From c895985e759522d813442b6e83372770158a9001 Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Sat, 6 Jul 2024 11:31:41 -0400 Subject: [PATCH] Make push_outlives_components into a visitor --- .../rustc_infer/src/infer/outlives/verify.rs | 7 +- compiler/rustc_type_ir/src/outlives.rs | 389 +++++++----------- 2 files changed, 142 insertions(+), 254 deletions(-) diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs index da9ba26373c..2392a82025a 100644 --- a/compiler/rustc_infer/src/infer/outlives/verify.rs +++ b/compiler/rustc_infer/src/infer/outlives/verify.rs @@ -124,12 +124,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { // see the extensive comment in projection_must_outlive let recursive_bound = { let mut components = smallvec![]; - compute_alias_components_recursive( - self.tcx, - alias_ty_as_ty, - &mut components, - &mut Default::default(), - ); + compute_alias_components_recursive(self.tcx, alias_ty_as_ty, &mut components); self.bound_from_components(&components) }; diff --git a/compiler/rustc_type_ir/src/outlives.rs b/compiler/rustc_type_ir/src/outlives.rs index 61dfa2643d8..10b6f3355d9 100644 --- a/compiler/rustc_type_ir/src/outlives.rs +++ b/compiler/rustc_type_ir/src/outlives.rs @@ -3,11 +3,10 @@ //! RFC for reference. use smallvec::{smallvec, SmallVec}; -use tracing::debug; use crate::data_structures::SsoHashSet; use crate::inherent::*; -use crate::visit::TypeVisitableExt as _; +use crate::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt as _, TypeVisitor}; use crate::{self as ty, Interner}; #[derive(derivative::Derivative)] @@ -55,217 +54,149 @@ pub enum Component { /// Push onto `out` all the things that must outlive `'a` for the condition /// `ty0: 'a` to hold. Note that `ty0` must be a **fully resolved type**. pub fn push_outlives_components( - tcx: I, - ty0: I::Ty, - out: &mut SmallVec<[Component; 4]>, -) { - let mut visited = SsoHashSet::new(); - compute_components_for_ty(tcx, ty0, out, &mut visited); - debug!("components({:?}) = {:?}", ty0, out); -} - -fn compute_components_for_arg( - tcx: I, - arg: I::GenericArg, - out: &mut SmallVec<[Component; 4]>, - visited: &mut SsoHashSet, -) { - match arg.kind() { - ty::GenericArgKind::Type(ty) => { - compute_components_for_ty(tcx, ty, out, visited); - } - ty::GenericArgKind::Lifetime(lt) => { - compute_components_for_lt(lt, out); - } - ty::GenericArgKind::Const(ct) => { - compute_components_for_const(tcx, ct, out, visited); - } - } -} - -fn compute_components_for_ty( tcx: I, ty: I::Ty, out: &mut SmallVec<[Component; 4]>, - visited: &mut SsoHashSet, ) { - if !visited.insert(ty.into()) { - return; + ty.visit_with(&mut OutlivesCollector { tcx, out, visited: Default::default() }); +} + +struct OutlivesCollector<'a, I: Interner> { + tcx: I, + out: &'a mut SmallVec<[Component; 4]>, + visited: SsoHashSet, +} + +impl TypeVisitor for OutlivesCollector<'_, I> { + fn visit_ty(&mut self, ty: I::Ty) -> Self::Result { + if !self.visited.insert(ty) { + return; + } + // Descend through the types, looking for the various "base" + // components and collecting them into `out`. This is not written + // with `collect()` because of the need to sometimes skip subtrees + // in the `subtys` iterator (e.g., when encountering a + // projection). + match ty.kind() { + ty::FnDef(_, args) => { + // HACK(eddyb) ignore lifetimes found shallowly in `args`. + // This is inconsistent with `ty::Adt` (including all args) + // and with `ty::Closure` (ignoring all args other than + // upvars, of which a `ty::FnDef` doesn't have any), but + // consistent