patch 8.2.4698: Vim9: script variable has no flag that it was setv8.2.4698

Problem:    Vim9: script variable has no flag that it was set.
Solution:   Add a flag that it was set, to avoid giving it a value when used.
            (closes #10088)

1 files changed, 10 insertions, 2 deletions

diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index b20ff144ca..9e60666d3d 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -153,14 +153,22 @@ def Test_add_list()
   END
   v9.CheckDefExecFailure(lines, 'E1130:', 2)
 
-  # Getting variable with NULL list allocates a new list at script level
+  # Getting an uninitialized variable allocates a new list at script level
   lines =<< trim END
       vim9script
-      var l: list<number> = test_null_list()
+      var l: list<number>
       add(l, 123)
   END
   v9.CheckScriptSuccess(lines)
 
+  # Adding to a variable set to a NULL list fails
+  lines =<< trim END
+      vim9script
+      var l: list<number> = test_null_list()
+      add(l, 123)
+  END
+  v9.CheckScriptFailure(lines, 'E1130:', 3)
+
   lines =<< trim END
       vim9script
       var l: list<string> = ['a']