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introduce UnevaluatedConstKind #157094

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8 changes: 5 additions & 3 deletions compiler/rustc_borrowck/src/type_check/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1760,9 +1760,11 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
let tcx = self.tcx();
let maybe_uneval = match constant.const_ {
Const::Ty(_, ct) => match ct.kind() {
ty::ConstKind::Unevaluated(uv) => {
Some(UnevaluatedConst { def: uv.def, args: uv.args, promoted: None })
}
ty::ConstKind::Unevaluated(uv) => Some(UnevaluatedConst {
def: uv.kind.def_id(),
args: uv.args,
promoted: None,
}),
_ => None,
},
Const::Unevaluated(uv, _) => Some(uv),
Expand Down
5 changes: 3 additions & 2 deletions compiler/rustc_codegen_ssa/src/mir/constant.rs
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Expand Up @@ -38,8 +38,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
&self,
constant: &mir::ConstOperand<'tcx>,
) -> Result<Result<ty::ValTree<'tcx>, Ty<'tcx>>, ErrorHandled> {
let tcx = self.cx.tcx();
let uv = match self.monomorphize(constant.const_) {
mir::Const::Unevaluated(uv, _) => uv.shrink(),
mir::Const::Unevaluated(uv, _) => uv.shrink(tcx),
mir::Const::Ty(_, c) => match c.kind() {
// A constant that came from a const generic but was then used as an argument to
// old-style simd_shuffle (passing as argument instead of as a generic param).
Expand All @@ -57,7 +58,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
other => span_bug!(constant.span, "{other:#?}"),
};
let uv = self.monomorphize(uv);
self.cx.tcx().const_eval_resolve_for_typeck(self.cx.typing_env(), uv, constant.span)
tcx.const_eval_resolve_for_typeck(self.cx.typing_env(), uv, constant.span)
}

/// process constant containing SIMD shuffle indices & constant vectors
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir_analysis/src/check/check.rs
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Expand Up @@ -776,7 +776,7 @@ pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Result<(),
// need to store default and type of default
let ct = tcx.const_param_default(param.def_id).skip_binder();
if let ty::ConstKind::Unevaluated(uv) = ct.kind() {
tcx.ensure_ok().type_of(uv.def);
tcx.ensure_ok().type_of(uv.kind.def_id());
}
}
}
Expand Down
8 changes: 5 additions & 3 deletions compiler/rustc_hir_analysis/src/check/wfcheck.rs
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Expand Up @@ -1535,9 +1535,11 @@ pub(super) fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, def_id:
| ty::ConstKind::Bound(_, _) => unreachable!(),
ty::ConstKind::Error(_) | ty::ConstKind::Expr(_) => continue,
ty::ConstKind::Value(cv) => cv.ty,
ty::ConstKind::Unevaluated(uv) => {
infcx.tcx.type_of(uv.def).instantiate(infcx.tcx, uv.args).skip_norm_wip()
}
ty::ConstKind::Unevaluated(uv) => infcx
.tcx
.type_of(uv.kind.def_id())
.instantiate(infcx.tcx, uv.args)
.skip_norm_wip(),
ty::ConstKind::Param(param_ct) => {
param_ct.find_const_ty_from_env(wfcx.param_env)
}
Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_hir_analysis/src/collect/predicates_of.rs
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Expand Up @@ -435,7 +435,7 @@ fn const_evaluatable_predicates_of<'tcx>(
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ConstCollector<'tcx> {
fn visit_const(&mut self, c: ty::Const<'tcx>) {
if let ty::ConstKind::Unevaluated(uv) = c.kind() {
if let Some(local) = uv.def.as_local()
if let Some(local) = uv.kind.def_id().as_local()
&& is_const_param_default(self.tcx, local)
{
// Do not look into const param defaults,
Expand All @@ -449,11 +449,11 @@ fn const_evaluatable_predicates_of<'tcx>(
}

