bjoernager/rust
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Normalize projection bounds when considering candidates

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This unfortunately requires some winnowing hacks to avoid
now ambiguous candidates.
This commit is contained in:
Matthew Jasper 2020-07-24 19:10:22 +01:00
parent cfee49593d
commit 34e5a4992c
16 changed files with 390 additions and 256 deletions
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58
compiler/rustc_trait_selection/src/traits/project.rs
View file

@ -884,6 +884,7 @@ fn assemble_candidates_from_param_env<'cx, 'tcx>(
candidate_set,
ProjectionTyCandidate::ParamEnv,
obligation.param_env.caller_bounds().iter(),
false,
);
}
@ -927,6 +928,7 @@ fn assemble_candidates_from_trait_def<'cx, 'tcx>(
candidate_set,
ProjectionTyCandidate::TraitDef,
bounds.iter(),
true,
)
}
@ -937,6 +939,7 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
candidate_set: &mut ProjectionTyCandidateSet<'tcx>,
ctor: fn(ty::PolyProjectionPredicate<'tcx>) -> ProjectionTyCandidate<'tcx>,
env_predicates: impl Iterator<Item = ty::Predicate<'tcx>>,
potentially_unnormalized_candidates: bool,
) {
debug!("assemble_candidates_from_predicates(obligation={:?})", obligation);
let infcx = selcx.infcx();
@ -948,16 +951,12 @@ fn assemble_candidates_from_predicates<'cx, 'tcx>(
let is_match = same_def_id
&& infcx.probe(|_| {
let data_poly_trait_ref = data.to_poly_trait_ref(infcx.tcx);
let obligation_poly_trait_ref = obligation_trait_ref.to_poly_trait_ref();
infcx
.at(&obligation.cause, obligation.param_env)
.sup(obligation_poly_trait_ref, data_poly_trait_ref)
.map(|InferOk { obligations: _, value: () }| {
// FIXME(#32730) -- do we need to take obligations
// into account in any way? At the moment, no.
})
.is_ok()
selcx.match_projection_projections(
obligation,
obligation_trait_ref,
&data,
potentially_unnormalized_candidates,
)
});
debug!(
@ -1157,9 +1156,12 @@ fn confirm_candidate<'cx, 'tcx>(
debug!("confirm_candidate(candidate={:?}, obligation={:?})", candidate, obligation);
let mut progress = match candidate {
ProjectionTyCandidate::ParamEnv(poly_projection)
| ProjectionTyCandidate::TraitDef(poly_projection) => {
confirm_param_env_candidate(selcx, obligation, poly_projection)
ProjectionTyCandidate::ParamEnv(poly_projection) => {
confirm_param_env_candidate(selcx, obligation, poly_projection, false)
}
ProjectionTyCandidate::TraitDef(poly_projection) => {
confirm_param_env_candidate(selcx, obligation, poly_projection, true)
}
ProjectionTyCandidate::Select(impl_source) => {
@ -1272,7 +1274,7 @@ fn confirm_object_candidate<'cx, 'tcx>(
}
};
confirm_param_env_candidate(selcx, obligation, env_predicate)
confirm_param_env_candidate(selcx, obligation, env_predicate, false)
}
fn confirm_generator_candidate<'cx, 'tcx>(
@ -1323,7 +1325,7 @@ fn confirm_generator_candidate<'cx, 'tcx>(
}
});
confirm_param_env_candidate(selcx, obligation, predicate)
confirm_param_env_candidate(selcx, obligation, predicate, false)
.with_addl_obligations(impl_source.nested)
.with_addl_obligations(obligations)
}
@ -1345,7 +1347,7 @@ fn confirm_discriminant_kind_candidate<'cx, 'tcx>(
ty: self_ty.discriminant_ty(tcx),
};
confirm_param_env_candidate(selcx, obligation, ty::Binder::bind(predicate))
confirm_param_env_candidate(selcx, obligation, ty::Binder::bind(predicate), false)
}
fn confirm_fn_pointer_candidate<'cx, 'tcx>(
@ -1420,13 +1422,14 @@ fn confirm_callable_candidate<'cx, 'tcx>(
ty: ret_type,
});
confirm_param_env_candidate(selcx, obligation, predicate)
confirm_param_env_candidate(selcx, obligation, predicate, false)
}
fn confirm_param_env_candidate<'cx, 'tcx>(
selcx: &mut SelectionContext<'cx, 'tcx>,
obligation: &ProjectionTyObligation<'tcx>,
poly_cache_entry: ty::PolyProjectionPredicate<'tcx>,
potentially_unnormalized_candidate: bool,
) -> Progress<'tcx> {
let infcx = selcx.infcx();
let cause = &obligation.cause;
@ -1440,8 +1443,27 @@ fn confirm_param_env_candidate<'cx, 'tcx>(
let cache_trait_ref = cache_entry.projection_ty.trait_ref(infcx.tcx);
let obligation_trait_ref = obligation.predicate.trait_ref(infcx.tcx);
let mut nested_obligations = Vec::new();
let cache_trait_ref = if potentially_unnormalized_candidate {
ensure_sufficient_stack(|| {
normalize_with_depth_to(
selcx,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
&cache_trait_ref,
&mut nested_obligations,
)
})
} else {
cache_trait_ref
};
match infcx.at(cause, param_env).eq(cache_trait_ref, obligation_trait_ref) {
Ok(InferOk { value: _, obligations }) => Progress { ty: cache_entry.ty, obligations },
Ok(InferOk { value: _, obligations }) => {
nested_obligations.extend(obligations);
Progress { ty: cache_entry.ty, obligations: nested_obligations }
}
Err(e) => {
let msg = format!(
"Failed to unify obligation `{:?}` with poly_projection `{:?}`: {:?}",