Rollup merge of #63394 - jackh726:issue-36804, r=jonas-schievink

Add test for issue 36804

I slightly reduced the repro that ICEs on nightly-2017-01-20.

Closes #36804

src/test/ui/specialization/issue-36804.rs

+// check-pass
+#![feature(specialization)]
+
+pub struct Cloned<I>(I);
+
+impl<'a, I, T: 'a> Iterator for Cloned<I>
+where
+    I: Iterator<Item = &'a T>,
+    T: Clone,
+{
+    type Item = T;
+
+    fn next(&mut self) -> Option<T> {
+        unimplemented!()
+    }
+}
+
+impl<'a, I, T: 'a> Iterator for Cloned<I>
+where
+    I: Iterator<Item = &'a T>,
+    T: Copy,
+{
+    fn count(self) -> usize {
+        unimplemented!()
+    }
+}
+
+fn main() {
+    let a = [1,2,3,4];
+    Cloned(a.iter()).count();
+}