viml/parser/expressions: Add support for comparison operators

6 files changed, 483 insertions, 82 deletions

diff --git a/src/nvim/viml/parser/expressions.c b/src/nvim/viml/parser/expressions.c
index 982465055e..8e6f991e03 100644
--- a/src/nvim/viml/parser/expressions.c
+++ b/src/nvim/viml/parser/expressions.c
@@ -102,7 +102,7 @@ LexExprToken viml_pexpr_next_token(ParserState *const pstate, const int flags)
     if (ret.len < pline.size \
         && strchr("?#", pline.data[ret.len]) != NULL) { \
       ret.data.cmp.ccs = \
-          (CaseCompareStrategy)pline.data[ret.len]; \
+          (ExprCaseCompareStrategy)pline.data[ret.len]; \
       ret.len++; \
     } else { \
       ret.data.cmp.ccs = kCCStrategyUseOption; \
@@ -240,7 +240,7 @@ LexExprToken viml_pexpr_next_token(ParserState *const pstate, const int flags)
           && ((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 = kExprLexCmpIdentical;
+        ret.data.cmp.type = kExprCmpIdentical;
         ret.data.cmp.inv = (ret.len == 5);
         GET_CCS(ret, pline);
       // Scope: `s:`, etc.
@@ -381,10 +381,10 @@ viml_pexpr_next_token_invalid_comparison:
       ret.type = kExprLexComparison;
       ret.data.cmp.inv = (schar == '!');
       if (pline.data[1] == '=') {
-        ret.data.cmp.type = kExprLexCmpEqual;
+        ret.data.cmp.type = kExprCmpEqual;
         ret.len++;
       } else if (pline.data[1] == '~') {
-        ret.data.cmp.type = kExprLexCmpMatches;
+        ret.data.cmp.type = kExprCmpMatches;
         ret.len++;
       } else {
         goto viml_pexpr_next_token_invalid_comparison;
@@ -404,8 +404,8 @@ viml_pexpr_next_token_invalid_comparison:
       GET_CCS(ret, pline);
       ret.data.cmp.inv = (schar == '<');
       ret.data.cmp.type = ((ret.data.cmp.inv ^ haseqsign)
-                           ? kExprLexCmpGreaterOrEqual
-                           : kExprLexCmpGreater);
+                           ? kExprCmpGreaterOrEqual
+                           : kExprCmpGreater);
       break;
     }
 
@@ -503,11 +503,11 @@ static const char *const eltkn_type_tab[] = {
 };
 
 static const char *const eltkn_cmp_type_tab[] = {
-  [kExprLexCmpEqual] = "Equal",
-  [kExprLexCmpMatches] = "Matches",
-  [kExprLexCmpGreater] = "Greater",
-  [kExprLexCmpGreaterOrEqual] = "GreaterOrEqual",
-  [kExprLexCmpIdentical] = "Identical",
+  [kExprCmpEqual] = "Equal",
+  [kExprCmpMatches] = "Matches",
+  [kExprCmpGreater] = "Greater",
+  [kExprCmpGreaterOrEqual] = "GreaterOrEqual",
+  [kExprCmpIdentical] = "Identical",
 };
 
 static const char *const ccs_tab[] = {
@@ -770,7 +770,8 @@ static inline void viml_pexpr_debug_print_token(
 // NVimOperator -> Operator
 // NVimUnaryOperator -> NVimOperator
 // NVimBinaryOperator -> NVimOperator
-// NVimComparisonOperator -> NVimOperator
+// NVimComparisonOperator -> NVimBinaryOperator
+// NVimComparisonOperatorModifier -> NVimComparisonOperator
 // NVimTernary -> NVimOperator
 // NVimTernaryColon -> NVimTernary
 //
@@ -805,6 +806,8 @@ static inline void viml_pexpr_debug_print_token(
 // NVimInvalidIdentifier -> NVimInvalidValue
 // NVimInvalidIdentifierScope -> NVimInvalidValue
 // NVimInvalidIdentifierScopeDelimiter -> NVimInvalidValue
+// NVimInvalidComparisonOperator -> NVimInvalidOperator
+// NVimInvalidComparisonOperatorModifier -> NVimInvalidComparisonOperator
 //
 // NVimUnaryPlus -> NVimUnaryOperator
 // NVimBinaryPlus -> NVimBinaryOperator
@@ -849,6 +852,8 @@ static const ExprOpLvl node_type_to_op_lvl[] = {
 
