patch 8.2.0350: Vim9: expression tests don't use recognized constants

Problem:    Vim9: expression tests don't use recognized constants.
Solution:   Recognize "true" and "false" as constants.  Make skipping work for
            assignment and expression evaluation.

diff --git a/src/version.c b/src/version.c
index 9c5fca8b2f0ba3bd3b26540ba759d2efc5a0200b..c0e1b914615e645d8613d45b1ac9e11fe9834113 100644 (file)
--- a/src/version.c
+++ b/src/version.c
@@ -738,6 +738,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    350,
 /**/
     349,
 /**/

diff --git a/src/vim9compile.c b/src/vim9compile.c
index 1f61566ab1b7200c0a2d70fe700f0d0ce8b16ec4..c9f72f52b320d7a2b254c69a1c82a07c9ee85df2 100644 (file)
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -260,6 +260,9 @@ get_dict_type(type_T *member_type, garray_T *type_list)
 /////////////////////////////////////////////////////////////////////
 // Following generate_ functions expect the caller to call ga_grow().
 
+#define RETURN_NULL_IF_SKIP(cctx) if (cctx->ctx_skip == TRUE) return NULL
+#define RETURN_OK_IF_SKIP(cctx) if (cctx->ctx_skip == TRUE) return OK
+
 /*
  * Generate an instruction without arguments.
  * Returns a pointer to the new instruction, NULL if failed.
@@ -270,6 +273,7 @@ generate_instr(cctx_T *cctx, isntype_T isn_type)
     garray_T   *instr = &cctx->ctx_instr;
     isn_T      *isn;
 
+    RETURN_NULL_IF_SKIP(cctx);
     if (ga_grow(instr, 1) == FAIL)
        return NULL;
     isn = ((isn_T *)instr->ga_data) + instr->ga_len;
@@ -290,6 +294,7 @@ generate_instr_drop(cctx_T *cctx, isntype_T isn_type, int drop)
 {
     garray_T   *stack = &cctx->ctx_type_stack;
 
+    RETURN_NULL_IF_SKIP(cctx);
     stack->ga_len -= drop;
     return generate_instr(cctx, isn_type);
 }
@@ -364,6 +369,8 @@ generate_two_op(cctx_T *cctx, char_u *op)
     vartype_T  vartype;
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
+
     // Get the known type of the two items on the stack.  If they are matching
     // use a type-specific instruction. Otherwise fall back to runtime type
     // checking.
@@ -461,6 +468,8 @@ generate_COMPARE(cctx_T *cctx, exptype_T exptype, int ic)
     vartype_T  type1;
     vartype_T  type2;
 
