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adjust obligation spans for super projections

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This commit is contained in:
Lukas Markeffsky 2024-02-08 16:56:47 +01:00
parent 6fa58be8f4
commit 189e7843e8
6 changed files with 84 additions and 52 deletions
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16
compiler/rustc_hir_analysis/src/check/wfcheck.rs
View file

@ -1294,8 +1294,9 @@ fn check_impl<'tcx>(
// Avoid bogus "type annotations needed `Foo: Bar`" errors on `impl Bar for Foo` in case
// other `Foo` impls are incoherent.
tcx.ensure().coherent_trait(trait_ref.def_id)?;
let trait_span = ast_trait_ref.path.span;
let trait_ref = wfcx.normalize(
ast_trait_ref.path.span,
trait_span,
Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
trait_ref,
);
@ -1306,12 +1307,21 @@ fn check_impl<'tcx>(
wfcx.param_env,
wfcx.body_def_id,
trait_pred,
ast_trait_ref.path.span,
trait_span,
item,
);
for obligation in &mut obligations {
if obligation.cause.span != trait_span {
// We already have a better span.
continue;
}
if let Some(pred) = obligation.predicate.to_opt_poly_trait_pred()
&& pred.self_ty().skip_binder() == trait_ref.self_ty()
&& pred.skip_binder().self_ty() == trait_ref.self_ty()
{
obligation.cause.span = ast_self_ty.span;
}
if let Some(pred) = obligation.predicate.to_opt_poly_projection_pred()
&& pred.skip_binder().self_ty() == trait_ref.self_ty()
{
obligation.cause.span = ast_self_ty.span;
}