   [kExprNodeTernaryValue] = kEOpLvlTernaryValue,
 
+  [kExprNodeComparison] = kEOpLvlComparison,
+
   [kExprNodeBinaryPlus] = kEOpLvlAddition,
 
   [kExprNodeUnaryPlus] = kEOpLvlUnary,
@@ -892,6 +897,8 @@ static const ExprOpAssociativity node_type_to_op_ass[] = {
 
   [kExprNodeTernaryValue] = kEOpAssRight,
 
+  [kExprNodeComparison] = kEOpAssRight,
+
   [kExprNodeBinaryPlus] = kEOpAssLeft,
 
   [kExprNodeUnaryPlus] = kEOpAssNo,
@@ -935,11 +942,23 @@ static inline ExprOpAssociativity node_ass(const ExprASTNode node)
 /// Handle binary operator
 ///
 /// This function is responsible for handling priority levels as well.
-static void viml_pexpr_handle_bop(ExprASTStack *const ast_stack,
+///
+/// @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)
+                                  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;
@@ -977,7 +996,6 @@ static void viml_pexpr_handle_bop(ExprASTStack *const ast_stack,
       break;
     }
   } while (kv_size(*ast_stack));
-  // FIXME: Handle no associativity
   if (top_node_ass == kEOpAssLeft || top_node_lvl != bop_node_lvl) {
     // outer(op(x,y)) -> outer(new_op(op(x,y),*))
     //
@@ -1008,10 +1026,18 @@ static void viml_pexpr_handle_bop(ExprASTStack *const ast_stack,
     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 = (*want_node_p == kENodeArgumentSeparator
                   ? kENodeArgument
                   : kENodeValue);
+  return ret;
 }
 
 /// ParserPosition literal based on ParserPosition pos with columns shifted
@@ -1074,6 +1100,13 @@ static inline ParserPosition shifted_pos(const ParserPosition pos,
 #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
@@ -1094,7 +1127,7 @@ static inline ParserPosition shifted_pos(const ParserPosition pos,
         ERROR_FROM_TOKEN_AND_MSG(cur_token, _("E15: Missing operator: %.*s")); \
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeOpMissing); \
         cur_node->len = 0; \
-        viml_pexpr_handle_bop(&ast_stack, cur_node, &want_node); \
+        ADD_OP_NODE(cur_node); \
         goto viml_pexpr_parse_process_token; \
       } \
     } while (0)
@@ -1120,34 +1153,33 @@ static inline ParserPosition shifted_pos(const ParserPosition pos,
 /// @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(ExprAST *const ret_ast,
-                                  const ParserState *const pstate,
+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->correct) {
+  if (ret_ast_err->msg != NULL) {
     return;
   }
   const ParserLine pline = pstate->reader.lines.items[start.line];
-  ret_ast->correct = false;
-  ret_ast->err.msg = msg;
-  ret_ast->err.arg_len = (int)(pline.size - start.col);
-  ret_ast->err.arg = pline.data + start.col;
+  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(&ast, pstate, msg, cur_token.start); \
+      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(&ast, pstate, msg, node->start); \
+      east_set_error(pstate, &ast.err, msg, node->start); \
     } while (0)
 
