eval: Add special variables v:false, v:null, v:none

11 files changed, 441 insertions, 116 deletions

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 2d08afff4f..572cf4c03f 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1418,6 +1418,13 @@ v:exception	The value of the exception most recently caught and not
 	:endtry
 <		Output: "caught oops".
 
+					*v:false* *false-variable*
+v:false		Special value used to put "false" in JSON and msgpack.  See 
+		|jsonencode()|.  This value is converted to "false" when used 
+		as a String (e.g. in |expr5| with string concatenation 
+		operator) and to zero when used as a Number (e.g. in |expr5| 
+		or |expr7| when used with numeric operators).
+
 					*v:fcs_reason* *fcs_reason-variable*
 v:fcs_reason	The reason why the |FileChangedShell| event was triggered.
 		Can be used in an autocommand to decide what to do and/or what
@@ -1557,6 +1564,20 @@ v:msgpack_types	Dictionary containing msgpack types used by |msgpackparse()|
 		(not editable) empty lists. To check whether some list is one 
 		of msgpack types, use |is| operator.
 
+					*v:null* *null-variable*
+v:null		Special value used to put "null" in JSON and NIL in msgpack.  
+		See |jsonencode()|.  This value is converted to "null" when 
+		used as a String (e.g. in |expr5| with string concatenation 
+		operator) and to zero when used as a Number (e.g. in |expr5| 
+		or |expr7| when used with numeric operators).
+
+					*v:none* *none-variable*
+v:none		Special value used to put an empty item in JSON.  See 
+		|jsonencode()|.  This value is converted to "none" when used 
+		as a String (e.g. in |expr5| with string concatenation 
+		operator) and to zero when used as a Number (e.g. in |expr5| 
+		or |expr7| when used with numeric operators).
+
 					*v:oldfiles* *oldfiles-variable*
 v:oldfiles	List of file names that is loaded from the |shada| file on
 		startup.  These are the files that Vim remembers marks for.
@@ -1722,6 +1743,13 @@ v:throwpoint	The point where the exception most recently caught and not
 	:endtry
 <		Output: "Exception from test.vim, line 2"
 
+					*v:true* *true-variable*
+v:true		Special value used to put "true" in JSON and msgpack.  See 
+		|jsonencode()|.  This value is converted to "true" when used 
+		as a String (e.g. in |expr5| with string concatenation 
+		operator) and to one when used as a Number (e.g. in |expr5| or 
+		|expr7| when used with numeric operators).
+
 						*v:val* *val-variable*
 v:val		Value of the current item of a |List| or |Dictionary|.	Only
 		valid while evaluating the expression used with |map()| and
@@ -4832,8 +4860,8 @@ msgpackdump({list})				   {Nvim} *msgpackdump()*
 		(dictionary with zero items is represented by 0x80 byte in
 		messagepack).
 
-		Limitations:					*E951* *E952*
-		1. |Funcref|s cannot be dumped.
+		Limitations:				*E951* *E952* *E953*
+		1. |Funcref|s and |v:none| cannot be dumped.
 		2. Containers that reference themselves cannot be dumped.
 		3. Dictionary keys are always dumped as STR strings.
 		4. Other strings are always dumped as BIN strings.
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index c770618ce4..a8082655fd 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -651,6 +651,22 @@ static Object vim_to_object_rec(typval_T *obj, PMap(ptr_t) *lookup)
   }
 
   switch (obj->v_type) {
+    case VAR_SPECIAL:
+      switch (obj->vval.v_special) {
+        case kSpecialVarTrue:
+        case kSpecialVarFalse: {
+          rv.type = kObjectTypeBoolean;
+          rv.data.boolean = (obj->vval.v_special == kSpecialVarTrue);
+          break;
+        }
+        case kSpecialVarNull:
+        case kSpecialVarNone: {
+          rv.type = kObjectTypeNil;
+          break;
+        }
+      }
+      break;
+
     case VAR_STRING:
       rv.type = kObjectTypeString;
       rv.data.string = cstr_to_string((char *) obj->vval.v_string);
@@ -730,6 +746,10 @@ static Object vim_to_object_rec(typval_T *obj, PMap(ptr_t) *lookup)
         }
       }
       break;
+
+    case VAR_UNKNOWN:
+    case VAR_FUNC:
+      break;
   }
 
   return rv;
diff --git a/src/nvim/encode.c b/src/nvim/encode.c
index 6fdbe67ec8..c80e9783e0 100644
--- a/src/nvim/encode.c
+++ b/src/nvim/encode.c
@@ -8,10 +8,12 @@
 
 #include <msgpack.h>
 #include <inttypes.h>
+#include <assert.h>
 
 #include "nvim/encode.h"
 #include "nvim/buffer_defs.h"  // vimconv_T
 #include "nvim/eval.h"
+#include "nvim/eval_defs.h"
 #include "nvim/garray.h"
 #include "nvim/mbyte.h"
 #include "nvim/message.h"
@@ -53,6 +55,13 @@ typedef struct {
 /// Stack used to convert VimL values to messagepack.
 typedef kvec_t(MPConvStackVal) MPConvStack;
 
