patch 8.2.3111: Vim9: confusing error with extra whitespace before colon

Problem:    Vim9: confusing error with extra whitespace before colon.
Solution:   Check for colon after white space. (closes #8513)

src/eval.c

@@ -1660,6 +1660,7 @@ eval_for_line(
     evalarg_T	*evalarg)
 {
     forinfo_T	*fi;
+    char_u	*var_list_end;
     char_u	*expr;
     typval_T	tv;
     list_T	*l;
@@ -1671,14 +1672,18 @@ eval_for_line(
     if (fi == NULL)
 	return NULL;
 
-    expr = skip_var_list(arg, TRUE, &fi->fi_varcount, &fi->fi_semicolon, FALSE);
+    var_list_end = skip_var_list(arg, TRUE, &fi->fi_varcount,
-    if (expr == NULL)
+						     &fi->fi_semicolon, FALSE);
+    if (var_list_end == NULL)
 	return fi;
 
-    expr = skipwhite_and_linebreak(expr, evalarg);
+    expr = skipwhite_and_linebreak(var_list_end, evalarg);
     if (expr[0] != 'i' || expr[1] != 'n'
 				  || !(expr[2] == NUL || VIM_ISWHITE(expr[2])))
     {
+	if (in_vim9script() && *expr == ':' && expr != var_list_end)
+	    semsg(_(e_no_white_space_allowed_before_colon_str), expr);
+	else
 	    emsg(_(e_missing_in));
 	return fi;
     }

src/testdir/test_vim9_script.vim

@@ -2566,6 +2566,13 @@ def Test_for_loop_fails()
       endfor
   END
   CheckDefAndScriptFailure(lines, 'E1012: Type mismatch; expected number but got string', 1)
+
+  lines =<< trim END
+      for n : number in [1, 2]
+        echo n
+      endfor
+  END
+  CheckDefAndScriptFailure(lines, 'E1059:', 1)
 enddef
 
 def Test_for_loop_script_var()

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3111,
 /**/
     3110,
 /**/

src/vim9compile.c

@@ -7775,6 +7775,9 @@ compile_for(char_u *arg_start, cctx_T *cctx)
 	return NULL;
     if (STRNCMP(p, "in", 2) != 0 || !IS_WHITE_OR_NUL(p[2]))
     {
+	if (*p == ':' && wp != p)
+	    semsg(_(e_no_white_space_allowed_before_colon_str), p);
+	else
 	    emsg(_(e_missing_in));
 	return NULL;
     }