Rollup merge of #91022 - compiler-errors:modulo_infer, r=estebank

Suggest `await` in more situations where infer types are involved

Currently we use `TyS::same_type` in diagnostics that suggest adding `.await` to opaque future types.

This change makes the suggestion slightly more general, when we're comparing types like `Result<T, E>` and `Result<_, _>` which happens sometimes in places like `match` patterns or `let` statements with partially-elaborated types.

----

Question:
1. Is this change worthwhile? Totally fine if it doesn't make sense adding.
2. Should `same_type_modulo_infer` live in `rustc_infer::infer::error_reporting` or alongside the other method in `rustc_middle::ty::util`?
3. Should we generalize this change? I wanted to change all usages, but I don't want erroneous suggestions when adding `.field_name`...

2 files changed, 54 insertions, 1 deletions

diff --git a/src/test/ui/async-await/suggest-missing-await.rs b/src/test/ui/async-await/suggest-missing-await.rs
index df74df79d9f..c7c5b51e733 100644
--- a/src/test/ui/async-await/suggest-missing-await.rs
+++ b/src/test/ui/async-await/suggest-missing-await.rs
@@ -54,4 +54,21 @@ async fn suggest_await_on_match_expr() {
     };
 }
 
+async fn dummy_result() -> Result<(), ()> {
+    Ok(())
+}
+
+#[allow(unused)]
+async fn suggest_await_in_generic_pattern() {
+    match dummy_result() {
+        //~^ HELP consider `await`ing on the `Future`
+        //~| HELP consider `await`ing on the `Future`
+        //~| SUGGESTION .await
+        Ok(_) => {}
+        //~^ ERROR mismatched types [E0308]
+        Err(_) => {}
+        //~^ ERROR mismatched types [E0308]
+    }
+}
+
 fn main() {}
diff --git a/src/test/ui/async-await/suggest-missing-await.stderr b/src/test/ui/async-await/suggest-missing-await.stderr
index bea50b3bfc0..3cca9616a35 100644
--- a/src/test/ui/async-await/suggest-missing-await.stderr
+++ b/src/test/ui/async-await/suggest-missing-await.stderr
@@ -106,6 +106,42 @@ help: consider `await`ing on the `Future`
 LL |     let _x = match dummy().await {
    |                           ++++++
 
-error: aborting due to 5 previous errors
+error[E0308]: mismatched types
+  --> $DIR/suggest-missing-await.rs:67:9
+   |
+LL |         Ok(_) => {}
+   |         ^^^^^ expected opaque type, found enum `Result`
+   |
+note: while checking the return type of the `async fn`
+  --> $DIR/suggest-missing-await.rs:57:28
+   |
+LL | async fn dummy_result() -> Result<(), ()> {
+   |                            ^^^^^^^^^^^^^^ checked the `Output` of this `async fn`, expected opaque type
+   = note: expected opaque type `impl Future<Output = Result<(), ()>>`
+                     found enum `Result<_, _>`
+help: consider `await`ing on the `Future`
+   |
+LL |     match dummy_result().await {
+   |                         ++++++
+
+error[E0308]: mismatched types
+  --> $DIR/suggest-missing-await.rs:69:9
+   |
+LL |         Err(_) => {}
+   |         ^^^^^^ expected opaque type, found enum `Result`
+   |
+note: while checking the return type of the `async fn`
+  --> $DIR/suggest-missing-await.rs:57:28
+   |
+LL | async fn dummy_result() -> Result<(), ()> {
+   |                            ^^^^^^^^^^^^^^ checked the `Output` of this `async fn`, expected opaque type
+   = note: expected opaque type `impl Future<Output = Result<(), ()>>`
+                     found enum `Result<_, _>`
+help: consider `await`ing on the `Future`
+   |
+LL |     match dummy_result().await {
+   |                         ++++++
+
+error: aborting due to 7 previous errors
 
 For more information about this error, try `rustc --explain E0308`.