Handle ambiguous projections

tests/ui/crashes/ice-rust-107877.rs

@@ -0,0 +1,17 @@
+#![allow(dead_code)]
+
+struct Foo;
+
+impl<'a> std::convert::TryFrom<&'a String> for Foo {
+    type Error = std::convert::Infallible;
+
+    fn try_from(_: &'a String) -> Result<Self, Self::Error> {
+        Ok(Foo)
+    }
+}
+
+fn find<E>(_: impl std::convert::TryInto<Foo, Error = E>) {}
+
+fn main() {
+    find(&String::new());
+}