with previous (accidental) behavior. + // See https://github.com/rust-lang/rust/issues/70917 + // for further background and discussion. + for child in args.iter() { + match child.kind() { + ty::GenericArgKind::Lifetime(_) => {} + ty::GenericArgKind::Type(_) | ty::GenericArgKind::Const(_) => { + child.visit_with(self); + } + } + } + } + + ty::Closure(_, args) => { + args.as_closure().tupled_upvars_ty().visit_with(self); + } + + ty::CoroutineClosure(_, args) => { + args.as_coroutine_closure().tupled_upvars_ty().visit_with(self); + } + + ty::Coroutine(_, args) => { + args.as_coroutine().tupled_upvars_ty().visit_with(self); + + // We ignore regions in the coroutine interior as we don't + // want these to affect region inference + } + + // All regions are bound inside a witness, and we don't emit + // higher-ranked outlives components currently. + ty::CoroutineWitness(..) => {} + + // OutlivesTypeParameterEnv -- the actual checking that `X:'a` + // is implied by the environment is done in regionck. + ty::Param(p) => { + self.out.push(Component::Param(p)); + } + + ty::Placeholder(p) => { + self.out.push(Component::Placeholder(p)); + } + + // For projections, we prefer to generate an obligation like + // `>::Foo: 'a`, because this gives the + // regionck more ways to prove that it holds. However, + // regionck is not (at least currently) prepared to deal with + // higher-ranked regions that may appear in the + // trait-ref. Therefore, if we see any higher-ranked regions, + // we simply fallback to the most restrictive rule, which + // requires that `Pi: 'a` for all `i`. + ty::Alias(_, alias_ty) => { + if !alias_ty.has_escaping_bound_vars() { + // best case: no escaping regions, so push the + // projection and skip the subtree (thus generating no + // constraints for Pi). This defers the choice between + // the rules OutlivesProjectionEnv, + // OutlivesProjectionTraitDef, and + // OutlivesProjectionComponents to regionck. + self.out.push(Component::Alias(alias_ty)); + } else { + // fallback case: hard code + // OutlivesProjectionComponents. Continue walking + // through and constrain Pi. + let mut subcomponents = smallvec![]; + compute_alias_components_recursive(self.tcx, ty, &mut subcomponents); + self.out.push(Component::EscapingAlias(subcomponents.into_iter().collect())); + } + } + + // We assume that inference variables are fully resolved. + // So, if we encounter an inference variable, just record + // the unresolved variable as a component. + ty::Infer(infer_ty) => { + self.out.push(Component::UnresolvedInferenceVariable(infer_ty)); + } + + // Most types do not introduce any region binders, nor + // involve any other subtle cases, and so the WF relation + // simply constraints any regions referenced directly by + // the type and then visits the types that are lexically + // contained within. + ty::Bool + | ty::Char + | ty::Int(_) + | ty::Uint(_) + | ty::Float(_) + | ty::Str + | ty::Never + | ty::Error(_) => { + // Trivial + } + + ty::Bound(_, _) => { + // FIXME: Bound vars matter here! + } + + ty::Adt(_, _) + | ty::Foreign(_) + | ty::Array(_, _) + | ty::Pat(_, _) + | ty::Slice(_) + | ty::RawPtr(_, _) + | ty::Ref(_, _, _) + | ty::FnPtr(_) + | ty::Dynamic(_, _, _) + | ty::Tuple(_) => { + ty.super_visit_with(self); + } + } } - // Descend through the types, looking for the various "base" - // components and collecting them into `out`. This is not written - // with `collect()` because of the need to sometimes skip subtrees - // in the `subtys` iterator (e.g., when encountering a - // projection). - match ty.kind() { - ty::FnDef(_, args) => { - // HACK(eddyb) ignore lifetimes found shallowly in `args`. - // This is inconsistent with `ty::Adt` (including all args) - // and with `ty::Closure` (ignoring all args other than - // upvars, of which a `ty::FnDef` doesn't have any), but - // consistent with previous (accidental) behavior. - // See https://github.com/rust-lang/rust/issues/70917 - // for further background and discussion. - for child in args.iter() { - match child.kind() { - ty::GenericArgKind::Type(ty) => { - compute_components_for_ty(tcx, ty, out, visited); - } - ty::GenericArgKind::Lifetime(_) => {} - ty::GenericArgKind::Const(ct) => { - compute_components_for_const(tcx, ct, out, visited); - } - } - } - } - ty::Pat(element, _) | ty::Array(element, _) => { - compute_components_for_ty(tcx, element, out, visited); - } - - ty::Closure(_, args) => { - let tupled_ty = args.as_closure().tupled_upvars_ty(); - compute_components_for_ty(tcx, tupled_ty, out, visited); - } - - ty::CoroutineClosure(_, args) => { - let tupled_ty = args.as_coroutine_closure().tupled_upvars_ty(); - compute_components_for_ty(tcx, tupled_ty, out, visited); - } - - ty::Coroutine(_, args) => { - // Same as the closure case - let tupled_ty = args.as_coroutine().tupled_upvars_ty(); - compute_components_for_ty(tcx, tupled_ty, out, visited); - - // We ignore regions in the coroutine interior as we don't - // want these to affect region inference - } - - // All regions are bound inside a witness, and we don't emit - // higher-ranked outlives components currently. - ty::CoroutineWitness(..) => {}, - - // OutlivesTypeParameterEnv -- the actual checking that `X:'a` - // is implied by the environment is done in regionck. - ty::Param(p) => { - out.push(Component::Param(p)); - } - - ty::Placeholder(p) => { - out.push(Component::Placeholder(p)); - } - - // For projections, we prefer to generate an obligation like - // `>::Foo: 'a`, because this gives the - // regionck more ways to prove that it holds. However, - // regionck is not (at least currently) prepared to deal with - // higher-ranked regions that may appear in the - // trait-ref. Therefore, if we see any higher-ranked regions, - // we simply fallback to the most restrictive rule, which - // requires that `Pi: 'a` for all `i`. - ty::Alias(_, alias_ty) => { - if !alias_ty.has_escaping_bound_vars() { - // best case: no escaping regions, so push the - // projection and skip the subtree (thus generating no - // constraints for Pi). This defers the choice between - // the rules OutlivesProjectionEnv, - // OutlivesProjectionTraitDef, and - // OutlivesProjectionComponents to regionck. - out.push(Component::Alias(alias_ty)); - } else { - // fallback case: hard code - // OutlivesProjectionComponents. Continue walking - // through and constrain Pi. - let mut subcomponents = smallvec![]; - let mut subvisited = SsoHashSet::new(); - compute_alias_components_recursive(tcx, ty, &mut subcomponents, &mut subvisited); - out.push(Component::EscapingAlias(subcomponents.into_iter().collect())); - } - } - - // We assume that inference variables are fully resolved. - // So, if we encounter an inference variable, just record - // the unresolved variable as a component. - ty::Infer(infer_ty) => { - out.push(Component::UnresolvedInferenceVariable(infer_ty)); - } - - // Most types do not introduce any region binders, nor - // involve any other subtle cases, and so the WF relation - // simply constraints any regions referenced directly by - // the type and then visits the types that