Auto merge of #83870 - jackh726:binder-refactor-fix, r=nikomatsakis
Don't concatenate binders across types Partially addresses #83737 There's actually two issues that I uncovered in #83737. The first is that we are concatenating bound vars across types, i.e. in ``` F: Fn(&()) -> &mut (dyn Future<Output = ()> + Unpin) ``` the bound vars on `Future` get set as `for<anon>` since those are the binders on `Fn(&()`. This is obviously wrong, since we should only concatenate directly nested trait refs. This is solved here by introducing a new `TraitRefBoundary` scope, that we put around the "syntactical" trait refs and basically don't allow concatenation across. Now, this alone *shouldn't* be a super terrible problem. At least not until you consider the other issue, which is a much more elusive and harder to design a "perfect" fix. A repro can be seen in: ``` use core::future::Future; async fn handle<F>(slf: &F) where F: Fn(&()) -> &mut (dyn for<'a> Future<Output = ()> + Unpin), { (slf)(&()).await; } ``` Notice the `for<'a>` around `Future`. Here, `'a` is unused, so the `for<'a>` Binder gets changed to a `for<>` Binder in the generator witness, but the "local decl" still has it. This has heavy intersections with region anonymization and erasing. Luckily, it's not *super* common to find this unique set of circumstances. It only became apparently because of the first issue mentioned here. However, this *is* still a problem, so I'm leaving #83737 open. r? `@nikomatsakis`
This commit is contained in:
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commit
cd56e255c4
4 changed files with 237 additions and 86 deletions
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@ -72,8 +72,8 @@ impl RegionExt for Region {
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let def_id = hir_map.local_def_id(param.hir_id);
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let origin = LifetimeDefOrigin::from_param(param);
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debug!(
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"Region::late: param={:?} depth={:?} def_id={:?} origin={:?}",
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param, depth, def_id, origin,
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"Region::late: idx={:?}, param={:?} depth={:?} def_id={:?} origin={:?}",
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idx, param, depth, def_id, origin,
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);
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(
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param.name.normalize_to_macros_2_0(),
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@ -326,6 +326,10 @@ enum Scope<'a> {
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s: ScopeRef<'a>,
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},
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TraitRefBoundary {
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s: ScopeRef<'a>,
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},
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Root,
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}
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@ -374,6 +378,7 @@ impl<'a> fmt::Debug for TruncatedScopeDebug<'a> {
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.field("lifetimes", lifetimes)
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.field("s", &"..")
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.finish(),
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Scope::TraitRefBoundary { s: _ } => f.debug_struct("TraitRefBoundary").finish(),
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Scope::Root => f.debug_struct("Root").finish(),
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}
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}
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@ -877,9 +882,12 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
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}
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hir::TyKind::TraitObject(bounds, ref lifetime, _) => {
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debug!(?bounds, ?lifetime, "TraitObject");
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for bound in bounds {
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self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
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}
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let scope = Scope::TraitRefBoundary { s: self.scope };
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self.with(scope, |_, this| {
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for bound in bounds {
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this.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
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}
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});
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match lifetime.name {
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LifetimeName::Implicit => {
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// For types like `dyn Foo`, we should
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@ -1058,9 +1066,12 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
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};
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this.with(scope, |_old_scope, this| {
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this.visit_generics(generics);
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for bound in bounds {
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this.visit_param_bound(bound);
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}
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let scope = Scope::TraitRefBoundary { s: this.scope };
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this.with(scope, |_, this| {
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for bound in bounds {
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this.visit_param_bound(bound);
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}
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})
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});
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});
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} else {
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@ -1074,10 +1085,13 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
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from_poly_trait_ref: false,
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};
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self.with(scope, |_old_scope, this| {
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this.visit_generics(generics);
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for bound in bounds {
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this.visit_param_bound(bound);
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}
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let scope = Scope::TraitRefBoundary { s: this.scope };
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this.with(scope, |_, this| {
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this.visit_generics(generics);
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for bound in bounds {
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this.visit_param_bound(bound);
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}
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})
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});
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}
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}
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@ -1131,13 +1145,16 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
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};
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self.with(scope, |old_scope, this| {
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this.check_lifetime_params(old_scope, &generics.params);
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this.visit_generics(generics);
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for bound in bounds {
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this.visit_param_bound(bound);
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}
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if let Some(ty) = ty {
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this.visit_ty(ty);
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}
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let scope = Scope::TraitRefBoundary { s: this.scope };
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this.with(scope, |_, this| {
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this.visit_generics(generics);
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for bound in bounds {
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this.visit_param_bound(bound);
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}
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if let Some(ty) = ty {
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this.visit_ty(ty);
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}
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})
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});
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self.missing_named_lifetime_spots.pop();
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}
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@ -1197,8 +1214,11 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
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};
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self.with(scope, |old_scope, this| {
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this.check_lifetime_params(old_scope, &generics.params);
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this.visit_generics(generics);
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this.visit_ty(ty);
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let scope = Scope::TraitRefBoundary { s: this.scope };
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this.with(scope, |_, this| {
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this.visit_generics(generics);
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this.visit_ty(ty);
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})
