Added another test.

src/test/ui/associated-type-bounds/ambiguous-associated-type.rs

@@ -0,0 +1,12 @@
+// build-pass (FIXME(62277): could be check-pass?)
+
+#![feature(associated_type_bounds)]
+
+pub struct Flatten<I>
+where
+    I: Iterator<Item: IntoIterator>,
+{
+    inner: <I::Item as IntoIterator>::IntoIter,
+}
+
+fn main() {}