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Diffstat (limited to 'compiler/rustc_traits/src/chalk/lowering.rs')
| -rw-r--r-- | compiler/rustc_traits/src/chalk/lowering.rs | 1172 |
1 files changed, 1172 insertions, 0 deletions
diff --git a/compiler/rustc_traits/src/chalk/lowering.rs b/compiler/rustc_traits/src/chalk/lowering.rs new file mode 100644 index 000000000..c7c604e14 --- /dev/null +++ b/compiler/rustc_traits/src/chalk/lowering.rs @@ -0,0 +1,1172 @@ +//! Contains the logic to lower rustc types into Chalk types +//! +//! In many cases there is a 1:1 relationship between a rustc type and a Chalk type. +//! For example, a `SubstsRef` maps almost directly to a `Substitution`. In some +//! other cases, such as `Param`s, there is no Chalk type, so we have to handle +//! accordingly. +//! +//! ## `Ty` lowering +//! Much of the `Ty` lowering is 1:1 with Chalk. (Or will be eventually). A +//! helpful table for what types lower to what can be found in the +//! [Chalk book](https://rust-lang.github.io/chalk/book/types/rust_types.html). +//! The most notable difference lies with `Param`s. To convert from rustc to +//! Chalk, we eagerly and deeply convert `Param`s to placeholders (in goals) or +//! bound variables (for clause generation through functions in `db`). +//! +//! ## `Region` lowering +//! Regions are handled in rustc and Chalk is quite differently. In rustc, there +//! is a difference between "early bound" and "late bound" regions, where only +//! the late bound regions have a `DebruijnIndex`. Moreover, in Chalk all +//! regions (Lifetimes) have an associated index. In rustc, only `BrAnon`s have +//! an index, whereas `BrNamed` don't. In order to lower regions to Chalk, we +//! convert all regions into `BrAnon` late-bound regions. +//! +//! ## `Const` lowering +//! Chalk doesn't handle consts currently, so consts are currently lowered to +//! an empty tuple. +//! +//! ## Bound variable collection +//! Another difference between rustc and Chalk lies in the handling of binders. +//! Chalk requires that we store the bound parameter kinds, whereas rustc does +//! not. To lower anything wrapped in a `Binder`, we first deeply find any bound +//! variables from the current `Binder`. + +use rustc_ast::ast; +use rustc_middle::traits::{ChalkEnvironmentAndGoal, ChalkRustInterner as RustInterner}; +use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef}; +use rustc_middle::ty::{ + self, Binder, Region, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, + TypeSuperVisitable, TypeVisitable, TypeVisitor, +}; +use rustc_span::def_id::DefId; + +use chalk_ir::{FnSig, ForeignDefId}; +use rustc_hir::Unsafety; +use std::collections::btree_map::{BTreeMap, Entry}; +use std::ops::ControlFlow; + +/// Essentially an `Into` with a `&RustInterner` parameter +pub(crate) trait LowerInto<'tcx, T> { + /// Lower a rustc construct (e.g., `ty::TraitPredicate`) to a chalk type, consuming `self`. + fn lower_into(self, interner: RustInterner<'tcx>) -> T; +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::Substitution<RustInterner<'tcx>>> for SubstsRef<'tcx> { + fn lower_into( + self, + interner: RustInterner<'tcx>, + ) -> chalk_ir::Substitution<RustInterner<'tcx>> { + chalk_ir::Substitution::from_iter(interner, self.iter().map(|s| s.lower_into(interner))) + } +} + +impl<'tcx> LowerInto<'tcx, SubstsRef<'tcx>> for &chalk_ir::Substitution<RustInterner<'tcx>> { + fn lower_into(self, interner: RustInterner<'tcx>) -> SubstsRef<'tcx> { + interner.tcx.mk_substs(self.iter(interner).map(|subst| subst.lower_into(interner))) + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::AliasTy<RustInterner<'tcx>>> for ty::ProjectionTy<'tcx> { + fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::AliasTy<RustInterner<'tcx>> { + chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy { + associated_ty_id: chalk_ir::AssocTypeId(self.item_def_id), + substitution: self.substs.lower_into(interner), + }) + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::InEnvironment<chalk_ir::Goal<RustInterner<'tcx>>>> + for ChalkEnvironmentAndGoal<'tcx> +{ + fn lower_into( + self, + interner: RustInterner<'tcx>, + ) -> chalk_ir::InEnvironment<chalk_ir::Goal<RustInterner<'tcx>>> { + let clauses = self.environment.into_iter().map(|predicate| { + let (predicate, binders, _named_regions) = + collect_bound_vars(interner, interner.tcx, predicate.kind()); + let consequence = match predicate { + ty::PredicateKind::TypeWellFormedFromEnv(ty) => { + chalk_ir::DomainGoal::FromEnv(chalk_ir::FromEnv::Ty(ty.lower_into(interner))) + } + ty::PredicateKind::Trait(predicate) => chalk_ir::DomainGoal::FromEnv( + chalk_ir::FromEnv::Trait(predicate.trait_ref.lower_into(interner)), + ), + ty::PredicateKind::RegionOutlives(predicate) => chalk_ir::DomainGoal::Holds( + chalk_ir::WhereClause::LifetimeOutlives(chalk_ir::LifetimeOutlives { + a: predicate.0.lower_into(interner), + b: predicate.1.lower_into(interner), + }), + ), + ty::PredicateKind::TypeOutlives(predicate) => chalk_ir::DomainGoal::Holds( + chalk_ir::WhereClause::TypeOutlives(chalk_ir::TypeOutlives { + ty: predicate.0.lower_into(interner), + lifetime: predicate.1.lower_into(interner), + }), + ), + ty::PredicateKind::Projection(predicate) => chalk_ir::DomainGoal::Holds( + chalk_ir::WhereClause::AliasEq(predicate.lower_into(interner)), + ), + ty::PredicateKind::WellFormed(arg) => match arg.unpack() { + ty::GenericArgKind::Type(ty) => chalk_ir::DomainGoal::WellFormed( + chalk_ir::WellFormed::Ty(ty.lower_into(interner)), + ), + // FIXME(chalk): we need to change `WellFormed` in Chalk to take a `GenericArg` + _ => chalk_ir::DomainGoal::WellFormed(chalk_ir::WellFormed::Ty( + interner.tcx.types.unit.lower_into(interner), + )), + }, + ty::PredicateKind::ObjectSafe(..) + | ty::PredicateKind::ClosureKind(..) + | ty::PredicateKind::Subtype(..) + | ty::PredicateKind::Coerce(..) + | ty::PredicateKind::ConstEvaluatable(..) + | ty::PredicateKind::ConstEquate(..) => bug!("unexpected predicate {}", predicate), + }; + let value = chalk_ir::ProgramClauseImplication { + consequence, + conditions: chalk_ir::Goals::empty(interner), + priority: chalk_ir::ClausePriority::High, + constraints: chalk_ir::Constraints::empty(interner), + }; + chalk_ir::ProgramClauseData(chalk_ir::Binders::new(binders, value)).intern(interner) + }); + + let goal: chalk_ir::GoalData<RustInterner<'tcx>> = self.goal.lower_into(interner); + chalk_ir::InEnvironment { + environment: chalk_ir::Environment { + clauses: chalk_ir::ProgramClauses::from_iter(interner, clauses), + }, + goal: goal.intern(interner), + } + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::GoalData<RustInterner<'tcx>>> for ty::Predicate<'tcx> { + fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::GoalData<RustInterner<'tcx>> { + let (predicate, binders, _named_regions) = + collect_bound_vars(interner, interner.tcx, self.kind()); + + let value = match predicate { + ty::PredicateKind::Trait(predicate) => { + chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds( + chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner)), + )) + } + ty::PredicateKind::RegionOutlives(predicate) => { + chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds( + chalk_ir::WhereClause::LifetimeOutlives(chalk_ir::LifetimeOutlives { + a: predicate.0.lower_into(interner), + b: predicate.1.lower_into(interner), + }), + )) + } + ty::PredicateKind::TypeOutlives(predicate) => { + chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds( + chalk_ir::WhereClause::TypeOutlives(chalk_ir::TypeOutlives { + ty: predicate.0.lower_into(interner), + lifetime: predicate.1.lower_into(interner), + }), + )) + } + ty::PredicateKind::Projection(predicate) => { + chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds( + chalk_ir::WhereClause::AliasEq(predicate.lower_into(interner)), + )) + } + ty::PredicateKind::WellFormed(arg) => match