Add regression test

Author: oli-obk

tests/ui/impl-trait/recursive-parent-trait-method-call.rs

@@ -0,0 +1,39 @@
+//@ edition: 2021
+
+use std::future::Future;
+use std::pin::Pin;
+
+trait FutureExt: Future + Sized + Send + 'static {
+    fn boxed(self) -> Pin<Box<dyn Future<Output = Self::Output> + Send + 'static>> {
+        Box::pin(self)
+    }
+}
+
+trait StreamExt: Future + Sized + Send + 'static {
+    fn boxed(self) -> Pin<Box<dyn Future<Output = Self::Output> + Send + 'static>> {
+        Box::pin(self)
+    }
+}
+
+impl<T: Future + Sized + Send + 'static> FutureExt for T {}
+
+fn go(i: usize) -> impl Future<Output = ()> + Send + 'static {
+    async move {
+        if i != 0 {
+            spawn(async move {
+                let fut = go(i - 1).boxed();
+                //~^ ERROR: multiple applicable items in scope
+                fut.await;
+            })
+            .await;
+        }
+    }
+}
+
+pub fn spawn<T: Send>(
+    _: impl Future<Output = T> + Send + 'static,
+) -> impl Future<Output = ()> + Send + 'static {
+    async move { todo!() }
+}
+
+fn main() {}

tests/ui/impl-trait/recursive-parent-trait-method-call.stderr

@@ -0,0 +1,28 @@
+error[E0034]: multiple applicable items in scope
+  --> $DIR/recursive-parent-trait-method-call.rs:24:37
+   |
+LL |                 let fut = go(i - 1).boxed();
+   |                                     ^^^^^ multiple `boxed` found
+   |
+note: candidate #1 is defined in the trait `StreamExt`
+  --> $DIR/recursive-parent-trait-method-call.rs:13:5
+   |
+LL |     fn boxed(self) -> Pin<Box<dyn Future<Output = Self::Output> + Send + 'static>> {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: candidate #2 is defined in an impl of the trait `FutureExt` for the type `T`
+  --> $DIR/recursive-parent-trait-method-call.rs:7:5
+   |
+LL |     fn boxed(self) -> Pin<Box<dyn Future<Output = Self::Output> + Send + 'static>> {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: disambiguate the method for candidate #1
+   |
+LL |                 let fut = StreamExt::boxed(go(i - 1));
+   |                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+help: disambiguate the method for candidate #2
+   |
+LL |                 let fut = FutureExt::boxed(go(i - 1));
+   |                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0034`.