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Rollup merge of #107201 - compiler-errors:confusing-async-fn-note, r=estebank

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Remove confusing 'while checking' note from opaque future type mismatches

Maybe I'm just misinterpreting the wording of the note. The only value I can see in this note is that it points out where the async's opaque future is coming from, but the way it's doing it is misleading IMO.

For example:

```rust
note: while checking the return type of the `async fn`
  --> $DIR/dont-suggest-missing-await.rs:7:24
   |
LL | async fn make_u32() -> u32 {
   |                        ^^^ checked the `Output` of this `async fn`, found opaque type
```

We point at the type `u32` in the HIR, but then say "found opaque type". We also say "while checking"... but we're typechecking a totally different function when we get this type mismatch!

r? ``@estebank`` but feel free to reassign and/or take your time reviewing this. I'd be inclined to also discuss reworking the presentation of this type mismatch to restore some of these labels in a way that makes it more clear what it's trying to point out.
This commit is contained in:
Matthias Krüger 2023-02-02 06:52:13 +01:00 • committed by GitHub
commit 480c4a18d5
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18 changed files with 35 additions and 236 deletions
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62
compiler/rustc_infer/src/infer/error_reporting/mod.rs
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@ -60,7 +60,7 @@ use crate::traits::{
use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
use rustc_errors::{pluralize, struct_span_err, Diagnostic, ErrorGuaranteed, IntoDiagnosticArg};
use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString, MultiSpan};
use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
use rustc_hir as hir;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LocalDefId};
@ -1470,51 +1470,17 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
for (key, values) in types.iter() {
let count = values.len();
let kind = key.descr();
let mut returned_async_output_error = false;
for &sp in values {
if sp.is_desugaring(DesugaringKind::Async) && !returned_async_output_error {
if [sp] != err.span.primary_spans() {
let mut span: MultiSpan = sp.into();
span.push_span_label(
sp,
format!(
"checked the `Output` of this `async fn`, {}{} {}{}",
if count > 1 { "one of the " } else { "" },
target,
kind,
pluralize!(count),
),
);
err.span_note(
span,
"while checking the return type of the `async fn`",
);
} else {
err.span_label(
sp,
format!(
"checked the `Output` of this `async fn`, {}{} {}{}",
if count > 1 { "one of the " } else { "" },
target,
kind,
pluralize!(count),
),
);
err.note("while checking the return type of the `async fn`");
}
returned_async_output_error = true;
} else {
err.span_label(
sp,
format!(
"{}{} {}{}",
if count == 1 { "the " } else { "one of the " },
target,
kind,
pluralize!(count),
),
);
}
err.span_label(
sp,
format!(
"{}{} {}{}",
if count == 1 { "the " } else { "one of the " },
target,
kind,
pluralize!(count),
),
);
}
}
}
@ -1537,7 +1503,11 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
// |
// = note: expected unit type `()`
// found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
if !self.ignore_span.overlaps(span) {
//
// Also ignore opaque `Future`s that come from async fns.
if !self.ignore_span.overlaps(span)
&& !span.is_desugaring(DesugaringKind::Async)
{
self.types.entry(kind).or_default().insert(span);
}
}