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Auto merge of #134122 - oli-obk:push-zqnyznxtpnll, r=<try>
Move impl constness into impl trait header The issue was that removing anything from the `constness` query makes it just return `NotConst`, which is wrong. So I had to change it to `bug!` out if used wrongly, and only then remove the impl blocks from the `constness` query.
2 parents b597d2a + 9498d5d commit 45d653e

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9 files changed

+57
-42
lines changed

9 files changed

+57
-42
lines changed

‎compiler/rustc_const_eval/src/const_eval/fn_queries.rs

+14-10
Original file line numberDiff line numberDiff line change
@@ -4,10 +4,15 @@ use rustc_hir::def_id::{DefId, LocalDefId};
44
use rustc_middle::query::Providers;
55
use rustc_middle::ty::TyCtxt;
66

7-
pub fn is_parent_const_impl_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
7+
fn parent_impl_constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Constness {
88
let parent_id = tcx.local_parent(def_id);
9-
matches!(tcx.def_kind(parent_id), DefKind::Impl { .. })
10-
&& tcx.constness(parent_id) == hir::Constness::Const
9+
if matches!(tcx.def_kind(parent_id), DefKind::Impl { .. })
10+
&& let Some(header) = tcx.impl_trait_header(parent_id)
11+
{
12+
header.constness
13+
} else {
14+
hir::Constness::NotConst
15+
}
1116
}
1217

1318
/// Checks whether an item is considered to be `const`. If it is a constructor, anonymous const,
@@ -18,13 +23,10 @@ fn constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Constness {
1823
let node = tcx.hir_node_by_def_id(def_id);
1924

2025
match node {
21-
hir::Node::Ctor(_)
22-
| hir::Node::AnonConst(_)
23-
| hir::Node::ConstBlock(_)
26+
hir::Node::Ctor(hir::VariantData::Tuple(..))
2427
| hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. }) => {
2528
hir::Constness::Const
2629
}
27-
hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.constness,
2830
hir::Node::ForeignItem(_) => {
2931
// Foreign items cannot be evaluated at compile-time.
3032
hir::Constness::NotConst
@@ -38,10 +40,12 @@ fn constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Constness {
3840

3941
// If the function itself is not annotated with `const`, it may still be a `const fn`
4042
// if it resides in a const trait impl.
41-
let is_const = is_parent_const_impl_raw(tcx, def_id);
42-
if is_const { hir::Constness::Const } else { hir::Constness::NotConst }
43+
parent_impl_constness(tcx, def_id)
4344
} else {
44-
hir::Constness::NotConst
45+
tcx.dcx().span_bug(
46+
tcx.def_span(def_id),
47+
format!("should not be requesting the constness of items that can't be const: {node:#?}: {:?}", tcx.def_kind(def_id))
48+
)
4549
}
4650
}
4751
}

‎compiler/rustc_hir/src/hir.rs

+1-3
Original file line numberDiff line numberDiff line change
@@ -4044,9 +4044,7 @@ impl<'hir> Node<'hir> {
40444044
_ => None,
40454045
},
40464046
Node::TraitItem(ti) => match ti.kind {
4047-
TraitItemKind::Fn(ref sig, TraitFn::Provided(_)) => {
4048-
Some(FnKind::Method(ti.ident, sig))
4049-
}
4047+
TraitItemKind::Fn(ref sig, _) => Some(FnKind::Method(ti.ident, sig)),
40504048
_ => None,
40514049
},
40524050
Node::ImplItem(ii) => match ii.kind {

‎compiler/rustc_hir_analysis/src/collect.rs

+13-11
Original file line numberDiff line numberDiff line change
@@ -1611,41 +1611,43 @@ fn impl_trait_header(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::ImplTrai
16111611
impl_.of_trait.as_ref().map(|ast_trait_ref| {
16121612
let selfty = tcx.type_of(def_id).instantiate_identity();
16131613

1614-
check_impl_constness(tcx, tcx.is_const_trait_impl(def_id.to_def_id()), ast_trait_ref);
1614+
check_impl_constness(tcx, impl_.constness, ast_trait_ref);
16151615

16161616
let trait_ref = icx.lowerer().lower_impl_trait_ref(ast_trait_ref, selfty);
16171617

16181618
ty::ImplTraitHeader {
16191619
trait_ref: ty::EarlyBinder::bind(trait_ref),
16201620
safety: impl_.safety,
16211621
polarity: polarity_of_impl(tcx, def_id, impl_, item.span),
1622+
constness: impl_.constness,
16221623
}
16231624
})
16241625
}
16251626

