1 files changed, 34 insertions, 0 deletions
diff --git a/tests/ui/traits/new-solver/alias-sub.rs b/tests/ui/traits/new-solver/alias-sub.rs
new file mode 100644
index 000000000..30c1981a9
--- /dev/null
+++ b/tests/ui/traits/new-solver/alias-sub.rs
@@ -0,0 +1,34 @@
+// compile-flags: -Ztrait-solver=next
+// check-pass
+
+trait Trait {
+    type Assoc: Sized;
+}
+
+impl Trait for &'static str {
+    type Assoc = &'static str;
+}
+
+// Wrapper is just here to get around stupid `Sized` obligations in mir typeck
+struct Wrapper<T: ?Sized>(std::marker::PhantomData<T>);
+fn mk<T: Trait>(x: T) -> Wrapper<<T as Trait>::Assoc> { todo!() }
+
+
+trait IsStaticStr {}
+impl IsStaticStr for (&'static str,) {}
+fn define<T: IsStaticStr>(_: T) {}
+
+fn foo<'a, T: Trait>() {
+    let y = Default::default();
+
+    // `<?0 as Trait>::Assoc <: &'a str`
+    // In the old solver, this would *equate* the LHS and RHS.
+    let _: Wrapper<&'a str> = mk(y);
+
+    // ... then later on, we constrain `?0 = &'static str`
+    // but that should not mean that `'a = 'static`, because
+    // we should use *sub* above.
+    define((y,));
+}
+
+fn main() {}