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Pass constness to SelectionContext

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This commit is contained in:
Deadbeef 2021-07-26 10:52:17 +08:00
parent a00f2bcf5c
commit 01bb3710b5
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GPG key ID: 027DF9338862ADDD
5 changed files with 101 additions and 23 deletions
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26
compiler/rustc_trait_selection/src/traits/fulfill.rs
View file

@ -3,6 +3,7 @@ use rustc_data_structures::obligation_forest::ProcessResult;
use rustc_data_structures::obligation_forest::{Error, ForestObligation, Outcome};
use rustc_data_structures::obligation_forest::{ObligationForest, ObligationProcessor};
use rustc_errors::ErrorReported;
use rustc_hir as hir;
use rustc_infer::traits::{SelectionError, TraitEngine, TraitEngineExt as _, TraitObligation};
use rustc_middle::mir::abstract_const::NotConstEvaluatable;
use rustc_middle::mir::interpret::ErrorHandled;
@ -228,6 +229,22 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx> {
if errors.is_empty() { Ok(()) } else { Err(errors) }
}
fn select_all_with_constness_or_error(
&mut self,
infcx: &InferCtxt<'_, 'tcx>,
constness: rustc_hir::Constness,
) -> Result<(), Vec<FulfillmentError<'tcx>>> {
self.select_with_constness_where_possible(infcx, constness)?;
let errors: Vec<_> = self
.predicates
.to_errors(CodeAmbiguity)
.into_iter()
.map(to_fulfillment_error)
.collect();
if errors.is_empty() { Ok(()) } else { Err(errors) }
}
fn select_where_possible(
&mut self,
infcx: &InferCtxt<'_, 'tcx>,
@ -236,6 +253,15 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx> {
self.select(&mut selcx)
}
fn select_with_constness_where_possible(
&mut self,
infcx: &InferCtxt<'_, 'tcx>,
constness: hir::Constness,
) -> Result<(), Vec<FulfillmentError<'tcx>>> {
let mut selcx = SelectionContext::with_constness(infcx, constness);
self.select(&mut selcx)
}
fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> {
self.predicates.map_pending_obligations(|o| o.obligation.clone())
}

65
compiler/rustc_trait_selection/src/traits/select/mod.rs
View file

@ -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);
}
}
}
}