Avoid overflow in `std::iter::Skip::count`

The call to `count` on the inner iterator can overflow even if `Skip` itself would return less that `usize::max_value()` items.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/test/ui/iterators/skip-count-overflow.rs b/src/test/ui/iterators/skip-count-overflow.rs
new file mode 100644
index 00000000000..d8efc948664
--- /dev/null
+++ b/src/test/ui/iterators/skip-count-overflow.rs
@@ -0,0 +1,8 @@
+// run-pass
+// only-32bit too impatient for 2⁶⁴ items
+// compile-flags: -C overflow-checks -C opt-level=3
+
+fn main() {
+    let i = (0..usize::max_value()).chain(0..10).skip(usize::max_value());
+    assert_eq!(i.count(), 10);
+}