arg.unpack() { + GenericArgKind::Type(ty) => match ty.kind() { + // FIXME(chalk): In Chalk, a placeholder is WellFormed if it + // `FromEnv`. However, when we "lower" Params, we don't update + // the environment. + ty::Placeholder(..) => { + chalk_ir::GoalData::All(chalk_ir::Goals::empty(interner)) + } + + _ => chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::WellFormed( + chalk_ir::WellFormed::Ty(ty.lower_into(interner)), + )), + }, + // FIXME(chalk): handle well formed consts + GenericArgKind::Const(..) => { + chalk_ir::GoalData::All(chalk_ir::Goals::empty(interner)) + } + GenericArgKind::Lifetime(lt) => bug!("unexpect well formed predicate: {:?}", lt), + }, + + ty::PredicateKind::ObjectSafe(t) => chalk_ir::GoalData::DomainGoal( + chalk_ir::DomainGoal::ObjectSafe(chalk_ir::TraitId(t)), + ), + + ty::PredicateKind::Subtype(ty::SubtypePredicate { a, b, a_is_expected: _ }) => { + chalk_ir::GoalData::SubtypeGoal(chalk_ir::SubtypeGoal { + a: a.lower_into(interner), + b: b.lower_into(interner), + }) + } + + // FIXME(chalk): other predicates + // + // We can defer this, but ultimately we'll want to express + // some of these in terms of chalk operations. + ty::PredicateKind::ClosureKind(..) + | ty::PredicateKind::Coerce(..) + | ty::PredicateKind::ConstEvaluatable(..) + | ty::PredicateKind::ConstEquate(..) => { + chalk_ir::GoalData::All(chalk_ir::Goals::empty(interner)) + } + ty::PredicateKind::TypeWellFormedFromEnv(ty) => chalk_ir::GoalData::DomainGoal( + chalk_ir::DomainGoal::FromEnv(chalk_ir::FromEnv::Ty(ty.lower_into(interner))), + ), + }; + + chalk_ir::GoalData::Quantified( + chalk_ir::QuantifierKind::ForAll, + chalk_ir::Binders::new(binders, value.intern(interner)), + ) + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::TraitRef<RustInterner<'tcx>>> + for rustc_middle::ty::TraitRef<'tcx> +{ + fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::TraitRef<RustInterner<'tcx>> { + chalk_ir::TraitRef { + trait_id: chalk_ir::TraitId(self.def_id), + substitution: self.substs.lower_into(interner), + } + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::AliasEq<RustInterner<'tcx>>> + for rustc_middle::ty::ProjectionPredicate<'tcx> +{ + fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::AliasEq<RustInterner<'tcx>> { + // FIXME(associated_const_equality): teach chalk about terms for alias eq. + chalk_ir::AliasEq { + ty: self.term.ty().unwrap().lower_into(interner), + alias: self.projection_ty.lower_into(interner), + } + } +} + +/* +// FIXME(...): Where do I add this to Chalk? I can't find it in the rustc repo anywhere. +impl<'tcx> LowerInto<'tcx, chalk_ir::Term<RustInterner<'tcx>>> for rustc_middle::ty::Term<'tcx> { + fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Term<RustInterner<'tcx>> { + match self { + ty::Term::Ty(ty) => ty.lower_into(interner).into(), + ty::Term::Const(c) => c.lower_into(interner).into(), + } + } +} +*/ + +impl<'tcx> LowerInto<'tcx, chalk_ir::Ty<RustInterner<'tcx>>> for Ty<'tcx> { + fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Ty<RustInterner<'tcx>> { + let int = |i| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Int(i)); + let uint = |i| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Uint(i)); + let float = |f| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Float(f)); + + match *self.kind() { + ty::Bool => chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Bool), + ty::Char => chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Char), + ty::Int(ty) => match ty { + ty::IntTy::Isize => int(chalk_ir::IntTy::Isize), + ty::IntTy::I8 => int(chalk_ir::IntTy::I8), + ty::IntTy::I16 => int(chalk_ir::IntTy::I16), + ty::IntTy::I32 => int(chalk_ir::IntTy::I32), + ty::IntTy::I64 => int(chalk_ir::IntTy::I64), + ty::IntTy::I128 => int(chalk_ir::IntTy::I128), + }, + ty::Uint(ty) => match ty { + ty::UintTy::Usize => uint(chalk_ir::UintTy::Usize), + ty::UintTy::U8 => uint(chalk_ir::UintTy::U8), + ty::UintTy::U16 => uint(chalk_ir::UintTy::U16), + ty::UintTy::U32 => uint(chalk_ir::UintTy::U32), + ty::UintTy::U64 => uint(chalk_ir::UintTy::U64), + ty::UintTy::U128 => uint(chalk_ir::UintTy::U128), + }, + ty::Float(ty) => match ty { + ty::FloatTy::F32 => float(chalk_ir::FloatTy::F32), + ty::FloatTy::F64 => float(chalk_ir::FloatTy::F64), + }, + ty::Adt(def, substs) => { + chalk_ir::TyKind::Adt(chalk_ir::AdtId(def), substs.lower_into(interner)) + } + ty::Foreign(def_id) => chalk_ir::TyKind::Foreign(ForeignDefId(def_id)), + ty::Str => chalk_ir::TyKind::Str, + ty::Array(ty, len) => { + chalk_ir::TyKind::Array(ty.lower_into(interner), len.lower_into(interner)) + } + ty::Slice(ty) => chalk_ir::TyKind::Slice(ty.lower_into(interner)), + + ty::RawPtr(ptr) => { + chalk_ir::TyKind::Raw(ptr.mutbl.lower_into(interner), ptr.ty.lower_into(interner)) + } + ty::Ref(region, ty, mutability) => chalk_ir::TyKind::Ref( + mutability.lower_into(interner), + region.lower_into(interner), + ty.lower_into(interner), + ), + ty::FnDef(def_id, substs) => { + chalk_ir::TyKind::FnDef(chalk_ir::FnDefId(def_id), substs.lower_into(interner)) + } + ty::FnPtr(sig) => { + let (inputs_and_outputs, binders, _named_regions) = + collect_bound_vars(interner, interner.tcx, sig.inputs_and_output()); + chalk_ir::TyKind::Function(chalk_ir::FnPointer { + num_binders: binders.len(interner), + sig: sig.lower_into(interner), + substitution: chalk_ir::FnSubst(chalk_ir::Substitution::from_iter( + interner, + inputs_and_outputs.iter().map(|ty| { + chalk_ir::GenericArgData::Ty(ty.lower_into(interner)).intern(interner) + }), + )), + }) + } + ty::Dynamic(predicates, region) => chalk_ir::TyKind::Dyn(chalk_ir::DynTy { + bounds: predicates.lower_into(interner), + lifetime: region.lower_into(interner), + }), + ty::Closure(def_id, substs) => { + chalk_ir::TyKind::Closure(chalk_ir::ClosureId(def_id), substs.lower_into(interner)) + } + ty::Generator(def_id, substs, _) => chalk_ir::TyKind::Generator( + chalk_ir::GeneratorId(def_id), + substs.lower_into(interner), + ), + ty::GeneratorWitness(_) => unimplemented!(), + ty::Never => chalk_ir::TyKind::Never, + ty::Tuple(types) => { + chalk_ir::TyKind::Tuple(types.len(), types.as_substs().lower_into(interner)) + } + ty::Projection(proj) => chalk_ir::TyKind::Alias(proj.lower_into(interner)), + ty::Opaque(def_id, substs) => { + chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Opaque(chalk_ir::OpaqueTy { + opaque_ty_id: chalk_ir::OpaqueTyId(def_id), + substitution: substs.lower_into(interner), + })) + } + // This should have been done eagerly prior to this, and all Params + // should have been substituted to placeholders + ty::Param(_) => panic!("Lowering Param when not expected."), + ty::Bound(db, bound) => chalk_ir::TyKind::BoundVar(chalk_ir::BoundVar::new( + chalk_ir::DebruijnIndex::new(db.as_u32()), + bound.var.index(), + )), + ty::Placeholder(_placeholder) => { + chalk_ir::TyKind::Placeholder(chalk_ir::PlaceholderIndex { + ui: chalk_ir::UniverseIndex { counter: _placeholder.universe.as_usize() }, + idx: _placeholder.name.as_usize(), + }) + } + ty::Infer(_infer) => unimplemented!(), + ty::Error(_) => chalk_ir::TyKind::Error, + } + .intern(interner) + } +} + +impl<'tcx> LowerInto<'tcx, Ty<'tcx>> for &chalk_ir::Ty<RustInterner<'tcx>> { + fn lower_into(self, interner: RustInterner<'tcx>) -> Ty<'tcx> { + use chalk_ir::TyKind; + + let kind = match self.kind(interner) { + TyKind::Adt(struct_id, substitution) => { + ty::Adt(struct_id.0, substitution.lower_into(interner)) + } + TyKind::Scalar(scalar) => match scalar { + chalk_ir::Scalar::Bool => ty::Bool, + chalk_ir::Scalar::Char => ty::Char, + chalk_ir::Scalar::Int(int_ty) => match int_ty { + chalk_ir::IntTy::Isize => ty::Int(ty::IntTy::Isize), + chalk_ir::IntTy::I8 => ty::Int(ty::IntTy::I8), + chalk_ir::IntTy::I16 => ty::Int(ty::IntTy::I16), + chalk_ir::IntTy::I32 => ty::Int(ty::IntTy::I32), + chalk_ir::IntTy::I64 => ty::Int(ty::IntTy::I64), + chalk_ir::IntTy::I128 => ty::Int(ty::IntTy::I128), + }, + chalk_ir::Scalar::Uint(int_ty) => match int_ty { + chalk_ir::UintTy::Usize => ty::Uint(ty::UintTy::Usize), + chalk_ir::UintTy::U8 => ty::Uint(ty::UintTy::U8), + chalk_ir::UintTy::U16 => ty::Uint(ty::UintTy::U16), + chalk_ir::UintTy::U32 => ty::Uint(ty::UintTy::U32), + chalk_ir::UintTy::U64 => ty::Uint(ty::UintTy::U64), + chalk_ir::UintTy::U128 => ty::Uint(ty::UintTy::U128), + }, + chalk_ir::Scalar::Float(float_ty) => match float_ty { + chalk_ir::FloatTy::F32 => ty::Float(ty::FloatTy::F32), + chalk_ir::FloatTy::F64 => ty::Float(ty::FloatTy::F64), + }, + }, + TyKind::Array(ty, c) => { + let ty = ty.lower_into(interner); + let c = c.lower_into(interner); + ty::Array(ty, c) + } + TyKind::FnDef(id, substitution) => ty::FnDef(id.0, substitution.lower_into(interner)), + TyKind::Closure(closure, substitution) => { + ty::Closure(closure.0, substitution.lower_into(interner)) + } + TyKind::Generator(..) => unimplemented!(), + TyKind::GeneratorWitness(..) => unimplemented!(), + TyKind::Never => ty::Never, + TyKind::Tuple(_len, substitution) => { + ty::Tuple(substitution.lower_into(interner).try_as_type_list().unwrap()) + } + TyKind::Slice(ty) => ty::Slice(ty.lower_into(interner)), + TyKind::Raw(mutbl, ty) => ty::RawPtr(ty::TypeAndMut { + ty: ty.lower_into(interner), + mutbl: mutbl.lower_into(interner), + }), + TyKind::Ref(mutbl, lifetime, ty) => ty::Ref( + lifetime.lower_into(interner), + ty.lower_into(interner), + mutbl.lower_into(interner), + ), + TyKind::Str => ty::Str, + TyKind::OpaqueType(opaque_ty, substitution) => { + ty::Opaque(opaque_ty.0, substitution.lower_into(interner)) + } + TyKind::AssociatedType(assoc_ty, substitution) => ty::Projection(ty::ProjectionTy { + substs: substitution.lower_into(interner), + item_def_id: assoc_ty.0, + }), + TyKind::Foreign(def_id) => ty::Foreign(def_id.0), + TyKind::Error => return interner.tcx.ty_error(), + TyKind::Placeholder(placeholder) => ty::Placeholder(ty::Placeholder { + universe: ty::UniverseIndex::from_usize(placeholder.ui.counter), + name: ty::BoundVar::from_usize(placeholder.idx), + }), + TyKind::Alias(alias_ty) => match alias_ty { + chalk_ir::AliasTy::Projection(projection) => ty::Projection(ty::ProjectionTy { + item_def_id: projection.associated_ty_id.0, + substs: projection.substitution.lower_into(interner), + }), + chalk_ir::AliasTy::Opaque(opaque) => { + ty::Opaque(opaque.opaque_ty_id.0, opaque.substitution.lower_into(interner)) + } + }, + TyKind::Function(_quantified_ty) => unimplemented!(), + TyKind::BoundVar(_bound) => ty::Bound( + ty::DebruijnIndex::from_usize(_bound.debruijn.depth() as usize), + ty::BoundTy { + var: ty::BoundVar::from_usize(_bound.index), + kind: ty::BoundTyKind::Anon, + }, + ), + TyKind::InferenceVar(_, _) => unimplemented!(), + TyKind::Dyn(_) => unimplemented!(), + }; + interner.tcx.mk_ty(kind) + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::Lifetime<RustInterner<'tcx>>> for Region<'tcx> { + fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Lifetime<RustInterner<'tcx>> { + match *self { + ty::ReEarlyBound(_) => { + panic!("Should have already been substituted."); + } + ty::ReLateBound(db, br) => chalk_ir::LifetimeData::BoundVar(chalk_ir::BoundVar::new( + chalk_ir::DebruijnIndex::new(db.as_u32()), + br.var.as_usize(), + )) + .intern(interner), + ty::ReFree(_) => unimplemented!(), + ty::ReStatic => chalk_ir::LifetimeData::Static.intern(interner), + ty::ReVar(_) => unimplemented!(), + ty::RePlaceholder(placeholder_region) => { + chalk_ir::LifetimeData::Placeholder(chalk_ir::PlaceholderIndex { + ui: chalk_ir::UniverseIndex { counter: placeholder_region.universe.index() }, + idx: 0, + }) + .intern(interner) + } + ty::ReEmpty(ui) => { + chalk_ir::LifetimeData::Empty(chalk_ir::UniverseIndex { counter: ui.index() }) + .intern(interner) + } + ty::ReErased => chalk_ir::LifetimeData::Erased.intern(interner), + } + } +} + +impl<'tcx> LowerInto<'tcx, Region<'tcx>> for &chalk_ir::Lifetime<RustInterner<'tcx>> { + fn lower_into(self, interner: RustInterner<'tcx>) -> Region<'tcx> { + let kind = match self.data(interner) { + chalk_ir::LifetimeData::BoundVar(var) => ty::ReLateBound( + ty::DebruijnIndex::from_u32(var.debruijn.depth()), + ty::BoundRegion { + var: ty::BoundVar::from_usize(var.index), + kind: ty::BrAnon(var.index as u32), + }, + ), + chalk_ir::LifetimeData::InferenceVar(_var) => unimplemented!