 /// Set error from the given kExprLexInvalid token
@@ -1231,7 +1263,6 @@ ExprAST viml_pexpr_parse(ParserState *const pstate, const int flags)
   FUNC_ATTR_WARN_UNUSED_RESULT FUNC_ATTR_NONNULL_ALL
 {
   ExprAST ast = {
-    .correct = true,
     .err = {
       .msg = NULL,
       .arg_len = 0,
@@ -1359,12 +1390,38 @@ viml_pexpr_parse_process_token:
           HL_CUR_TOKEN(UnaryPlus);
         } else {
           NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeBinaryPlus);
-          viml_pexpr_handle_bop(&ast_stack, cur_node, &want_node);
+          ADD_OP_NODE(cur_node);
           HL_CUR_TOKEN(BinaryPlus);
         }
         want_node = kENodeValue;
         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(ComparisonOperator));
+          viml_parser_highlight(
+              pstate, shifted_pos(cur_token.start, cur_token.len - 1), 1,
+              HL(ComparisonOperatorModifier));
+        } else {
+          HL_CUR_TOKEN(ComparisonOperator);
+        }
+        want_node = kENodeValue;
+        break;
+      }
       case kExprLexComma: {
         assert(want_node != kENodeArgument);
         if (want_node == kENodeValue) {
@@ -1415,7 +1472,7 @@ viml_pexpr_parse_invalid_comma:
           }
         }
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeComma);
-        viml_pexpr_handle_bop(&ast_stack, cur_node, &want_node);
+        ADD_OP_NODE(cur_node);
         HL_CUR_TOKEN(Comma);
         break;
       }
@@ -1474,7 +1531,7 @@ viml_pexpr_parse_invalid_colon:
           HL_CUR_TOKEN(TernaryColon);
         } else {
           NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeColon);
-          viml_pexpr_handle_bop(&ast_stack, cur_node, &want_node);
+          ADD_OP_NODE(cur_node);
           HL_CUR_TOKEN(Colon);
         }
         want_node = kENodeValue;
@@ -1646,7 +1703,7 @@ viml_pexpr_parse_figure_brace_closing_error:
           ERROR_FROM_TOKEN_AND_MSG(
               cur_token, _("E15: Arrow outside of lambda: %.*s"));
           NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeArrow);
-          viml_pexpr_handle_bop(&ast_stack, cur_node, &want_node);
+          ADD_OP_NODE(cur_node);
         }
         want_node = kENodeValue;
         HL_CUR_TOKEN(Arrow);
@@ -1775,7 +1832,7 @@ viml_pexpr_parse_no_paren_closing_error: {}
               }
             }
             NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeCall);
-            viml_pexpr_handle_bop(&ast_stack, cur_node, &want_node);
+            ADD_OP_NODE(cur_node);
             HL_CUR_TOKEN(CallingParenthesis);
           } else {
             // Currently it is impossible to reach this.
@@ -1788,7 +1845,7 @@ viml_pexpr_parse_no_paren_closing_error: {}
       case kExprLexQuestion: {
         ADD_VALUE_IF_MISSING(_("E15: Expected value, got question mark: %.*s"));
         NEW_NODE_WITH_CUR_POS(cur_node, kExprNodeTernary);
-        viml_pexpr_handle_bop(&ast_stack, cur_node, &want_node);
+        ADD_OP_NODE(cur_node);
         HL_CUR_TOKEN(Ternary);
         ExprASTNode *ter_val_node;
         NEW_NODE_WITH_CUR_POS(ter_val_node, kExprNodeTernaryValue);
@@ -1808,7 +1865,7 @@ viml_pexpr_parse_cycle_end:
   } while (true);
 viml_pexpr_parse_end:
   if (want_node == kENodeValue) {
-    east_set_error(&ast, pstate, _("E15: Expected value, got EOC: %.*s"),
+    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.
@@ -1819,7 +1876,7 @@ viml_pexpr_parse_end:
     // 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.correct && kv_size(ast_stack)) {
+    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);
@@ -1832,14 +1889,14 @@ viml_pexpr_parse_end:
         }
         case kExprNodeCall: {
           east_set_error(
-              &ast, pstate,
+              pstate, &ast.err,
               _("E116: Missing closing parenthesis for function call: %.*s"),
               cur_node->start);
           break;
         }
         case kExprNodeNested: {
           east_set_error(
-              &ast, pstate,
+              pstate, &ast.err,
               _("E110: Missing closing parenthesis for nested expression"
                 ": %.*s"),
               cur_node->start);
@@ -1855,7 +1912,7 @@ viml_pexpr_parse_end:
           if (!cur_node->data.ter.got_colon) {
             // Actually Vim throws E109 in more cases.
             east_set_error(
-                &ast, pstate, _("E109: Missing ':' after '?': %.*s"),
+                pstate, &ast.err, _("E109: Missing ':' after '?': %.*s"),
                 cur_node->start);
           }
           break;
diff --git a/src/nvim/viml/parser/expressions.h b/src/nvim/viml/parser/expressions.h
index cf0907850a..8ca3ceacb9 100644
--- a/src/nvim/viml/parser/expressions.h
+++ b/src/nvim/viml/parser/expressions.h
@@ -16,7 +16,7 @@ typedef enum {
   kCCStrategyUseOption = 0,  // 0 for xcalloc
   kCCStrategyMatchCase = '#',
   kCCStrategyIgnoreCase = '?',
-} CaseCompareStrategy;
+} ExprCaseCompareStrategy;
 