+    RETURN_OK_IF_SKIP(cctx);
+
     // Get the known type of the two items on the stack.  If they are matching
     // use a type-specific instruction. Otherwise fall back to runtime type
     // checking.
@@ -536,6 +545,7 @@ generate_2BOOL(cctx_T *cctx, int invert)
     isn_T      *isn;
     garray_T   *stack = &cctx->ctx_type_stack;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_2BOOL)) == NULL)
        return FAIL;
     isn->isn_arg.number = invert;
@@ -552,6 +562,7 @@ generate_TYPECHECK(cctx_T *cctx, type_T *vartype, int offset)
     isn_T      *isn;
     garray_T   *stack = &cctx->ctx_type_stack;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_CHECKTYPE)) == NULL)
        return FAIL;
     isn->isn_arg.type.ct_type = vartype->tt_type;  // TODO: whole type
@@ -571,6 +582,7 @@ generate_PUSHNR(cctx_T *cctx, varnumber_T number)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHNR, &t_number)) == NULL)
        return FAIL;
     isn->isn_arg.number = number;
@@ -586,6 +598,7 @@ generate_PUSHBOOL(cctx_T *cctx, varnumber_T number)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHBOOL, &t_bool)) == NULL)
        return FAIL;
     isn->isn_arg.number = number;
@@ -601,6 +614,7 @@ generate_PUSHSPEC(cctx_T *cctx, varnumber_T number)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHSPEC, &t_special)) == NULL)
        return FAIL;
     isn->isn_arg.number = number;
@@ -617,6 +631,7 @@ generate_PUSHF(cctx_T *cctx, float_T fnumber)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHF, &t_float)) == NULL)
        return FAIL;
     isn->isn_arg.fnumber = fnumber;
@@ -634,6 +649,7 @@ generate_PUSHS(cctx_T *cctx, char_u *str)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHS, &t_string)) == NULL)
        return FAIL;
     isn->isn_arg.string = str;
@@ -650,6 +666,7 @@ generate_PUSHCHANNEL(cctx_T *cctx, channel_T *channel)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHCHANNEL, &t_channel)) == NULL)
        return FAIL;
     isn->isn_arg.channel = channel;
@@ -666,6 +683,7 @@ generate_PUSHJOB(cctx_T *cctx, job_T *job)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHJOB, &t_channel)) == NULL)
        return FAIL;
     isn->isn_arg.job = job;
@@ -682,6 +700,7 @@ generate_PUSHBLOB(cctx_T *cctx, blob_T *blob)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHBLOB, &t_blob)) == NULL)
        return FAIL;
     isn->isn_arg.blob = blob;
@@ -698,6 +717,7 @@ generate_PUSHFUNC(cctx_T *cctx, char_u *name)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHFUNC, &t_func_void)) == NULL)
        return FAIL;
     isn->isn_arg.string = name;
@@ -714,6 +734,7 @@ generate_PUSHPARTIAL(cctx_T *cctx, partial_T *part)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, ISN_PUSHPARTIAL,
                                                      &t_partial_any)) == NULL)
        return FAIL;
@@ -730,6 +751,7 @@ generate_STORE(cctx_T *cctx, isntype_T isn_type, int idx, char_u *name)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_drop(cctx, isn_type, 1)) == NULL)
        return FAIL;
     if (name != NULL)
@@ -748,6 +770,7 @@ generate_STORENR(cctx_T *cctx, int idx, varnumber_T value)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_STORENR)) == NULL)
        return FAIL;
     isn->isn_arg.storenr.str_idx = idx;
@@ -764,6 +787,7 @@ generate_STOREOPT(cctx_T *cctx, char_u *name, int opt_flags)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_STOREOPT)) == NULL)
        return FAIL;
     isn->isn_arg.storeopt.so_name = vim_strsave(name);
@@ -785,6 +809,7 @@ generate_LOAD(
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_type(cctx, isn_type, type)) == NULL)
        return FAIL;
     if (name != NULL)
@@ -807,6 +832,7 @@ generate_LOADV(
     // load v:var
     int vidx = find_vim_var(name);
 
+    RETURN_OK_IF_SKIP(cctx);
     if (vidx < 0)
     {
        if (error)
@@ -831,6 +857,7 @@ generate_OLDSCRIPT(
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if (isn_type == ISN_LOADS)
        isn = generate_instr_type(cctx, isn_type, type);
     else
@@ -856,6 +883,7 @@ generate_VIM9SCRIPT(
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if (isn_type == ISN_LOADSCRIPT)
        isn = generate_instr_type(cctx, isn_type, type);
     else
@@ -879,6 +907,7 @@ generate_NEWLIST(cctx_T *cctx, int count)
     type_T     *type;
     type_T     *member;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_NEWLIST)) == NULL)
        return FAIL;
     isn->isn_arg.number = count;
@@ -915,6 +944,7 @@ generate_NEWDICT(cctx_T *cctx, int count)
     type_T     *type;
     type_T     *member;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_NEWDICT)) == NULL)
        return FAIL;
     isn->isn_arg.number = count;
@@ -948,6 +978,7 @@ generate_FUNCREF(cctx_T *cctx, int dfunc_idx)
     isn_T      *isn;
     garray_T   *stack = &cctx->ctx_type_stack;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_FUNCREF)) == NULL)
        return FAIL;
     isn->isn_arg.number = dfunc_idx;
@@ -970,6 +1001,7 @@ generate_JUMP(cctx_T *cctx, jumpwhen_T when, int where)
     isn_T      *isn;
     garray_T   *stack = &cctx->ctx_type_stack;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_JUMP)) == NULL)
        return FAIL;
     isn->isn_arg.jump.jump_when = when;
@@ -987,6 +1019,7 @@ generate_FOR(cctx_T *cctx, int loop_idx)
     isn_T      *isn;
     garray_T   *stack = &cctx->ctx_type_stack;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_FOR)) == NULL)
        return FAIL;
     isn->isn_arg.forloop.for_idx = loop_idx;
@@ -1012,6 +1045,7 @@ generate_BCALL(cctx_T *cctx, int func_idx, int argcount)
     type_T     *argtypes[MAX_FUNC_ARGS];
     int                i;
 