16261627
fn check_impl_constness(
16271628
tcx: TyCtxt<'_>,
1628-
is_const: bool,
1629+
constness: hir::Constness,
16291630
hir_trait_ref: &hir::TraitRef<'_>,
1630-
) -> Option<ErrorGuaranteed> {
1631-
if !is_const {
1632-
return None;
1631+
) {
1632+
if let hir::Constness::NotConst = constness {
1633+
return;
16331634
}
16341635

1635-
let trait_def_id = hir_trait_ref.trait_def_id()?;
1636+
let Some(trait_def_id) = hir_trait_ref.trait_def_id() else { return };
16361637
if tcx.is_const_trait(trait_def_id) {
1637-
return None;
1638+
return;
16381639
}
16391640

16401641
let trait_name = tcx.item_name(trait_def_id).to_string();
1641-
Some(tcx.dcx().emit_err(errors::ConstImplForNonConstTrait {
1642+
tcx.dcx().emit_err(errors::ConstImplForNonConstTrait {
16421643
trait_ref_span: hir_trait_ref.path.span,
16431644
trait_name,
1644-
local_trait_span:
1645-
trait_def_id.as_local().map(|_| tcx.def_span(trait_def_id).shrink_to_lo()),
1645+
local_trait_span: trait_def_id
1646+
.as_local()
1647+
.map(|_| tcx.def_span(trait_def_id).shrink_to_lo()),
16461648
marking: (),
16471649
adding: (),
1648-
}))
1650+
});
16491651
}
16501652

16511653
fn polarity_of_impl(

‎compiler/rustc_metadata/src/rmeta/encoder.rs

+4-7
Original file line numberDiff line numberDiff line change
@@ -1264,12 +1264,7 @@ fn should_encode_fn_sig(def_kind: DefKind) -> bool {
12641264

12651265
fn should_encode_constness(def_kind: DefKind) -> bool {
12661266
match def_kind {
1267-
DefKind::Fn
1268-
| DefKind::AssocFn
1269-
| DefKind::Closure
1270-
| DefKind::Impl { of_trait: true }
1271-
| DefKind::Variant
1272-
| DefKind::Ctor(..) => true,
1267+
DefKind::Fn | DefKind::AssocFn | DefKind::Closure | DefKind::Ctor(_, CtorKind::Fn) => true,
12731268

12741269
DefKind::Struct
12751270
| DefKind::Union
@@ -1281,7 +1276,7 @@ fn should_encode_constness(def_kind: DefKind) -> bool {
12811276
| DefKind::Static { .. }
12821277
| DefKind::TyAlias
12831278
| DefKind::OpaqueTy
1284-
| DefKind::Impl { of_trait: false }
1279+
| DefKind::Impl { .. }
12851280
| DefKind::ForeignTy
12861281
| DefKind::ConstParam
12871282
| DefKind::InlineConst
@@ -1296,6 +1291,8 @@ fn should_encode_constness(def_kind: DefKind) -> bool {
12961291
| DefKind::LifetimeParam
12971292
| DefKind::GlobalAsm
12981293
| DefKind::ExternCrate
1294+
| DefKind::Ctor(_, CtorKind::Const)
1295+
| DefKind::Variant
12991296
| DefKind::SyntheticCoroutineBody => false,
13001297
}
13011298
}

‎compiler/rustc_middle/src/query/mod.rs

+4-1
Original file line numberDiff line numberDiff line change
@@ -746,7 +746,10 @@ rustc_queries! {
746746
desc { |tcx| "computing drop-check constraints for `{}`", tcx.def_path_str(key) }
747747
}
748748

749-
/// Returns `true` if this is a const fn / const impl.
749+
/// Returns the constness of function-like things (tuple struct/variant constructors, functions,
750+
/// methods)
751+
///
752+
/// Will ICE if used on things that are always const or never const.
750753
///
751754
/// **Do not call this function manually.** It is only meant to cache the base data for the
752755
/// higher-level functions. Consider using `is_const_fn` or `is_const_trait_impl` instead.