// Skip type consts as mGCA doesn't support evaluatable clauses.
if self.tcx.is_type_const(uv.def) {
if self.tcx.is_type_const(uv.kind.def_id()) {
return;
}

let span = self.tcx.def_span(uv.def);
let span = self.tcx.def_span(uv.kind.def_id());
self.preds.insert((ty::ClauseKind::ConstEvaluatable(c).upcast(self.tcx), span));
}
}
Expand Down
36 changes: 28 additions & 8 deletions compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
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Expand Up @@ -1518,7 +1518,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
)? {
TypeRelativePath::AssocItem(def_id, args) => {
self.require_type_const_attribute(def_id, span)?;
let ct = Const::new_unevaluated(tcx, ty::UnevaluatedConst::new(def_id, args));
let ct = Const::new_unevaluated(
tcx,
ty::UnevaluatedConst::new(
tcx,
ty::UnevaluatedConstKind::new_from_def_id(tcx, def_id),
args,
),
);
let ct = self.check_param_uses_if_mcg(ct, span, false);
Ok(ct)
}
Expand Down Expand Up @@ -2008,6 +2015,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
trait_segment: Option<&hir::PathSegment<'tcx>>,
item_segment: &hir::PathSegment<'tcx>,
) -> Result<Const<'tcx>, ErrorGuaranteed> {
let tcx = self.tcx();
let (item_def_id, item_args) = self.lower_resolved_assoc_item_path(
span,
opt_self_ty,
Expand All @@ -2017,8 +2025,12 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
ty::AssocTag::Const,
)?;
self.require_type_const_attribute(item_def_id, span)?;
let uv = ty::UnevaluatedConst::new(item_def_id, item_args);
Ok(Const::new_unevaluated(self.tcx(), uv))
let uv = ty::UnevaluatedConst::new(
tcx,
ty::UnevaluatedConstKind::new_from_def_id(tcx, item_def_id),
item_args,
);
Ok(Const::new_unevaluated(tcx, uv))
}

/// Lower a [resolved][hir::QPath::Resolved] (type-level) associated item path.
Expand Down Expand Up @@ -2860,7 +2872,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
let _ = self
.prohibit_generic_args(leading_segments.iter(), GenericsArgsErrExtend::None);
let args = self.lower_generic_args_of_path_segment(span, did, segment);
ty::Const::new_unevaluated(tcx, ty::UnevaluatedConst::new(did, args))
ty::Const::new_unevaluated(
tcx,
ty::UnevaluatedConst::new(
tcx,
ty::UnevaluatedConstKind::new_from_def_id(tcx, did),
args,
),
)
}
Res::Def(DefKind::Ctor(ctor_of, CtorKind::Const), did) => {
assert_eq!(opt_self_ty, None);
Expand Down Expand Up @@ -2984,10 +3003,11 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
Some(v) => v,
None => ty::Const::new_unevaluated(
tcx,
ty::UnevaluatedConst {
def: anon.def_id.to_def_id(),
args: ty::GenericArgs::identity_for_item(tcx, anon.def_id.to_def_id()),
},
ty::UnevaluatedConst::new(
tcx,
ty::UnevaluatedConstKind::Anon { def_id: anon.def_id.to_def_id() },
ty::GenericArgs::identity_for_item(tcx, anon.def_id.to_def_id()),
),
),
}
}
Expand Down
16 changes: 8 additions & 8 deletions compiler/rustc_infer/src/infer/relate/generalize.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -184,7 +184,7 @@ impl<'tcx> InferCtxt<'tcx> {

