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Rollup merge of #131981 - compiler-errors:bound-constness, r=cjgillot
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Remove the `BoundConstness::NotConst` variant

I find it easier to represent `BoundConstness::NotConst` as just `None` for some refactorings I'm doing.
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@matthiaskrgr
matthiaskrgr authored Oct 21, 2024
2 parents 4f6750b + 61ed4cb commit 62b7293
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Showing 7 changed files with 46 additions and 41 deletions.
21 changes: 11 additions & 10 deletions compiler/rustc_hir_analysis/src/bounds.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@ impl<'tcx> Bounds<'tcx> {
bound_trait_ref: ty::PolyTraitRef<'tcx>,
span: Span,
polarity: ty::PredicatePolarity,
constness: ty::BoundConstness,
constness: Option<ty::BoundConstness>,
predicate_filter: PredicateFilter,
) {
let clause = (
Expand Down Expand Up @@ -88,19 +88,20 @@ impl<'tcx> Bounds<'tcx> {
// associated type of `<T as Tr>` and make sure that the effect is compatible.
let compat_val = match (tcx.def_kind(defining_def_id), constness) {
// FIXME(effects): revisit the correctness of this
(_, ty::BoundConstness::Const) => tcx.consts.false_,
(_, Some(ty::BoundConstness::Const)) => tcx.consts.false_,
// body owners that can have trait bounds
(DefKind::Const | DefKind::Fn | DefKind::AssocFn, ty::BoundConstness::ConstIfConst) => {
tcx.expected_host_effect_param_for_body(defining_def_id)
}
(
DefKind::Const | DefKind::Fn | DefKind::AssocFn,
Some(ty::BoundConstness::ConstIfConst),
) => tcx.expected_host_effect_param_for_body(defining_def_id),

(_, ty::BoundConstness::NotConst) => {
(_, None) => {
if !tcx.is_const_trait(bound_trait_ref.def_id()) {
return;
}
tcx.consts.true_
}
(DefKind::Trait, ty::BoundConstness::ConstIfConst) => {
(DefKind::Trait, Some(ty::BoundConstness::ConstIfConst)) => {
// we are in a trait, where `bound_trait_ref` could be:
// (1) a super trait `trait Foo: ~const Bar`.
// - This generates `<Self as Foo>::Effects: TyCompat<<Self as Bar>::Effects>`
Expand Down Expand Up @@ -138,7 +139,7 @@ impl<'tcx> Bounds<'tcx> {
return;
}