 /// Lexer token type
 typedef enum {
@@ -52,6 +52,14 @@ typedef enum {
   kExprLexArrow,  ///< Arrow, like from lambda expressions.
 } LexExprTokenType;
 
+typedef enum {
+  kExprCmpEqual,  ///< Equality, unequality.
+  kExprCmpMatches,  ///< Matches regex, not matches regex.
+  kExprCmpGreater,  ///< `>` or `<=`
+  kExprCmpGreaterOrEqual,  ///< `>=` or `<`.
+  kExprCmpIdentical,  ///< `is` or `isnot`
+} ExprComparisonType;
+
 /// Lexer token
 typedef struct {
   ParserPosition start;
@@ -59,14 +67,8 @@ typedef struct {
   LexExprTokenType type;
   union {
     struct {
-      enum {
-        kExprLexCmpEqual,  ///< Equality, unequality.
-        kExprLexCmpMatches,  ///< Matches regex, not matches regex.
-        kExprLexCmpGreater,  ///< `>` or `<=`
-        kExprLexCmpGreaterOrEqual,  ///< `>=` or `<`.
-        kExprLexCmpIdentical,  ///< `is` or `isnot`
-      } type;  ///< Comparison type.
-      CaseCompareStrategy ccs;  ///< Case comparison strategy.
+      ExprComparisonType type;  ///< Comparison type.
+      ExprCaseCompareStrategy ccs;  ///< Case comparison strategy.
       bool inv;  ///< True if comparison is to be inverted.
     } cmp;  ///< For kExprLexComparison.
 
@@ -171,6 +173,7 @@ typedef enum {
   kExprNodeComma = ',',  ///< Comma “operator”.
   kExprNodeColon = ':',  ///< Colon “operator”.
   kExprNodeArrow = '>',  ///< Arrow “operator”.
+  kExprNodeComparison = '=',  ///< Various comparison operators.
 } ExprASTNodeType;
 
 typedef struct expr_ast_node ExprASTNode;
@@ -214,6 +217,11 @@ struct expr_ast_node {
     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.
   } data;
 };
 