+const char *const encode_special_var_names[] = {
+  [kSpecialVarNull] = "null",
+  [kSpecialVarNone] = "none",
+  [kSpecialVarTrue] = "true",
+  [kSpecialVarFalse] = "false",
+};
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "encode.c.generated.h"
 #endif
@@ -355,7 +364,7 @@ static int name##_convert_one_value(firstargtype firstargname, \
           break; \
         } \
         case kSpecialVarNone: { \
-          CONV_NONE(); \
+          CONV_NONE_VAL(); \
           break; \
         } \
       } \
@@ -558,8 +567,7 @@ scope int encode_vim_to_##name(firstargtype firstargname, typval_T *const tv, \
                                const char *const objname) \
   FUNC_ATTR_WARN_UNUSED_RESULT \
 { \
-  current_copyID += COPYID_INC; \
-  const int copyID = current_copyID; \
+  const int copyID = get_copyID(); \
   MPConvStack mpstack; \
   kv_init(mpstack); \
   if (name##_convert_one_value(firstargname, &mpstack, tv, copyID, objname) \
@@ -717,13 +725,13 @@ encode_vim_to_##name##_error_ret: \
     ga_concat(gap, "{}")
 
 #define CONV_NIL() \
-    ga_append(gap, "v:null")
+    ga_concat(gap, "v:null")
 
 #define CONV_BOOL(num) \
-    ga_append(gap, ((num)? "v:true": "v:false"))
+    ga_concat(gap, ((num)? "v:true": "v:false"))
 
-#define CONV_NONE() \
-    ga_append(gap, "v:none")
+#define CONV_NONE_VAL() \
+    ga_concat(gap, "v:none")
 
 #define CONV_UNSIGNED_NUMBER(num)
 
@@ -1069,8 +1077,8 @@ static inline bool check_json_key(const typval_T *const tv)
       } \
     } while (0)
 
-#undef CONV_NONE
-#define CONV_NONE()
+#undef CONV_NONE_VAL
+#define CONV_NONE_VAL()
 
 DEFINE_VIML_CONV_FUNCTIONS(static, json, garray_T *const, gap)
 
@@ -1085,7 +1093,7 @@ DEFINE_VIML_CONV_FUNCTIONS(static, json, garray_T *const, gap)
 #undef CONV_EMPTY_DICT
 #undef CONV_NIL
 #undef CONV_BOOL
-#undef CONV_NONE
+#undef CONV_NONE_VAL
 #undef CONV_UNSIGNED_NUMBER
 #undef CONV_DICT_START
 #undef CONV_DICT_END
@@ -1221,7 +1229,7 @@ char *encode_tv2json(typval_T *tv, size_t *len)
 #define CONV_NIL() \
     msgpack_pack_nil(packer)
 
-#define CONV_NONE() \
+#define CONV_NONE_VAL() \
     return conv_error(_("E953: Attempt to convert v:none in %s, %s"), \
                       mpstack, objname)
 
@@ -1272,6 +1280,7 @@ DEFINE_VIML_CONV_FUNCTIONS(, msgpack, msgpack_packer *const, packer)
 #undef CONV_EMPTY_DICT
 #undef CONV_NIL
 #undef CONV_BOOL
+#undef CONV_NONE_VAL
 #undef CONV_UNSIGNED_NUMBER
 #undef CONV_DICT_START
 #undef CONV_DICT_END
diff --git a/src/nvim/encode.h b/src/nvim/encode.h
index 799850aab9..5b81ed84dc 100644
--- a/src/nvim/encode.h
+++ b/src/nvim/encode.h
@@ -51,6 +51,9 @@ static inline ListReaderState encode_init_lrstate(const list_T *const list)
   };
 }
 
+/// Array mapping values from SpecialVarValue enum to names
+extern const char *const encode_special_var_names[];
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "encode.h.generated.h"
 #endif
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 114368d621..819b3059e2 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -178,8 +178,6 @@ static dictitem_T globvars_var;                 /* variable used for g: */
  */
 static hashtab_T compat_hashtab;
 
-int current_copyID = 0;
-
 hashtab_T func_hashtab;
 
 /*
@@ -366,11 +364,16 @@ static struct vimvar {
   { VV_NAME("errors",           VAR_LIST), 0 },
   { VV_NAME("msgpack_types",    VAR_DICT), VV_RO },
   { VV_NAME("event",            VAR_DICT), VV_RO },
+  { VV_NAME("false",            VAR_SPECIAL), VV_RO },
+  { VV_NAME("true",             VAR_SPECIAL), VV_RO },
+  { VV_NAME("null",             VAR_SPECIAL), VV_RO },
+  { VV_NAME("none",             VAR_SPECIAL), VV_RO },
 };
 
