patch 8.2.1821: Vim9: concatenating to a NULL list doesn't work
Problem: Vim9: concatenating to a NULL list doesn't work.
Solution: Handle a NULL list like an empty list. (closes #7064)
diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index 189ff4d..1b56df5 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -236,6 +236,18 @@
assert_equal(#{one: 1}, d)
END
CheckScriptSuccess(lines)
+
+ # appending to NULL list from a function
+ lines =<< trim END
+ vim9script
+ var list: list<string>
+ def Func()
+ list += ['a', 'b']
+ enddef
+ Func()
+ assert_equal(['a', 'b'], list)
+ END
+ CheckScriptSuccess(lines)
enddef
def Test_single_letter_vars()