement in
+  //     viml_expressions_parser.c, nvim_parse_expression() flags parsing
+  //     alongside with its documentation and flag sets in check_parsing()
+  //     function in expressions parser functional and unit tests.
+} ExprParserFlags;
+
+/// AST error definition
+typedef struct {
+  /// Error message. Must contain a single printf format atom: %.*s.
+  const char *msg;
+  /// Error message argument: points to the location of the error.
+  const char *arg;
+  /// Message argument length: length till the end of string.
+  int arg_len;
+} ExprASTError;
+
+/// Structure representing complety AST for one expression
+typedef struct {
+  /// When AST is not correct this message will be printed.
+  ///
+  /// Uses `emsgf(msg, arg_len, arg);`, `msg` is assumed to contain only `%.*s`.
+  ExprASTError err;
+  /// Root node of the AST.
+  ExprASTNode *root;
+} ExprAST;
+
+/// Array mapping ExprASTNodeType to maximum amount of children node may have
+extern const uint8_t node_maxchildren[];
+
+/// Array mapping ExprASTNodeType values to their stringified versions
+extern const char *const east_node_type_tab[];
+
+/// Array mapping ExprComparisonType values to their stringified versions
+extern const char *const eltkn_cmp_type_tab[];
+
+/// Array mapping ExprCaseCompareStrategy values to their stringified versions
+extern const char *const ccs_tab[];
+
+/// Array mapping ExprAssignmentType values to their stringified versions
+extern const char *const expr_asgn_type_tab[];
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "viml/parser/expressions.h.generated.h"
+#endif
+
+#endif  // NVIM_VIML_PARSER_EXPRESSIONS_H
diff --git a/src/nvim/viml/parser/parser.c b/src/nvim/viml/parser/parser.c
new file mode 100644
index 0000000000..08d8846018
--- /dev/null
+++ b/src/nvim/viml/parser/parser.c
@@ -0,0 +1,13 @@
+#include "nvim/viml/parser/parser.h"
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "viml/parser/parser.c.generated.h"
+#endif
+
+
+void parser_simple_get_line(void *cookie, ParserLine *ret_pline)
+{
+  ParserLine **plines_p = (ParserLine **)cookie;
+  *ret_pline = **plines_p;
+  (*plines_p)++;
+}
diff --git a/src/nvim/viml/parser/parser.h b/src/nvim/viml/parser/parser.h
new file mode 100644
index 0000000000..7ac49709d8
--- /dev/null
+++ b/src/nvim/viml/parser/parser.h
@@ -0,0 +1,244 @@
+#ifndef NVIM_VIML_PARSER_PARSER_H
+#define NVIM_VIML_PARSER_PARSER_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <assert.h>
+
+#include "nvim/lib/kvec.h"
+#include "nvim/func_attr.h"
+#include "nvim/mbyte.h"
+#include "nvim/memory.h"
+
+/// One parsed line
+typedef struct {
+  const char *data;  ///< Parsed line pointer
+  size_t size;  ///< Parsed line size
+  bool allocated;  ///< True if line may be freed.
+} ParserLine;
+
+/// Line getter type for parser
+///
+/// Line getter must return {NULL, 0} for EOF.
+typedef void (*ParserLineGetter)(void *cookie, ParserLine *ret_pline);
+
+/// Parser position in the input
+typedef struct {
+  size_t line;  ///< Line index in ParserInputReader.lines.
+  size_t col;  ///< Byte index in the line.
+} ParserPosition;
+
+/// Parser state item.
+typedef struct {
+  enum {
+    kPTopStateParsingCommand = 0,
+    kPTopStateParsingExpression,
+  } type;
+  union {
+    struct {
+      enum {
+        kExprUnknown = 0,
+      } type;
+    } expr;
+  } data;
+} ParserStateItem;
+
+/// Structure defining input reader
+typedef struct {
+  /// Function used to get next line.
+  ParserLineGetter get_line;
+  /// Data for get_line function.
+  void *cookie;
+  /// All lines obtained by get_line.
+  kvec_withinit_t(ParserLine, 4) lines;
+  /// Conversion, for :scriptencoding.
+  vimconv_T conv;
+} ParserInputReader;
+
+/// Highlighted region definition
+///
+/// Note: one chunk may highlight only one line.
+typedef struct {
+  ParserPosition start;  ///< Start of the highlight: line and column.
+  size_t end_col;  ///< End column, points to the start of the next character.
+  const char *group;  ///< Highlight group.
+} ParserHighlightChunk;
+
+/// Highlighting defined by a parser
+typedef kvec_withinit_t(ParserHighlightChunk, 16) ParserHighlight;
+
+/// Structure defining parser state
+typedef struct {
+  /// Line reader.
+  ParserInputReader reader;
+  /// Position up to which input was parsed.
+  ParserPosition pos;
+  /// Parser state stack.
+  kvec_withinit_t(ParserStateItem, 16) stack;
+  /// Highlighting support.
+  ParserHighlight *colors;
+  /// True if line continuation can be used.
+  bool can_continuate;
+} ParserState;
+
+static inline void viml_parser_init(
+    ParserState *const ret_pstate,
+    const ParserLineGetter get_line, void *const cookie,
+    ParserHighlight *const colors)
+  REAL_FATTR_ALWAYS_INLINE REAL_FATTR_NONNULL_ARG(1, 2);
+
+/// Initialize a new parser state instance
+///
+/// @param[out]  ret_pstate  Parser state to initialize.
+/// @param[in]  get_line  Line getter function.
+/// @param[in]  cookie  Argument for the get_line function.
