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Merged
rust-bors merged 1 commit into from
Sep 17, 2026
Merged

yeet alias new_from_def_id #162760

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12 changes: 6 additions & 6 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/bounds.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -476,12 +476,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
);
debug!(?alias_args);

ty::AliasTerm::new_from_def_id(
tcx,
assoc_item.def_id,
alias_args,
ty::AliasConstInherentArgsKind::WithSelf,
)
let kind = if let ty::AssocTag::Const = assoc_tag {
ty::AliasTermKind::ProjectionConst { def_id: assoc_item.def_id }
} else {
ty::AliasTermKind::ProjectionTy { def_id: assoc_item.def_id }
};
ty::AliasTerm::new_from_args(tcx, kind, alias_args)
})
};

Expand Down
10 changes: 4 additions & 6 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -480,12 +480,10 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
&item_segment,
trait_ref.args,
);
ty::AliasTerm::new_from_def_id(
tcx,
assoc_item.def_id,
alias_args,
ty::AliasConstInherentArgsKind::WithSelf,
)
let kind = ty::AliasTermKind::ProjectionConst {
def_id: assoc_item.def_id,
};
ty::AliasTerm::new_from_args(tcx, kind, alias_args)
});

// FIXME(mgca): code duplication with other places we lower
Expand Down
32 changes: 12 additions & 20 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1608,12 +1608,16 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
);
}

Ok(TypeRelativePath::AssocItem(ty::AliasTerm::new_from_def_id(
tcx,
item_def_id,
args,
ty::AliasConstInherentArgsKind::WithSelf,
)))
let kind = match mode {
LowerTypeRelativePathMode::Type(..) => {
ty::AliasTermKind::ProjectionTy { def_id: item_def_id }
}
LowerTypeRelativePathMode::Const => {
ty::AliasTermKind::ProjectionConst { def_id: item_def_id }
}
};

Ok(TypeRelativePath::AssocItem(ty::AliasTerm::new_from_args(tcx, kind, args)))
}

/// Resolve a [type-relative](hir::QPath::TypeRelative) (and type-level) path.
Expand Down Expand Up @@ -1947,11 +1951,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
self.check_const_item_in_type_system(item_def_id, span)?;
let alias_const = ty::AliasConst::new(
tcx,
ty::AliasConstKind::new_from_def_id(
tcx,
item_def_id,
ty::AliasConstInherentArgsKind::WithSelf,
),
ty::AliasConstKind::Projection { def_id: item_def_id },
item_args,
);
Ok(Const::new_alias(tcx, ty::IsRigid::No, alias_const))
Expand Down Expand Up @@ -2911,15 +2911,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
ty::Const::new_alias(
tcx,
ty::IsRigid::No,
ty::AliasConst::new(
tcx,
ty::AliasConstKind::new_from_def_id(
tcx,
did,
ty::AliasConstInherentArgsKind::WithSelf,
),
args,
),
ty::AliasConst::new(tcx, ty::AliasConstKind::Free { def_id: did }, args),
)
}
Res::Def(kind @ DefKind::Ctor(ctor_of, CtorKind::Const), did) => {
Expand Down
25 changes: 16 additions & 9 deletions compiler/rustc_middle/src/mir/consts.rs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
use std::fmt::{self, Debug, Display, Formatter};

use rustc_abi::{HasDataLayout, Size};
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
use rustc_macros::{Lift, StableHash, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
use rustc_span::{DUMMY_SP, RemapPathScopeComponents, Span, Symbol, bug};
Expand Down Expand Up @@ -478,15 +479,21 @@ impl<'tcx> UnevaluatedConst<'tcx> {
#[inline]
pub fn shrink(self, tcx: TyCtxt<'tcx>) -> ty::AliasConst<'tcx> {
assert_eq!(self.promoted, None);
ty::AliasConst::new(
tcx,
ty::AliasConstKind::new_from_def_id(
tcx,
self.def,
ty::AliasConstInherentArgsKind::Impl,
),
self.args,
)

let kind = match tcx.def_kind(self.def) {
DefKind::AssocConst => {
if let DefKind::Impl { of_trait: false } = tcx.def_kind(tcx.parent(self.def)) {
ty::AliasConstKind::InherentImpl { def_id: self.def }
} else {
ty::AliasConstKind::Projection { def_id: self.def }
}
}
DefKind::Const => ty::AliasConstKind::Free { def_id: self.def },
DefKind::AnonConst => ty::AliasConstKind::Anon { def_id: self.def },
kind => bug!("unexpected DefKind in MIR UnevaluatedConst: {kind:?}"),
};