(), + chalk_ir::LifetimeData::Placeholder(p) => ty::RePlaceholder(ty::Placeholder { + universe: ty::UniverseIndex::from_usize(p.ui.counter), + name: ty::BoundRegionKind::BrAnon(p.idx as u32), + }), + chalk_ir::LifetimeData::Static => return interner.tcx.lifetimes.re_static, + chalk_ir::LifetimeData::Empty(ui) => { + ty::ReEmpty(ty::UniverseIndex::from_usize(ui.counter)) + } + chalk_ir::LifetimeData::Erased => return interner.tcx.lifetimes.re_erased, + chalk_ir::LifetimeData::Phantom(void, _) => match *void {}, + }; + interner.tcx.mk_region(kind) + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::Const<RustInterner<'tcx>>> for ty::Const<'tcx> { + fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Const<RustInterner<'tcx>> { + let ty = self.ty().lower_into(interner); + let value = match self.kind() { + ty::ConstKind::Value(val) => { + chalk_ir::ConstValue::Concrete(chalk_ir::ConcreteConst { interned: val }) + } + ty::ConstKind::Bound(db, bound) => chalk_ir::ConstValue::BoundVar( + chalk_ir::BoundVar::new(chalk_ir::DebruijnIndex::new(db.as_u32()), bound.index()), + ), + _ => unimplemented!("Const not implemented. {:?}", self), + }; + chalk_ir::ConstData { ty, value }.intern(interner) + } +} + +impl<'tcx> LowerInto<'tcx, ty::Const<'tcx>> for &chalk_ir::Const<RustInterner<'tcx>> { + fn lower_into(self, interner: RustInterner<'tcx>) -> ty::Const<'tcx> { + let data = self.data(interner); + let ty = data.ty.lower_into(interner); + let kind = match data.value { + chalk_ir::ConstValue::BoundVar(var) => ty::ConstKind::Bound( + ty::DebruijnIndex::from_u32(var.debruijn.depth()), + ty::BoundVar::from_u32(var.index as u32), + ), + chalk_ir::ConstValue::InferenceVar(_var) => unimplemented!(), + chalk_ir::ConstValue::Placeholder(_p) => unimplemented!(), + chalk_ir::ConstValue::Concrete(c) => ty::ConstKind::Value(c.interned), + }; + interner.tcx.mk_const(ty::ConstS { ty, kind }) + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::GenericArg<RustInterner<'tcx>>> for GenericArg<'tcx> { + fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::GenericArg<RustInterner<'tcx>> { + match self.unpack() { + ty::subst::GenericArgKind::Type(ty) => { + chalk_ir::GenericArgData::Ty(ty.lower_into(interner)) + } + ty::subst::GenericArgKind::Lifetime(lifetime) => { + chalk_ir::GenericArgData::Lifetime(lifetime.lower_into(interner)) + } + ty::subst::GenericArgKind::Const(c) => { + chalk_ir::GenericArgData::Const(c.lower_into(interner)) + } + } + .intern(interner) + } +} + +impl<'tcx> LowerInto<'tcx, ty::subst::GenericArg<'tcx>> + for &chalk_ir::GenericArg<RustInterner<'tcx>> +{ + fn lower_into(self, interner: RustInterner<'tcx>) -> ty::subst::GenericArg<'tcx> { + match self.data(interner) { + chalk_ir::GenericArgData::Ty(ty) => { + let t: Ty<'tcx> = ty.lower_into(interner); + t.into() + } + chalk_ir::GenericArgData::Lifetime(lifetime) => { + let r: Region<'tcx> = lifetime.lower_into(interner); + r.into() + } + chalk_ir::GenericArgData::Const(c) => { + let c: ty::Const<'tcx> = c.lower_into(interner); + c.into() + } + } + } +} + +// We lower into an Option here since there are some predicates which Chalk +// doesn't have a representation for yet (as a `WhereClause`), but are so common +// that we just are accepting the unsoundness for now. The `Option` will +// eventually be removed. +impl<'tcx> LowerInto<'tcx, Option<chalk_ir::QuantifiedWhereClause<RustInterner<'tcx>>>> + for ty::Predicate<'tcx> +{ + fn lower_into( + self, + interner: RustInterner<'tcx>, + ) -> Option<chalk_ir::QuantifiedWhereClause<RustInterner<'tcx>>> { + let (predicate, binders, _named_regions) = + collect_bound_vars(interner, interner.tcx, self.kind()); + let value = match predicate { + ty::PredicateKind::Trait(predicate) => { + Some(chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner))) + } + ty::PredicateKind::RegionOutlives(predicate) => { + Some(chalk_ir::WhereClause::LifetimeOutlives(chalk_ir::LifetimeOutlives { + a: predicate.0.lower_into(interner), + b: predicate.1.lower_into(interner), + })) + } + ty::PredicateKind::TypeOutlives(predicate) => { + Some(chalk_ir::WhereClause::TypeOutlives(chalk_ir::TypeOutlives { + ty: predicate.0.lower_into(interner), + lifetime: predicate.1.lower_into(interner), + })) + } + ty::PredicateKind::Projection(predicate) => { + Some(chalk_ir::WhereClause::AliasEq(predicate.lower_into(interner))) + } + ty::PredicateKind::WellFormed(_ty) => None, + + ty::PredicateKind::ObjectSafe(..) + | ty::PredicateKind::ClosureKind(..) + | ty::PredicateKind::Subtype(..) + | ty::PredicateKind::Coerce(..) + | ty::PredicateKind::ConstEvaluatable(..) + | ty::PredicateKind::ConstEquate(..) + | ty::PredicateKind::TypeWellFormedFromEnv(..) => { + bug!("unexpected predicate {}", &self) + } + }; + value.map(|value| chalk_ir::Binders::new(binders, value)) + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::Binders<chalk_ir::QuantifiedWhereClauses<RustInterner<'tcx>>>> + for &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>> +{ + fn lower_into( + self, + interner: RustInterner<'tcx>, + ) -> chalk_ir::Binders<chalk_ir::QuantifiedWhereClauses<RustInterner<'tcx>>> { + // `Self` has one binder: + // Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>> + // The return type has two: + // Binders<&[Binders<WhereClause<I>>]> + // This means that any variables that are escaping `self` need to be + // shifted in by one so that they are still escaping. + let predicates = ty::fold::shift_vars(interner.tcx, self, 1); + + let self_ty = interner.tcx.mk_ty(ty::Bound( + // This is going to be wrapped in a binder + ty::DebruijnIndex::from_usize(1), + ty::BoundTy { var: ty::BoundVar::from_usize(0), kind: ty::BoundTyKind::Anon }, + )); + let where_clauses = predicates.into_iter().map(|predicate| { + let (predicate, binders, _named_regions) = + collect_bound_vars(interner, interner.tcx, predicate); + match predicate { + ty::ExistentialPredicate::Trait(ty::ExistentialTraitRef { def_id, substs }) => { + chalk_ir::Binders::new( + binders.clone(), + chalk_ir::WhereClause::Implemented(chalk_ir::TraitRef { + trait_id: chalk_ir::TraitId(def_id), + substitution: interner + .tcx + .mk_substs_trait(self_ty, substs) + .lower_into(interner), + }), + ) + } + ty::ExistentialPredicate::Projection(predicate) => chalk_ir::Binders::new( + binders.clone(), + chalk_ir::WhereClause::AliasEq(chalk_ir::AliasEq { + alias: chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy { + associated_ty_id: chalk_ir::AssocTypeId(predicate.item_def_id), + substitution: interner + .tcx + .mk_substs_trait(self_ty, predicate.substs) + .lower_into(interner), + }), + // FIXME(associated_const_equality): teach chalk about terms for alias eq. + ty: predicate.term.ty().unwrap().lower_into(interner), + }), + ), + ty::ExistentialPredicate::AutoTrait(def_id) => chalk_ir::Binders::new( + binders.clone(), + chalk_ir::WhereClause::Implemented(chalk_ir::TraitRef { + trait_id: chalk_ir::TraitId(def_id), + substitution: interner + .tcx + .mk_substs_trait(self_ty, &[]) + .lower_into(interner), + }), + ), + } + }); + + // Binder for the bound variable representing the concrete underlying type. + let existential_binder = chalk_ir::VariableKinds::from1( + interner, + chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General), + ); + let value = chalk_ir::QuantifiedWhereClauses::from_iter(interner, where_clauses); + chalk_ir::Binders::new(existential_binder, value) + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::FnSig<RustInterner<'tcx>>> + for