+    RETURN_OK_IF_SKIP(cctx);
     if (check_internal_func(func_idx, argcount) == FAIL)
        return FAIL;
 
@@ -1045,6 +1079,7 @@ generate_CALL(cctx_T *cctx, ufunc_T *ufunc, int pushed_argcount)
     int                regular_args = ufunc->uf_args.ga_len;
     int                argcount = pushed_argcount;
 
+    RETURN_OK_IF_SKIP(cctx);
     if (argcount > regular_args && !has_varargs(ufunc))
     {
        semsg(_(e_toomanyarg), ufunc->uf_name);
@@ -1105,6 +1140,7 @@ generate_UCALL(cctx_T *cctx, char_u *name, int argcount)
     isn_T      *isn;
     garray_T   *stack = &cctx->ctx_type_stack;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_UCALL)) == NULL)
        return FAIL;
     isn->isn_arg.ufunc.cuf_name = vim_strsave(name);
@@ -1129,6 +1165,7 @@ generate_PCALL(cctx_T *cctx, int argcount, int at_top)
     isn_T      *isn;
     garray_T   *stack = &cctx->ctx_type_stack;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_PCALL)) == NULL)
        return FAIL;
     isn->isn_arg.pfunc.cpf_top = at_top;
@@ -1152,6 +1189,7 @@ generate_MEMBER(cctx_T *cctx, char_u *name, size_t len)
     garray_T   *stack = &cctx->ctx_type_stack;
     type_T     *type;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_MEMBER)) == NULL)
        return FAIL;
     isn->isn_arg.string = vim_strnsave(name, (int)len);
@@ -1178,6 +1216,7 @@ generate_ECHO(cctx_T *cctx, int with_white, int count)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr_drop(cctx, ISN_ECHO, count)) == NULL)
        return FAIL;
     isn->isn_arg.echo.echo_with_white = with_white;
@@ -1206,6 +1245,7 @@ generate_EXEC(cctx_T *cctx, char_u *line)
 {
     isn_T      *isn;
 
+    RETURN_OK_IF_SKIP(cctx);
     if ((isn = generate_instr(cctx, ISN_EXEC)) == NULL)
        return FAIL;
     isn->isn_arg.string = vim_strsave(line);
@@ -2878,37 +2918,12 @@ compile_expr5(char_u **arg, cctx_T *cctx)
     return OK;
 }
 
-/*
- * expr5a == expr5b
- * expr5a =~ expr5b
- * expr5a != expr5b
- * expr5a !~ expr5b
- * expr5a > expr5b
- * expr5a >= expr5b
- * expr5a < expr5b
- * expr5a <= expr5b
- * expr5a is expr5b
- * expr5a isnot expr5b
- *
- * Produces instructions:
- *     EVAL expr5a             Push result of "expr5a"
- *     EVAL expr5b             Push result of "expr5b"
- *     COMPARE                 one of the compare instructions
- */
-    static int
-compile_expr4(char_u **arg, cctx_T *cctx)
+    static exptype_T
+get_compare_type(char_u *p, int *len, int *type_is)
 {
     exptype_T  type = EXPR_UNKNOWN;
-    char_u     *p;
-    int                len = 2;
     int                i;
-    int                type_is = FALSE;
-
-    // get the first variable
-    if (compile_expr5(arg, cctx) == FAIL)
-       return FAIL;
 
