patch 8.2.0981: Vim9: cannot compile "[var, var] = list"

Problem:    Vim9: cannot compile "[var, var] = list".
Solution:   Implement list assignment.

src/eval.c

@@ -1431,7 +1431,7 @@ eval_for_line(
     if (fi == NULL)
 	return NULL;
 
-    expr = skip_var_list(arg, TRUE, &fi->fi_varcount, &fi->fi_semicolon);
+    expr = skip_var_list(arg, TRUE, &fi->fi_varcount, &fi->fi_semicolon, FALSE);
     if (expr == NULL)
 	return fi;
 

src/evalvars.c

@@ -164,7 +164,6 @@ static dict_T		vimvardict;		// Dictionary with v: variables
 // for VIM_VERSION_ defines
 #include "version.h"
 
-static char_u *skip_var_one(char_u *arg, int include_type);
 static void list_glob_vars(int *first);
 static void list_buf_vars(int *first);
 static void list_win_vars(int *first);
@@ -709,7 +708,7 @@ ex_let(exarg_T *eap)
     if (eap->arg == eap->cmd)
 	flags |= LET_NO_COMMAND;
 
-    argend = skip_var_list(arg, TRUE, &var_count, &semicolon);
+    argend = skip_var_list(arg, TRUE, &var_count, &semicolon, FALSE);
     if (argend == NULL)
 	return;
     if (argend > arg && argend[-1] == '.')  // for var.='str'
@@ -916,15 +915,17 @@ ex_let_vars(
  * Skip over assignable variable "var" or list of variables "[var, var]".
  * Used for ":let varvar = expr" and ":for varvar in expr".
  * For "[var, var]" increment "*var_count" for each variable.
- * for "[var, var; var]" set "semicolon".
+ * for "[var, var; var]" set "semicolon" to 1.
+ * If "silent" is TRUE do not give an "invalid argument" error message.
  * Return NULL for an error.
  */
     char_u *
 skip_var_list(
     char_u	*arg,
     int		include_type,
     int		*var_count,
-    int		*semicolon)
+    int		*semicolon,
+    int		silent)
 {
     char_u	*p, *s;
 
@@ -935,10 +936,11 @@ skip_var_list(
 	for (;;)
 	{
 	    p = skipwhite(p + 1);	// skip whites after '[', ';' or ','
-	    s = skip_var_one(p, TRUE);
+	    s = skip_var_one(p, FALSE);
 	    if (s == p)
 	    {
-		semsg(_(e_invarg2), p);
+		if (!silent)
+		    semsg(_(e_invarg2), p);
 		return NULL;
 	    }
 	    ++*var_count;
@@ -957,7 +959,8 @@ skip_var_list(
 	    }
 	    else if (*p != ',')
 	    {
-		semsg(_(e_invarg2), p);
+		if (!silent)
+		    semsg(_(e_invarg2), p);
 		return NULL;
 	    }
 	}
@@ -972,7 +975,7 @@ skip_var_list(
  * l[idx].
  * In Vim9 script also skip over ": type" if "include_type" is TRUE.
  */
-    static char_u *
+    char_u *
 skip_var_one(char_u *arg, int include_type)
 {
     char_u *end;
@@ -981,10 +984,13 @@ skip_var_one(char_u *arg, int include_type)
 	return arg + 2;
     end = find_name_end(*arg == '$' || *arg == '&' ? arg + 1 : arg,
 				   NULL, NULL, FNE_INCL_BR | FNE_CHECK_START);
-    if (include_type && current_sctx.sc_version == SCRIPT_VERSION_VIM9
-								&& *end == ':')
+    if (include_type && current_sctx.sc_version == SCRIPT_VERSION_VIM9)
     {
-	end = skip_type(skipwhite(end + 1));
+	// "a: type" is declaring variable "a" with a type, not "a:".
+	if (end == arg + 2 && end[-1] == ':')
+	    --end;
+	if (*end == ':')
+	    end = skip_type(skipwhite(end + 1));
     }
     return end;
 }

src/proto/evalvars.pro

@@ -16,7 +16,8 @@ void restore_vimvar(int idx, typval_T *save_tv);
 list_T *heredoc_get(exarg_T *eap, char_u *cmd, int script_get);
 void ex_let(exarg_T *eap);
 int ex_let_vars(char_u *arg_start, typval_T *tv, int copy, int semicolon, int var_count, int flags, char_u *op);
-char_u *skip_var_list(char_u *arg, int include_type, int *var_count, int *semicolon);
+char_u *skip_var_list(char_u *arg, int include_type, int *var_count, int *semicolon, int silent);
+char_u *skip_var_one(char_u *arg, int include_type);
 void list_hashtable_vars(hashtab_T *ht, char *prefix, int empty, int *first);
 void ex_unlet(exarg_T *eap);
 void ex_lockvar(exarg_T *eap);

src/testdir/test_vim9_script.vim

@@ -223,6 +223,14 @@ def Test_assignment_default()
   assert_equal(5678, nr)
 enddef
 
+def Test_assignment_var_list()
+  let v1: string
+  let v2: string
+  [v1, v2] = ['one', 'two']
+  assert_equal('one', v1)
+  assert_equal('two', v2)
+enddef
+
 def Mess(): string
   v:foldstart = 123
   return 'xxx'

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    981,
 /**/
     980,
 /**/

src/vim9.h

@@ -112,6 +112,7 @@ typedef enum {
     // expression operations
     ISN_CONCAT,
     ISN_INDEX,	    // [expr] list index
+    ISN_GETITEM,    // push list item, isn_arg.number is the index
     ISN_MEMBER,	    // dict[member]
     ISN_STRINGMEMBER, // dict.member using isn_arg.string
     ISN_2BOOL,	    // convert value to bool, invert if isn_arg.number != 0