92
compiler/rustc_trait_selection/src/traits/wf.rs
View file

@ -223,60 +223,84 @@ enum Elaborate {
None,
}
/// Points the cause span of a super predicate at the relevant associated type.
///
/// Given a trait impl item:
///
/// ```ignore (incomplete)
/// impl TargetTrait for TargetType {
/// type Assoc = SomeType;
/// }
/// ```
///
/// And a super predicate of `TargetTrait` that has any of the following forms:
///
/// 1. `<OtherType as OtherTrait>::Assoc = <TargetType as TargetTrait>::Assoc`
/// 2. `<<TargetType as TargetTrait>::Assoc as OtherTrait>::Assoc = OtherType`
/// 3. `<TargetType as TargetTrait>::Assoc: OtherTrait`
///
/// Replace the span of the cause with the span of the associated item:
///
/// ```ignore (incomplete)
/// impl TargetTrait for TargetType {
/// type Assoc = SomeType;
/// // ^^^^^^^^ this span
/// }
/// ```
///
/// Note that bounds that can be expressed as associated item bounds are **not**
/// super predicates. This means that form 2 and 3 from above are only relevant if
/// the [`GenericArgsRef`] of the projection type are not its identity arguments.
fn extend_cause_with_original_assoc_item_obligation<'tcx>(
tcx: TyCtxt<'tcx>,
trait_ref: ty::TraitRef<'tcx>,
item: Option<&hir::Item<'tcx>>,
cause: &mut traits::ObligationCause<'tcx>,
pred: ty::Predicate<'tcx>,
) {
debug!(
"extended_cause_with_original_assoc_item_obligation {:?} {:?} {:?} {:?}",
trait_ref, item, cause, pred
);
debug!(?item, ?cause, ?pred, "extended_cause_with_original_assoc_item_obligation");
let (items, impl_def_id) = match item {
Some(hir::Item { kind: hir::ItemKind::Impl(impl_), owner_id, .. }) => {
(impl_.items, *owner_id)
}
_ => return,
};
let fix_span =
|impl_item_ref: &hir::ImplItemRef| match tcx.hir().impl_item(impl_item_ref.id).kind {
hir::ImplItemKind::Const(ty, _) | hir::ImplItemKind::Type(ty) => ty.span,
_ => impl_item_ref.span,
};
let ty_to_impl_span = |ty: Ty<'_>| {
if let ty::Alias(ty::Projection, projection_ty) = ty.kind()
&& let Some(&impl_item_id) =
tcx.impl_item_implementor_ids(impl_def_id).get(&projection_ty.def_id)
&& let Some(impl_item) =
items.iter().find(|item| item.id.owner_id.to_def_id() == impl_item_id)
{
Some(tcx.hir().impl_item(impl_item.id).expect_type().span)
} else {
None
}
};
// It is fine to skip the binder as we don't care about regions here.
match pred.kind().skip_binder() {
ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj)) => {
// The obligation comes not from the current `impl` nor the `trait` being implemented,
// but rather from a "second order" obligation, where an associated type has a
// projection coming from another associated type. See
// `tests/ui/associated-types/point-at-type-on-obligation-failure.rs` and
// `traits-assoc-type-in-supertrait-bad.rs`.
if let Some(ty::Alias(ty::Projection, projection_ty)) =
proj.term.ty().map(|ty| ty.kind())
&& let Some(&impl_item_id) =
tcx.impl_item_implementor_ids(impl_def_id).get(&projection_ty.def_id)
&& let Some(impl_item_span) = items
.iter()
.find(|item| item.id.owner_id.to_def_id() == impl_item_id)
.map(fix_span)
// Form 1: The obligation comes not from the current `impl` nor the `trait` being
// implemented, but rather from a "second order" obligation, where an associated
// type has a projection coming from another associated type.
// See `tests/ui/traits/assoc-type-in-superbad.rs` for an example.
if let Some(term_ty) = proj.term.ty()
&& let Some(impl_item_span) = ty_to_impl_span(term_ty)
{
cause.span = impl_item_span;
}
// Form 2: A projection obligation for an associated item failed to be met.
if let Some(impl_item_span) = ty_to_impl_span(proj.self_ty()) {
cause.span = impl_item_span;
}
}
ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => {
// An associated item obligation born out of the `trait` failed to be met. An example
// can be seen in `ui/associated-types/point-at-type-on-obligation-failure-2.rs`.
// Form 3: A trait obligation for an associated item failed to be met.
debug!("extended_cause_with_original_assoc_item_obligation trait proj {:?}", pred);
if let ty::Alias(ty::Projection, ty::AliasTy { def_id, .. }) = *pred.self_ty().kind()
&& let Some(&impl_item_id) = tcx.impl_item_implementor_ids(impl_def_id).get(&def_id)
&& let Some(impl_item_span) = items
.iter()
.find(|item| item.id.owner_id.to_def_id() == impl_item_id)
.map(fix_span)
{
if let Some(impl_item_span) = ty_to_impl_span(pred.self_ty()) {
cause.span = impl_item_span;
}
}
@ -355,9 +379,7 @@ fn compute_trait_pred(&mut self, trait_pred: ty::TraitPredicate<'tcx>, elaborate
traits::ObligationCauseCode::DerivedObligation,
);
}
extend_cause_with_original_assoc_item_obligation(
tcx, trait_ref, item, &mut cause, predicate,
);
extend_cause_with_original_assoc_item_obligation(tcx, item, &mut cause, predicate);
traits::Obligation::with_depth(tcx, cause, depth, param_env, predicate)
};

2
tests/ui/associated-types/hr-associated-type-projection-1.rs
View file

@ -11,8 +11,8 @@ fn bug(item: &Self::Item) -> () {
}
impl<T: Copy + std::ops::Deref> UnsafeCopy<'_, T> for T {
//~^ type mismatch resolving `<T as Deref>::Target == T`
type Item = T;
//~^ type mismatch resolving `<T as Deref>::Target == T`
}
pub fn main() {