relation.register_predicates([ty::PredicateKind::AliasRelate(lhs, rhs, direction)]);
} else {
let Some(source_alias) = source_term.to_alias_term(self.tcx) else {
let Some(source_alias) = source_term.to_alias_term() else {
bug!("generalized `{source_term:?} to infer, not an alias");
};
match source_alias.kind(self.tcx) {
Expand All @@ -207,7 +207,7 @@ impl<'tcx> InferCtxt<'tcx> {
}
ty::AliasTermKind::InherentConst { .. }
| ty::AliasTermKind::FreeConst { .. }
| ty::AliasTermKind::UnevaluatedConst { .. } => {
| ty::AliasTermKind::AnonConst { .. } => {
return Err(TypeError::CyclicConst(source_term.expect_const()));
}
}
Expand Down Expand Up @@ -701,6 +701,7 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
c: ty::Const<'tcx>,
c2: ty::Const<'tcx>,
) -> RelateResult<'tcx, ty::Const<'tcx>> {
let tcx = self.cx();
assert_eq!(c, c2); // we are misusing TypeRelation here; both LHS and RHS ought to be ==

match c.kind() {
Expand Down Expand Up @@ -741,7 +742,7 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
{
variable_table.union(vid, new_var_id);
}
Ok(ty::Const::new_var(self.cx(), new_var_id))
Ok(ty::Const::new_var(tcx, new_var_id))
}
}
}
Expand All @@ -755,19 +756,18 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
// Hack: Fall back to old behavior if GCE is enabled (it used to just be the Yes
// path), as doing this new No path breaks some GCE things. I expect GCE to be
// ripped out soon so this shouldn't matter soon.
StructurallyRelateAliases::No if !self.cx().features().generic_const_exprs() => {
self.generalize_alias_term(ty::AliasTerm::from_unevaluated_const(self.cx(), uv))
.map(|v| v.expect_const())
StructurallyRelateAliases::No if !tcx.features().generic_const_exprs() => {
self.generalize_alias_term(uv.into()).map(|v| v.expect_const())
}
_ => {
let ty::UnevaluatedConst { def, args } = uv;
let ty::UnevaluatedConst { kind, args, .. } = uv;
let args = self.relate_with_variance(
ty::Invariant,
ty::VarianceDiagInfo::default(),
args,
args,
)?;
Ok(ty::Const::new_unevaluated(self.cx(), ty::UnevaluatedConst { def, args }))
Ok(ty::Const::new_unevaluated(tcx, ty::UnevaluatedConst::new(tcx, kind, args)))
}
},
ty::ConstKind::Placeholder(placeholder) => {
Expand Down
8 changes: 6 additions & 2 deletions compiler/rustc_middle/src/mir/consts.rs
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Expand Up @@ -467,9 +467,13 @@ pub struct UnevaluatedConst<'tcx> {

impl<'tcx> UnevaluatedConst<'tcx> {
#[inline]
pub fn shrink(self) -> ty::UnevaluatedConst<'tcx> {
pub fn shrink(self, tcx: TyCtxt<'tcx>) -> ty::UnevaluatedConst<'tcx> {
assert_eq!(self.promoted, None);
ty::UnevaluatedConst { def: self.def, args: self.args }
ty::UnevaluatedConst::new(
tcx,
ty::UnevaluatedConstKind::new_from_def_id(tcx, self.def),
self.args,
)
}
}

Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_middle/src/mir/interpret/queries.rs
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Expand Up @@ -103,7 +103,7 @@ impl<'tcx> TyCtxt<'tcx> {
bug!("did not expect inference variables here");
}

