add rust-lang/rust#117432 reproduce

Signed-off-by: Bugen Zhao <i@bugenzhao.com>

src/bin/error_box_provide.rs

@@ -0,0 +1,35 @@
+// https://github.com/rust-lang/rust/issues/117432
+
+#![feature(error_generic_member_access)]
+
+#[derive(Debug)]
+struct Foo;
+
+#[derive(Debug)]
+struct MyError {
+ foo: Foo,
+}
+
+impl std::fmt::Display for MyError {
+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+ write!(f, "MyError")
+ }
+}
+
+impl std::error::Error for MyError {
+ fn provide<'a>(&'a self, request: &mut std::error::Request<'a>) {
+ request.provide_ref::<Foo>(&Foo);
+ }
+}
+
+fn foo_provided<T: std::error::Error>(e: &T) -> bool {
+ std::error::request_ref::<Foo>(e).is_some()
+}
+
+fn main() {
+ let e = MyError { foo: Foo };
+
+ assert!(foo_provided::<MyError>(&e)); // ok
+ assert!(foo_provided::<&MyError>(&&e)); // ok
+ assert!(foo_provided::<Box<MyError>>(&Box::new(e))); // fails
+}