+/// @param[in]  colors  Where to save highlighting. May be NULL if it is not
+///                     needed.
+static inline void viml_parser_init(
+    ParserState *const ret_pstate,
+    const ParserLineGetter get_line, void *const cookie,
+    ParserHighlight *const colors)
+{
+  *ret_pstate = (ParserState) {
+    .reader = {
+      .get_line = get_line,
+      .cookie = cookie,
+      .conv = MBYTE_NONE_CONV,
+    },
+    .pos = { 0, 0 },
+    .colors = colors,
+    .can_continuate = false,
+  };
+  kvi_init(ret_pstate->reader.lines);
+  kvi_init(ret_pstate->stack);
+}
+
+static inline void viml_parser_destroy(ParserState *const pstate)
+  REAL_FATTR_NONNULL_ALL REAL_FATTR_ALWAYS_INLINE;
+
+/// Free all memory allocated by the parser on heap
+///
+/// @param  pstate  Parser state to free.
+static inline void viml_parser_destroy(ParserState *const pstate)
+{
+  for (size_t i = 0; i < kv_size(pstate->reader.lines); i++) {
+    ParserLine pline = kv_A(pstate->reader.lines, i);
+    if (pline.allocated) {
+      xfree((void *)pline.data);
+    }
+  }
+  kvi_destroy(pstate->reader.lines);
+  kvi_destroy(pstate->stack);
+}
+
+static inline void viml_preader_get_line(ParserInputReader *const preader,
+                                         ParserLine *const ret_pline)
+  REAL_FATTR_NONNULL_ALL;
+
+/// Get one line from ParserInputReader
+static inline void viml_preader_get_line(ParserInputReader *const preader,
+                                         ParserLine *const ret_pline)
+{
+  ParserLine pline;
+  preader->get_line(preader->cookie, &pline);
+  if (preader->conv.vc_type != CONV_NONE && pline.size) {
+    ParserLine cpline = {
+      .allocated = true,
+      .size = pline.size,
+    };
+    cpline.data = (char *)string_convert(&preader->conv,
+                                         (char_u *)pline.data,
+                                         &cpline.size);
+    if (pline.allocated) {
+      xfree((void *)pline.data);
+    }
+    pline = cpline;
+  }
+  kvi_push(preader->lines, pline);
+  *ret_pline = pline;
+}
+
+static inline bool viml_parser_get_remaining_line(ParserState *const pstate,
+                                                  ParserLine *const ret_pline)
+  REAL_FATTR_ALWAYS_INLINE REAL_FATTR_WARN_UNUSED_RESULT REAL_FATTR_NONNULL_ALL;
+
+/// Get currently parsed line, shifted to pstate->pos.col
+///
+/// @param  pstate  Parser state to operate on.
+///
+/// @return True if there is a line, false in case of EOF.
+static inline bool viml_parser_get_remaining_line(ParserState *const pstate,
+                                                  ParserLine *const ret_pline)
+{
+  const size_t num_lines = kv_size(pstate->reader.lines);
+  if (pstate->pos.line == num_lines) {
+    viml_preader_get_line(&pstate->reader, ret_pline);
+  } else {
+    *ret_pline = kv_last(pstate->reader.lines);
+  }
+  assert(pstate->pos.line == kv_size(pstate->reader.lines) - 1);
+  if (ret_pline->data != NULL) {
+    ret_pline->data += pstate->pos.col;
+    ret_pline->size -= pstate->pos.col;
+  }
+  return ret_pline->data != NULL;
+}
+
+static inline void viml_parser_advance(ParserState *const pstate,
+                                       const size_t len)
+  REAL_FATTR_ALWAYS_INLINE REAL_FATTR_NONNULL_ALL;
+
+/// Advance position by a given number of bytes
+///
+/// At maximum advances to the next line.
+///
+/// @param  pstate  Parser state to advance.
+/// @param[in]  len  Number of bytes to advance.
+static inline void viml_parser_advance(ParserState *const pstate,
+                                       const size_t len)
+{
+  assert(pstate->pos.line == kv_size(pstate->reader.lines) - 1);
+  const ParserLine pline = kv_last(pstate->reader.lines);
+  if (pstate->pos.col + len >= pline.size) {
+    pstate->pos.line++;
+    pstate->pos.col = 0;
+  } else {
+    pstate->pos.col += len;
+  }
+}
+
+static inline void viml_parser_highlight(ParserState *const pstate,
+                                         const ParserPosition start,
+                                         const size_t end_col,
+                                         const char *const group)
+  REAL_FATTR_ALWAYS_INLINE REAL_FATTR_NONNULL_ALL;
+
+/// Record highlighting of some region of text
+///
+/// @param  pstate  Parser state to work with.
+/// @param[in]  start  Start position of the highlight.
+/// @param[in]  len  Highlighting chunk length.
+/// @param[in]  group  Highlight group.
+static inline void viml_parser_highlight(ParserState *const pstate,
+                                         const ParserPosition start,
+                                         const size_t len,
+                                         const char *const group)
+{
+  if (pstate->colors == NULL || len == 0) {
+    return;
+  }
+  assert(kv_size(*pstate->colors) == 0
+         || kv_Z(*pstate->colors, 0).start.line < start.line
+         || kv_Z(*pstate->colors, 0).end_col <= start.col);
+  kvi_push(*pstate->colors, ((ParserHighlightChunk) {
+      .start = start,
+      .end_col = start.col + len,
+      .group = group,
+  }));
+}
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "viml/parser/parser.h.generated.h"
+#endif
+
+#endif  // NVIM_VIML_PARSER_PARSER_H