 /* shorthand */
 #define vv_type         vv_di.di_tv.v_type
 #define vv_nr           vv_di.di_tv.vval.v_number
+#define vv_special      vv_di.di_tv.vval.v_special
 #define vv_float        vv_di.di_tv.vval.v_float
 #define vv_str          vv_di.di_tv.vval.v_string
 #define vv_list         vv_di.di_tv.vval.v_list
@@ -506,7 +509,13 @@ void eval_init(void)
   set_vim_var_list(VV_ERRORS, list_alloc());
   set_vim_var_nr(VV_SEARCHFORWARD, 1L);
   set_vim_var_nr(VV_HLSEARCH, 1L);
-  set_reg_var(0);    /* default for v:register is not 0 but '"' */
+
+  set_vim_var_special(VV_FALSE, kSpecialVarFalse);
+  set_vim_var_special(VV_TRUE, kSpecialVarTrue);
+  set_vim_var_special(VV_NONE, kSpecialVarNone);
+  set_vim_var_special(VV_NULL, kSpecialVarNull);
+
+  set_reg_var(0);  // default for v:register is not 0 but '"'
 }
 
 #if defined(EXITFREE)
@@ -2368,11 +2377,12 @@ static int tv_op(typval_T *tv1, typval_T *tv2, char_u *op)
   char_u numbuf[NUMBUFLEN];
   char_u      *s;
 
-  /* Can't do anything with a Funcref or a Dict on the right. */
+  // Can't do anything with a Funcref, a Dict or special value on the right.
   if (tv2->v_type != VAR_FUNC && tv2->v_type != VAR_DICT) {
     switch (tv1->v_type) {
     case VAR_DICT:
     case VAR_FUNC:
+    case VAR_SPECIAL:
       break;
 
     case VAR_LIST:
@@ -2440,6 +2450,9 @@ static int tv_op(typval_T *tv1, typval_T *tv2, char_u *op)
         tv1->vval.v_float -= f;
     }
       return OK;
+
+    case VAR_UNKNOWN:
+      assert(false);
     }
   }
 
@@ -3077,6 +3090,15 @@ static void item_lock(typval_T *tv, int deep, int lock)
         }
       }
     }
+    break;
+  case VAR_NUMBER:
+  case VAR_FLOAT:
+  case VAR_STRING:
+  case VAR_FUNC:
+  case VAR_SPECIAL:
+    break;
+  case VAR_UNKNOWN:
+    assert(false);
   }
   --recurse;
 }
@@ -4306,6 +4328,11 @@ eval_index (
     if (verbose)
       EMSG(_(e_float_as_string));
     return FAIL;
+  } else if (rettv->v_type == VAR_SPECIAL) {
+    if (verbose) {
+      EMSG(_("E15: Cannot index a special value"));
+    }
+    return FAIL;
   }
 
   init_tv(&var1);
@@ -4496,6 +4523,11 @@ eval_index (
         *rettv = var1;
       }
       break;
+    case VAR_FUNC:
+    case VAR_FLOAT:
+    case VAR_UNKNOWN:
+    case VAR_SPECIAL:
+      assert(false);
     }
   }
 
@@ -5040,6 +5072,12 @@ tv_equal (
     s1 = get_tv_string_buf(tv1, buf1);
     s2 = get_tv_string_buf(tv2, buf2);
     return (ic ? mb_stricmp(s1, s2) : STRCMP(s1, s2)) == 0;
+
+  case VAR_SPECIAL:
+    return tv1->vval.v_special == tv2->vval.v_special;
+
+  case VAR_UNKNOWN:
+    break;
   }
 
   EMSG2(_(e_intern2), "tv_equal()");
@@ -5505,6 +5543,22 @@ static int list_join(garray_T *const gap, list_T *const l,
   return retval;
 }
 
+/// Get next (unique) copy ID
+///
+/// Used for traversing nested structures e.g. when serializing them or garbage
+/// collecting.
+int get_copyID(void)
+  FUNC_ATTR_WARN_UNUSED_RESULT
+{
+  // CopyID for recursively traversing lists and dicts
+  //
+  // This value is needed to avoid endless recursiveness. Last bit is used for
+  // previous_funccal and normally ignored when comparing.
+  static int current_copyID = 0;
+  current_copyID += COPYID_INC;
+  return current_copyID;
+}
+
 /*
  * Garbage collection for lists and dictionaries.
  *
@@ -5540,8 +5594,7 @@ bool garbage_collect(void)
 
   // We advance by two because we add one for items referenced through
   // previous_funccal.
-  current_copyID += COPYID_INC;
-  int copyID = current_copyID;
+  const int copyID = get_copyID();
 