-    p = skipwhite(*arg);
     switch (p[0])
     {
        case '=':   if (p[1] == '=')
@@ -2924,7 +2939,7 @@ compile_expr4(char_u **arg, cctx_T *cctx)
        case '>':   if (p[1] != '=')
                    {
                        type = EXPR_GREATER;
-                       len = 1;
+                       *len = 1;
                    }
                    else
                        type = EXPR_GEQUAL;
@@ -2932,7 +2947,7 @@ compile_expr4(char_u **arg, cctx_T *cctx)
        case '<':   if (p[1] != '=')
                    {
                        type = EXPR_SMALLER;
-                       len = 1;
+                       *len = 1;
                    }
                    else
                        type = EXPR_SEQUAL;
@@ -2941,16 +2956,50 @@ compile_expr4(char_u **arg, cctx_T *cctx)
                    {
                        // "is" and "isnot"; but not a prefix of a name
                        if (p[2] == 'n' && p[3] == 'o' && p[4] == 't')
-                           len = 5;
-                       i = p[len];
+                           *len = 5;
+                       i = p[*len];
                        if (!isalnum(i) && i != '_')
                        {
-                           type = len == 2 ? EXPR_IS : EXPR_ISNOT;
-                           type_is = TRUE;
+                           type = *len == 2 ? EXPR_IS : EXPR_ISNOT;
+                           *type_is = TRUE;
                        }
                    }
                    break;
     }
+    return type;
+}
+
+/*
+ * expr5a == expr5b
+ * expr5a =~ expr5b
+ * expr5a != expr5b
+ * expr5a !~ expr5b
+ * expr5a > expr5b
+ * expr5a >= expr5b
+ * expr5a < expr5b
+ * expr5a <= expr5b
+ * expr5a is expr5b
+ * expr5a isnot expr5b
+ *
+ * Produces instructions:
+ *     EVAL expr5a             Push result of "expr5a"
+ *     EVAL expr5b             Push result of "expr5b"
+ *     COMPARE                 one of the compare instructions
+ */
+    static int
+compile_expr4(char_u **arg, cctx_T *cctx)
+{
+    exptype_T  type = EXPR_UNKNOWN;
+    char_u     *p;
+    int                len = 2;
+    int                type_is = FALSE;
+
+    // get the first variable
+    if (compile_expr5(arg, cctx) == FAIL)
+       return FAIL;
+
+    p = skipwhite(*arg);
+    type = get_compare_type(p, &len, &type_is);
 
     /*
      * If there is a comparative operator, use it.
@@ -3324,128 +3373,131 @@ compile_assignment(char_u *arg, exarg_T *eap, cmdidx_T cmdidx, cctx_T *cctx)
     if (name == NULL)
        return NULL;
 
