patch 8.2.2525: Vim9: only local variables checked for a name

Problem:    Vim9: only local variables checked for a name.
Solution:   Also check arguments and script variables. (closes #7838)
diff --git a/src/vim9compile.c b/src/vim9compile.c
index 6d0a748..84c9108 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -373,6 +373,19 @@
 }
 
 /*
+ * Return TRUE if "name" is a local variable, argument, script variable or
+ * imported.
+ */
+    static int
+variable_exists(char_u *name, size_t len, cctx_T *cctx)
+{
+    return lookup_local(name, len, NULL, cctx) == OK
+	    || arg_exists(name, len, NULL, NULL, NULL, cctx) == OK
+	    || script_var_exists(name, len, FALSE, cctx) == OK
+	    || find_imported(name, len, cctx) != NULL;
+}
+
+/*
  * Check if "p[len]" is already defined, either in script "import_sid" or in
  * compilation context "cctx".  "cctx" is NULL at the script level.
  * Does not check the global namespace.
@@ -6444,10 +6457,7 @@
 		    || *eap->cmd == '$'
 		    || *eap->cmd == '@'
 		    || ((len) > 2 && eap->cmd[1] == ':')
-		    || lookup_local(eap->cmd, len, NULL, cctx) == OK
-		    || arg_exists(eap->cmd, len, NULL, NULL, NULL, cctx) == OK
-		    || script_var_exists(eap->cmd, len, FALSE, cctx) == OK
-		    || find_imported(eap->cmd, len, cctx) != NULL)
+		    || variable_exists(eap->cmd, len, cctx))
 	    {
 		*line = compile_assignment(eap->cmd, eap, CMD_SIZE, cctx);
 		if (*line == NULL || *line == eap->cmd)
@@ -8332,7 +8342,7 @@
 	    }
 	}
 	p = find_ex_command(&ea, NULL, starts_with_colon ? NULL
-		   : (int (*)(char_u *, size_t, void *, cctx_T *))lookup_local,
+		   : (int (*)(char_u *, size_t, cctx_T *))variable_exists,
 									&cctx);
 
 	if (p == NULL)