   // 1. Go through all accessible variables and mark all lists and dicts
   // with copyID.
@@ -5886,6 +5939,15 @@ bool set_ref_in_item(typval_T *tv, int copyID, ht_stack_T **ht_stack,
       }
       break;
     }
+
+    case VAR_FUNC:
+    case VAR_UNKNOWN:
+    case VAR_SPECIAL:
+    case VAR_FLOAT:
+    case VAR_NUMBER:
+    case VAR_STRING: {
+      break;
+    }
   }
   return abort;
 }
@@ -8260,9 +8322,8 @@ static void f_deepcopy(typval_T *argvars, typval_T *rettv)
   if (noref < 0 || noref > 1)
     EMSG(_(e_invarg));
   else {
-    current_copyID += COPYID_INC;
     var_item_copy(NULL, &argvars[0], rettv, true, (noref == 0
-                                                   ? current_copyID
+                                                   ? get_copyID()
                                                    : 0));
   }
 }
@@ -8477,7 +8538,7 @@ static void f_empty(typval_T *argvars, typval_T *rettv)
   case VAR_SPECIAL:
     n = argvars[0].vval.v_special != kSpecialVarTrue;
     break;
-  default:
+  case VAR_UNKNOWN:
     EMSG2(_(e_intern2), "f_empty()");
     n = 0;
   }
@@ -16386,13 +16447,28 @@ static void f_type(typval_T *argvars, typval_T *rettv)
   int n;
 
   switch (argvars[0].v_type) {
-  case VAR_NUMBER: n = 0; break;
-  case VAR_STRING: n = 1; break;
-  case VAR_FUNC:   n = 2; break;
-  case VAR_LIST:   n = 3; break;
-  case VAR_DICT:   n = 4; break;
-  case VAR_FLOAT:  n = 5; break;
-  default: EMSG2(_(e_intern2), "f_type()"); n = 0; break;
+    case VAR_NUMBER: n = 0; break;
+    case VAR_STRING: n = 1; break;
+    case VAR_FUNC:   n = 2; break;
+    case VAR_LIST:   n = 3; break;
+    case VAR_DICT:   n = 4; break;
+    case VAR_FLOAT:  n = 5; break;
+    case VAR_SPECIAL: {
+      switch (argvars[0].vval.v_special) {
+        case kSpecialVarTrue:
+        case kSpecialVarFalse: {
+          n = 6;
+          break;
+        }
+        case kSpecialVarNone:
+        case kSpecialVarNull: {
+          n = 7;
+          break;
+        }
+      }
+      break;
+    }
+    case VAR_UNKNOWN: EMSG2(_(e_intern2), "f_type()"); n = 0; break;
   }
   rettv->vval.v_number = n;
 }
@@ -17226,6 +17302,12 @@ void set_vim_var_nr(int idx, long val)
   vimvars[idx].vv_nr = val;
 }
 
+/// Set special v: variable to "val"
+void set_vim_var_special(const int idx, const SpecialVarValue val)
+{
+  vimvars[idx].vv_special = val;
+}
+
 /*
  * Get number v: variable value.
  */
@@ -17574,7 +17656,7 @@ handle_subscript (
 void free_tv(typval_T *varp)
 {
   if (varp != NULL) {
-    switch ((VarType) varp->v_type) {
+    switch (varp->v_type) {
       case VAR_FUNC:
         func_unref(varp->vval.v_string);
         /*FALLTHROUGH*/
@@ -17592,9 +17674,6 @@ void free_tv(typval_T *varp)
       case VAR_FLOAT:
       case VAR_UNKNOWN:
         break;
-      default:
-        EMSG2(_(e_intern2), "free_tv()");
-        break;
     }
     xfree(varp);
   }
@@ -17632,10 +17711,11 @@ void clear_tv(typval_T *varp)
     case VAR_FLOAT:
       varp->vval.v_float = 0.0;
       break;
+    case VAR_SPECIAL:
+      varp->vval.v_special = kSpecialVarFalse;
+      break;
     case VAR_UNKNOWN:
       break;
-    default:
-      EMSG2(_(e_intern2), "clear_tv()");
     }
     varp->v_lock = 0;
   }
@@ -17690,7 +17770,19 @@ long get_tv_number_chk(typval_T *varp, int *denote)
   case VAR_DICT:
     EMSG(_("E728: Using a Dictionary as a Number"));
     break;
-  default:
+  case VAR_SPECIAL:
+    switch (varp->vval.v_special) {
+      case kSpecialVarTrue: {
+        return 1;
+      }
+      case kSpecialVarFalse:
+      case kSpecialVarNone:
+      case kSpecialVarNull: {
+        return 0;
+      }
+    }
+    break;
+  case VAR_UNKNOWN:
     EMSG2(_(e_intern2), "get_tv_number()");
     break;
   }
@@ -17796,7 +17888,10 @@ static char_u *get_tv_string_buf_chk(const typval_T *varp, char_u *buf)
     if (varp->vval.v_string != NULL)
       return varp->vval.v_string;
     return (char_u *)"";
-  default:
+  case VAR_SPECIAL:
+    STRCPY(buf, encode_special_var_names[varp->vval.v_special]);
+    return buf;
+  case VAR_UNKNOWN:
     EMSG2(_(e_intern2), "get_tv_string_buf()");
     break;
   }
@@ -18345,42 +18440,34 @@ void copy_tv(typval_T *from, typval_T *to)
 {
   to->v_type = from->v_type;
   to->v_lock = 0;
+  memmove(&to->vval, &from->vval, sizeof(to->vval));
   switch (from->v_type) {
-  case VAR_NUMBER:
-    to->vval.v_number = from->vval.v_number;
-    break;
-  case VAR_FLOAT:
-    to->vval.v_float = from->vval.v_float;
-    break;
-  case VAR_STRING:
-  case VAR_FUNC:
-    if (from->vval.v_string == NULL)
-      to->vval.v_string = NULL;
-    else {
-      to->vval.v_string = vim_strsave(from->vval.v_string);
-      if (from->v_type == VAR_FUNC)
-        func_ref(to->vval.v_string);
-    }
-    break;
-  case VAR_LIST:
-    if (from->vval.v_list == NULL)
-      to->vval.v_list = NULL;
-    else {
-      to->vval.v_list = from->vval.v_list;
-      ++to->vval.v_list->lv_refcount;
-    }
-    break;
-  case VAR_DICT:
-    if (from->vval.v_dict == NULL)
-      to->vval.v_dict = NULL;
-    else {
-      to->vval.v_dict = from->vval.v_dict;
-      ++to->vval.v_dict->dv_refcount;
-    }
-    break;
-  default:
-    EMSG2(_(e_intern2), "copy_tv()");
-    break;
+    case VAR_NUMBER:
+    case VAR_FLOAT:
+    case VAR_SPECIAL:
+      break;
+    case VAR_STRING:
+    case VAR_FUNC:
+      if (from->vval.v_string != NULL) {
+        to->vval.v_string = vim_strsave(from->vval.v_string);
+        if (from->v_type == VAR_FUNC) {
+          func_ref(to->vval.v_string);
+        }
+      }
+      break;
+    case VAR_LIST:
+      if (from->vval.v_list != NULL) {
+        to->vval.v_list->lv_refcount++;
+      }
+      break;
+    case VAR_DICT:
+      if (from->vval.v_dict != NULL) {
+        to->vval.v_dict->dv_refcount++;
+      }
+      break;
+    case VAR_UNKNOWN:
+      EMSG2(_(e_intern2), "copy_tv()");
+      break;
   }
 }
 
