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For a rigid projection, recursively look at the self type's item bounds

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This commit is contained in:
Michael Goulet 2024-02-01 23:48:04 +00:00
parent 98aa3624be
commit 22d582a38d
23 changed files with 273 additions and 431 deletions
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129
compiler/rustc_trait_selection/src/solve/assembly/mod.rs
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@ -542,50 +542,97 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
goal: Goal<'tcx, G>,
candidates: &mut Vec<Candidate<'tcx>>,
) {
let alias_ty = match goal.predicate.self_ty().kind() {
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Adt(_, _)
| ty::Foreign(_)
| ty::Str
| ty::Array(_, _)
| ty::Slice(_)
| ty::RawPtr(_)
| ty::Ref(_, _, _)
| ty::FnDef(_, _)
| ty::FnPtr(_)
| ty::Dynamic(..)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Coroutine(..)
| ty::CoroutineWitness(..)
| ty::Never
| ty::Tuple(_)
| ty::Param(_)
| ty::Placeholder(..)
| ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
| ty::Alias(ty::Inherent, _)
| ty::Alias(ty::Weak, _)
| ty::Error(_) => return,
ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_))
| ty::Bound(..) => bug!("unexpected self type for `{goal:?}`"),
// Excluding IATs and type aliases here as they don't have meaningful item bounds.
ty::Alias(ty::Projection | ty::Opaque, alias_ty) => alias_ty,
};
let _ = self.probe(|_| ProbeKind::NormalizedSelfTyAssembly).enter(|ecx| {
let mut self_ty = goal.predicate.self_ty();
for assumption in
self.tcx().item_bounds(alias_ty.def_id).instantiate(self.tcx(), alias_ty.args)
{
match G::consider_alias_bound_candidate(self, goal, assumption) {
Ok(result) => {
candidates.push(Candidate { source: CandidateSource::AliasBound, result })
// For some deeply nested `<T>::A::B::C::D` rigid associated type,
// we should explore the item bounds for all levels, since the
// `associated_type_bounds` feature means that a parent associated
// type may carry bounds for a nested associated type.
loop {
let (kind, alias_ty) = match *self_ty.kind() {
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Adt(_, _)
| ty::Foreign(_)
| ty::Str
| ty::Array(_, _)
| ty::Slice(_)
| ty::RawPtr(_)
| ty::Ref(_, _, _)
| ty::FnDef(_, _)
| ty::FnPtr(_)
| ty::Dynamic(..)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Coroutine(..)
| ty::CoroutineWitness(..)
| ty::Never
| ty::Tuple(_)
| ty::Param(_)
| ty::Placeholder(..)
| ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
| ty::Error(_) => break,
ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_))
| ty::Bound(..) => bug!("unexpected self type for `{goal:?}`"),
// If we hit infer when normalizing the self type of an alias,
// then bail with ambiguity.
ty::Infer(ty::TyVar(_)) => {
if let Ok(result) = ecx
.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS)
{
candidates
.push(Candidate { source: CandidateSource::AliasBound, result });
}
break;
}
ty::Alias(kind @ (ty::Projection | ty::Opaque), alias_ty) => (kind, alias_ty),
ty::Alias(ty::Inherent | ty::Weak, _) => {
unreachable!("Weak and Inherent aliases should have been normalized away")
}
};
for assumption in
ecx.tcx().item_bounds(alias_ty.def_id).instantiate(ecx.tcx(), alias_ty.args)
{
match G::consider_alias_bound_candidate(ecx, goal, assumption) {
Ok(result) => {
candidates
.push(Candidate { source: CandidateSource::AliasBound, result });
}
Err(NoSolution) => {}
}
}
// If we have a projection, check that its self type is a rigid projection.
// If so, continue searching.
if kind == ty::Projection {
match ecx.try_normalize_ty(goal.param_env, alias_ty.self_ty()) {
Some(next_self_ty) => self_ty = next_self_ty,
None => {
if let Ok(result) = ecx
.evaluate_added_goals_and_make_canonical_response(
Certainty::OVERFLOW,
)
{
candidates.push(Candidate {
source: CandidateSource::AliasBound,
result,
});
}
break;
}
}
} else {
break;
}
Err(NoSolution) => (),
}
}
});
}
/// Check that we are allowed to use an alias bound originating from the self