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Auto merge of #64939 - nnethercote:snapshot-cleanups, r=nikomatsakis

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Snapshot clean-ups

Two minor clean-ups involving snapshots.
This commit is contained in:
bors 2019-10-10 00:19:29 +00:00
commit aa45e032d9
3 changed files with 28 additions and 37 deletions
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22
src/librustc/infer/mod.rs
View file

@ -814,16 +814,16 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
/// Executes `f` and commit the bindings.
pub fn commit_unconditionally<R, F>(&self, f: F) -> R
where
F: FnOnce() -> R,
F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
{
debug!("commit()");
debug!("commit_unconditionally()");
let snapshot = self.start_snapshot();
let r = f();
let r = f(&snapshot);
self.commit_from(snapshot);
r
}
/// Executes `f` and commit the bindings if closure `f` returns `Ok(_)`.
/// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`.
pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>
where
F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>,
@ -843,19 +843,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
r
}
/// Execute `f` in a snapshot, and commit the bindings it creates.
pub fn in_snapshot<T, F>(&self, f: F) -> T
where
F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> T,
{
debug!("in_snapshot()");
let snapshot = self.start_snapshot();
let r = f(&snapshot);
self.commit_from(snapshot);
r
}
/// Executes `f` then unroll any bindings it creates.
/// Execute `f` then unroll any bindings it creates.
pub fn probe<R, F>(&self, f: F) -> R
where
F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,

8
src/librustc/infer/region_constraints/leak_check.rs
View file

@ -14,9 +14,11 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
/// retain the older (arguably incorrect) behavior of the
/// compiler.
///
/// NB. The use of snapshot here is mostly an efficiency thing --
/// we could search *all* region constraints, but that'd be a
/// bigger set and the data structures are not setup for that. If
/// NB. Although `_snapshot` isn't used, it's passed in to prove
/// that we are in a snapshot, which guarantees that we can just
/// search the "undo log" for edges. This is mostly an efficiency
/// thing -- we could search *all* region constraints, but that'd be
/// a bigger set and the data structures are not setup for that. If
/// we wind up keeping some form of this check long term, it would
/// probably be better to remove the snapshot parameter and to
/// refactor the constraint set.

35
src/librustc/traits/select.rs
View file

@ -2819,7 +2819,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// binder moved -\
let ty: ty::Binder<Ty<'tcx>> = ty::Binder::bind(ty); // <----/
self.infcx.in_snapshot(|_| {
self.infcx.commit_unconditionally(|_| {
let (skol_ty, _) = self.infcx
.replace_bound_vars_with_placeholders(&ty);
let Normalized {
@ -2932,7 +2932,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
fn confirm_projection_candidate(&mut self, obligation: &TraitObligation<'tcx>) {
self.infcx.in_snapshot(|snapshot| {
self.infcx.commit_unconditionally(|snapshot| {
let result =
self.match_projection_obligation_against_definition_bounds(
obligation,
@ -3054,19 +3054,20 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
nested,
);
let trait_obligations: Vec<PredicateObligation<'_>> = self.infcx.in_snapshot(|_| {
let poly_trait_ref = obligation.predicate.to_poly_trait_ref();
let (trait_ref, _) = self.infcx
.replace_bound_vars_with_placeholders(&poly_trait_ref);
let cause = obligation.derived_cause(ImplDerivedObligation);
self.impl_or_trait_obligations(
cause,
obligation.recursion_depth + 1,
obligation.param_env,
trait_def_id,
&trait_ref.substs,
)
});
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);
let cause = obligation.derived_cause(ImplDerivedObligation);
self.impl_or_trait_obligations(
cause,
obligation.recursion_depth + 1,
obligation.param_env,
trait_def_id,
&trait_ref.substs,
)
});
// Adds the predicates from the trait. Note that this contains a `Self: Trait`
// predicate as usual. It won't have any effect since auto traits are coinductive.
@ -3089,7 +3090,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// First, create the substitutions by matching the impl again,
// this time not in a probe.
self.infcx.in_snapshot(|snapshot| {
self.infcx.commit_unconditionally(|snapshot| {
let substs = self.rematch_impl(impl_def_id, obligation, snapshot);
debug!("confirm_impl_candidate: substs={:?}", substs);
let cause = obligation.derived_cause(ImplDerivedObligation);
@ -3253,7 +3254,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
obligation, alias_def_id
);
self.infcx.in_snapshot(|_| {
self.infcx.commit_unconditionally(|_| {
let (predicate, _) = self.infcx()
.replace_bound_vars_with_placeholders(&obligation.predicate);
let trait_ref = predicate.trait_ref;