-    if (*arg == '&')
-    {
-       int         cc;
-       long        numval;
-       char_u      *stringval = NULL;
-
-       dest = dest_option;
-       if (cmdidx == CMD_const)
-       {
-           emsg(_(e_const_option));
-           return NULL;
-       }
-       if (is_decl)
-       {
-           semsg(_("E1052: Cannot declare an option: %s"), arg);
-           goto theend;
-       }
-       p = arg;
-       p = find_option_end(&p, &opt_flags);
-       if (p == NULL)
-       {
-           emsg(_(e_letunexp));
-           return NULL;
-       }
-       cc = *p;
-       *p = NUL;
-       opt_type = get_option_value(arg + 1, &numval, &stringval, opt_flags);
-       *p = cc;
-       if (opt_type == -3)
-       {
-           semsg(_(e_unknown_option), *arg);
-           return NULL;
-       }
-       if (opt_type == -2 || opt_type == 0)
-           type = &t_string;
-       else
-           type = &t_number;   // both number and boolean option
-    }
-    else if (*arg == '$')
+    if (cctx->ctx_skip != TRUE)
     {
-       dest = dest_env;
-       if (is_decl)
+       if (*arg == '&')
        {
-           semsg(_("E1065: Cannot declare an environment variable: %s"), name);
-           goto theend;
-       }
-    }
-    else if (*arg == '@')
-    {
-       if (!valid_yank_reg(arg[1], TRUE))
-       {
-           emsg_invreg(arg[1]);
-           return FAIL;
+           int     cc;
+           long            numval;
+           char_u          *stringval = NULL;
+
+           dest = dest_option;
+           if (cmdidx == CMD_const)
+           {
+               emsg(_(e_const_option));
+               return NULL;
+           }
+           if (is_decl)
+           {
+               semsg(_("E1052: Cannot declare an option: %s"), arg);
+               goto theend;
+           }
+           p = arg;
+           p = find_option_end(&p, &opt_flags);
+           if (p == NULL)
+           {
+               emsg(_(e_letunexp));
+               return NULL;
+           }
+           cc = *p;
+           *p = NUL;
+           opt_type = get_option_value(arg + 1, &numval, &stringval, opt_flags);
+           *p = cc;
+           if (opt_type == -3)
+           {
+               semsg(_(e_unknown_option), *arg);
+               return NULL;
+           }
+           if (opt_type == -2 || opt_type == 0)
+               type = &t_string;
+           else
+               type = &t_number;       // both number and boolean option
        }
-       dest = dest_reg;
-       if (is_decl)
+       else if (*arg == '$')
        {
-           semsg(_("E1066: Cannot declare a register: %s"), name);
-           goto theend;
+           dest = dest_env;
+           if (is_decl)
+           {
+               semsg(_("E1065: Cannot declare an environment variable: %s"), name);
+               goto theend;
+           }
        }
-    }
-    else if (STRNCMP(arg, "g:", 2) == 0)
-    {
-       dest = dest_global;
-       if (is_decl)
+       else if (*arg == '@')
        {
-           semsg(_("E1016: Cannot declare a global variable: %s"), name);
-           goto theend;
+           if (!valid_yank_reg(arg[1], TRUE))
+           {
+               emsg_invreg(arg[1]);
+               return FAIL;
+           }
+           dest = dest_reg;
+           if (is_decl)
+           {
+               semsg(_("E1066: Cannot declare a register: %s"), name);
+               goto theend;
+           }
        }
-    }
-    else if (STRNCMP(arg, "v:", 2) == 0)
-    {
-       vimvaridx = find_vim_var(name + 2);
-       if (vimvaridx < 0)
+       else if (STRNCMP(arg, "g:", 2) == 0)
        {
-           semsg(_(e_var_notfound), arg);
-           goto theend;
+           dest = dest_global;
+           if (is_decl)
+           {
+               semsg(_("E1016: Cannot declare a global variable: %s"), name);
+               goto theend;
+           }
        }
-       dest = dest_vimvar;
-       if (is_decl)
+       else if (STRNCMP(arg, "v:", 2) == 0)
        {
-           semsg(_("E1064: Cannot declare a v: variable: %s"), name);
-           goto theend;
-       }
-    }
-    else
-    {
-       for (idx = 0; reserved[idx] != NULL; ++idx)
-           if (STRCMP(reserved[idx], name) == 0)
+           vimvaridx = find_vim_var(name + 2);
+           if (vimvaridx < 0)
            {
-               semsg(_("E1034: Cannot use reserved name %s"), name);
+               semsg(_(e_var_notfound), arg);
                goto theend;
            }
-
-       idx = lookup_local(arg, varlen, cctx);
-       if (idx >= 0)
-       {
+           dest = dest_vimvar;
            if (is_decl)
            {
-               semsg(_("E1017: Variable already declared: %s"), name);
+               semsg(_("E1064: Cannot declare a v: variable: %s"), name);
                goto theend;
            }
-           else
+       }
+       else
+       {
+           for (idx = 0; reserved[idx] != NULL; ++idx)
+               if (STRCMP(reserved[idx], name) == 0)
+               {
+                   semsg(_("E1034: Cannot use reserved name %s"), name);
+                   goto theend;
+               }
+
+           idx = lookup_local(arg, varlen, cctx);
+           if (idx >= 0)
            {
-               lvar = ((lvar_T *)cctx->ctx_locals.ga_data) + idx;
-               if (lvar->lv_const)
+               if (is_decl)
                {
-                   semsg(_("E1018: Cannot assign to a constant: %s"), name);
+                   semsg(_("E1017: Variable already declared: %s"), name);
                    goto theend;
                }
+               else
+               {
+                   lvar = ((lvar_T *)cctx->ctx_locals.ga_data) + idx;
+                   if (lvar->lv_const)
+                   {
+                       semsg(_("E1018: Cannot assign to a constant: %s"), name);
+                       goto theend;
+                   }
+               }
            }
-       }
-       else if (STRNCMP(arg, "s:", 2) == 0
-               || lookup_script(arg, varlen) == OK
-               || find_imported(arg, varlen, cctx) != NULL)
-       {
-           dest = dest_script;
-           if (is_decl)
+           else if (STRNCMP(arg, "s:", 2) == 0
+                   || lookup_script(arg, varlen) == OK
+                   || find_imported(arg, varlen, cctx) != NULL)
            {
-               semsg(_("E1054: Variable already declared in the script: %s"),
-                                                                        name);
-               goto theend;
+               dest = dest_script;
+               if (is_decl)
+               {
+                   semsg(_("E1054: Variable already declared in the script: %s"),
+                                                                            name);
+                   goto theend;
+               }
            }
        }
     }
@@ -3493,7 +3545,7 @@ compile_assignment(char_u *arg, exarg_T *eap, cmdidx_T cmdidx, cctx_T *cctx)
     }
 