@@ -18420,6 +18507,7 @@ int var_item_copy(const vimconv_T *const conv,
   case VAR_NUMBER:
   case VAR_FLOAT:
   case VAR_FUNC:
+  case VAR_SPECIAL:
     copy_tv(from, to);
     break;
   case VAR_STRING:
@@ -18466,7 +18554,7 @@ int var_item_copy(const vimconv_T *const conv,
     if (to->vval.v_dict == NULL)
       ret = FAIL;
     break;
-  default:
+  case VAR_UNKNOWN:
     EMSG2(_(e_intern2), "var_item_copy()");
     ret = FAIL;
   }
@@ -21705,4 +21793,3 @@ static bool is_watched(dict_T *d)
 {
   return d && !QUEUE_EMPTY(&d->watchers);
 }
-
diff --git a/src/nvim/eval.h b/src/nvim/eval.h
index e8b5964775..89aa263434 100644
--- a/src/nvim/eval.h
+++ b/src/nvim/eval.h
@@ -15,12 +15,6 @@
 // All user-defined functions are found in this hashtable.
 extern hashtab_T func_hashtab;
 
-/// CopyID for recursively traversing lists and dicts
-///
-/// This value is needed to avoid endless recursiveness. Last bit is used for
-/// previous_funccal and normally ignored when comparing.
-extern int current_copyID;
-
 // Structure to hold info for a user function.
 typedef struct ufunc ufunc_T;
 
@@ -127,7 +121,11 @@ enum {
     VV_ERRORS,
     VV_MSGPACK_TYPES,
     VV_EVENT,
-    VV_LEN,  // number of v: vars
+    VV_FALSE,
+    VV_TRUE,
+    VV_NULL,
+    VV_NONE,
+    VV_LEN,  ///< Number of v: variables
 };
 
 /// All recognized msgpack types
diff --git a/src/nvim/eval_defs.h b/src/nvim/eval_defs.h
index 56833f97d8..bcd9e80f9a 100644
--- a/src/nvim/eval_defs.h
+++ b/src/nvim/eval_defs.h
@@ -18,12 +18,32 @@ typedef struct dictvar_S dict_T;
 
 /// Special variable values
 typedef enum {
-  kSpecialVarNull,   ///< v:null
-  kSpecialVarNone,   ///< v:none
   kSpecialVarFalse,  ///< v:false
   kSpecialVarTrue,   ///< v:true
+  kSpecialVarNone,   ///< v:none
+  kSpecialVarNull,   ///< v:null
 } SpecialVarValue;
 
