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Add ty::BoundConstness

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Deadbeef 2021-08-27 05:02:23 +00:00
parent c75aeaac0b
commit 80e1ee5aee
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18 changed files with 80 additions and 80 deletions
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36
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -32,7 +32,6 @@ use rustc_data_structures::sync::Lrc;
use rustc_errors::ErrorReported;
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_hir::Constness;
use rustc_infer::infer::LateBoundRegionConversionTime;
use rustc_middle::dep_graph::{DepKind, DepNodeIndex};
use rustc_middle::mir::abstract_const::NotConstEvaluatable;
@ -130,8 +129,8 @@ pub struct SelectionContext<'cx, 'tcx> {
/// and a negative impl
allow_negative_impls: bool,
/// Do we only want const impls when we have a const trait predicate?
const_impls_required: bool,
/// Are we in a const context that needs `~const` bounds to be const?
is_in_const_context: bool,
/// The mode that trait queries run in, which informs our error handling
/// policy. In essence, canonicalized queries need their errors propagated
@ -224,7 +223,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: false,
is_in_const_context: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -236,7 +235,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: true,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: false,
is_in_const_context: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -252,7 +251,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls,
const_impls_required: false,
is_in_const_context: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -268,7 +267,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: false,
is_in_const_context: false,
query_mode,
}
}
@ -283,7 +282,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: matches!(constness, hir::Constness::Const),
is_in_const_context: matches!(constness, hir::Constness::Const),
query_mode: TraitQueryMode::Standard,
}
}
@ -316,14 +315,19 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
self.infcx.tcx
}
/// Returns `true` if the trait predicate is considerd `const` to this selection context.
pub fn is_trait_predicate_const(&self, pred: ty::TraitPredicate<'_>) -> bool {
match pred.constness {
ty::BoundConstness::ConstIfConst if self.is_in_const_context => true,
_ => false
}
}
/// Returns `true` if the predicate is considered `const` to
/// this selection context.
pub fn is_predicate_const(&self, pred: ty::Predicate<'_>) -> bool {
match pred.kind().skip_binder() {
ty::PredicateKind::Trait(ty::TraitPredicate {
constness: hir::Constness::Const,
..
}) if self.const_impls_required => true,
ty::PredicateKind::Trait(pred) => self.is_trait_predicate_const(pred),
_ => false,
}
}
@ -1074,8 +1078,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
) -> SelectionResult<'tcx, SelectionCandidate<'tcx>> {
let tcx = self.tcx();
// Respect const trait obligations
if self.const_impls_required {
if let hir::Constness::Const = obligation.predicate.skip_binder().constness {
if self.is_trait_predicate_const(obligation.predicate.skip_binder()) {
if Some(obligation.predicate.skip_binder().trait_ref.def_id)
!= tcx.lang_items().sized_trait()
// const Sized bounds are skipped
@ -1086,7 +1089,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
if tcx.impl_constness(def_id) == hir::Constness::Const => {}
// const param
ParamCandidate(ty::ConstnessAnd {
constness: hir::Constness::Const,
constness: ty::BoundConstness::ConstIfConst,
..
}) => {}
// auto trait impl
@ -1100,7 +1103,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
}
}
}
}
// Treat negative impls as unimplemented, and reservation impls as ambiguity.
if let ImplCandidate(def_id) = candidate {
@ -1495,7 +1497,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// probably best characterized as a "hack", since we might prefer to just do our
// best to *not* create essentially duplicate candidates in the first place.
other.value.bound_vars().len() <= victim.value.bound_vars().len()
} else if other.value == victim.value && victim.constness == Constness::NotConst {
} else if other.value == victim.value && victim.constness == ty::BoundConstness::NotConst {
// Drop otherwise equivalent non-const candidates in favor of const candidates.
true
} else {