are lexically - // contained within. (The comments refer to relevant rules - // from RFC1214.) - - ty::Bool | // OutlivesScalar - ty::Char | // OutlivesScalar - ty::Int(..) | // OutlivesScalar - ty::Uint(..) | // OutlivesScalar - ty::Float(..) | // OutlivesScalar - ty::Never | // OutlivesScalar - ty::Foreign(..) | // OutlivesNominalType - ty::Str | // OutlivesScalar (ish) - ty::Bound(..) | - ty::Error(_) => { - // Trivial. - } - - // OutlivesNominalType - ty::Adt(_, args) => { - for arg in args.iter() { - compute_components_for_arg(tcx, arg, out, visited); - } - } - - // OutlivesNominalType - ty::Slice(ty) | - ty::RawPtr(ty, _) => { - compute_components_for_ty(tcx, ty, out, visited); - } - ty::Tuple(tys) => { - for ty in tys.iter() { - compute_components_for_ty(tcx, ty, out, visited); - } - } - - // OutlivesReference - ty::Ref(lt, ty, _) => { - compute_components_for_lt(lt, out); - compute_components_for_ty(tcx, ty, out, visited); - } - - ty::Dynamic(preds, lt, _) => { - compute_components_for_lt(lt, out); - for pred in preds.iter() { - match pred.skip_binder() { - ty::ExistentialPredicate::Trait(tr) => { - for arg in tr.args.iter() { - compute_components_for_arg(tcx, arg, out, visited); - } - } - ty::ExistentialPredicate::Projection(proj) => { - for arg in proj.args.iter() { - compute_components_for_arg(tcx, arg, out, visited); - } - match proj.term.kind() { - ty::TermKind::Ty(ty) => { - compute_components_for_ty(tcx, ty, out, visited) - } - ty::TermKind::Const(ct) => { - compute_components_for_const(tcx, ct, out, visited) - } - } - } - ty::ExistentialPredicate::AutoTrait(..) => {} - } - } - } - - ty::FnPtr(sig) => { - for ty in sig.skip_binder().inputs_and_output.iter() { - compute_components_for_ty(tcx, ty, out, visited); - } + fn visit_region(&mut self, lt: I::Region) -> Self::Result { + if !lt.is_bound() { + self.out.push(Component::Region(lt)); } } } @@ -278,7 +209,6 @@ pub fn compute_alias_components_recursive( tcx: I, alias_ty: I::Ty, out: &mut SmallVec<[Component; 4]>, - visited: &mut SsoHashSet, ) { let ty::Alias(kind, alias_ty) = alias_ty.kind() else { unreachable!("can only call `compute_alias_components_recursive` on an alias type") @@ -287,49 +217,12 @@ pub fn compute_alias_components_recursive( let opt_variances = if kind == ty::Opaque { Some(tcx.variances_of(alias_ty.def_id)) } else { None }; + let mut visitor = OutlivesCollector { tcx, out, visited: Default::default() }; + for (index, child) in alias_ty.args.iter().enumerate() { if opt_variances.and_then(|variances| variances.get(index)) == Some(ty::Bivariant) { continue; } - compute_components_for_arg(tcx, child, out, visited); - } -} - -fn compute_components_for_lt(lt: I::Region, out: &mut SmallVec<[Component; 4]>) { - if !lt.is_bound() { - out.push(Component::Region(lt)); - } -} - -fn compute_components_for_const( - tcx: I, - ct: I::Const, - out: &mut SmallVec<[Component; 4]>, - visited: &mut SsoHashSet, -) { - if !visited.insert(ct.into()) { - return; - } - match ct.kind() { - ty::ConstKind::Param(_) - | ty::ConstKind::Bound(_, _) - | ty::ConstKind::Infer(_) - | ty::ConstKind::Placeholder(_) - | ty::ConstKind::Error(_) => { - // Trivial - } - ty::ConstKind::Expr(e) => { - for arg in e.args().iter() { - compute_components_for_arg(tcx, arg, out, visited); - } - } - ty::ConstKind::Value(ty, _) => { - compute_components_for_ty(tcx, ty, out, visited); - } - ty::ConstKind::Unevaluated(uv) => { - for arg in uv.args.iter() { - compute_components_for_arg(tcx, arg, out, visited); - } - } + child.visit_with(&mut visitor); } }