     // +=, /=, etc. require an existing variable
-    if (idx < 0 && dest == dest_local)
+    if (idx < 0 && dest == dest_local && cctx->ctx_skip != TRUE)
     {
        if (oplen > 1 && !heredoc)
        {
@@ -3840,8 +3892,23 @@ evaluate_const_expr7(char_u **arg, cctx_T *cctx UNUSED, typval_T *tv)
     end_leader = *arg;
 
     /*
-     * Recognize only has() for now.
+     * Recognize only a few types of constants for now.
      */
+    if (STRNCMP("true", *arg, 4) == 0 && !ASCII_ISALNUM((*arg)[4]))
+    {
+       tv->v_type = VAR_SPECIAL;
+       tv->vval.v_number = VVAL_TRUE;
+       *arg += 4;
+       return OK;
+    }
+    if (STRNCMP("false", *arg, 5) == 0 && !ASCII_ISALNUM((*arg)[5]))
+    {
+       tv->v_type = VAR_SPECIAL;
+       tv->vval.v_number = VVAL_FALSE;
+       *arg += 5;
+       return OK;
+    }
+
     if (STRNCMP("has(", *arg, 4) != 0)
        return FAIL;
     *arg = skipwhite(*arg + 4);
@@ -3881,6 +3948,33 @@ evaluate_const_expr7(char_u **arg, cctx_T *cctx UNUSED, typval_T *tv)
     return OK;
 }
 
+    static int
+evaluate_const_expr4(char_u **arg, cctx_T *cctx UNUSED, typval_T *tv)
+{
+    exptype_T  type = EXPR_UNKNOWN;
+    char_u     *p;
+    int                len = 2;
+    int                type_is = FALSE;
+
+    // get the first variable
+    if (evaluate_const_expr7(arg, cctx, tv) == FAIL)
+       return FAIL;
+
+    p = skipwhite(*arg);
+    type = get_compare_type(p, &len, &type_is);
+
+    /*
+     * If there is a comparative operator, use it.
+     */
+    if (type != EXPR_UNKNOWN)
+    {
+       // TODO
+       return FAIL;
+    }
+
+    return OK;
+}
+
 static int evaluate_const_expr3(char_u **arg, cctx_T *cctx, typval_T *tv);
 
 /*
@@ -3911,7 +4005,7 @@ evaluate_const_and_or(char_u **arg, cctx_T *cctx, char *op, typval_T *tv)
            tv2.v_type = VAR_UNKNOWN;
            tv2.v_lock = 0;
            if ((opchar == '|' ? evaluate_const_expr3(arg, cctx, &tv2)
-                              : evaluate_const_expr7(arg, cctx, &tv2)) == FAIL)
+                              : evaluate_const_expr4(arg, cctx, &tv2)) == FAIL)
            {
                clear_tv(&tv2);
                return FAIL;
@@ -3940,7 +4034,7 @@ evaluate_const_and_or(char_u **arg, cctx_T *cctx, char *op, typval_T *tv)
 evaluate_const_expr3(char_u **arg, cctx_T *cctx, typval_T *tv)
 {
     // evaluate the first expression
-    if (evaluate_const_expr7(arg, cctx, tv) == FAIL)
+    if (evaluate_const_expr4(arg, cctx, tv) == FAIL)
        return FAIL;
 
     // || and && work almost the same