@@ -235,19 +243,22 @@ enum {
   // viml_expressions_parser.c.
 } 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 {
-  /// True if represented AST is correct and can be executed. Incorrect ones may
-  /// still be used for completion, or in linters.
-  bool correct;
   /// When AST is not correct this message will be printed.
   ///
   /// Uses `emsgf(msg, arg_len, arg);`, `msg` is assumed to contain only `%.*s`.
-  struct {
-    const char *msg;
-    int arg_len;
-    const char *arg;
-  } err;
+  ExprASTError err;
   /// Root node of the AST.
   ExprASTNode *root;
 } ExprAST;
diff --git a/test/symbolic/klee/viml_expressions_parser.c b/test/symbolic/klee/viml_expressions_parser.c
index 2bad1adc53..5ad592b99f 100644
--- a/test/symbolic/klee/viml_expressions_parser.c
+++ b/test/symbolic/klee/viml_expressions_parser.c
@@ -91,12 +91,6 @@ int main(const int argc, const char *const *const argv,
   const ExprAST ast = viml_pexpr_parse(&pstate, flags);
   assert(ast.root != NULL
          || plines[0].size == 0);
-  assert(ast.root != NULL || !ast.correct);
-  assert(ast.correct
-         || (ast.err.msg != NULL
-             && ast.err.arg != NULL
-             && ast.err.arg >= plines[0].data
-             && ((size_t)(ast.err.arg - plines[0].data) + ast.err.arg_len
-                 <= plines[0].size)));
+  assert(ast.root != NULL || ast.err.msg);
   // FIXME: free memory and assert no memory leaks
 }
diff --git a/test/unit/viml/expressions/lexer_spec.lua b/test/unit/viml/expressions/lexer_spec.lua
index 972478c2e5..d201d54526 100644
--- a/test/unit/viml/expressions/lexer_spec.lua
+++ b/test/unit/viml/expressions/lexer_spec.lua
@@ -1,7 +1,7 @@
 local helpers = require('test.unit.helpers')(after_each)
-local viml_helpers = require('test.unit.viml.helpers')
 local global_helpers = require('test.helpers')
 local itp = helpers.gen_itp(it)
+local viml_helpers = require('test.unit.viml.helpers')
 
 local child_call_once = helpers.child_call_once
 local conv_enum = helpers.conv_enum
@@ -9,17 +9,18 @@ local cimport = helpers.cimport
 local ffi = helpers.ffi
 local eq = helpers.eq
 
+local conv_ccs = viml_helpers.conv_ccs
 local pline2lua = viml_helpers.pline2lua
 local new_pstate = viml_helpers.new_pstate
 local intchar2lua = viml_helpers.intchar2lua
+local conv_cmp_type = viml_helpers.conv_cmp_type
 local pstate_set_str = viml_helpers.pstate_set_str
 
 local shallowcopy = global_helpers.shallowcopy
 
 local lib = cimport('./src/nvim/viml/parser/expressions.h')
 
-local eltkn_type_tab, eltkn_cmp_type_tab, ccs_tab, eltkn_mul_type_tab
-local eltkn_opt_scope_tab
+local eltkn_type_tab, eltkn_mul_type_tab, eltkn_opt_scope_tab
 child_call_once(function()
   eltkn_type_tab = {
     [tonumber(lib.kExprLexInvalid)] = 'Invalid',
@@ -54,20 +55,6 @@ child_call_once(function()
     [tonumber(lib.kExprLexArrow)] = 'Arrow',
   }
 
-  eltkn_cmp_type_tab = {
-    [tonumber(lib.kExprLexCmpEqual)] = 'Equal',
-    [tonumber(lib.kExprLexCmpMatches)] = 'Matches',
-    [tonumber(lib.kExprLexCmpGreater)] = 'Greater',
-    [tonumber(lib.kExprLexCmpGreaterOrEqual)] = 'GreaterOrEqual',
-    [tonumber(lib.kExprLexCmpIdentical)] = 'Identical',
-  }
-
-  ccs_tab = {
-    [tonumber(lib.kCCStrategyUseOption)] = 'UseOption',
-    [tonumber(lib.kCCStrategyMatchCase)] = 'MatchCase',
-    [tonumber(lib.kCCStrategyIgnoreCase)] = 'IgnoreCase',
-  }
-
   eltkn_mul_type_tab = {
     [tonumber(lib.kExprLexMulMul)] = 'Mul',
     [tonumber(lib.kExprLexMulDiv)] = 'Div',
@@ -101,8 +88,8 @@ local function eltkn2lua(pstate, tkn)
   end
   if ret.type == 'Comparison' then
     ret.data = {
-      type = conv_enum(eltkn_cmp_type_tab, tkn.data.cmp.type),
-      ccs = conv_enum(ccs_tab, tkn.data.cmp.ccs),
+      type = conv_cmp_type(tkn.data.cmp.type),
+      ccs = conv_ccs(tkn.data.cmp.ccs),
       inv = (not not tkn.data.cmp.inv),
     }
   elseif ret.type == 'Multiplication' then
diff --git a/test/unit/viml/expressions/parser_spec.lua b/test/unit/viml/expressions/parser_spec.lua
index 2c80b437dc..efa88455e4 100644
--- a/test/unit/viml/expressions/parser_spec.lua
+++ b/test/unit/viml/expressions/parser_spec.lua
@@ -1,7 +1,7 @@
 local helpers = require('test.unit.helpers')(after_each)
-local viml_helpers = require('test.unit.viml.helpers')
 local global_helpers = require('test.helpers')
 local itp = helpers.gen_itp(it)
+local viml_helpers = require('test.unit.viml.helpers')
 