ty::AliasConst::new(tcx, kind, self.args)
}
}

Expand Down
65 changes: 0 additions & 65 deletions compiler/rustc_middle/src/ty/context/impl_interner.rs
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Expand Up @@ -220,71 +220,6 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
self.adt_def(adt_def_id)
}

fn alias_const_kind_from_def_id(
self,
def_id: Self::DefId,
inherent_args: ty::AliasConstInherentArgsKind,
) -> ty::AliasConstKind<'tcx> {
match self.def_kind(def_id) {
DefKind::AssocConst => {
if let DefKind::Impl { of_trait: false } = self.def_kind(self.parent(def_id)) {
match inherent_args {
ty::AliasConstInherentArgsKind::WithSelf => {
ty::AliasConstKind::InherentSelf { def_id }
}
ty::AliasConstInherentArgsKind::Impl => {
ty::AliasConstKind::InherentImpl { def_id }
}
}
} else {
ty::AliasConstKind::Projection { def_id }
}
}
DefKind::Const => ty::AliasConstKind::Free { def_id },
DefKind::AnonConst | DefKind::Ctor(_, CtorKind::Const) => {
ty::AliasConstKind::Anon { def_id }
}
kind => bug!("unexpected DefKind in AliasConst: {kind:?}"),
}
}

fn alias_term_kind_from_def_id(
self,
def_id: DefId,
inherent_args: ty::AliasConstInherentArgsKind,
) -> ty::AliasTermKind<'tcx> {
match self.def_kind(def_id) {
DefKind::AssocTy => {
if let DefKind::Impl { of_trait: false } = self.def_kind(self.parent(def_id)) {
ty::AliasTermKind::InherentTy { def_id }
} else {
ty::AliasTermKind::ProjectionTy { def_id }
}
}
DefKind::AssocConst => {
if let DefKind::Impl { of_trait: false } = self.def_kind(self.parent(def_id)) {
match inherent_args {
ty::AliasConstInherentArgsKind::WithSelf => {
ty::AliasTermKind::InherentConstSelf { def_id }
}
ty::AliasConstInherentArgsKind::Impl => {
ty::AliasTermKind::InherentConstImpl { def_id }
}
}
} else {
ty::AliasTermKind::ProjectionConst { def_id }
}
}
DefKind::OpaqueTy => ty::AliasTermKind::OpaqueTy { def_id },
DefKind::TyAlias => ty::AliasTermKind::FreeTy { def_id },
DefKind::Const => ty::AliasTermKind::FreeConst { def_id },
DefKind::AnonConst | DefKind::Ctor(_, CtorKind::Const) => {
ty::AliasTermKind::AnonConst { def_id }
}
kind => bug!("unexpected DefKind in AliasTy: {kind:?}"),
}
}

fn trait_ref_and_own_args_for_alias(
self,
def_id: DefId,
Expand Down
30 changes: 17 additions & 13 deletions compiler/rustc_mir_build/src/builder/expr/as_constant.rs
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Expand Up @@ -73,33 +73,37 @@ pub(crate) fn as_constant_inner<'tcx>(
}
ExprKind::NamedConst { def_id, args, ref user_ty } => {
let user_ty = user_ty.as_ref().and_then(push_cuta);

// Under generic_const_args, `def_id` might be a regular const declared in a trait, but
// is `impl`d as a directly represented const. We do not know whether it is here, so we
// must use type system normalization for all consts under generic_const_args.
Comment on lines 75 to 79

@bit-aloo bit-aloo Sep 14, 2026

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Can we reword this?