8
tests/ui/associated-types/hr-associated-type-projection-1.stderr
View file

@ -1,10 +1,10 @@
error[E0271]: type mismatch resolving `<T as Deref>::Target == T`
--> $DIR/hr-associated-type-projection-1.rs:13:33
--> $DIR/hr-associated-type-projection-1.rs:14:17
|
LL | impl<T: Copy + std::ops::Deref> UnsafeCopy<'_, T> for T {
| - ^^^^^^^^^^^^^^^^^ expected type parameter `T`, found associated type
| |
| expected this type parameter
| - expected this type parameter
LL | type Item = T;
| ^ expected type parameter `T`, found associated type
|
= note: expected type parameter `T`
found associated type `<T as Deref>::Target`

2
tests/ui/trait-bounds/super-assoc-mismatch.rs
View file

@ -29,9 +29,9 @@ trait BoundOnGat where Self::Assoc<u8>: Sub {
type Assoc<T>;
}
impl BoundOnGat for u8 {
//~^ ERROR type mismatch resolving `<() as Super>::Assoc == u16`
type Assoc<T> = ();
//~^ ERROR the trait bound `(): Sub` is not satisfied
//~| ERROR type mismatch resolving `<() as Super>::Assoc == u16`
}
fn trivial_bound() where (): Sub {}

16
tests/ui/trait-bounds/super-assoc-mismatch.stderr
View file

@ -16,10 +16,10 @@ LL | trait BoundOnSelf: Sub {}
| ^^^ required by this bound in `BoundOnSelf`
error[E0271]: type mismatch resolving `<() as Super>::Assoc == u16`
--> $DIR/super-assoc-mismatch.rs:10:6
--> $DIR/super-assoc-mismatch.rs:10:22
|
LL | impl BoundOnSelf for () {}
| ^^^^^^^^^^^ type mismatch resolving `<() as Super>::Assoc == u16`
| ^^ type mismatch resolving `<() as Super>::Assoc == u16`
|
note: expected this to be `u16`
--> $DIR/super-assoc-mismatch.rs:5:18
@ -55,10 +55,10 @@ LL | trait BoundOnParam<T: Sub> {}
| ^^^ required by this bound in `BoundOnParam`
error[E0271]: type mismatch resolving `<() as Super>::Assoc == u16`
--> $DIR/super-assoc-mismatch.rs:15:6
--> $DIR/super-assoc-mismatch.rs:15:27
|
LL | impl BoundOnParam<()> for () {}
| ^^^^^^^^^^^^^^^^ type mismatch resolving `<() as Super>::Assoc == u16`
| ^^ type mismatch resolving `<() as Super>::Assoc == u16`
|
note: expected this to be `u16`
--> $DIR/super-assoc-mismatch.rs:5:18
@ -116,7 +116,7 @@ LL | type Assoc: Sub;
| ^^^ required by this bound in `BoundOnAssoc::Assoc`
error[E0277]: the trait bound `(): Sub` is not satisfied
--> $DIR/super-assoc-mismatch.rs:33:21
--> $DIR/super-assoc-mismatch.rs:32:21
|
LL | type Assoc<T> = ();
| ^^ the trait `Sub` is not implemented for `()`, which is required by `<u8 as BoundOnGat>::Assoc<u8>: Sub`
@ -133,10 +133,10 @@ LL | trait BoundOnGat where Self::Assoc<u8>: Sub {
| ^^^ required by this bound in `BoundOnGat`
error[E0271]: type mismatch resolving `<() as Super>::Assoc == u16`
--> $DIR/super-assoc-mismatch.rs:31:6
--> $DIR/super-assoc-mismatch.rs:32:21
|
LL | impl BoundOnGat for u8 {
| ^^^^^^^^^^ type mismatch resolving `<() as Super>::Assoc == u16`
LL | type Assoc<T> = ();
| ^^ type mismatch resolving `<() as Super>::Assoc == u16`
|
note: expected this to be `u16`
--> $DIR/super-assoc-mismatch.rs:5:18