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Auto merge of #99509 - lcnr:commit_unconditionally, r=jackh726

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remove `commit_unconditionally`

`commit_unconditionally` is a noop unless we somehow inspect the current state of our snapshot. The only thing which does that is the leak check which was only used in one place where `commit_if_ok` is probably at least as, or even more, correct.

r? rust-lang/types
This commit is contained in:
bors 2022-08-03 01:55:20 +00:00
commit b759b2efad
4 changed files with 164 additions and 195 deletions
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299
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
View file

@ -144,67 +144,65 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
obligation: &TraitObligation<'tcx>,
idx: usize,
) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
self.infcx.commit_unconditionally(|_| {
let tcx = self.tcx();
let tcx = self.tcx();
let trait_predicate = self.infcx.shallow_resolve(obligation.predicate);
let placeholder_trait_predicate =
self.infcx().replace_bound_vars_with_placeholders(trait_predicate).trait_ref;
let placeholder_self_ty = placeholder_trait_predicate.self_ty();
let placeholder_trait_predicate = ty::Binder::dummy(placeholder_trait_predicate);
let (def_id, substs) = match *placeholder_self_ty.kind() {
ty::Projection(proj) => (proj.item_def_id, proj.substs),
ty::Opaque(def_id, substs) => (def_id, substs),
_ => bug!("projection candidate for unexpected type: {:?}", placeholder_self_ty),
};
let trait_predicate = self.infcx.shallow_resolve(obligation.predicate);
let placeholder_trait_predicate =
self.infcx().replace_bound_vars_with_placeholders(trait_predicate).trait_ref;
let placeholder_self_ty = placeholder_trait_predicate.self_ty();
let placeholder_trait_predicate = ty::Binder::dummy(placeholder_trait_predicate);
let (def_id, substs) = match *placeholder_self_ty.kind() {
ty::Projection(proj) => (proj.item_def_id, proj.substs),
ty::Opaque(def_id, substs) => (def_id, substs),
_ => bug!("projection candidate for unexpected type: {:?}", placeholder_self_ty),
};
let candidate_predicate =
tcx.bound_item_bounds(def_id).map_bound(|i| i[idx]).subst(tcx, substs);
let candidate = candidate_predicate
.to_opt_poly_trait_pred()
.expect("projection candidate is not a trait predicate")
.map_bound(|t| t.trait_ref);
let mut obligations = Vec::new();
let candidate = normalize_with_depth_to(
self,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
candidate,
&mut obligations,
);
let candidate_predicate =
tcx.bound_item_bounds(def_id).map_bound(|i| i[idx]).subst(tcx, substs);
let candidate = candidate_predicate
.to_opt_poly_trait_pred()
.expect("projection candidate is not a trait predicate")
.map_bound(|t| t.trait_ref);
let mut obligations = Vec::new();
let candidate = normalize_with_depth_to(
self,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
candidate,
&mut obligations,
);
obligations.extend(self.infcx.commit_if_ok(|_| {
self.infcx
.at(&obligation.cause, obligation.param_env)
.sup(placeholder_trait_predicate, candidate)
.map(|InferOk { obligations, .. }| obligations)
.map_err(|_| Unimplemented)
})?);
obligations.extend(self.infcx.commit_if_ok(|_| {
self.infcx
.at(&obligation.cause, obligation.param_env)
.sup(placeholder_trait_predicate, candidate)
.map(|InferOk { obligations, .. }| obligations)
.map_err(|_| Unimplemented)
})?);
if let ty::Projection(..) = placeholder_self_ty.kind() {
let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs).predicates;
debug!(?predicates, "projection predicates");
for predicate in predicates {
let normalized = normalize_with_depth_to(
self,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
predicate,
&mut obligations,
);
obligations.push(Obligation::with_depth(
obligation.cause.clone(),
obligation.recursion_depth + 1,
obligation.param_env,
normalized,
));
}
if let ty::Projection(..) = placeholder_self_ty.kind() {
let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs).predicates;
debug!(?predicates, "projection predicates");