// FIXME(generic_const_args): there's a lot to consider here! `Const::Ty` uses valtrees
// and `Const::Unevaluated` does not, we should revisit this before stabilization.
let def_kind = tcx.def_kind(def_id);
if tcx.features().generic_const_args()
|| matches!(tcx.def_kind(def_id), DefKind::Const | DefKind::AssocConst)
|| matches!(def_kind, DefKind::Const | DefKind::AssocConst)
&& tcx.is_direct_const(def_id)
{
let uneval = ty::AliasConst::new(
tcx,
ty::AliasConstKind::new_from_def_id(
tcx,
def_id,
ty::AliasConstInherentArgsKind::Impl,
),
args,
);
let ct = ty::Const::new_alias(tcx, ty::IsRigid::No, uneval);

let kind = match def_kind {
DefKind::AssocConst => {
if let DefKind::Impl { of_trait: false } = tcx.def_kind(tcx.parent(def_id))
{
ty::AliasConstKind::InherentImpl { def_id }
} else {
ty::AliasConstKind::Projection { def_id }
}
}
DefKind::Const => ty::AliasConstKind::Free { def_id },
_ => unreachable!(),

@matthiaskrgr matthiaskrgr Sep 17, 2026

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reachable via #162923

Its always better here to print the actual Defkind or whatever we are not expecting to be reachable as this makes categorizing the ICE a bit easier imho :)

@khyperia khyperia Sep 18, 2026

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aaaah sorry!! #162937

};
let alias = ty::AliasConst::new(tcx, kind, args);
let ct = ty::Const::new_alias(tcx, ty::IsRigid::No, alias);
let const_ = Const::Ty(ty, ct);
return ConstOperand { span, user_ty, const_ };
}

let uneval = mir::UnevaluatedConst::new(def_id, args);
let const_ = Const::Unevaluated(uneval, ty);

ConstOperand { user_ty, span, const_ }
}
ExprKind::ConstParam { param, def_id: _ } => {
Expand Down
4 changes: 3 additions & 1 deletion compiler/rustc_mir_build/src/thir/cx/expr.rs
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Expand Up @@ -327,7 +327,7 @@ impl<'tcx> ThirBuildCx<'tcx> {
} else if let hir::ExprKind::Path(ref qpath) = source.kind
&& let res = self.typeck_results.qpath_res(qpath, source.hir_id)
&& let ty = self.typeck_results.node_type(source.hir_id)
&& let ty::Adt(adt_def, args) = ty.kind()
&& let ty::Adt(adt_def, _) = ty.kind()
Comment thread
bit-aloo marked this conversation as resolved.
&& let Res::Def(DefKind::Ctor(CtorOf::Variant, CtorKind::Const), variant_ctor_id) = res
{
// Check whether this is casting an enum variant discriminant.
Expand Down Expand Up @@ -369,6 +369,8 @@ impl<'tcx> ThirBuildCx<'tcx> {
// in case we are offsetting from a computed discriminant
// and not the beginning of discriminants (which is always `0`)
Some(did) => {
let args = self.tcx.mk_args(&[]);
self.tcx.debug_assert_args_compatible(did, args);
let kind = ExprKind::NamedConst { def_id: did, args, user_ty: None };
let lhs =
self.thir.exprs.push(Expr { temp_scope_id, ty: discr_ty, span, kind });
Expand Down
33 changes: 14 additions & 19 deletions compiler/rustc_mir_build/src/thir/pattern/mod.rs
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Expand Up @@ -635,9 +635,17 @@ impl<'tcx, 'ptcx> PatCtxt<'tcx, 'ptcx> {
let ty = self.typeck_results.node_type(id);
let res = self.typeck_results.qpath_res(qpath, id);

let (def_id, user_ty) = match res {
Res::Def(DefKind::Const, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
(def_id, self.typeck_results.user_provided_types().get(id))
let kind = match res {
Res::Def(DefKind::Const, def_id) => ty::AliasConstKind::Free { def_id },

Res::Def(DefKind::AssocConst, def_id) => {
if let DefKind::Impl { of_trait: false } =
self.tcx.def_kind(self.tcx.parent(def_id))
{
ty::AliasConstKind::InherentImpl { def_id }
} else {
ty::AliasConstKind::Projection { def_id }
}
}

_ => {
Expand All @@ -649,26 +657,13 @@ impl<'tcx, 'ptcx> PatCtxt<'tcx, 'ptcx> {

// Lower the named constant to a THIR pattern.
let args = self.typeck_results.node_args(id);
// FIXME(mgca): we will need to special case IACs here to have type system compatible
// generic args, instead of how we represent them in body expressions.
let c = ty::Const::new_alias(
self.tcx,
ty::IsRigid::No,
ty::AliasConst::new(
self.tcx,
ty::AliasConstKind::new_from_def_id(
self.tcx,
def_id,
ty::AliasConstInherentArgsKind::Impl,
),
args,
),
);
let alias = ty::AliasConst::new(self.tcx, kind, args);
let c = ty::Const::new_alias(self.tcx, ty::IsRigid::No, alias);
let mut pattern = self.const_to_pat(c, ty, id, span);