(DefKind::Impl { of_trait: true }, ty::BoundConstness::ConstIfConst) => {
(DefKind::Impl { of_trait: true }, Some(ty::BoundConstness::ConstIfConst)) => {
// this is a where clause on an impl header.
// push `<T as Tr>::Effects` into the set for the `Min` bound.
let Some(assoc) = tcx.associated_type_for_effects(bound_trait_ref.def_id()) else {
Expand Down Expand Up @@ -172,12 +173,12 @@ impl<'tcx> Bounds<'tcx> {
//
// FIXME(effects) this is equality for now, which wouldn't be helpful for a non-const implementor
// that uses a `Bar` that implements `Trait` with `Maybe` effects.
(DefKind::AssocTy, ty::BoundConstness::ConstIfConst) => {
(DefKind::AssocTy, Some(ty::BoundConstness::ConstIfConst)) => {
// FIXME(effects): implement this
return;
}
// probably illegal in this position.
(_, ty::BoundConstness::ConstIfConst) => {
(_, Some(ty::BoundConstness::ConstIfConst)) => {
tcx.dcx().span_delayed_bug(span, "invalid `~const` encountered");
return;
}
Expand Down
15 changes: 7 additions & 8 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 @@ -171,16 +171,15 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
hir::GenericBound::Trait(poly_trait_ref) => {
let (constness, polarity) = match poly_trait_ref.modifiers {
hir::TraitBoundModifier::Const => {
(ty::BoundConstness::Const, ty::PredicatePolarity::Positive)
}
hir::TraitBoundModifier::MaybeConst => {
(ty::BoundConstness::ConstIfConst, ty::PredicatePolarity::Positive)
}
hir::TraitBoundModifier::None => {
(ty::BoundConstness::NotConst, ty::PredicatePolarity::Positive)
(Some(ty::BoundConstness::Const), ty::PredicatePolarity::Positive)
}
hir::TraitBoundModifier::MaybeConst => (
Some(ty::BoundConstness::ConstIfConst),
ty::PredicatePolarity::Positive,
),
hir::TraitBoundModifier::None => (None, ty::PredicatePolarity::Positive),
hir::TraitBoundModifier::Negative => {
(ty::BoundConstness::NotConst, ty::PredicatePolarity::Negative)
(None, ty::PredicatePolarity::Negative)
}
hir::TraitBoundModifier::Maybe => continue,
};
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_compatibility.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
} = self.lower_poly_trait_ref(
&trait_bound.trait_ref,
trait_bound.span,
ty::BoundConstness::NotConst,
None,
ty::PredicatePolarity::Positive,
dummy_self,
&mut bounds,
Expand Down
4 changes: 2 additions & 2 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 @@ -652,7 +652,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
&self,
trait_ref: &hir::TraitRef<'tcx>,
span: Span,
constness: ty::BoundConstness,
constness: Option<ty::BoundConstness>,
polarity: ty::PredicatePolarity,
self_ty: Ty<'tcx>,
bounds: &mut Bounds<'tcx>,
Expand All @@ -675,7 +675,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
Some(self_ty),
);

if let ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst = constness
if let Some(constness) = constness
&& !self.tcx().is_const_trait(trait_def_id)
{
self.dcx().emit_err(crate::errors::ConstBoundForNonConstTrait {
Expand Down
12 changes: 8 additions & 4 deletions compiler/rustc_middle/src/ty/print/pretty.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1956,7 +1956,6 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
define_scoped_cx!(self);

match constness {
ty::BoundConstness::NotConst => {}
ty::BoundConstness::Const => {
p!("const ");
}
Expand Down Expand Up @@ -2948,7 +2947,10 @@ impl<'tcx> ty::TraitPredicate<'tcx> {
}

#[derive(Copy, Clone, TypeFoldable, TypeVisitable, Lift)]
pub struct TraitPredPrintWithBoundConstness<'tcx>(ty::TraitPredicate<'tcx>, ty::BoundConstness);
pub struct TraitPredPrintWithBoundConstness<'tcx>(
ty::TraitPredicate<'tcx>,
Option<ty::BoundConstness>,
);

impl<'tcx> fmt::Debug for TraitPredPrintWithBoundConstness<'tcx> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
Expand All @@ -2966,7 +2968,7 @@ impl<'tcx> ty::PolyTraitPredicate<'tcx> {

fn print_with_bound_constness(
self,
constness: ty::BoundConstness,
constness: Option<ty::BoundConstness>,
) -> ty::Binder<'tcx, TraitPredPrintWithBoundConstness<'tcx>> {
self.map_bound(|trait_pred| TraitPredPrintWithBoundConstness(trait_pred, constness))
}
Expand Down Expand Up @@ -3206,7 +3208,9 @@ define_print_and_forward_display! {

TraitPredPrintWithBoundConstness<'tcx> {
p!(print(self.0.trait_ref.self_ty()), ": ");
p!(pretty_print_bound_constness(self.1));
if let Some(constness) = self.1 {
p!(pretty_print_bound_constness(constness));
}
if let ty::PredicatePolarity::Negative = self.0.polarity {
p!("!");
}
Expand Down
27 changes: 15 additions & 12 deletions compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -290,7 +290,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
}

