Rollup merge of rust-lang#63577 - meffij:test-hrtb, r=alexcrichton

Test HRTB issue accepted by compiler

Hi! First Rust PR, so if anything needs changing just let me know and I'll take care of it right away.

Closes rust-lang#50301 which was marked E-needstest

Author: Centril

src/test/ui/issues/issue-50301.rs

@@ -0,0 +1,31 @@
+// Tests that HRTBs are correctly accepted -- https://github.com/rust-lang/rust/issues/50301
+// check-pass
+trait Trait
+where
+    for<'a> &'a Self::IntoIter: IntoIterator<Item = u32>,
+{
+    type IntoIter;
+    fn get(&self) -> Self::IntoIter;
+}
+
+struct Impl(Vec<u32>);
+
+impl Trait for Impl {
+    type IntoIter = ImplIntoIter;
+    fn get(&self) -> Self::IntoIter {
+        ImplIntoIter(self.0.clone())
+    }
+}
+
+struct ImplIntoIter(Vec<u32>);
+
+impl<'a> IntoIterator for &'a ImplIntoIter {
+    type Item = <Self::IntoIter as Iterator>::Item;
+    type IntoIter = std::iter::Cloned<std::slice::Iter<'a, u32>>;
+    fn into_iter(self) -> Self::IntoIter {
+        (&self.0).into_iter().cloned()
+    }
+}
+
+fn main() {
+}