Rollup merge of #98371 - compiler-errors:better-opaque-printing, r=oli-obk

Fix printing `impl trait` under binders

Before, we would render `impl for<'a> Trait<'a>` like `impl Trait<for<'a> 'a>`, lol.

3 files changed, 46 insertions, 1 deletions

diff --git a/src/test/ui/async-await/issue-70935-complex-spans.drop_tracking.stderr b/src/test/ui/async-await/issue-70935-complex-spans.drop_tracking.stderr
index 43b7cb8cece..e9b76b19dc4 100644
--- a/src/test/ui/async-await/issue-70935-complex-spans.drop_tracking.stderr
+++ b/src/test/ui/async-await/issue-70935-complex-spans.drop_tracking.stderr
@@ -22,7 +22,7 @@ LL |   async fn baz<T>(_c: impl FnMut() -> T) where T: Future<Output=()> {
 LL | |
 LL | | }
    | |_^
-   = note: required because it captures the following types: `ResumeTy`, `impl Future<Output = ()>`, `()`
+   = note: required because it captures the following types: `ResumeTy`, `impl for<'r, 's, 't0> Future<Output = ()>`, `()`
 note: required because it's used within this `async` block
   --> $DIR/issue-70935-complex-spans.rs:23:16
    |
diff --git a/src/test/ui/impl-trait/printing-binder.rs b/src/test/ui/impl-trait/printing-binder.rs
new file mode 100644
index 00000000000..273b5dcdb09
--- /dev/null
+++ b/src/test/ui/impl-trait/printing-binder.rs
@@ -0,0 +1,14 @@
+trait Trait<'a> {}
+impl<T> Trait<'_> for T {}
+fn whatever() -> impl for<'a> Trait<'a> + for<'b> Trait<'b> {}
+
+fn whatever2() -> impl for<'c> Fn(&'c ()) {
+    |_: &()| {}
+}
+
+fn main() {
+    let x: u32 = whatever();
+    //~^ ERROR mismatched types
+    let x2: u32 = whatever2();
+    //~^ ERROR mismatched types
+}
diff --git a/src/test/ui/impl-trait/printing-binder.stderr b/src/test/ui/impl-trait/printing-binder.stderr
new file mode 100644
index 00000000000..5ffec8af102
--- /dev/null
+++ b/src/test/ui/impl-trait/printing-binder.stderr
@@ -0,0 +1,31 @@
+error[E0308]: mismatched types
+  --> $DIR/printing-binder.rs:10:18
+   |
+LL | fn whatever() -> impl for<'a> Trait<'a> + for<'b> Trait<'b> {}
+   |                  ------------------------------------------ the found opaque type
+...
+LL |     let x: u32 = whatever();
+   |            ---   ^^^^^^^^^^ expected `u32`, found opaque type
+   |            |
+   |            expected due to this
+   |
+   = note:     expected type `u32`
+           found opaque type `impl for<'a> Trait<'a> + for<'b> Trait<'b>`
+
+error[E0308]: mismatched types
+  --> $DIR/printing-binder.rs:12:19
+   |
+LL | fn whatever2() -> impl for<'c> Fn(&'c ()) {
+   |                   ----------------------- the found opaque type
+...
+LL |     let x2: u32 = whatever2();
+   |             ---   ^^^^^^^^^^^ expected `u32`, found opaque type
+   |             |
+   |             expected due to this
+   |
+   = note:     expected type `u32`
+           found opaque type `impl for<'c> Fn(&'c ())`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.