 local make_enum_conv_tab = helpers.make_enum_conv_tab
 local child_call_once = helpers.child_call_once
@@ -11,9 +11,11 @@ local cimport = helpers.cimport
 local ffi = helpers.ffi
 local eq = helpers.eq
 
+local conv_ccs = viml_helpers.conv_ccs
 local pline2lua = viml_helpers.pline2lua
 local new_pstate = viml_helpers.new_pstate
 local intchar2lua = viml_helpers.intchar2lua
+local conv_cmp_type = viml_helpers.conv_cmp_type
 local pstate_set_str = viml_helpers.pstate_set_str
 
 local format_string = global_helpers.format_string
@@ -83,6 +85,7 @@ make_enum_conv_tab(lib, {
   'kExprNodeComma',
   'kExprNodeColon',
   'kExprNodeArrow',
+  'kExprNodeComparison',
 }, 'kExprNode', function(ret) east_node_type_tab = ret end)
 
 local function conv_east_node_type(typ)
@@ -121,6 +124,10 @@ local function eastnode2lua(pstate, eastnode, checked_nodes)
       (eastnode.data.fig.type_guesses.allow_lambda and '\\' or '-')
       .. (eastnode.data.fig.type_guesses.allow_dict and 'd' or '-')
       .. (eastnode.data.fig.type_guesses.allow_ident and 'i' or '-'))
+  elseif typ == 'Comparison' then
+    typ = typ .. ('(type=%s,inv=%u,ccs=%s)'):format(
+      conv_cmp_type(eastnode.data.cmp.type), eastnode.data.cmp.inv and 1 or 0,
+      conv_ccs(eastnode.data.cmp.ccs))
   end
   ret_str = typ .. ':' .. ret_str
   local can_simplify = true
@@ -150,7 +157,7 @@ end
 local function east2lua(pstate, east)
   local checked_nodes = {}
   return {
-    err = (not east.correct) and {
+    err = east.err.msg ~= nil and {
       msg = ffi.string(east.err.msg),
       arg = ('%s'):format(
         ffi.string(east.err.arg, east.err.arg_len)),
@@ -3328,4 +3335,318 @@ describe('Expressions parser', function()
       hl('Identifier', 'h'),
     })
   end)
+  itp('works with comparison operators', function()
+    check_parsing('a == b', 0, {
+      --           012345
+      ast = {
+        {
+          'Comparison(type=Equal,inv=0,ccs=UseOption):0:1: ==',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:4: b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', '==', 1),
+      hl('Identifier', 'b', 1),
+    })
+
+    check_parsing('a ==? b', 0, {
+      --           0123456
+      ast = {
+        {
+          'Comparison(type=Equal,inv=0,ccs=IgnoreCase):0:1: ==?',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:5: b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', '==', 1),
+      hl('ComparisonOperatorModifier', '?'),
+      hl('Identifier', 'b', 1),
+    })
+
+    check_parsing('a ==# b', 0, {
+      --           0123456
+      ast = {
+        {
+          'Comparison(type=Equal,inv=0,ccs=MatchCase):0:1: ==#',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:5: b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', '==', 1),
+      hl('ComparisonOperatorModifier', '#'),
+      hl('Identifier', 'b', 1),
+    })
+
+    check_parsing('a !=# b', 0, {
+      --           0123456
+      ast = {
+        {
+          'Comparison(type=Equal,inv=1,ccs=MatchCase):0:1: !=#',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:5: b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', '!=', 1),
+      hl('ComparisonOperatorModifier', '#'),
+      hl('Identifier', 'b', 1),
+    })
+
+    check_parsing('a <=# b', 0, {
+      --           0123456
+      ast = {
+        {
+          'Comparison(type=Greater,inv=1,ccs=MatchCase):0:1: <=#',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:5: b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', '<=', 1),
+      hl('ComparisonOperatorModifier', '#'),
+      hl('Identifier', 'b', 1),
+    })
+
+    check_parsing('a >=# b', 0, {
+      --           0123456
+      ast = {
+        {
+          'Comparison(type=GreaterOrEqual,inv=0,ccs=MatchCase):0:1: >=#',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:5: b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', '>=', 1),
+      hl('ComparisonOperatorModifier', '#'),
+      hl('Identifier', 'b', 1),
+    })
+
+    check_parsing('a ># b', 0, {
+      --           012345
+      ast = {
+        {
+          'Comparison(type=Greater,inv=0,ccs=MatchCase):0:1: >#',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:4: b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', '>', 1),
+      hl('ComparisonOperatorModifier', '#'),
+      hl('Identifier', 'b', 1),
+    })
+
+    check_parsing('a <# b', 0, {
+      --           012345
+      ast = {
+        {
+          'Comparison(type=GreaterOrEqual,inv=1,ccs=MatchCase):0:1: <#',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:4: b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', '<', 1),
+      hl('ComparisonOperatorModifier', '#'),
+      hl('Identifier', 'b', 1),