if tcx.is_lang_item(leaf_trait_ref.def_id(), LangItem::Drop)
&& matches!(predicate_constness, ty::BoundConstness::ConstIfConst | ty::BoundConstness::Const)
&& matches!(predicate_constness, Some(ty::BoundConstness::ConstIfConst | ty::BoundConstness::Const))
{
err.note("`~const Drop` was renamed to `~const Destruct`");
err.note("See <https://github.com/rust-lang/rust/pull/94901> for more details");
Expand Down Expand Up @@ -2192,27 +2192,29 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
&self,
trait_predicate: ty::PolyTraitPredicate<'tcx>,
message: Option<String>,
predicate_constness: ty::BoundConstness,
predicate_constness: Option<ty::BoundConstness>,
append_const_msg: Option<AppendConstMessage>,
post_message: String,
) -> String {
message
.and_then(|cannot_do_this| {
match (predicate_constness, append_const_msg) {
// do nothing if predicate is not const
(ty::BoundConstness::NotConst, _) => Some(cannot_do_this),
(None, _) => Some(cannot_do_this),
// suggested using default post message
(
ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst,
Some(ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst),
Some(AppendConstMessage::Default),
) => Some(format!("{cannot_do_this} in const contexts")),
// overridden post message
(
ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst,
Some(ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst),
Some(AppendConstMessage::Custom(custom_msg, _)),
) => Some(format!("{cannot_do_this}{custom_msg}")),
// fallback to generic message
(ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst, None) => None,
(Some(ty::BoundConstness::Const | ty::BoundConstness::ConstIfConst), None) => {
None
}
}
})
.unwrap_or_else(|| {
Expand Down Expand Up @@ -2358,26 +2360,27 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
p: ty::PolyTraitPredicate<'tcx>,
leaf: ty::PolyTraitPredicate<'tcx>,
span: Span,
) -> (ty::PolyTraitPredicate<'tcx>, ty::PolyTraitPredicate<'tcx>, ty::BoundConstness) {
) -> (ty::PolyTraitPredicate<'tcx>, ty::PolyTraitPredicate<'tcx>, Option<ty::BoundConstness>)
{
let trait_ref = p.to_poly_trait_ref();
if !self.tcx.is_lang_item(trait_ref.def_id(), LangItem::EffectsCompat) {
return (p, leaf, ty::BoundConstness::NotConst);
return (p, leaf, None);
}

let Some(ty::Alias(ty::AliasTyKind::Projection, projection)) =
trait_ref.self_ty().no_bound_vars().map(Ty::kind)
else {
return (p, leaf, ty::BoundConstness::NotConst);
return (p, leaf, None);
};

let constness = trait_ref.skip_binder().args.const_at(1);

let constness = if constness == self.tcx.consts.true_ || constness.is_ct_infer() {
ty::BoundConstness::NotConst
None
} else if constness == self.tcx.consts.false_ {
ty::BoundConstness::Const
Some(ty::BoundConstness::Const)
} else if matches!(constness.kind(), ty::ConstKind::Param(_)) {
ty::BoundConstness::ConstIfConst
Some(ty::BoundConstness::ConstIfConst)
} else {
self.dcx().span_bug(span, format!("Unknown constness argument: {constness:?}"));
};
Expand Down
6 changes: 2 additions & 4 deletions compiler/rustc_type_ir/src/predicate.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -726,9 +726,9 @@ pub struct CoercePredicate<I: Interner> {
#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "nightly", derive(HashStable_NoContext, TyEncodable, TyDecodable))]
pub enum BoundConstness {
/// `Type: Trait`
NotConst,
/// `Type: const Trait`
///
/// A bound is required to be unconditionally const, even in a runtime function.
Const,
/// `Type: ~const Trait`
///
Expand All @@ -739,7 +739,6 @@ pub enum BoundConstness {
impl BoundConstness {
pub fn as_str(self) -> &'static str {
match self {
Self::NotConst => "",
Self::Const => "const",
Self::ConstIfConst => "~const",
}
Expand All @@ -749,7 +748,6 @@ impl BoundConstness {
impl fmt::Display for BoundConstness {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::NotConst => f.write_str("normal"),
Self::Const => f.write_str("const"),
Self::ConstIfConst => f.write_str("~const"),
}
Expand Down

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