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Rollup merge of #121863 - lukas-code:silence-mismatched-super-projections, r=lcnr

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silence mismatched types errors for implied projections

Currently, if a trait bound is not satisfied, then we suppress any errors for the trait's supertraits not being satisfied, but still report errors for super projections not being satisfied.

For example:
```rust
trait Super {
    type Assoc;
}
trait Sub: Super<Assoc = ()> {}
```
Before this PR, if `T: Sub` is not satisfied, then errors for `T: Super` are suppressed, but errors for `<T as Super>::Assoc == ()` are still shown. This PR makes it so that errors about super projections not being satisfied are also suppressed.

The errors are only suppressed if the span of the trait obligation matches the span of the super predicate obligation to avoid silencing error that are not related. This PR removes some differences between the spans of supertraits and super projections to make the suppression work correctly.

This PR fixes the majority of the diagnostics fallout when making `Thin` a supertrait of `Sized` (in a future PR).
cc https://github.com/rust-lang/rust/pull/120354#issuecomment-1930585382
cc `@lcnr`
This commit is contained in:
Guillaume Gomez 2024-03-07 15:07:05 +01:00 • committed by GitHub
commit 0e3764889d
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10 changed files with 310 additions and 102 deletions
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46
compiler/rustc_hir_analysis/src/check/wfcheck.rs
View file

@ -298,31 +298,31 @@ fn check_item<'tcx>(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) -> Result<()
hir::ItemKind::Const(ty, ..) => {
check_item_type(tcx, def_id, ty.span, UnsizedHandling::Forbid)
}
hir::ItemKind::Struct(_, ast_generics) => {
hir::ItemKind::Struct(_, hir_generics) => {
let res = check_type_defn(tcx, item, false);
check_variances_for_type_defn(tcx, item, ast_generics);
check_variances_for_type_defn(tcx, item, hir_generics);
res
}
hir::ItemKind::Union(_, ast_generics) => {
hir::ItemKind::Union(_, hir_generics) => {
let res = check_type_defn(tcx, item, true);
check_variances_for_type_defn(tcx, item, ast_generics);
check_variances_for_type_defn(tcx, item, hir_generics);
res
}
hir::ItemKind::Enum(_, ast_generics) => {
hir::ItemKind::Enum(_, hir_generics) => {
let res = check_type_defn(tcx, item, true);
check_variances_for_type_defn(tcx, item, ast_generics);
check_variances_for_type_defn(tcx, item, hir_generics);
res
}
hir::ItemKind::Trait(..) => check_trait(tcx, item),
hir::ItemKind::TraitAlias(..) => check_trait(tcx, item),
// `ForeignItem`s are handled separately.
hir::ItemKind::ForeignMod { .. } => Ok(()),
hir::ItemKind::TyAlias(hir_ty, ast_generics) => {
hir::ItemKind::TyAlias(hir_ty, hir_generics) => {
if tcx.type_alias_is_lazy(item.owner_id) {
// Bounds of lazy type aliases and of eager ones that contain opaque types are respected.
// E.g: `type X = impl Trait;`, `type X = (impl Trait, Y);`.
let res = check_item_type(tcx, def_id, hir_ty.span, UnsizedHandling::Allow);
check_variances_for_type_defn(tcx, item, ast_generics);
check_variances_for_type_defn(tcx, item, hir_generics);
res
} else {
Ok(())
@ -1277,16 +1277,16 @@ fn check_item_type(
})
}
#[instrument(level = "debug", skip(tcx, ast_self_ty, ast_trait_ref))]
#[instrument(level = "debug", skip(tcx, hir_self_ty, hir_trait_ref))]
fn check_impl<'tcx>(
tcx: TyCtxt<'tcx>,
item: &'tcx hir::Item<'tcx>,
ast_self_ty: &hir::Ty<'_>,
ast_trait_ref: &Option<hir::TraitRef<'_>>,
hir_self_ty: &hir::Ty<'_>,
hir_trait_ref: &Option<hir::TraitRef<'_>>,
) -> Result<(), ErrorGuaranteed> {
enter_wf_checking_ctxt(tcx, item.span, item.owner_id.def_id, |wfcx| {
match ast_trait_ref {
Some(ast_trait_ref) => {
match hir_trait_ref {
Some(hir_trait_ref) => {
// `#[rustc_reservation_impl]` impls are not real impls and
// therefore don't need to be WF (the trait's `Self: Trait` predicate
// won't hold).
@ -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 = hir_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,
);
@ -1306,14 +1307,23 @@ 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;
obligation.cause.span = hir_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 = hir_self_ty.span;
}
}
debug!(?obligations);
@ -1327,7 +1337,7 @@ fn check_impl<'tcx>(
self_ty,
);
wfcx.register_wf_obligation(
ast_self_ty.span,
hir_self_ty.span,
Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
self_ty.into(),
);