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rust-bors merged 7 commits into from
Apr 7, 2026
Merged

ty::Alias refactor #154758

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cf96c5f
`ty::Alias` refactor: change APIs
WaffleLapkin Mar 5, 2026
0f76708
`ty::Alias` refactor: fixup all the compiler code
WaffleLapkin Mar 5, 2026
5d5cdef
`ty::Alias` refactor: fix rustdoc
WaffleLapkin Apr 3, 2026
2ea74a9
`ty::Alias` refactor: fix clippy
WaffleLapkin Apr 3, 2026
8c490f3
track caller
WaffleLapkin Apr 3, 2026
ec8c489
`ty::Alias` refactor: bless tests
WaffleLapkin Apr 3, 2026
6ab50d5
`ty::Alias` review comments
WaffleLapkin Apr 6, 2026
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14 changes: 7 additions & 7 deletions compiler/rustc_borrowck/src/diagnostics/opaque_types.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -219,11 +219,11 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for FindOpaqueRegion<'_, 'tcx> {
fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
// If we find an opaque in a local ty, then for each of its captured regions,
// try to find a path between that captured regions and our borrow region...
if let ty::Alias(ty::Opaque, opaque) = *ty.kind()
if let ty::Alias(opaque @ ty::AliasTy { kind: ty::Opaque { def_id }, .. }) = *ty.kind()
&& let hir::OpaqueTyOrigin::FnReturn { parent, in_trait_or_impl: None } =
self.tcx.opaque_ty_origin(opaque.def_id)
self.tcx.opaque_ty_origin(def_id)
{
let variances = self.tcx.variances_of(opaque.def_id);
let variances = self.tcx.variances_of(def_id);
for (idx, (arg, variance)) in std::iter::zip(opaque.args, variances).enumerate() {
// Skip uncaptured args.
if *variance == ty::Bivariant {
Expand Down Expand Up @@ -252,7 +252,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for FindOpaqueRegion<'_, 'tcx> {
&& call_def_id == parent
&& let Locations::Single(location) = constraint.locations
{
return ControlFlow::Break((opaque.def_id, idx, location));
return ControlFlow::Break((def_id, idx, location));
}
}
}
Expand All @@ -276,11 +276,11 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for CheckExplicitRegionMentionAndCollectGen

fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
match *ty.kind() {
ty::Alias(ty::Opaque, opaque) => {
if self.seen_opaques.insert(opaque.def_id) {
ty::Alias(opaque @ ty::AliasTy { kind: ty::Opaque { def_id }, .. }) => {
if self.seen_opaques.insert(def_id) {
for (bound, _) in self
.tcx
.explicit_item_bounds(opaque.def_id)
.explicit_item_bounds(def_id)
.iter_instantiated_copied(self.tcx, opaque.args)
{
bound.visit_with(self)?;
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_borrowck/src/diagnostics/region_errors.rs
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Expand Up @@ -594,7 +594,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
let ErrorConstraintInfo { outlived_fr, span, .. } = errci;

let mut output_ty = self.regioncx.universal_regions().unnormalized_output_ty;
if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) = *output_ty.kind() {
if let ty::Alias(ty::AliasTy { kind: ty::Opaque { def_id }, .. }) = *output_ty.kind() {
output_ty = self.infcx.tcx.type_of(def_id).instantiate_identity()
};

Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_borrowck/src/lib.rs
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Expand Up @@ -1899,7 +1899,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
| ty::Never
| ty::Tuple(_)
| ty::UnsafeBinder(_)
| ty::Alias(_, _)
| ty::Alias(_)
| ty::Param(_)
| ty::Bound(_, _)
| ty::Infer(_)
Expand Down Expand Up @@ -1941,7 +1941,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
| ty::CoroutineWitness(..)
| ty::Never
| ty::UnsafeBinder(_)
| ty::Alias(_, _)
| ty::Alias(_)
| ty::Param(_)
| ty::Bound(_, _)
| ty::Infer(_)
Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_borrowck/src/region_infer/opaque_types/member_constraints.rs
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Expand Up @@ -176,8 +176,8 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for CollectMemberConstraintsVisitor<'_, '_,
| ty::CoroutineClosure(def_id, args)
| ty::Coroutine(def_id, args) => self.visit_closure_args(def_id, args),

