1 files changed, 45 insertions, 0 deletions
diff --git a/tests/ui/type-alias-impl-trait/wf-in-associated-type.rs b/tests/ui/type-alias-impl-trait/wf-in-associated-type.rs
new file mode 100644
index 00000000000..31fbef9f78f
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+++ b/tests/ui/type-alias-impl-trait/wf-in-associated-type.rs
@@ -0,0 +1,45 @@
+// WF check for impl Trait in associated type position.
+//
+// revisions: pass fail
+// [pass] check-pass
+// [fail] check-fail
+
+#![feature(impl_trait_in_assoc_type)]
+
+// The hidden type here (`&'a T`) requires proving `T: 'a`.
+// We know it holds because of implied bounds from the impl header.
+#[cfg(pass)]
+mod pass {
+    trait Trait<Req> {
+        type Opaque1;
+        fn constrain_opaque1(req: Req) -> Self::Opaque1;
+    }
+
+    impl<'a, T> Trait<&'a T> for () {
+        type Opaque1 = impl IntoIterator<Item = impl Sized + 'a>;
+        fn constrain_opaque1(req: &'a T) -> Self::Opaque1 {
+            [req]
+        }
+    }
+}
+
+// The hidden type here (`&'a T`) requires proving `T: 'a`,
+// but that is not known to hold in the impl.
+#[cfg(fail)]
+mod fail {
+    trait Trait<'a, T> {
+        type Opaque;
+        fn constrain_opaque(req: &'a T) -> Self::Opaque;
+    }
+
+    impl<'a, T> Trait<'a, T> for () {
+        type Opaque = impl Sized + 'a;
+        //[fail]~^ ERROR the parameter type `T` may not live long enough
+        //[fail]~| ERROR the parameter type `T` may not live long enough
+        fn constrain_opaque(req: &'a T) -> Self::Opaque {
+            req
+        }
+    }
+}
+
+fn main() {}