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});
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self.missing_named_lifetime_spots.pop();
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}
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@ -1292,29 +1312,31 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
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})
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.unzip();
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self.map.late_bound_vars.insert(bounded_ty.hir_id, binders.clone());
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if !lifetimes.is_empty() {
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let next_early_index = self.next_early_index();
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let scope = Scope::Binder {
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hir_id: bounded_ty.hir_id,
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lifetimes,
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s: self.scope,
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next_early_index,
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track_lifetime_uses: true,
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opaque_type_parent: false,
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from_poly_trait_ref: true,
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};
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let result = self.with(scope, |old_scope, this| {
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this.check_lifetime_params(old_scope, &bound_generic_params);
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let scope = Scope::TraitRefBoundary { s: self.scope };
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self.with(scope, |_, this| {
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if !lifetimes.is_empty() {
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let next_early_index = this.next_early_index();
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let scope = Scope::Binder {
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hir_id: bounded_ty.hir_id,
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lifetimes,
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s: this.scope,
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next_early_index,
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track_lifetime_uses: true,
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opaque_type_parent: false,
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from_poly_trait_ref: true,
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};
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this.with(scope, |old_scope, this| {
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this.check_lifetime_params(old_scope, &bound_generic_params);
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this.visit_ty(&bounded_ty);
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this.trait_ref_hack = Some(bounded_ty.hir_id);
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walk_list!(this, visit_param_bound, bounds);
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this.trait_ref_hack = None;
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})
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} else {
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this.visit_ty(&bounded_ty);
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this.trait_ref_hack = Some(bounded_ty.hir_id);
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walk_list!(this, visit_param_bound, bounds);
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this.trait_ref_hack = None;
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});
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result
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} else {
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self.visit_ty(&bounded_ty);
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walk_list!(self, visit_param_bound, bounds);
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}
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}
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})
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}
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&hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
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ref lifetime,
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@ -1438,6 +1460,12 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
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scope = s;
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}
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Scope::TraitRefBoundary { .. } => {
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// We should only see super trait lifetimes if there is a `Binder` above
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assert!(supertrait_lifetimes.is_empty());
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break vec![];
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}
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Scope::Binder { hir_id, from_poly_trait_ref, .. } => {
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if !from_poly_trait_ref {
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// We should only see super trait lifetimes if there is a `Binder` above
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@ -1653,7 +1681,8 @@ fn extract_labels(ctxt: &mut LifetimeContext<'_, '_>, body: &hir::Body<'_>) {
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| Scope::Elision { s, .. }
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| Scope::ObjectLifetimeDefault { s, .. }
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| Scope::TraitRefHackInner { s, .. }
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| Scope::Supertrait { s, .. } => {
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| Scope::Supertrait { s, .. }
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| Scope::TraitRefBoundary { s, .. } => {
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scope = s;
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}
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@ -2261,7 +2290,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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| Scope::Elision { s, .. }
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| Scope::ObjectLifetimeDefault { s, .. }
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| Scope::TraitRefHackInner { s, .. }
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| Scope::Supertrait { s, .. } => scope = s,
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| Scope::Supertrait { s, .. }
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| Scope::TraitRefBoundary { s, .. } => scope = s,
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}
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}
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}
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@ -2311,6 +2341,24 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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break None;
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}
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Scope::TraitRefBoundary { s, .. } => {
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// We've exited nested poly trait refs; mark that we are no longer in nested trait refs.
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// We don't increase the late depth because this isn't a `Binder` scope.
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//
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// This came up in #83737, which boiled down to a case like this:
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//
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// ```
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// F: for<> Fn(&()) -> Box<dyn for<> Future<Output = ()> + Unpin>,
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// // ^^^^^
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// ```
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//
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// Here, as we traverse upwards from the `dyn for<>` binder, we want to reset `in_poly_trait_ref`
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// to false, so that we avoid excess contaenation when we encounter the outer `for<>` binder.
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in_poly_trait_ref = false;
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scope = s;
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}
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Scope::Binder { ref lifetimes, from_poly_trait_ref, s, .. } => {
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match lifetime_ref.name {
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LifetimeName::Param(param_name) => {
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@ -2332,6 +2380,17 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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// We've already seen a binder that is a poly trait ref and this one is too,
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// that means that they are nested and we are concatenating the bound vars;
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// don't increase the late depth.
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//
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// This happens specifically with associated trait bounds like the following:
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//
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// ```
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// for<'a> T: Iterator<Item: for<'b> Foo<'a, 'b>>
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// ```
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//
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// In this case, as we traverse `for<'b>`, we would increment `late_depth` but
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// set `in_poly_trait_ref` to true. Then when we traverse `for<'a>`, we would
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// not increment `late_depth` again. (NB: Niko thinks this logic is actually
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// wrong.)