ty::Alias(kind, ty::AliasTy { def_id, args, .. })
if let Some(variances) = self.cx().opt_alias_variances(kind, def_id) =>
ty::Alias(ty::AliasTy { kind, args, .. })
if let Some(variances) = self.cx().opt_alias_variances(kind, kind.def_id()) =>
{
// Skip lifetime parameters that are not captured, since they do
// not need member constraints registered for them; we'll erase
Expand Down
20 changes: 11 additions & 9 deletions compiler/rustc_borrowck/src/region_infer/opaque_types/mod.rs
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Expand Up @@ -367,9 +367,10 @@ fn compute_definition_site_hidden_types_from_defining_uses<'tcx>(
// usage of the opaque type and we can ignore it. This check is mirrored in typeck's
// writeback.
if !rcx.infcx.tcx.use_typing_mode_borrowck() {
if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.skip_binder().kind()
&& alias_ty.def_id == opaque_type_key.def_id.to_def_id()
&& alias_ty.args == opaque_type_key.args
if let &ty::Alias(ty::AliasTy { kind: ty::Opaque { def_id }, args, .. }) =
hidden_type.ty.skip_binder().kind()
&& def_id == opaque_type_key.def_id.to_def_id()
&& args == opaque_type_key.args
{
continue;
}
Expand Down Expand Up @@ -499,8 +500,8 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for ToArgRegionsFolder<'_, 'tcx> {
Ty::new_coroutine(tcx, def_id, self.fold_closure_args(def_id, args)?)
}

ty::Alias(kind, ty::AliasTy { def_id, args, .. })
if let Some(variances) = tcx.opt_alias_variances(kind, def_id) =>
ty::Alias(ty::AliasTy { kind, args, .. })
if let Some(variances) = tcx.opt_alias_variances(kind, kind.def_id()) =>
{
let args = tcx.mk_args_from_iter(std::iter::zip(variances, args.iter()).map(
|(&v, s)| {
Expand All @@ -511,7 +512,7 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for ToArgRegionsFolder<'_, 'tcx> {
}
},
))?;
ty::AliasTy::new_from_args(tcx, def_id, args).to_ty(tcx)
ty::AliasTy::new_from_args(tcx, kind, args).to_ty(tcx)
}

_ => ty.try_super_fold_with(self)?,
Expand Down Expand Up @@ -540,9 +541,10 @@ pub(crate) fn apply_definition_site_hidden_types<'tcx>(
for &(key, hidden_type) in opaque_types {
let Some(expected) = hidden_types.get(&key.def_id) else {
if !tcx.use_typing_mode_borrowck() {
if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
&& alias_ty.def_id == key.def_id.to_def_id()
&& alias_ty.args == key.args
if let &ty::Alias(ty::AliasTy { kind: ty::Opaque { def_id }, args, .. }) =
hidden_type.ty.kind()
&& def_id == key.def_id.to_def_id()
&& args == key.args
{
continue;
} else {
Expand Down
3 changes: 2 additions & 1 deletion compiler/rustc_borrowck/src/type_check/mod.rs
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Expand Up @@ -450,7 +450,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
// Necessary for non-trivial patterns whose user-type annotation is an opaque type,
// e.g. `let (_a,): Tait = whatever`, see #105897
if !self.infcx.next_trait_solver()
&& let ty::Alias(ty::Opaque, ..) = curr_projected_ty.ty.kind()
&& let ty::Alias(ty::AliasTy { kind: ty::Opaque { .. }, .. }) =
curr_projected_ty.ty.kind()
{
// There is nothing that we can compare here if we go through an opaque type.
// We're always in its defining scope as we can otherwise not project through
Expand Down
16 changes: 10 additions & 6 deletions compiler/rustc_borrowck/src/type_check/relate_tys.rs
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Expand Up @@ -150,8 +150,12 @@ impl<'a, 'b, 'tcx> NllTypeRelating<'a, 'b, 'tcx> {
};

let (a, b) = match (a.kind(), b.kind()) {
(&ty::Alias(ty::Opaque, ..), _) => (a, enable_subtyping(b, true)?),
(_, &ty::Alias(ty::Opaque, ..)) => (enable_subtyping(a, false)?, b),
(&ty::Alias(ty::AliasTy { kind: ty::Opaque { .. }, .. }), _) => {
(a, enable_subtyping(b, true)?)
}
(_, &ty::Alias(ty::AliasTy { kind: ty::Opaque { .. }, .. })) => {
(enable_subtyping(a, false)?, b)
}
_ => unreachable!(
"expected at least one opaque type in `relate_opaques`, got {a} and {b}."
),
Expand Down Expand Up @@ -382,8 +386,8 @@ impl<'b, 'tcx> TypeRelation<TyCtxt<'tcx>> for NllTypeRelating<'_, 'b, 'tcx> {
}

