1 files changed, 75 insertions, 0 deletions
diff --git a/tests/ui/traits/issue-103563.rs b/tests/ui/traits/issue-103563.rs
new file mode 100644
index 000000000..cd3eea09b
--- /dev/null
+++ b/tests/ui/traits/issue-103563.rs
@@ -0,0 +1,75 @@
+// build-pass
+
+fn main() {
+    let mut log_service = LogService { inner: Inner };
+    log_service.call(());
+}
+
+pub trait Service<Request> {
+    type Response;
+
+    fn call(&mut self, req: Request) -> Self::Response;
+}
+
+pub struct LogService<S> {
+    inner: S,
+}
+
+impl<T, U, S> Service<T> for LogService<S>
+where
+    S: Service<T, Response = U>,
+    U: Extension + 'static,
+    for<'a> U::Item<'a>: std::fmt::Debug,
+{
+    type Response = S::Response;
+
+    fn call(&mut self, req: T) -> Self::Response {
+        self.inner.call(req)
+    }
+}
+
+pub struct Inner;
+
+impl Service<()> for Inner {
+    type Response = Resp;
+
+    fn call(&mut self, req: ()) -> Self::Response {
+        Resp::A(req)
+    }
+}
+
+pub trait Extension {
+    type Item<'a>;
+
+    fn touch<F>(self, f: F) -> Self
+    where
+        for<'a> F: Fn(Self::Item<'a>);
+}
+
+pub enum Resp {
+    A(()),
+}
+
+impl Extension for Resp {
+    type Item<'a> = RespItem<'a>;
+    fn touch<F>(self, _f: F) -> Self
+    where
+        for<'a> F: Fn(Self::Item<'a>),
+    {
+        match self {
+            Self::A(a) => Self::A(a),
+        }
+    }
+}
+
+pub enum RespItem<'a> {
+    A(&'a ()),
+}
+
+impl<'a> std::fmt::Debug for RespItem<'a> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::A(arg0) => f.debug_tuple("A").field(arg0).finish(),
+        }
+    }
+}