+/// Variable lock status for typval_T.v_lock
+typedef enum {
+  VAR_UNLOCKED = 0,  ///< Not locked.
+  VAR_LOCKED,        ///< User lock, can be unlocked.
+  VAR_FIXED,         ///< Locked forever.
+} VarLockStatus;
+
+/// VimL variable types, for use in typval_T.v_type
+typedef enum {
+  VAR_UNKNOWN = 0,  ///< Unknown (unspecified) value.
+  VAR_NUMBER,       ///< Number, .v_number is used.
+  VAR_STRING,       ///< String, .v_string is used.
+  VAR_FUNC,         ///< Function referene, .v_string is used for function name.
+  VAR_LIST,         ///< List, .v_list is used.
+  VAR_DICT,         ///< Dictionary, .v_dict is used.
+  VAR_FLOAT,        ///< Floating-point value, .v_float is used.
+  VAR_SPECIAL,      ///< Special value (true, false, null, none), .v_special
+                    ///< is used.
+} VarType;
+
 /// Structure that holds an internal variable value
 typedef struct {
   VarType v_type;  ///< Variable type.
@@ -38,34 +58,11 @@ typedef struct {
   }           vval;  ///< Actual value.
 } typval_T;
 
-/// VimL variable types, for use in typval_T.v_type
-///
-/// @warning Numbers are part of the user API (returned by type()), so they must
-/// not be changed.
-typedef enum {
-  VAR_UNKNOWN = 0,  ///< Unknown (unspecified) value.
-  VAR_NUMBER = 1,   ///< Number, .v_number is used.
-  VAR_STRING = 2,   ///< String, .v_string is used.
-  VAR_FUNC = 3,     ///< Function referene, .v_string is used for function name.
-  VAR_LIST = 4,     ///< List, .v_list is used.
-  VAR_DICT = 5,     ///< Dictionary, .v_dict is used.
-  VAR_FLOAT = 6,    ///< Floating-point value, .v_float is used.
-  VAR_SPECIAL = 7,  ///< Special value (true, false, null, none), .v_special
-                    ///< is used.
-} VarType;
-
 /* Values for "dv_scope". */
 #define VAR_SCOPE     1 /* a:, v:, s:, etc. scope dictionaries */
 #define VAR_DEF_SCOPE 2 /* l:, g: scope dictionaries: here funcrefs are not
                            allowed to mask existing functions */
 
-/// Variable lock status for typval_T.v_lock
-typedef enum {
-  VAR_UNLOCKED = 0,  ///< Not locked.
-  VAR_LOCKED,        ///< User lock, can be unlocked.
-  VAR_FIXED,         ///< Locked forever.
-} VarLockStatus;
-
 /*
  * Structure to hold an item of a list: an internal variable without a name.
  */
diff --git a/src/nvim/version.c b/src/nvim/version.c
index 8f45620570..9ccd53f76b 100644
--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -195,18 +195,18 @@ static int included_patches[] = {
   // 1170 NA
   // 1169 NA
   1168,
-  // 1167,
-  // 1166,
+  1167,
+  1166,
   // 1165 NA
-  // 1164,
-  // 1163,
+  1164,
+  1163,
   // 1162 NA
   // 1161,
-  // 1160,
+  1160,
   // 1159 NA
   // 1158 NA
-  // 1157,
-  // 1156,
+  1157,
+  // 1156 NA
   // 1155 NA
   // 1154,
   // 1153,
diff --git a/test/functional/eval/msgpack_functions_spec.lua b/test/functional/eval/msgpack_functions_spec.lua
index fc0aad7902..0c91471656 100644
--- a/test/functional/eval/msgpack_functions_spec.lua
+++ b/test/functional/eval/msgpack_functions_spec.lua
@@ -1,5 +1,6 @@
 local helpers = require('test.functional.helpers')
 local clear = helpers.clear
+local funcs = helpers.funcs
 local eval, eq = helpers.eval, helpers.eq
 local execute = helpers.execute
 local nvim = helpers.nvim
@@ -517,6 +518,19 @@ describe('msgpackdump() function', function()
     eq({'\129\128\128'}, eval('msgpackdump([todump])'))
   end)
 
+  it('can dump v:true', function()
+    eq({'\195'}, funcs.msgpackdump({true}))
+  end)
+
+  it('can dump v:false', function()
+    eq({'\194'}, funcs.msgpackdump({false}))
+  end)
+
+  it('can v:null', function()
+    execute('let todump = v:null')
+    eq({'\192'}, eval('msgpackdump([todump])'))
+  end)
+
   it('can dump special ext mapping', function()
     execute('let todump = {"_TYPE": v:msgpack_types.ext, "_VAL": [5, ["",""]]}')
     eq({'\212\005', ''}, eval('msgpackdump([todump])'))
@@ -620,6 +634,11 @@ describe('msgpackdump() function', function()
        exc_exec('call msgpackdump([todump])'))
   end)
 