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(true, true) => {}
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// We've exited nested poly trait refs; add one to the late depth and mark
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// that we are no longer in nested trait refs
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@ -2504,7 +2563,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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| Scope::Elision { s, .. }
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| Scope::ObjectLifetimeDefault { s, .. }
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| Scope::TraitRefHackInner { s, .. }
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| Scope::Supertrait { s, .. } => {
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| Scope::Supertrait { s, .. }
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| Scope::TraitRefBoundary { s, .. } => {
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scope = s;
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}
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}
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@ -2700,7 +2760,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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Scope::Body { id, .. } => break id.hir_id,
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Scope::ObjectLifetimeDefault { ref s, .. }
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| Scope::Elision { ref s, .. }
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| Scope::Supertrait { ref s, .. } => {
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| Scope::Supertrait { ref s, .. }
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| Scope::TraitRefBoundary { ref s, .. } => {
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scope = *s;
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}
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Scope::Root => bug!("In fn_like_elision without appropriate scope above"),
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@ -2982,6 +3043,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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self.have_bound_regions = true;
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}
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_ => {
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// FIXME(jackh726): nested trait refs?
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self.lifetimes.insert(lifetime.shifted_out_to_binder(self.outer_index));
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}
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}
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@ -3047,6 +3109,13 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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Scope::Root => break None,
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Scope::TraitRefBoundary { s, .. } => {
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// We've exited nested poly trait refs; mark that we are no longer in nested trait refs.
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// We don't increase the late depth because this isn't a `Binder` scope
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in_poly_trait_ref = false;
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scope = s;
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}
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Scope::Binder { s, ref lifetimes, from_poly_trait_ref, .. } => {
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// collect named lifetimes for suggestions
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for name in lifetimes.keys() {
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@ -3100,7 +3169,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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scope = s;
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}
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Scope::ObjectLifetimeDefault { ref s, .. }
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| Scope::Elision { ref s, .. } => {
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| Scope::Elision { ref s, .. }
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| Scope::TraitRefBoundary { ref s, .. } => {
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scope = s;
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}
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_ => break,
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@ -3228,6 +3298,13 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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let mut scope = self.scope;
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let lifetime = loop {
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match *scope {
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Scope::TraitRefBoundary { s, .. } => {
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// We've exited nested poly trait refs; mark that we are no longer in nested trait refs.
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// We don't increase the late depth because this isn't a `Binder` scope
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in_poly_trait_ref = false;
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scope = s;
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}
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Scope::Binder { s, from_poly_trait_ref, .. } => {
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match (from_poly_trait_ref, in_poly_trait_ref) {
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(true, false) => {
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@ -3380,7 +3457,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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| Scope::Elision { s, .. }
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| Scope::ObjectLifetimeDefault { s, .. }
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| Scope::TraitRefHackInner { s, .. }
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| Scope::Supertrait { s, .. } => {
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| Scope::Supertrait { s, .. }
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| Scope::TraitRefBoundary { s, .. } => {
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old_scope = s;
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}
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@ -3438,7 +3516,8 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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Scope::ObjectLifetimeDefault { s, .. }
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| Scope::TraitRefHackInner { s, .. }
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| Scope::Supertrait { s, .. } => scope = s,
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| Scope::Supertrait { s, .. }
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| Scope::TraitRefBoundary { s, .. } => scope = s,
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}
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}
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}
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@ -3492,13 +3571,12 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
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/// "Constrained" basically means that it appears in any type but
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/// not amongst the inputs to a projection. In other words, `<&'a
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/// T as Trait<''b>>::Foo` does not constrain `'a` or `'b`.
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#[tracing::instrument(level = "debug", skip(map))]
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fn insert_late_bound_lifetimes(
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map: &mut NamedRegionMap,
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decl: &hir::FnDecl<'_>,
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generics: &hir::Generics<'_>,
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) {
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debug!("insert_late_bound_lifetimes(decl={:?}, generics={:?})", decl, generics);
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let mut constrained_by_input = ConstrainedCollector::default();
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for arg_ty in decl.inputs {
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constrained_by_input.visit_ty(arg_ty);
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@ -3507,7 +3585,7 @@ fn insert_late_bound_lifetimes(
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let mut appears_in_output = AllCollector::default();
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intravisit::walk_fn_ret_ty(&mut appears_in_output, &decl.output);
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debug!("insert_late_bound_lifetimes: constrained_by_input={:?}", constrained_by_input.regions);
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debug!(?constrained_by_input.regions);
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// Walk the lifetimes that appear in where clauses.
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//
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@ -3527,10 +3605,7 @@ fn insert_late_bound_lifetimes(
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}
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}
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debug!(
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"insert_late_bound_lifetimes: appears_in_where_clause={:?}",
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appears_in_where_clause.regions
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);
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debug!(?appears_in_where_clause.regions);
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// Late bound regions are those that:
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// - appear in the inputs
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@ -3557,11 +3632,7 @@ fn insert_late_bound_lifetimes(
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continue;
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}
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debug!(
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"insert_late_bound_lifetimes: lifetime {:?} with id {:?} is late-bound",
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param.name.ident(),
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param.hir_id
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);
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debug!("lifetime {:?} with id {:?} is late-bound", param.name.ident(), param.hir_id);
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let inserted = map.late_bound.insert(param.hir_id);
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assert!(inserted, "visited lifetime {:?} twice", param.hir_id);
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|
|
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|||
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