bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Auto merge of #113312 - Ddystopia:auto-trait-fun, r=lcnr

Browse source 
discard default auto trait impls if explicit ones exist (rebase of #85048)

Rebase of #85048
This commit is contained in:
bors 2023-07-28 10:41:00 +00:00
commit e4c98caffe
8 changed files with 146 additions and 20 deletions
Download patch file Download diff file Expand all files Collapse all files

66
compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
View file

@ -124,11 +124,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
self.assemble_candidates_from_projected_tys(obligation, &mut candidates);
self.assemble_candidates_from_caller_bounds(stack, &mut candidates)?;
// Auto implementations have lower priority, so we only
// consider triggering a default if there is no other impl that can apply.
if candidates.vec.is_empty() {
self.assemble_candidates_from_auto_impls(obligation, &mut candidates);
}
self.assemble_candidates_from_auto_impls(obligation, &mut candidates);
}
debug!("candidate list size: {}", candidates.vec.len());
Ok(candidates)
@ -513,7 +509,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// for an example of a test case that exercises
// this path.
}
ty::Infer(ty::TyVar(_)) => {
ty::Infer(ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_)) => {
// The auto impl might apply; we don't know.
candidates.ambiguous = true;
}
@ -533,7 +529,63 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
}
_ => candidates.vec.push(AutoImplCandidate),
ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
bug!(
"asked to assemble auto trait candidates of unexpected type: {:?}",
self_ty
);
}
ty::Alias(_, _)
if candidates.vec.iter().any(|c| matches!(c, ProjectionCandidate(..))) =>
{
// We do not generate an auto impl candidate for `impl Trait`s which already
// reference our auto trait.
//
// For example during candidate assembly for `impl Send: Send`, we don't have
// to look at the constituent types for this opaque types to figure out that this
// trivially holds.
//
// Note that this is only sound as projection candidates of opaque types
// are always applicable for auto traits.
}
ty::Alias(_, _) => candidates.vec.push(AutoImplCandidate),
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Str
| ty::Array(_, _)
| ty::Slice(_)
| ty::Adt(..)
| ty::RawPtr(_)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(_)
| ty::Closure(_, _)
| ty::Generator(..)
| ty::Never
| ty::Tuple(_)
| ty::GeneratorWitness(_)
| ty::GeneratorWitnessMIR(..) => {
// Only consider auto impls if there are no manual impls for the root of `self_ty`.
//
// For example, we only consider auto candidates for `&i32: Auto` if no explicit impl
// for `&SomeType: Auto` exists. Due to E0321 the only crate where impls
// for `&SomeType: Auto` can be defined is the crate where `Auto` has been defined.
//
// Generally, we have to guarantee that for all `SimplifiedType`s the only crate
// which may define impls for that type is either the crate defining the type
// or the trait. This should be guaranteed by the orphan check.
let mut has_impl = false;
self.tcx().for_each_relevant_impl(def_id, self_ty, |_| has_impl = true);
if !has_impl {
candidates.vec.push(AutoImplCandidate)
}
}
ty::Error(_) => {} // do not add an auto trait impl for `ty::Error` for now.
}
}
}

25
compiler/rustc_trait_selection/src/traits/select/mod.rs
View file

@ -1783,6 +1783,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
/// candidates and prefer where-clause candidates.
///
/// See the comment for "SelectionCandidate" for more details.
#[instrument(level = "debug", skip(self))]
fn candidate_should_be_dropped_in_favor_of(
&mut self,
victim: &EvaluatedCandidate<'tcx>,
@ -1806,13 +1807,6 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
// This is a fix for #53123 and prevents winnowing from accidentally extending the
// lifetime of a variable.
match (&other.candidate, &victim.candidate) {
(_, AutoImplCandidate) | (AutoImplCandidate, _) => {
bug!(
"default implementations shouldn't be recorded \
when there are other valid candidates"
);
}
// FIXME(@jswrenn): this should probably be more sophisticated
(TransmutabilityCandidate, _) | (_, TransmutabilityCandidate) => DropVictim::No,
@ -1854,6 +1848,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
(
ParamCandidate(ref other_cand),
ImplCandidate(..)
| AutoImplCandidate
| ClosureCandidate { .. }
| GeneratorCandidate
| FutureCandidate
@ -1881,6 +1876,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
}
(
ImplCandidate(_)
| AutoImplCandidate
| ClosureCandidate { .. }
| GeneratorCandidate
| FutureCandidate
@ -1914,6 +1910,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
(
ObjectCandidate(_) | ProjectionCandidate(..),
ImplCandidate(..)
| AutoImplCandidate
| ClosureCandidate { .. }
| GeneratorCandidate
| FutureCandidate
@ -1927,6 +1924,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
(
ImplCandidate(..)
| AutoImplCandidate
| ClosureCandidate { .. }
| GeneratorCandidate
| FutureCandidate
@ -2017,6 +2015,19 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
}
}
(AutoImplCandidate, ImplCandidate(_)) | (ImplCandidate(_), AutoImplCandidate) => {
DropVictim::No
}
(AutoImplCandidate, _) | (_, AutoImplCandidate) => {
bug!(
"default implementations shouldn't be recorded \
when there are other global candidates: {:?} {:?}",
other,
victim
);
}
// Everything else is ambiguous
(
ImplCandidate(_)