patch 8.2.2540: Vim9: no error for using script var name for argument

Problem:    Vim9: no error for using script var name for argument.
Solution:   Check for this error. (closes #7868)

src/testdir/test_vim9_func.vim

@@ -589,6 +589,15 @@ def Test_call_wrong_args()
   END
   CheckScriptFailure(lines, 'E1013: Argument 1: type mismatch, expected string but got list<unknown>', 5)
 
+  lines =<< trim END
+    vim9script
+    var name = 'piet'
+    def FuncOne(name: string)
+      echo nr
+    enddef
+  END
+  CheckScriptFailure(lines, 'E1054:')
+
   lines =<< trim END
     vim9script
     def FuncOne(nr: number)