(
&ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, .. }),
&ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, .. }),
&ty::Alias(ty::AliasTy { kind: ty::Opaque { def_id: a_def_id }, .. }),
&ty::Alias(ty::AliasTy { kind: ty::Opaque { def_id: b_def_id }, .. }),
) if a_def_id == b_def_id || infcx.next_trait_solver() => {
super_combine_tys(&infcx.infcx, self, a, b).map(|_| ()).or_else(|err| {
// This behavior is only there for the old solver, the new solver
Expand All @@ -397,8 +401,8 @@ impl<'b, 'tcx> TypeRelation<TyCtxt<'tcx>> for NllTypeRelating<'_, 'b, 'tcx> {
if a_def_id.is_local() { self.relate_opaques(a, b) } else { Err(err) }
})?;
}
(&ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }), _)
| (_, &ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }))
(&ty::Alias(ty::AliasTy { kind: ty::Opaque { def_id }, .. }), _)
| (_, &ty::Alias(ty::AliasTy { kind: ty::Opaque { def_id }, .. }))
if def_id.is_local() && !self.type_checker.infcx.next_trait_solver() =>
{
self.relate_opaques(a, b)?;
Expand Down
14 changes: 11 additions & 3 deletions compiler/rustc_const_eval/src/util/type_name.rs
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Expand Up @@ -53,14 +53,22 @@ impl<'tcx> Printer<'tcx> for TypeNamePrinter<'tcx> {
// Types with identity (print the module path).
ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), args)
| ty::FnDef(def_id, args)
| ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, args, .. })
| ty::Alias(ty::AliasTy {
kind: ty::Projection { def_id } | ty::Opaque { def_id },
args,
..
})
| ty::Closure(def_id, args)
| ty::CoroutineClosure(def_id, args)
| ty::Coroutine(def_id, args) => self.print_def_path(def_id, args),
ty::Foreign(def_id) => self.print_def_path(def_id, &[]),

ty::Alias(ty::Free, _) => bug!("type_name: unexpected free alias"),
ty::Alias(ty::Inherent, _) => bug!("type_name: unexpected inherent projection"),
ty::Alias(ty::AliasTy { kind: ty::Free { .. }, .. }) => {
bug!("type_name: unexpected free alias")
}
ty::Alias(ty::AliasTy { kind: ty::Inherent { .. }, .. }) => {
bug!("type_name: unexpected inherent projection")
}
ty::CoroutineWitness(..) => bug!("type_name: unexpected `CoroutineWitness`"),
}
}
Expand Down
14 changes: 7 additions & 7 deletions compiler/rustc_hir_analysis/src/check/check.rs
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Expand Up @@ -523,8 +523,8 @@ fn sanity_check_found_hidden_type<'tcx>(
// Nothing was actually constrained.
return Ok(());
}
if let ty::Alias(ty::Opaque, alias) = ty.ty.kind() {
if alias.def_id == key.def_id.to_def_id() && alias.args == key.args {
if let &ty::Alias(alias @ ty::AliasTy { kind: ty::Opaque { def_id }, .. }) = ty.ty.kind() {
if def_id == key.def_id.to_def_id() && alias.args == key.args {
// Nothing was actually constrained, this is an opaque usage that was
// only discovered to be opaque after inference vars resolved.
return Ok(());
Expand Down Expand Up @@ -2150,7 +2150,7 @@ fn opaque_type_cycle_error(tcx: TyCtxt<'_>, opaque_def_id: LocalDefId) -> ErrorG
impl<'tcx> ty::TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector {
fn visit_ty(&mut self, t: Ty<'tcx>) {
match *t.kind() {
ty::Alias(ty::Opaque, ty::AliasTy { def_id: def, .. }) => {
ty::Alias(ty::AliasTy { kind: ty::Opaque { def_id: def }, .. }) => {
self.opaques.push(def);
}
ty::Closure(def_id, ..) | ty::Coroutine(def_id, ..) => {
Expand Down Expand Up @@ -2183,10 +2183,10 @@ fn opaque_type_cycle_error(tcx: TyCtxt<'_>, opaque_def_id: LocalDefId) -> ErrorG
let mut label_match = |ty: Ty<'_>, span| {
for arg in ty.walk() {
if let ty::GenericArgKind::Type(ty) = arg.kind()
&& let ty::Alias(
ty::Opaque,
ty::AliasTy { def_id: captured_def_id, .. },
) = *ty.kind()
&& let ty::Alias(ty::AliasTy {
kind: ty::Opaque { def_id: captured_def_id },
..
}) = *ty.kind()
&& captured_def_id == opaque_def_id.to_def_id()
{
err.span_label(
Expand Down
26 changes: 15 additions & 11 deletions compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
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Expand Up @@ -820,10 +820,10 @@ where
}

fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
if let ty::Alias(ty::Projection, proj) = ty.kind()
&& self.cx().is_impl_trait_in_trait(proj.def_id)
if let &ty::Alias(proj @ ty::AliasTy { kind: ty::Projection { def_id }, .. }) = ty.kind()
&& self.cx().is_impl_trait_in_trait(def_id)
{
if let Some((ty, _)) = self.types.get(&proj.def_id) {
if let Some((ty, _)) = self.types.get(&def_id) {
return *ty;
}
//FIXME(RPITIT): Deny nested RPITIT in args too
Expand All @@ -832,11 +832,11 @@ where
}
// Replace with infer var
let infer_ty = self.ocx.infcx.next_ty_var(self.span);
self.types.insert(proj.def_id, (infer_ty, proj.args));
self.types.insert(def_id, (infer_ty, proj.args));
// Recurse into bounds
for (pred, pred_span) in self
.cx()
.explicit_item_bounds(proj.def_id)
.explicit_item_bounds(def_id)
.iter_instantiated_copied(self.cx(), proj.args)
{
let pred = pred.fold_with(self);
Expand All @@ -851,7 +851,7 @@ where
ObligationCause::new(
self.span,
self.body_id,
ObligationCauseCode::WhereClause(proj.def_id, pred_span),
ObligationCauseCode::WhereClause(def_id, pred_span),
),
self.param_env,
pred,
Expand Down Expand Up @@ -922,8 +922,12 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
} else {
let guar = match region.opt_param_def_id(self.tcx, self.impl_m_def_id) {
Some(def_id) => {
let return_span = if let ty::Alias(ty::Opaque, opaque_ty) = self.ty.kind() {
self.tcx.def_span(opaque_ty.def_id)
let return_span = if let &ty::Alias(ty::AliasTy {
kind: ty::Opaque { def_id: opaque_ty_def_id },
..
}) = self.ty.kind()
{
self.tcx.def_span(opaque_ty_def_id)
} else {
self.return_span
};
Expand Down Expand Up @@ -2703,8 +2707,8 @@ fn param_env_with_gat_bounds<'tcx>(
let bound_vars = tcx.mk_bound_variable_kinds(&bound_vars);

match normalize_impl_ty.kind() {
ty::Alias(ty::Projection, proj)
if proj.def_id == trait_ty.def_id && proj.args == rebased_args =>
&ty::Alias(proj @ ty::AliasTy { kind: ty::Projection { def_id }, .. })
if def_id == trait_ty.def_id && proj.args == rebased_args =>
{
// Don't include this predicate if the projected type is
// exactly the same as the projection. This can occur in
Expand Down Expand Up @@ -2746,7 +2750,7 @@ fn try_report_async_mismatch<'tcx>(
return Ok(());
}

let ty::Alias(ty::Projection, ty::AliasTy { def_id: async_future_def_id, .. }) =
let ty::Alias(ty::AliasTy { kind: ty::Projection { def_id: async_future_def_id }, .. }) =
*tcx.fn_sig(trait_m.def_id).skip_binder().skip_binder().output().kind()
else {
bug!("expected `async fn` to return an RPITIT");
Expand Down
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