1 files changed, 185 insertions, 0 deletions
diff --git a/library/core/tests/iter/adapters/mod.rs b/library/core/tests/iter/adapters/mod.rs
new file mode 100644
index 000000000..567d9fe49
--- /dev/null
+++ b/library/core/tests/iter/adapters/mod.rs
@@ -0,0 +1,185 @@
+mod chain;
+mod cloned;
+mod copied;
+mod cycle;
+mod enumerate;
+mod filter;
+mod filter_map;
+mod flat_map;
+mod flatten;
+mod fuse;
+mod inspect;
+mod intersperse;
+mod map;
+mod peekable;
+mod scan;
+mod skip;
+mod skip_while;
+mod step_by;
+mod take;
+mod take_while;
+mod zip;
+
+use core::cell::Cell;
+
+/// An iterator that panics whenever `next` or next_back` is called
+/// after `None` has already been returned. This does not violate
+/// `Iterator`'s contract. Used to test that iterator adapters don't
+/// poll their inner iterators after exhausting them.
+pub struct NonFused<I> {
+    iter: I,
+    done: bool,
+}
+
+impl<I> NonFused<I> {
+    pub fn new(iter: I) -> Self {
+        Self { iter, done: false }
+    }
+}
+
+impl<I> Iterator for NonFused<I>
+where
+    I: Iterator,
+{
+    type Item = I::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        assert!(!self.done, "this iterator has already returned None");
+        self.iter.next().or_else(|| {
+            self.done = true;
+            None
+        })
+    }
+}
+
+impl<I> DoubleEndedIterator for NonFused<I>
+where
+    I: DoubleEndedIterator,
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        assert!(!self.done, "this iterator has already returned None");
+        self.iter.next_back().or_else(|| {
+            self.done = true;
+            None
+        })
+    }
+}
+
+/// An iterator wrapper that panics whenever `next` or `next_back` is called
+/// after `None` has been returned.
+pub struct Unfuse<I> {
+    iter: I,
+    exhausted: bool,
+}
+
+impl<I> Unfuse<I> {
+    pub fn new<T>(iter: T) -> Self
+    where
+        T: IntoIterator<IntoIter = I>,
+    {
+        Self { iter: iter.into_iter(), exhausted: false }
+    }
+}
+
+impl<I> Iterator for Unfuse<I>
+where
+    I: Iterator,
+{
+    type Item = I::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        assert!(!self.exhausted);
+        let next = self.iter.next();
+        self.exhausted = next.is_none();
+        next
+    }
+}
+
+impl<I> DoubleEndedIterator for Unfuse<I>
+where
+    I: DoubleEndedIterator,
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        assert!(!self.exhausted);
+        let next = self.iter.next_back();
+        self.exhausted = next.is_none();
+        next
+    }
+}
+
+pub struct Toggle {
+    is_empty: bool,
+}
+
+impl Iterator for Toggle {
+    type Item = ();
+
+    // alternates between `None` and `Some(())`
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.is_empty {
+            self.is_empty = false;
+            None
+        } else {
+            self.is_empty = true;
+            Some(())
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        if self.is_empty { (0, Some(0)) } else { (1, Some(1)) }
+    }
+}
+
+impl DoubleEndedIterator for Toggle {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.next()
+    }
+}
+
+/// This is an iterator that follows the Iterator contract,
+/// but it is not fused. After having returned None once, it will start
+/// producing elements if .next() is called again.
+pub struct CycleIter<'a, T> {
+    index: usize,
+    data: &'a [T],
+}
+
+impl<'a, T> CycleIter<'a, T> {
+    pub fn new(data: &'a [T]) -> Self {
+        Self { index: 0, data }
+    }
+}
+
+impl<'a, T> Iterator for CycleIter<'a, T> {
+    type Item = &'a T;
+    fn next(&mut self) -> Option<Self::Item> {
+        let elt = self.data.get(self.index);
+        self.index += 1;
+        self.index %= 1 + self.data.len();
+        elt
+    }
+}
+
+#[derive(Debug)]
+struct CountClone(Cell<i32>);
+
+impl CountClone {
+    pub fn new() -> Self {
+        Self(Cell::new(0))
+    }
+}
+
+impl PartialEq<i32> for CountClone {
+    fn eq(&self, rhs: &i32) -> bool {
+        self.0.get() == *rhs
+    }
+}
+
+impl Clone for CountClone {
+    fn clone(&self) -> Self {
+        let ret = CountClone(self.0.clone());
+        let n = self.0.get();
+        self.0.set(n + 1);
+        ret
+    }
+}