skylark: do not leave zip arguments frozen (#5)

2 files changed, 13 insertions, 0 deletions

diff --git a/library.go b/library.go
index d954f4a..fcd857c 100644
--- a/library.go
+++ b/library.go
@@ -1036,6 +1036,13 @@ func zip(thread *Thread, _ *Builtin, args Tuple, kwargs []Tuple) (Value, error)
 	}
 	rows, cols := 0, len(args)
 	iters := make([]Iterator, cols)
+	defer func() {
+		for _, iter := range iters {
+			if iter != nil {
+				iter.Done()
+			}
+		}
+	}()
 	for i, seq := range args {
 		it := Iterate(seq)
 		if it == nil {
diff --git a/testdata/builtins.sky b/testdata/builtins.sky
index 9fe7c91..2f845db 100644
--- a/testdata/builtins.sky
+++ b/testdata/builtins.sky
@@ -104,6 +104,12 @@ assert.eq(zip(list("abc".split_bytes()),
               list("def".split_bytes()),
               list("hijk".split_bytes())),
           [("a", "d", "h"), ("b", "e", "i"), ("c", "f", "j")])
+z1 = [1]
+assert.eq(zip(z1), [(1,)])
+z1.append(2)
+assert.eq(zip(z1), [(1,), (2,)])
+assert.fails(lambda: zip(z1, 1), "zip: argument #2 is not iterable: int")
+z1.append(3)
 
 # dir for builtins
 assert.eq(dir(None), [])