for predicate in predicates {
let normalized = normalize_with_depth_to(
self,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
predicate,
&mut obligations,
);
obligations.push(Obligation::with_depth(
obligation.cause.clone(),
obligation.recursion_depth + 1,
obligation.param_env,
normalized,
));
}
}
Ok(obligations)
})
Ok(obligations)
}
fn confirm_param_candidate(
@ -347,19 +345,16 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
ensure_sufficient_stack(|| {
let cause = obligation.derived_cause(BuiltinDerivedObligation);
let trait_obligations: Vec<PredicateObligation<'_>> =
self.infcx.commit_unconditionally(|_| {
let poly_trait_ref = obligation.predicate.to_poly_trait_ref();
let trait_ref = self.infcx.replace_bound_vars_with_placeholders(poly_trait_ref);
self.impl_or_trait_obligations(
&cause,
obligation.recursion_depth + 1,
obligation.param_env,
trait_def_id,
&trait_ref.substs,
obligation.predicate,
)
});
let poly_trait_ref = obligation.predicate.to_poly_trait_ref();
let trait_ref = self.infcx.replace_bound_vars_with_placeholders(poly_trait_ref);
let trait_obligations: Vec<PredicateObligation<'_>> = self.impl_or_trait_obligations(
&cause,
obligation.recursion_depth + 1,
obligation.param_env,
trait_def_id,
&trait_ref.substs,
obligation.predicate,
);
let mut obligations = self.collect_predicates_for_types(
obligation.param_env,
@ -388,19 +383,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// First, create the substitutions by matching the impl again,
// this time not in a probe.
self.infcx.commit_unconditionally(|_| {
let substs = self.rematch_impl(impl_def_id, obligation);
debug!(?substs, "impl substs");
ensure_sufficient_stack(|| {
self.vtable_impl(
impl_def_id,
substs,
&obligation.cause,
obligation.recursion_depth + 1,
obligation.param_env,
obligation.predicate,
)
})
let substs = self.rematch_impl(impl_def_id, obligation);
debug!(?substs, "impl substs");
ensure_sufficient_stack(|| {
self.vtable_impl(
impl_def_id,
substs,
&obligation.cause,
obligation.recursion_depth + 1,
obligation.param_env,
obligation.predicate,
)
})
}
@ -647,25 +640,23 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
) -> ImplSourceTraitAliasData<'tcx, PredicateObligation<'tcx>> {
debug!(?obligation, ?alias_def_id, "confirm_trait_alias_candidate");
self.infcx.commit_unconditionally(|_| {
let predicate = self.infcx().replace_bound_vars_with_placeholders(obligation.predicate);
let trait_ref = predicate.trait_ref;
let trait_def_id = trait_ref.def_id;
let substs = trait_ref.substs;
let predicate = self.infcx().replace_bound_vars_with_placeholders(obligation.predicate);
let trait_ref = predicate.trait_ref;
let trait_def_id = trait_ref.def_id;
let substs = trait_ref.substs;
let trait_obligations = self.impl_or_trait_obligations(
&obligation.cause,
obligation.recursion_depth,
obligation.param_env,
trait_def_id,
&substs,
obligation.predicate,
);
let trait_obligations = self.impl_or_trait_obligations(
&obligation.cause,
obligation.recursion_depth,
obligation.param_env,
trait_def_id,
&substs,
obligation.predicate,
);
debug!(?trait_def_id, ?trait_obligations, "trait alias obligations");
debug!(?trait_def_id, ?trait_obligations, "trait alias obligations");
ImplSourceTraitAliasData { alias_def_id, substs, nested: trait_obligations }
})
ImplSourceTraitAliasData { alias_def_id, substs, nested: trait_obligations }
}
fn confirm_generator_candidate(
@ -763,15 +754,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// Normalize the obligation and expected trait refs together, because why not
let Normalized { obligations: nested, value: (obligation_trait_ref, expected_trait_ref) } =
ensure_sufficient_stack(|| {
self.infcx.commit_unconditionally(|_| {
normalize_with_depth(
self,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
(obligation_trait_ref, expected_trait_ref),
)
})
normalize_with_depth(
self,
obligation.param_env,
obligation.cause.clone(),
obligation.recursion_depth + 1,
(obligation_trait_ref, expected_trait_ref),
)
});
self.infcx
@ -1147,32 +1136,30 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// first check it like a regular impl candidate.
