patch 8.2.2738: extending a list with itself can give wrong result
Problem: Extending a list with itself can give wrong result.
Solution: Remember the item before where the insertion happens and skip to
after the already inserted items. (closes #1112)
diff --git a/src/testdir/test_listdict.vim b/src/testdir/test_listdict.vim
index 051a37c..1b0796d 100644
--- a/src/testdir/test_listdict.vim
+++ b/src/testdir/test_listdict.vim
@@ -862,6 +862,20 @@
" Extend g: dictionary with an invalid variable name
call assert_fails("call extend(g:, {'-!' : 10})", 'E461:')
+
+ " Extend a list with itself.
+ let l = [1, 5, 7]
+ call extend(l, l, 0)
+ call assert_equal([1, 5, 7, 1, 5, 7], l)
+ let l = [1, 5, 7]
+ call extend(l, l, 1)
+ call assert_equal([1, 1, 5, 7, 5, 7], l)
+ let l = [1, 5, 7]
+ call extend(l, l, 2)
+ call assert_equal([1, 5, 1, 5, 7, 7], l)
+ let l = [1, 5, 7]
+ call extend(l, l, 3)
+ call assert_equal([1, 5, 7, 1, 5, 7], l)
endfunc
func Test_listdict_extendnew()