+  it('fails to dump v:none', function()
+    eq('Vim(call):E953: Attempt to convert v:none in msgpackdump() argument, index 0, itself',
+       exc_exec('call msgpackdump([v:none])'))
+  end)
+
   it('fails when called with no arguments', function()
     eq('Vim(call):E119: Not enough arguments for function: msgpackdump',
        exc_exec('call msgpackdump()'))
@@ -654,4 +673,11 @@ describe('msgpackdump() function', function()
     eq('Vim(call):E686: Argument of msgpackdump() must be a List',
        exc_exec('call msgpackdump(0.0)'))
   end)
+
+  it('fails to dump special value', function()
+    for _, val in ipairs({'v:true', 'v:false', 'v:null', 'v:none'}) do
+      eq('Vim(call):E686: Argument of msgpackdump() must be a List',
+        exc_exec('call msgpackdump(' .. val .. ')'))
+    end
+  end)
 end)
diff --git a/test/functional/eval/special_vars_spec.lua b/test/functional/eval/special_vars_spec.lua
index 7adc529c88..c7df847946 100644
--- a/test/functional/eval/special_vars_spec.lua
+++ b/test/functional/eval/special_vars_spec.lua
@@ -1,8 +1,12 @@
 local helpers = require('test.functional.helpers')
+local exc_exec = helpers.exc_exec
 local execute = helpers.execute
+local meths = helpers.meths
 local funcs = helpers.funcs
+local meths = helpers.meths
 local clear = helpers.clear
 local eval = helpers.eval
+local eq = helpers.eq
 
 describe('Special values', function()
   before_each(clear)
@@ -17,20 +21,166 @@ describe('Special values', function()
         endtry
       endfunction
     ]])
-    eq(true, funcs.Test())
+    eq(0, exc_exec('call Test()'))
   end)
 
   it('work with empty()', function()
     eq(0, funcs.empty(true))
     eq(1, funcs.empty(false))
-    eq(1, funcs.empty(nil))
+    eq(1, eval('empty(v:null)'))
     eq(1, eval('empty(v:none)'))
   end)
 
