Avoid ICE in printing RPITIT type

2 files changed, 38 insertions, 0 deletions

diff --git a/src/test/ui/impl-trait/in-trait/issue-102571.rs b/src/test/ui/impl-trait/in-trait/issue-102571.rs
new file mode 100644
index 00000000000..61c91e64417
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/issue-102571.rs
@@ -0,0 +1,24 @@
+#![feature(return_position_impl_trait_in_trait)]
+#![allow(incomplete_features)]
+
+use std::fmt::Display;
+use std::ops::Deref;
+
+trait Foo {
+    fn bar(self) -> impl Deref<Target = impl Display + ?Sized>;
+}
+
+struct A;
+
+impl Foo for A {
+    fn bar(self) -> &'static str {
+        "Hello, world"
+    }
+}
+
+fn foo<T: Foo>(t: T) {
+    let () = t.bar();
+    //~^ ERROR mismatched types
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/in-trait/issue-102571.stderr b/src/test/ui/impl-trait/in-trait/issue-102571.stderr
new file mode 100644
index 00000000000..87219941d91
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/issue-102571.stderr
@@ -0,0 +1,14 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-102571.rs:20:9
+   |
+LL |     let () = t.bar();
+   |         ^^   ------- this expression has type `impl Deref<Target = impl std::fmt::Display + ?Sized>`
+   |         |
+   |         expected associated type, found `()`
+   |
+   = note: expected associated type `impl Deref<Target = impl std::fmt::Display + ?Sized>`
+                    found unit type `()`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.