‎compiler/rustc_middle/src/ty/context.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -3141,7 +3141,7 @@ impl<'tcx> TyCtxt<'tcx> {
31413141
/// Whether the trait impl is marked const. This does not consider stability or feature gates.
31423142
pub fn is_const_trait_impl(self, def_id: DefId) -> bool {
31433143
self.def_kind(def_id) == DefKind::Impl { of_trait: true }
3144-
&& self.constness(def_id) == hir::Constness::Const
3144+
&& self.impl_trait_header(def_id).unwrap().constness == hir::Constness::Const
31453145
}
31463146

31473147
pub fn intrinsic(self, def_id: impl IntoQueryParam<DefId> + Copy) -> Option<ty::IntrinsicDef> {

‎compiler/rustc_middle/src/ty/mod.rs

+16-7
Original file line numberDiff line numberDiff line change
@@ -253,6 +253,7 @@ pub struct ImplTraitHeader<'tcx> {
253253
pub trait_ref: ty::EarlyBinder<'tcx, ty::TraitRef<'tcx>>,
254254
pub polarity: ImplPolarity,
255255
pub safety: hir::Safety,
256+
pub constness: hir::Constness,
256257
}
257258

258259
#[derive(Copy, Clone, PartialEq, Eq, Debug, TypeFoldable, TypeVisitable)]
@@ -2004,17 +2005,25 @@ impl<'tcx> TyCtxt<'tcx> {
20042005
let def_id: DefId = def_id.into();
20052006
match self.def_kind(def_id) {
20062007
DefKind::Impl { of_trait: true } => {
2007-
self.constness(def_id) == hir::Constness::Const
2008-
&& self.is_const_trait(
2009-
self.trait_id_of_impl(def_id)
2010-
.expect("expected trait for trait implementation"),
2011-
)
2008+
let header = self.impl_trait_header(def_id).unwrap();
2009+
header.constness == hir::Constness::Const
2010+
&& self.is_const_trait(header.trait_ref.skip_binder().def_id)
20122011
}
20132012
DefKind::Fn | DefKind::Ctor(_, CtorKind::Fn) => {
20142013
self.constness(def_id) == hir::Constness::Const
20152014
}
20162015
DefKind::Trait => self.is_const_trait(def_id),
2017-
DefKind::AssocTy | DefKind::AssocFn => {
2016+
DefKind::AssocTy => {
2017+
let parent_def_id = self.parent(def_id);
2018+
match self.def_kind(parent_def_id) {
2019+
DefKind::Impl { of_trait: false } => false,
2020+
DefKind::Impl { of_trait: true } | DefKind::Trait => {
2021+
self.is_conditionally_const(parent_def_id)
2022+
}
2023+
_ => bug!("unexpected parent item of associated type: {parent_def_id:?}"),
2024+
}
2025+
}
2026+
DefKind::AssocFn => {
20182027
let parent_def_id = self.parent(def_id);
20192028
match self.def_kind(parent_def_id) {
20202029
DefKind::Impl { of_trait: false } => {
@@ -2023,7 +2032,7 @@ impl<'tcx> TyCtxt<'tcx> {
20232032
DefKind::Impl { of_trait: true } | DefKind::Trait => {
20242033
self.is_conditionally_const(parent_def_id)
20252034
}
2026-
_ => bug!("unexpected parent item of associated item: {parent_def_id:?}"),
2035+
_ => bug!("unexpected parent item of associated fn: {parent_def_id:?}"),
20272036
}
20282037
}
20292038
DefKind::OpaqueTy => match self.opaque_ty_origin(def_id) {

‎compiler/rustc_middle/src/ty/util.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -389,7 +389,7 @@ impl<'tcx> TyCtxt<'tcx> {
389389
.delay_as_bug();
390390
}
391391

392-
dtor_candidate = Some((*item_id, self.constness(impl_did)));
392+
dtor_candidate = Some((*item_id, self.impl_trait_header(impl_did).unwrap().constness));
393393
});
394394

395395
let (did, constness) = dtor_candidate?;

‎compiler/rustc_trait_selection/src/traits/effects.rs

+3-1
Original file line numberDiff line numberDiff line change
@@ -128,7 +128,9 @@ fn evaluate_host_effect_from_selection_candiate<'tcx>(
128128
Err(_) => Err(EvaluationFailure::NoSolution),
129129
Ok(Some(source)) => match source {
130130
ImplSource::UserDefined(impl_) => {
131-
if tcx.constness(impl_.impl_def_id) != hir::Constness::Const {
131+
if tcx.impl_trait_header(impl_.impl_def_id).unwrap().constness
132+
!= hir::Constness::Const
133+
{
132134
return Err(EvaluationFailure::NoSolution);
133135
}
134136

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