let cid = match ty::Instance::try_resolve(self, typing_env, ct.def, ct.args) {
let cid = match ty::Instance::try_resolve(self, typing_env, ct.kind.def_id(), ct.args) {
Ok(Some(instance)) => GlobalId { instance, promoted: None },
// For errors during resolution, we deliberately do not point at the usage site of the constant,
// since for these errors the place the constant is used shouldn't matter.
Expand Down Expand Up @@ -138,11 +138,11 @@ impl<'tcx> TyCtxt<'tcx> {
{
let mir_body = self.mir_for_ctfe(cid.instance.def_id());
if mir_body.is_polymorphic {
let Some(local_def_id) = ct.def.as_local() else { return };
let Some(local_def_id) = ct.kind.def_id().as_local() else { return };
self.emit_node_span_lint(
lint::builtin::CONST_EVALUATABLE_UNCHECKED,
self.local_def_id_to_hir_id(local_def_id),
self.def_span(ct.def),
self.def_span(ct.kind.def_id()),
rustc_errors::DiagDecorator(|lint| {
lint.primary_message(
"cannot use constants which depend on generic parameters in types",
Expand Down
6 changes: 5 additions & 1 deletion compiler/rustc_middle/src/mir/pretty.rs
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Expand Up @@ -1429,7 +1429,11 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
Const::Ty(_, ct) => match ct.kind() {
ty::ConstKind::Param(p) => format!("ty::Param({p})"),
ty::ConstKind::Unevaluated(uv) => {
format!("ty::Unevaluated({}, {:?})", self.tcx.def_path_str(uv.def), uv.args,)
format!(
"ty::Unevaluated({}, {:?})",
self.tcx.def_path_str(uv.kind.def_id()),
uv.args,
)
}
ty::ConstKind::Value(cv) => {
format!("ty::Valtree({})", fmt_valtree(&cv))
Expand Down
18 changes: 10 additions & 8 deletions compiler/rustc_middle/src/ty/abstract_const.rs
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Expand Up @@ -52,15 +52,17 @@ impl<'tcx> TyCtxt<'tcx> {
}
fn fold_const(&mut self, c: Const<'tcx>) -> Const<'tcx> {
let ct = match c.kind() {
ty::ConstKind::Unevaluated(uv) => match self.tcx.thir_abstract_const(uv.def) {
Err(e) => ty::Const::new_error(self.tcx, e),
Ok(Some(bac)) => {
let args = self.tcx.erase_and_anonymize_regions(uv.args);
let bac = bac.instantiate(self.tcx, args).skip_norm_wip();
return bac.fold_with(self);
ty::ConstKind::Unevaluated(uv) => {
match self.tcx.thir_abstract_const(uv.kind.def_id()) {
Err(e) => ty::Const::new_error(self.tcx, e),
Ok(Some(bac)) => {
let args = self.tcx.erase_and_anonymize_regions(uv.args);
let bac = bac.instantiate(self.tcx, args).skip_norm_wip();
return bac.fold_with(self);
}
Ok(None) => c,
}
Ok(None) => c,
},
}
_ => c,
};
ct.super_fold_with(self)
Expand Down
4 changes: 2 additions & 2 deletions compiler/rustc_middle/src/ty/consts.rs
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Expand Up @@ -22,9 +22,10 @@ pub use valtree::*;

pub type ConstKind<'tcx> = ir::ConstKind<TyCtxt<'tcx>>;
pub type UnevaluatedConst<'tcx> = ir::UnevaluatedConst<TyCtxt<'tcx>>;
pub type UnevaluatedConstKind<'tcx> = ir::UnevaluatedConstKind<TyCtxt<'tcx>>;

#[cfg(target_pointer_width = "64")]
rustc_data_structures::static_assert_size!(ConstKind<'_>, 24);
rustc_data_structures::static_assert_size!(ConstKind<'_>, 32);
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@khyperia khyperia May 29, 2026

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N.B.


