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Consolidate trait upcasting and unsize into one normalization

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This commit is contained in:
Michael Goulet 2023-07-20 18:36:34 +00:00
parent c02d1a6553
commit de81007d13
4 changed files with 272 additions and 232 deletions
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25
compiler/rustc_trait_selection/src/solve/assembly/mod.rs
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@ -94,6 +94,7 @@ pub(super) enum CandidateSource {
#[derive(Debug, Clone, Copy)]
pub(super) enum BuiltinImplSource {
TraitUpcasting,
TupleUnsize,
Object,
Misc,
Ambiguity,
@ -281,20 +282,19 @@ pub(super) trait GoalKind<'tcx>:
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
/// Consider (possibly several) goals to upcast or unsize a type to another
/// type.
///
/// The most common forms of unsizing are array to slice, and concrete (Sized)
/// type into a `dyn Trait`. ADTs and Tuples can also have their final field
/// unsized if it's generic.
fn consider_builtin_unsize_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx>;
///
/// `dyn Trait1` can be unsized to `dyn Trait2` if they are the same trait, or
/// if `Trait2` is a (transitive) supertrait of `Trait2`.
fn consider_builtin_dyn_upcast_candidates(
ecx: &mut EvalCtxt<'_, 'tcx>,
fn consider_builtin_unsize_and_upcast_candidates(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Vec<CanonicalResponse<'tcx>>;
) -> Vec<(CanonicalResponse<'tcx>, BuiltinImplSource)>;
fn consider_builtin_discriminant_kind_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
@ -610,8 +610,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
G::consider_builtin_future_candidate(self, goal)
} else if lang_items.gen_trait() == Some(trait_def_id) {
G::consider_builtin_generator_candidate(self, goal)
} else if lang_items.unsize_trait() == Some(trait_def_id) {
G::consider_builtin_unsize_candidate(self, goal)
} else if lang_items.discriminant_kind_trait() == Some(trait_def_id) {
G::consider_builtin_discriminant_kind_candidate(self, goal)
} else if lang_items.destruct_trait() == Some(trait_def_id) {
@ -633,11 +631,8 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
// There may be multiple unsize candidates for a trait with several supertraits:
// `trait Foo: Bar<A> + Bar<B>` and `dyn Foo: Unsize<dyn Bar<_>>`
if lang_items.unsize_trait() == Some(trait_def_id) {
for result in G::consider_builtin_dyn_upcast_candidates(self, goal) {
candidates.push(Candidate {
source: CandidateSource::BuiltinImpl(BuiltinImplSource::TraitUpcasting),
result,
});
for (result, source) in G::consider_builtin_unsize_and_upcast_candidates(self, goal) {
candidates.push(Candidate { source: CandidateSource::BuiltinImpl(source), result });
}
}
}