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Pass constness to SelectionContext

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Deadbeef 2021-07-26 10:52:17 +08:00
parent a00f2bcf5c
commit 01bb3710b5
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5 changed files with 101 additions and 23 deletions
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65
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -130,6 +130,9 @@ 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,
/// The mode that trait queries run in, which informs our error handling
/// policy. In essence, canonicalized queries need their errors propagated
/// rather than immediately reported because we do not have accurate spans.
@ -221,6 +224,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -232,6 +236,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: true,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -247,6 +252,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls,
const_impls_required: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -262,10 +268,26 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: false,
query_mode,
}
}
pub fn with_constness(
infcx: &'cx InferCtxt<'cx, 'tcx>,
constness: hir::Constness,
) -> SelectionContext<'cx, 'tcx> {
SelectionContext {
infcx,
freshener: infcx.freshener_keep_static(),
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
const_impls_required: matches!(constness, hir::Constness::Const),
query_mode: TraitQueryMode::Standard,
}
}
/// Enables tracking of intercrate ambiguity causes. These are
/// used in coherence to give improved diagnostics. We don't do
/// this until we detect a coherence error because it can lead to
@ -1024,26 +1046,29 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
) -> SelectionResult<'tcx, SelectionCandidate<'tcx>> {
let tcx = self.tcx();
// Respect const trait obligations
if let hir::Constness::Const = obligation.predicate.skip_binder().constness {
if Some(obligation.predicate.skip_binder().trait_ref.def_id)
!= tcx.lang_items().sized_trait()
// const Sized bounds are skipped
{
match candidate {
// const impl
ImplCandidate(def_id)
if tcx.impl_constness(def_id) == hir::Constness::Const => {}
// const param
ParamCandidate(ty::ConstnessAnd {
constness: hir::Constness::Const, ..
}) => {}
// auto trait impl
AutoImplCandidate(..) => {}
// FIXME check if this is right, but this would allow Sized impls
// BuiltinCandidate { .. } => {}
_ => {
// reject all other types of candidates
return Err(Unimplemented);
if self.const_impls_required {
if let hir::Constness::Const = obligation.predicate.skip_binder().constness {
if Some(obligation.predicate.skip_binder().trait_ref.def_id)
!= tcx.lang_items().sized_trait()
// const Sized bounds are skipped
{
match candidate {
// const impl
ImplCandidate(def_id)
if tcx.impl_constness(def_id) == hir::Constness::Const => {}
// const param
ParamCandidate(ty::ConstnessAnd {
constness: hir::Constness::Const,
..
}) => {}
// auto trait impl
AutoImplCandidate(..) => {}
// FIXME check if this is right, but this would allow Sized impls
// BuiltinCandidate { .. } => {}
_ => {
// reject all other types of candidates
return Err(Unimplemented);
}
}
}
}