// If this is an associated constant with an explicit user-written
// type, add an ascription node (e.g. `<Foo<'a> as MyTrait>::CONST`).
if let Some(&user_ty) = user_ty {
if let Some(&user_ty) = self.typeck_results.user_provided_types().get(id) {
let annotation = CanonicalUserTypeAnnotation {
user_ty: Box::new(user_ty),
span,
Expand Down
25 changes: 12 additions & 13 deletions compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs
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Expand Up @@ -245,24 +245,23 @@ fn trait_object_ty<'tcx>(tcx: TyCtxt<'tcx>, poly_trait_ref: ty::PolyTraitRef<'tc
.filter(|item| !tcx.generics_require_sized_self(item.def_id))
.map(move |assoc_item| {
super_poly_trait_ref.map_bound(|super_trait_ref| {
let projection_term = ty::AliasTerm::new_from_def_id(
tcx,
assoc_item.def_id,
super_trait_ref.args,
ty::AliasConstInherentArgsKind::WithSelf,
);
let term = tcx.normalize_erasing_regions(
let kind = if assoc_item.is_type() {
ty::AliasTermKind::ProjectionTy { def_id: assoc_item.def_id }
} else {
ty::AliasTermKind::ProjectionConst { def_id: assoc_item.def_id }
};
let projection_term =
ty::AliasTerm::new_from_args(tcx, kind, super_trait_ref.args);
let term = projection_term.to_term(tcx, ty::IsRigid::No);
let normalized_term = tcx.normalize_erasing_regions(
ty::TypingEnv::fully_monomorphized(),
Unnormalized::new_wip(projection_term.to_term(tcx, ty::IsRigid::No)),
);
debug!(
"Projection {:?} -> {term}",
projection_term.to_term(tcx, ty::IsRigid::No)
Unnormalized::new_wip(term),
);
debug!("Projection {term} -> {normalized_term}");
ty::ExistentialPredicate::Projection(
ty::ExistentialProjection::erase_self_ty(
tcx,
ty::ProjectionClause { projection_term, term },
ty::ProjectionClause { projection_term, term: normalized_term },
),
)
})
Expand Down
27 changes: 16 additions & 11 deletions compiler/rustc_ty_utils/src/consts.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ use rustc_middle::thir::visit::Visitor;
use rustc_middle::ty::abstract_const::CastKind;
use rustc_middle::ty::{self, Expr, LitToConstInput, TyCtxt, TypeVisitableExt};
use rustc_middle::{mir, thir};
use rustc_span::Span;
use rustc_span::{Span, bug};
use tracing::instrument;

use crate::diagnostics::{GenericConstantTooComplex, GenericConstantTooComplexSub};
Expand Down Expand Up @@ -70,16 +70,21 @@ fn recurse_build<'tcx>(
}
&ExprKind::ZstLiteral { user_ty: _ } => ty::Const::zero_sized(tcx, node.ty),
&ExprKind::NamedConst { def_id, args, user_ty: _ } => {
let uneval = ty::AliasConst::new(
tcx,
ty::AliasConstKind::new_from_def_id(
tcx,
def_id,
ty::AliasConstInherentArgsKind::Impl,
),
args,
);
ty::Const::new_alias(tcx, ty::IsRigid::No, uneval)
let kind = match tcx.def_kind(def_id) {
DefKind::AssocConst => {
if let DefKind::Impl { of_trait: false } = tcx.def_kind(tcx.parent(def_id)) {
ty::AliasConstKind::InherentImpl { def_id }
} else {
ty::AliasConstKind::Projection { def_id }
}
}
DefKind::Const => ty::AliasConstKind::Free { def_id },
DefKind::AnonConst => ty::AliasConstKind::Anon { def_id },
kind => bug!("unexpected DefKind in THIR ExprKind::NamedConst: {kind:?}"),
};

let alias = ty::AliasConst::new(tcx, kind, args);
ty::Const::new_alias(tcx, ty::IsRigid::No, alias)
}
ExprKind::ConstParam { param, .. } => ty::Const::new_param(tcx, *param),

Expand Down
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