vim-patch:8.2.1306: checking for first character of dict key is inconsistent

Problem:    Checking for first character of dict key is inconsistent.
Solution:   Add eval_isdictc(). (closes vim/vim#6546)

b13ab99908

Omit handle_subscript() change: only affects Vim9 script.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/eval.c

@@ -3418,7 +3418,7 @@ static int eval_index(char **arg, typval_T *rettv, int evaluate, int verbose)
   if (**arg == '.') {
     // dict.name
     key = *arg + 1;
-    for (len = 0; ASCII_ISALNUM(key[len]) || key[len] == '_'; len++) {}
+    for (len = 0; eval_isdictc(key[len]); len++) {}
     if (len == 0) {
       return FAIL;
     }
@@ -6695,7 +6695,7 @@ const char *find_name_end(const char *arg, const char **expr_start, const char *
        && (eval_isnamec(*p)
            || *p == '{'
            || ((flags & FNE_INCL_BR) && (*p == '['
-                                         || (*p == '.' && eval_isnamec1(p[1]))))
+                                         || (*p == '.' && eval_isdictc(p[1]))))
            || mb_nest != 0
            || br_nest != 0); MB_PTR_ADV(p)) {
     if (*p == '\'') {
@@ -6808,18 +6808,25 @@ static char *make_expanded_name(const char *in_start, char *expr_start, char *ex
 
 /// @return  true if character "c" can be used in a variable or function name.
 ///          Does not include '{' or '}' for magic braces.
-int eval_isnamec(int c)
+bool eval_isnamec(int c)
 {
   return ASCII_ISALNUM(c) || c == '_' || c == ':' || c == AUTOLOAD_CHAR;
 }
 
 /// @return  true if character "c" can be used as the first character in a
 ///          variable or function name (excluding '{' and '}').
-int eval_isnamec1(int c)
+bool eval_isnamec1(int c)
 {
   return ASCII_ISALPHA(c) || c == '_';
 }
 
+/// @return  true if character "c" can be used as the first character of a
+///          dictionary key.
+bool eval_isdictc(int c)
+{
+  return ASCII_ISALNUM(c) || c == '_';
+}
+
 /// Get typval_T v: variable value.
 typval_T *get_vim_var_tv(int idx)
 {

src/nvim/testdir/test_let.vim

@@ -276,7 +276,7 @@ func Test_let_errors()
   let s = "var"
   let var = 1
   call assert_fails('let var += [1,2]', 'E734:')
-  call assert_fails('let {s}.1 = 2', 'E15:')
+  call assert_fails('let {s}.1 = 2', 'E18:')
   call assert_fails('let a[1] = 5', 'E121:')
   let l = [[1,2]]
   call assert_fails('let l[:][0] = [5]', 'E708:')

src/nvim/testdir/test_listdict.vim

@@ -289,6 +289,13 @@ func Test_dict_func()
   call assert_equal('xxx3', Fn('xxx'))
 endfunc
 
+func Test_dict_assign()
+  let d = {}
+  let d.1 = 1
+  let d._ = 2
+  call assert_equal({'1': 1, '_': 2}, d)
+endfunc
+
 " Function in script-local List or Dict
 func Test_script_local_dict_func()
   let g:dict = {}