patch 8.2.0657: Vim9: no check if called variable is a FuncRef

Problem:    Vim9: no check if called variable is a FuncRef.
Solution:   Add a type check.
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 4c821ec..bc1f873 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -345,6 +345,9 @@
   call CheckDefFailure(['let var: pam'], 'E1010:')
   call CheckDefFailure(['let var: sam'], 'E1010:')
   call CheckDefFailure(['let var: vim'], 'E1010:')
+
+  call CheckDefFailure(['let Ref: number', 'Ref()'], 'E1085:')
+  call CheckDefFailure(['let Ref: string', 'let res = Ref()'], 'E1085:')
 endfunc
 
 func Test_const()