+    })
+
+    check_parsing('a is#b', 0, {
+      --           012345
+      ast = {
+        {
+          'Comparison(type=Identical,inv=0,ccs=MatchCase):0:1: is#',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:5:b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', 'is', 1),
+      hl('ComparisonOperatorModifier', '#'),
+      hl('Identifier', 'b'),
+    })
+
+    check_parsing('a is?b', 0, {
+      --           012345
+      ast = {
+        {
+          'Comparison(type=Identical,inv=0,ccs=IgnoreCase):0:1: is?',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:5:b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', 'is', 1),
+      hl('ComparisonOperatorModifier', '?'),
+      hl('Identifier', 'b'),
+    })
+
+    check_parsing('a isnot b', 0, {
+      --           012345678
+      ast = {
+        {
+          'Comparison(type=Identical,inv=1,ccs=UseOption):0:1: isnot',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            'PlainIdentifier(scope=0,ident=b):0:7: b',
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', 'isnot', 1),
+      hl('Identifier', 'b', 1),
+    })
+
+    check_parsing('a < b < c', 0, {
+      --           012345678
+      ast = {
+        {
+          'Comparison(type=GreaterOrEqual,inv=1,ccs=UseOption):0:1: <',
+          children = {
+            'PlainIdentifier(scope=0,ident=a):0:0:a',
+            {
+              'Comparison(type=GreaterOrEqual,inv=1,ccs=UseOption):0:5: <',
+              children = {
+                'PlainIdentifier(scope=0,ident=b):0:3: b',
+                'PlainIdentifier(scope=0,ident=c):0:7: c',
+              },
+            },
+          },
+        },
+      },
+      err = {
+        arg = ' < c',
+        msg = 'E15: Operator is not associative: %.*s',
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('ComparisonOperator', '<', 1),
+      hl('Identifier', 'b', 1),
+      hl('InvalidComparisonOperator', '<', 1),
+      hl('Identifier', 'c', 1),
+    })
+    check_parsing('a += b', 0, {
+      --           012345
+      ast = {
+        {
+          'Comparison(type=Equal,inv=0,ccs=UseOption):0:3:=',
+          children = {
+            {
+              'BinaryPlus:0:1: +',
+              children = {
+                'PlainIdentifier(scope=0,ident=a):0:0:a',
+                'Missing:0:3:',
+              },
+            },
+            'PlainIdentifier(scope=0,ident=b):0:4: b',
+          },
+        },
+      },
+      err = {
+        arg = '= b',
+        msg = 'E15: Expected == or =~: %.*s',
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('BinaryPlus', '+', 1),
+      hl('InvalidComparisonOperator', '='),
+      hl('Identifier', 'b', 1),
+    })
+    check_parsing('a + b == c + d', 0, {
+      --           01234567890123
+      --           0         1
+      ast = {
+        {
+          'Comparison(type=Equal,inv=0,ccs=UseOption):0:5: ==',
+          children = {
+            {
+              'BinaryPlus:0:1: +',
+              children = {
+                'PlainIdentifier(scope=0,ident=a):0:0:a',
+                'PlainIdentifier(scope=0,ident=b):0:3: b',
+              },
+            },
+            {
+              'BinaryPlus:0:10: +',
+              children = {
+                'PlainIdentifier(scope=0,ident=c):0:8: c',
+                'PlainIdentifier(scope=0,ident=d):0:12: d',
+              },
+            },
+          },
+        },
+      },
+    }, {
+      hl('Identifier', 'a'),
+      hl('BinaryPlus', '+', 1),
+      hl('Identifier', 'b', 1),
+      hl('ComparisonOperator', '==', 1),
+      hl('Identifier', 'c', 1),
+      hl('BinaryPlus', '+', 1),
+      hl('Identifier', 'd', 1),
+    })
+    check_parsing('+ a == + b', 0, {
+      --           0123456789
+      ast = {
+        {
+          'Comparison(type=Equal,inv=0,ccs=UseOption):0:3: ==',
+          children = {
+            {
+              'UnaryPlus:0:0:+',
+              children = {
+                'PlainIdentifier(scope=0,ident=a):0:1: a',
+              },
+            },
+            {
+              'UnaryPlus:0:6: +',
+              children = {
+                'PlainIdentifier(scope=0,ident=b):0:8: b',
+              },
+            },
+          },
+        },
+      },
+    }, {
+      hl('UnaryPlus', '+'),
+      hl('Identifier', 'a', 1),
+      hl('ComparisonOperator', '==', 1),
+      hl('UnaryPlus', '+', 1),
+      hl('Identifier', 'b', 1),
+    })
+  end)
 end)
diff --git a/test/unit/viml/helpers.lua b/test/unit/viml/helpers.lua
index 2cb60499eb..0b92be2654 100644
--- a/test/unit/viml/helpers.lua
+++ b/test/unit/viml/helpers.lua
@@ -1,8 +1,13 @@
 local helpers = require('test.unit.helpers')(nil)
 