#[derive(Copy, Clone, PartialEq, Eq, Hash, StableHash)]
#[rustc_pass_by_value]
Expand Down Expand Up @@ -107,7 +108,6 @@ impl<'tcx> Const<'tcx> {

#[inline]
pub fn new_unevaluated(tcx: TyCtxt<'tcx>, uv: ty::UnevaluatedConst<'tcx>) -> Const<'tcx> {
tcx.debug_assert_args_compatible(uv.def, uv.args);
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@khyperia khyperia May 29, 2026

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this assert has moved to the UnevaluatedConstKind constructor, which is what AliasTyKind does

Const::new(tcx, ty::ConstKind::Unevaluated(uv))
}

Expand Down
22 changes: 21 additions & 1 deletion compiler/rustc_middle/src/ty/context/impl_interner.rs
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Expand Up @@ -219,6 +219,26 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
}
}

fn unevaluated_const_kind_from_def_id(
self,
def_id: Self::DefId,
) -> ty::UnevaluatedConstKind<'tcx> {
match self.def_kind(def_id) {
DefKind::AssocConst { .. } => {
if let DefKind::Impl { of_trait: false } = self.def_kind(self.parent(def_id)) {
ty::UnevaluatedConstKind::Inherent { def_id }
} else {
ty::UnevaluatedConstKind::Projection { def_id }
}
}
DefKind::Const { .. } => ty::UnevaluatedConstKind::Free { def_id },
DefKind::AnonConst | DefKind::InlineConst | DefKind::Ctor(_, CtorKind::Const) => {
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I am unsure about DefKind::InlineConst. alias_term_kind_from_def_id does not include it. Removing it causes MIR stuff to panic: rustc_codegen_ssa immediate_const_vector -> eval_unevaluated_mir_constant_to_valtree -> MIR::UnevaluatedConst::shrink -> unevaluated_const_kind_from_def_id -> unexpected DefKind in UnevaluatedConst: InlineConst

ty::UnevaluatedConstKind::Anon { def_id }
}
kind => bug!("unexpected DefKind in UnevaluatedConst: {kind:?}"),
}
}

fn alias_term_kind_from_def_id(self, def_id: DefId) -> ty::AliasTermKind<'tcx> {
match self.def_kind(def_id) {
DefKind::AssocTy => {
Expand All @@ -239,7 +259,7 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
DefKind::TyAlias => ty::AliasTermKind::FreeTy { def_id },
DefKind::Const { .. } => ty::AliasTermKind::FreeConst { def_id },
DefKind::AnonConst | DefKind::Ctor(_, CtorKind::Const) => {
ty::AliasTermKind::UnevaluatedConst { def_id }
ty::AliasTermKind::AnonConst { def_id }
}
kind => bug!("unexpected DefKind in AliasTy: {kind:?}"),
}
Expand Down
8 changes: 4 additions & 4 deletions compiler/rustc_middle/src/ty/mod.rs
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Expand Up @@ -79,8 +79,8 @@ pub use self::closure::{
};
pub use self::consts::{
AtomicOrdering, Const, ConstInt, ConstKind, ConstToValTreeResult, Expr, ExprKind,
LitToConstInput, ScalarInt, SimdAlign, UnevaluatedConst, ValTree, ValTreeKindExt, Value,
const_lit_matches_ty,
LitToConstInput, ScalarInt, SimdAlign, UnevaluatedConst, UnevaluatedConstKind, ValTree,
ValTreeKindExt, Value, const_lit_matches_ty,
};
pub use self::context::{
CtxtInterners, CurrentGcx, FreeRegionInfo, GlobalCtxt, Lift, TyCtxt, TyCtxtFeed, tls,
Expand Down Expand Up @@ -669,14 +669,14 @@ impl<'tcx> Term<'tcx> {
}
}

pub fn to_alias_term(self, tcx: TyCtxt<'tcx>) -> Option<AliasTerm<'tcx>> {
pub fn to_alias_term(self) -> Option<AliasTerm<'tcx>> {
match self.kind() {
TermKind::Ty(ty) => match *ty.kind() {
ty::Alias(alias_ty) => Some(alias_ty.into()),
_ => None,
},
TermKind::Const(ct) => match ct.kind() {
ConstKind::Unevaluated(uv) => Some(AliasTerm::from_unevaluated_const(tcx, uv)),
ConstKind::Unevaluated(uv) => Some(uv.into()),
_ => None,
},
}
Expand Down
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