// This is copied from confirm_impl_candidate but remaps the predicate to `~const Drop` beforehand.
if let Some(impl_def_id) = impl_def_id {
let obligations = self.infcx.commit_unconditionally(|_| {
let mut new_obligation = obligation.clone();
new_obligation.predicate = new_obligation.predicate.map_bound(|mut trait_pred| {
trait_pred.trait_ref.def_id = drop_trait;
trait_pred
});
let substs = self.rematch_impl(impl_def_id, &new_obligation);
debug!(?substs, "impl substs");
let mut new_obligation = obligation.clone();
new_obligation.predicate = new_obligation.predicate.map_bound(|mut trait_pred| {
trait_pred.trait_ref.def_id = drop_trait;
trait_pred
});
let substs = self.rematch_impl(impl_def_id, &new_obligation);
debug!(?substs, "impl substs");
let cause = obligation.derived_cause(|derived| {
ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
derived,
impl_def_id,
span: obligation.cause.span,
}))
});
ensure_sufficient_stack(|| {
self.vtable_impl(
impl_def_id,
substs,
&cause,
new_obligation.recursion_depth + 1,
new_obligation.param_env,
obligation.predicate,
)
})
let cause = obligation.derived_cause(|derived| {
ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
derived,
impl_def_id,
span: obligation.cause.span,
}))
});
let obligations = ensure_sufficient_stack(|| {
self.vtable_impl(
impl_def_id,
substs,
&cause,
new_obligation.recursion_depth + 1,
new_obligation.param_env,
obligation.predicate,
)
});
nested.extend(obligations.nested);
}
@ -1223,34 +1210,30 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// If we have a projection type, make sure to normalize it so we replace it
// with a fresh infer variable
ty::Projection(..) => {
self.infcx.commit_unconditionally(|_| {
let predicate = normalize_with_depth_to(
self,
obligation.param_env,
cause.clone(),
obligation.recursion_depth + 1,
self_ty
.rebind(ty::TraitPredicate {
trait_ref: ty::TraitRef {
def_id: self
.tcx()
.require_lang_item(LangItem::Destruct, None),
substs: self.tcx().mk_substs_trait(nested_ty, &[]),
},
constness: ty::BoundConstness::ConstIfConst,
polarity: ty::ImplPolarity::Positive,
})
.to_predicate(tcx),
&mut nested,
);
let predicate = normalize_with_depth_to(
self,
obligation.param_env,
cause.clone(),
obligation.recursion_depth + 1,
self_ty
.rebind(ty::TraitPredicate {
trait_ref: ty::TraitRef {
def_id: self.tcx().require_lang_item(LangItem::Destruct, None),
substs: self.tcx().mk_substs_trait(nested_ty, &[]),
},
constness: ty::BoundConstness::ConstIfConst,
polarity: ty::ImplPolarity::Positive,
})
.to_predicate(tcx),
&mut nested,
);
nested.push(Obligation::with_depth(
cause.clone(),
obligation.recursion_depth + 1,
obligation.param_env,
predicate,
));
});
nested.push(Obligation::with_depth(
cause.clone(),
obligation.recursion_depth + 1,
obligation.param_env,
predicate,
));
}
// If we have any other type (e.g. an ADT), just register a nested obligation