 local ffi = helpers.ffi
+local cimport = helpers.cimport
 local kvi_new = helpers.kvi_new
 local kvi_init = helpers.kvi_init
+local conv_enum = helpers.conv_enum
+local make_enum_conv_tab = helpers.make_enum_conv_tab
+
+local lib = cimport('./src/nvim/viml/parser/expressions.h')
 
 local function new_pstate(strings)
   local strings_idx = 0
@@ -88,10 +93,36 @@ local function pstate_set_str(pstate, start, len, ret)
   return ret
 end
 
+local eltkn_cmp_type_tab
+make_enum_conv_tab(lib, {
+  'kExprCmpEqual',
+  'kExprCmpMatches',
+  'kExprCmpGreater',
+  'kExprCmpGreaterOrEqual',
+  'kExprCmpIdentical',
+}, 'kExprCmp', function(ret) eltkn_cmp_type_tab = ret end)
+
+local function conv_cmp_type(typ)
+  return conv_enum(eltkn_cmp_type_tab, typ)
+end
+
+local ccs_tab
+make_enum_conv_tab(lib, {
+  'kCCStrategyUseOption',
+  'kCCStrategyMatchCase',
+  'kCCStrategyIgnoreCase',
+}, 'kCCStrategy', function(ret) ccs_tab = ret end)
+
+local function conv_ccs(ccs)
+  return conv_enum(ccs_tab, ccs)
+end
+
 return {
+  conv_ccs = conv_ccs,
   pline2lua = pline2lua,
   pstate_str = pstate_str,
   new_pstate = new_pstate,
   intchar2lua = intchar2lua,
+  conv_cmp_type = conv_cmp_type,
   pstate_set_str = pstate_set_str,
 }