patch 9.0.0444: trying to declare g:variable gives confusing errorv9.0.0444

Problem:    Trying to declare g:variable gives confusing error.
Solution:   Give a better error message. (closes #11108)

1 files changed, 13 insertions, 2 deletions

diff --git a/src/evalvars.c b/src/evalvars.c
index facafc7dd2..7de785bc4b 100644
--- a/src/evalvars.c
+++ b/src/evalvars.c
@@ -603,6 +603,18 @@ list_script_vars(int *first)
 }
 
 /*
+ * Return TRUE if "name" starts with "g:", "w:", "t:" or "b:".
+ * But only when an identifier character follows.
+ */
+    int
+is_scoped_variable(char_u *name)
+{
+    return vim_strchr((char_u *)"gwbt", name[0]) != NULL
+	&& name[1] == ':'
+	&& eval_isnamec(name[2]);
+}
+
+/*
  * Evaluate one Vim expression {expr} in string "p" and append the
  * resulting string to "gap".  "p" points to the opening "{".
  * When "evaluate" is FALSE only skip over the expression.
@@ -3679,8 +3691,7 @@ set_var_const(
 	vim9_declare_error(name);
 	goto failed;
     }
-    if ((flags & ASSIGN_FOR_LOOP) && name[1] == ':'
-			      && vim_strchr((char_u *)"gwbt", name[0]) != NULL)
+    if ((flags & ASSIGN_FOR_LOOP) && is_scoped_variable(name))
 	// Do not make g:var, w:var, b:var or t:var final.
 	flags &= ~ASSIGN_FINAL;