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Compute layout with spans for better cycle errors in coroutines #117858

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Nov 13, 2023
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Compute layout with spans for better cycle errors in coroutines #117858

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7 changes: 5 additions & 2 deletions compiler/rustc_ast_lowering/src/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -792,8 +792,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
// debuggers and debugger extensions expect it to be called `__awaitee`. They use
// this name to identify what is being awaited by a suspended async functions.
let awaitee_ident = Ident::with_dummy_span(sym::__awaitee);
let (awaitee_pat, awaitee_pat_hid) =
self.pat_ident_binding_mode(span, awaitee_ident, hir::BindingAnnotation::MUT);
let (awaitee_pat, awaitee_pat_hid) = self.pat_ident_binding_mode(
gen_future_span,
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we use the whole expression span here rather than the span of the .await, when pointing to the local that we use to store the IntoFuture::into_future result. That's because the user probably cares more about the whole async call, not just the fact that the future was awaited.

This matters a lot more when pointing out recursive calls in #117703, but it does make the span a bit better here too.

awaitee_ident,
hir::BindingAnnotation::MUT,
);

let task_context_ident = Ident::with_dummy_span(sym::_task_context);

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10 changes: 5 additions & 5 deletions compiler/rustc_ty_utils/src/layout.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -740,11 +740,11 @@ fn coroutine_layout<'tcx>(
};
let tag_layout = cx.tcx.mk_layout(LayoutS::scalar(cx, tag));

let promoted_layouts = ineligible_locals
.iter()
.map(|local| subst_field(info.field_tys[local].ty))
.map(|ty| Ty::new_maybe_uninit(tcx, ty))
.map(|ty| Ok(cx.layout_of(ty)?.layout));
let promoted_layouts = ineligible_locals.iter().map(|local| {
let field_ty = subst_field(info.field_tys[local].ty);
let uninit_ty = Ty::new_maybe_uninit(tcx, field_ty);
Ok(cx.spanned_layout_of(uninit_ty, info.field_tys[local].source_info.span)?.layout)
});
let prefix_layouts = args
.as_coroutine()
.prefix_tys()
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4 changes: 2 additions & 2 deletions tests/mir-opt/building/async_await.b-{closure#0}.coroutine_resume.0.mir
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@
Static,
),
source_info: SourceInfo {
span: $DIR/async_await.rs:16:9: 16:14 (#8),
span: $DIR/async_await.rs:16:5: 16:14 (#9),
scope: scope[0],
},
ignore_for_traits: false,
Expand All @@ -32,7 +32,7 @@
Static,
),
source_info: SourceInfo {
span: $DIR/async_await.rs:17:9: 17:14 (#10),
span: $DIR/async_await.rs:17:5: 17:14 (#11),
scope: scope[0],
},
ignore_for_traits: false,
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2 changes: 1 addition & 1 deletion tests/ui/type-alias-impl-trait/indirect-recursion-issue-112047.rs
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@@ -1,6 +1,5 @@
// edition: 2021
// build-fail
//~^^ ERROR cycle detected when computing layout of

#![feature(impl_trait_in_assoc_type)]

Expand All @@ -21,6 +20,7 @@ impl Recur for () {

fn recur(self) -> Self::Recur {
async move { recur(self).await; }
//~^ ERROR cycle detected when computing layout of
}
}

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26 changes: 17 additions & 9 deletions tests/ui/type-alias-impl-trait/indirect-recursion-issue-112047.stderr
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Original file line number Diff line number Diff line change
@@ -1,14 +1,22 @@
error[E0391]: cycle detected when computing layout of `{async block@$DIR/indirect-recursion-issue-112047.rs:23:9: 23:42}`
error[E0391]: cycle detected when computing layout of `{async block@$DIR/indirect-recursion-issue-112047.rs:22:9: 22:42}`
--> $DIR/indirect-recursion-issue-112047.rs:22:22
|
= note: ...which requires computing layout of `core::mem::maybe_uninit::MaybeUninit<{async fn body@$DIR/indirect-recursion-issue-112047.rs:15:31: 17:2}>`...
= note: ...which requires computing layout of `core::mem::manually_drop::ManuallyDrop<{async fn body@$DIR/indirect-recursion-issue-112047.rs:15:31: 17:2}>`...
= note: ...which requires computing layout of `{async fn body@$DIR/indirect-recursion-issue-112047.rs:15:31: 17:2}`...
LL | async move { recur(self).await; }
| ^^^^^^^^^^^^^^^^^
|
= note: ...which requires computing layout of `core::mem::maybe_uninit::MaybeUninit<{async fn body@$DIR/indirect-recursion-issue-112047.rs:14:31: 16:2}>`...
= note: ...which requires computing layout of `core::mem::manually_drop::ManuallyDrop<{async fn body@$DIR/indirect-recursion-issue-112047.rs:14:31: 16:2}>`...
note: ...which requires computing layout of `{async fn body@$DIR/indirect-recursion-issue-112047.rs:14:31: 16:2}`...
--> $DIR/indirect-recursion-issue-112047.rs:15:5
|
LL | t.recur().await;
| ^^^^^^^^^^^^^^^
= note: ...which requires computing layout of `core::mem::maybe_uninit::MaybeUninit<<() as Recur>::Recur>`...
= note: ...which requires computing layout of `core::mem::maybe_uninit::MaybeUninit<{async block@$DIR/indirect-recursion-issue-112047.rs:23:9: 23:42}>`...
= note: ...which requires computing layout of `core::mem::manually_drop::ManuallyDrop<{async block@$DIR/indirect-recursion-issue-112047.rs:23:9: 23:42}>`...
= note: ...which again requires computing layout of `{async block@$DIR/indirect-recursion-issue-112047.rs:23:9: 23:42}`, completing the cycle
note: cycle used when elaborating drops for `<impl at $DIR/indirect-recursion-issue-112047.rs:19:1: 19:18>::recur`
--> $DIR/indirect-recursion-issue-112047.rs:22:5
= note: ...which requires computing layout of `core::mem::maybe_uninit::MaybeUninit<{async block@$DIR/indirect-recursion-issue-112047.rs:22:9: 22:42}>`...
= note: ...which requires computing layout of `core::mem::manually_drop::ManuallyDrop<{async block@$DIR/indirect-recursion-issue-112047.rs:22:9: 22:42}>`...
= note: ...which again requires computing layout of `{async block@$DIR/indirect-recursion-issue-112047.rs:22:9: 22:42}`, completing the cycle
note: cycle used when elaborating drops for `<impl at $DIR/indirect-recursion-issue-112047.rs:18:1: 18:18>::recur`
--> $DIR/indirect-recursion-issue-112047.rs:21:5
|
LL | fn recur(self) -> Self::Recur {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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