   it('can be stringified and eval’ed back', function()
     eq(true, funcs.eval(funcs.string(true)))
     eq(false, funcs.eval(funcs.string(false)))
-    eq(nil, funcs.eval(funcs.string(nil)))
+    eq(nil, eval('eval(string(v:null))'))
     eq(1, eval('eval(string(v:none)) is# v:none'))
   end)
+
+  it('work with is/isnot properly', function()
+    eq(1, eval('v:none is v:none'))
+    eq(0, eval('v:none is v:null'))
+    eq(0, eval('v:none is v:true'))
+    eq(0, eval('v:none is v:false'))
+    eq(1, eval('v:null is v:null'))
+    eq(0, eval('v:null is v:true'))
+    eq(0, eval('v:null is v:false'))
+    eq(1, eval('v:true is v:true'))
+    eq(0, eval('v:true is v:false'))
+    eq(1, eval('v:false is v:false'))
+
+    eq(0, eval('v:none  is 0'))
+    eq(0, eval('v:null  is 0'))
+    eq(0, eval('v:true  is 0'))
+    eq(0, eval('v:false is 0'))
+
+    eq(0, eval('v:none  is 1'))
+    eq(0, eval('v:null  is 1'))
+    eq(0, eval('v:true  is 1'))
+    eq(0, eval('v:false is 1'))
+
+    eq(0, eval('v:none  is ""'))
+    eq(0, eval('v:null  is ""'))
+    eq(0, eval('v:true  is ""'))
+    eq(0, eval('v:false is ""'))
+
+    eq(0, eval('v:none  is "none"'))
+    eq(0, eval('v:null  is "null"'))
+    eq(0, eval('v:true  is "true"'))
+    eq(0, eval('v:false is "false"'))
+
+    eq(0, eval('v:none  is []'))
+    eq(0, eval('v:null  is []'))
+    eq(0, eval('v:true  is []'))
+    eq(0, eval('v:false is []'))
+
+    eq(0, eval('v:none isnot v:none'))
+    eq(1, eval('v:none isnot v:null'))
+    eq(1, eval('v:none isnot v:true'))
+    eq(1, eval('v:none isnot v:false'))
+    eq(0, eval('v:null isnot v:null'))
+    eq(1, eval('v:null isnot v:true'))
+    eq(1, eval('v:null isnot v:false'))
+    eq(0, eval('v:true isnot v:true'))
+    eq(1, eval('v:true isnot v:false'))
+    eq(0, eval('v:false isnot v:false'))
+
+    eq(1, eval('v:none  isnot 0'))
+    eq(1, eval('v:null  isnot 0'))
+    eq(1, eval('v:true  isnot 0'))
+    eq(1, eval('v:false isnot 0'))
+
+    eq(1, eval('v:none  isnot 1'))
+    eq(1, eval('v:null  isnot 1'))
+    eq(1, eval('v:true  isnot 1'))
+    eq(1, eval('v:false isnot 1'))
+
+    eq(1, eval('v:none  isnot ""'))
+    eq(1, eval('v:null  isnot ""'))
+    eq(1, eval('v:true  isnot ""'))
+    eq(1, eval('v:false isnot ""'))
+
+    eq(1, eval('v:none  isnot "none"'))
+    eq(1, eval('v:null  isnot "null"'))
+    eq(1, eval('v:true  isnot "true"'))
+    eq(1, eval('v:false isnot "false"'))
+
+    eq(1, eval('v:none  isnot []'))
+    eq(1, eval('v:null  isnot []'))
+    eq(1, eval('v:true  isnot []'))
+    eq(1, eval('v:false isnot []'))
+  end)
+
+  it('work with +/-/* properly', function()
+    eq(1, eval('0 + v:true'))
+    eq(0, eval('0 + v:none'))
+    eq(0, eval('0 + v:null'))
+    eq(0, eval('0 + v:false'))
+
+    eq(-1, eval('0 - v:true'))
+    eq( 0, eval('0 - v:none'))
+    eq( 0, eval('0 - v:null'))
+    eq( 0, eval('0 - v:false'))
+
+    eq(1, eval('1 * v:true'))
+    eq(0, eval('1 * v:none'))
+    eq(0, eval('1 * v:null'))
+    eq(0, eval('1 * v:false'))
+  end)
+
+  it('does not work with +=/-=/.=', function()
+    meths.set_var('true', true)
+    meths.set_var('false', false)
+    execute('let none = v:none')
+    execute('let null = v:null')
+
+    eq('Vim(let):E734: Wrong variable type for +=', exc_exec('let true  += 1'))
+    eq('Vim(let):E734: Wrong variable type for +=', exc_exec('let false += 1'))
+    eq('Vim(let):E734: Wrong variable type for +=', exc_exec('let none  += 1'))
+    eq('Vim(let):E734: Wrong variable type for +=', exc_exec('let null  += 1'))
+
+    eq('Vim(let):E734: Wrong variable type for -=', exc_exec('let true  -= 1'))
+    eq('Vim(let):E734: Wrong variable type for -=', exc_exec('let false -= 1'))
+    eq('Vim(let):E734: Wrong variable type for -=', exc_exec('let none  -= 1'))
+    eq('Vim(let):E734: Wrong variable type for -=', exc_exec('let null  -= 1'))
+
+    eq('Vim(let):E734: Wrong variable type for .=', exc_exec('let true  .= 1'))
+    eq('Vim(let):E734: Wrong variable type for .=', exc_exec('let false .= 1'))
+    eq('Vim(let):E734: Wrong variable type for .=', exc_exec('let none  .= 1'))
+    eq('Vim(let):E734: Wrong variable type for .=', exc_exec('let null  .= 1'))
+  end)
+
+  it('work with . (concat) properly', function()
+    eq("true", eval('"" . v:true'))
+    eq("none", eval('"" . v:none'))
+    eq("null", eval('"" . v:null'))
+    eq("false", eval('"" . v:false'))
+  end)
+
+  it('work with type()', function()
+    eq(6, funcs.type(true))
+    eq(6, funcs.type(false))
+    eq(7, eval('type(v:null)'))
+    eq(7, eval('type(v:none)'))
+  end)
+
+  it('work with copy() and deepcopy()', function()
+    eq(true, funcs.deepcopy(true))
+    eq(false, funcs.deepcopy(false))
+    eq(nil, eval('deepcopy(v:null)'))
+    eq(nil, eval('deepcopy(v:none)'))
+
+    eq(true, funcs.copy(true))
+    eq(false, funcs.copy(false))
+    eq(nil, eval('copy(v:null)'))
+    eq(nil, eval('copy(v:none)'))
+  end)
+
+  it('fails in index', function()
+    eq('Vim(echo):E15: Cannot index a special value', exc_exec('echo v:true[0]'))
+    eq('Vim(echo):E15: Cannot index a special value', exc_exec('echo v:false[0]'))
+    eq('Vim(echo):E15: Cannot index a special value', exc_exec('echo v:none[0]'))
+    eq('Vim(echo):E15: Cannot index a special value', exc_exec('echo v:null[0]'))
+  end)
 end)
diff --git a/test/functional/eval/string_spec.lua b/test/functional/eval/string_spec.lua
index f7f5dca70a..fe79708910 100644
--- a/test/functional/eval/string_spec.lua
+++ b/test/functional/eval/string_spec.lua
@@ -28,6 +28,13 @@ describe('string() function', function()
       eq('0.0', eval('string(0.0)'))
     end)
 
+    it('dumps special v: values', function()
+      eq('v:true', eval('string(v:true)'))
+      eq('v:false', eval('string(v:false)'))
+      eq('v:none', eval('string(v:none)'))
+      eq('v:null', eval('string(v:null)'))
+    end)
+
     it('dumps values with at most six digits after the decimal point',
     function()
       eq('1.234568e-20', funcs.string(1.23456789123456789123456789e-020))