Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/src/test/ui/associated-types/associated-types-where-clause-impl-ambiguity.rs b/src/test/ui/associated-types/associated-types-where-clause-impl-ambiguity.rs
new file mode 100644
index 000000000..f2a4c6e42
--- /dev/null
+++ b/src/test/ui/associated-types/associated-types-where-clause-impl-ambiguity.rs
@@ -0,0 +1,46 @@
+// run-pass
+#![allow(dead_code)]
+#![allow(unused_imports)]
+// Test how resolving a projection interacts with inference.  In this
+// case, we were eagerly unifying the type variable for the iterator
+// type with `I` from the where clause, ignoring the in-scope `impl`
+// for `ByRef`. The right answer was to consider the result ambiguous
+// until more type information was available.
+
+#![feature(lang_items)]
+#![no_implicit_prelude]
+
+use std::marker::Sized;
+use std::option::Option::{None, Some, self};
+
+trait Iterator {
+    type Item;
+
+    fn next(&mut self) -> Option<Self::Item>;
+}
+
+trait IteratorExt: Iterator + Sized {
+    fn by_ref(&mut self) -> ByRef<Self> {
+        ByRef(self)
+    }
+}
+
+impl<I> IteratorExt for I where I: Iterator {}
+
+struct ByRef<'a, I: 'a + Iterator>(&'a mut I);
+
+impl<'a, A, I> Iterator for ByRef<'a, I> where I: Iterator<Item=A> {
+    type Item = A;
+
+    fn next(&mut self) -> Option< <I as Iterator>::Item > {
+        self.0.next()
+    }
+}
+
+fn is_iterator_of<A, I: Iterator<Item=A>>(_: &I) {}
+
+fn test<A, I: Iterator<Item=A>>(mut it: I) {
+    is_iterator_of::<A, _>(&it.by_ref());
+}
+
+fn main() { }