ty::Binder<'tcx, ty::FnSig<'tcx>> +{ + fn lower_into(self, _interner: RustInterner<'_>) -> FnSig<RustInterner<'tcx>> { + chalk_ir::FnSig { + abi: self.abi(), + safety: match self.unsafety() { + Unsafety::Normal => chalk_ir::Safety::Safe, + Unsafety::Unsafe => chalk_ir::Safety::Unsafe, + }, + variadic: self.c_variadic(), + } + } +} + +// We lower into an Option here since there are some predicates which Chalk +// doesn't have a representation for yet (as an `InlineBound`). The `Option` will +// eventually be removed. +impl<'tcx> LowerInto<'tcx, Option<chalk_solve::rust_ir::QuantifiedInlineBound<RustInterner<'tcx>>>> + for ty::Predicate<'tcx> +{ + fn lower_into( + self, + interner: RustInterner<'tcx>, + ) -> Option<chalk_solve::rust_ir::QuantifiedInlineBound<RustInterner<'tcx>>> { + let (predicate, binders, _named_regions) = + collect_bound_vars(interner, interner.tcx, self.kind()); + match predicate { + ty::PredicateKind::Trait(predicate) => Some(chalk_ir::Binders::new( + binders, + chalk_solve::rust_ir::InlineBound::TraitBound( + predicate.trait_ref.lower_into(interner), + ), + )), + ty::PredicateKind::Projection(predicate) => Some(chalk_ir::Binders::new( + binders, + chalk_solve::rust_ir::InlineBound::AliasEqBound(predicate.lower_into(interner)), + )), + ty::PredicateKind::TypeOutlives(_predicate) => None, + ty::PredicateKind::WellFormed(_ty) => None, + + ty::PredicateKind::RegionOutlives(..) + | ty::PredicateKind::ObjectSafe(..) + | ty::PredicateKind::ClosureKind(..) + | ty::PredicateKind::Subtype(..) + | ty::PredicateKind::Coerce(..) + | ty::PredicateKind::ConstEvaluatable(..) + | ty::PredicateKind::ConstEquate(..) + | ty::PredicateKind::TypeWellFormedFromEnv(..) => { + bug!("unexpected predicate {}", &self) + } + } + } +} + +impl<'tcx> LowerInto<'tcx, chalk_solve::rust_ir::TraitBound<RustInterner<'tcx>>> + for ty::TraitRef<'tcx> +{ + fn lower_into( + self, + interner: RustInterner<'tcx>, + ) -> chalk_solve::rust_ir::TraitBound<RustInterner<'tcx>> { + chalk_solve::rust_ir::TraitBound { + trait_id: chalk_ir::TraitId(self.def_id), + args_no_self: self.substs[1..].iter().map(|arg| arg.lower_into(interner)).collect(), + } + } +} + +impl<'tcx> LowerInto<'tcx, chalk_ir::Mutability> for ast::Mutability { + fn lower_into(self, _interner: RustInterner<'tcx>) -> chalk_ir::Mutability { + match self { + rustc_ast::Mutability::Mut => chalk_ir::Mutability::Mut, + rustc_ast::Mutability::Not => chalk_ir::Mutability::Not, + } + } +} + +impl<'tcx> LowerInto<'tcx, ast::Mutability> for chalk_ir::Mutability { + fn lower_into(self, _interner: RustInterner<'tcx>) -> ast::Mutability { + match self { + chalk_ir::Mutability::Mut => ast::Mutability::Mut, + chalk_ir::Mutability::Not => ast::Mutability::Not, + } + } +} + +impl<'tcx> LowerInto<'tcx, chalk_solve::rust_ir::Polarity> for ty::ImplPolarity { + fn lower_into(self, _interner: RustInterner<'tcx>) -> chalk_solve::rust_ir::Polarity { + match self { + ty::ImplPolarity::Positive => chalk_solve::rust_ir::Polarity::Positive, + ty::ImplPolarity::Negative => chalk_solve::rust_ir::Polarity::Negative, + // FIXME(chalk) reservation impls + ty::ImplPolarity::Reservation => chalk_solve::rust_ir::Polarity::Negative, + } + } +} +impl<'tcx> LowerInto<'tcx, chalk_ir::Variance> for ty::Variance { + fn lower_into(self, _interner: RustInterner<'tcx>) -> chalk_ir::Variance { + match self { + ty::Variance::Covariant => chalk_ir::Variance::Covariant, + ty::Variance::Invariant => chalk_ir::Variance::Invariant, + ty::Variance::Contravariant => chalk_ir::Variance::Contravariant, + ty::Variance::Bivariant => unimplemented!(), + } + } +} + +impl<'tcx> LowerInto<'tcx, chalk_solve::rust_ir::AliasEqBound<RustInterner<'tcx>>> + for ty::ProjectionPredicate<'tcx> +{ + fn lower_into( + self, + interner: RustInterner<'tcx>, + ) -> chalk_solve::rust_ir::AliasEqBound<RustInterner<'tcx>> { + let (trait_ref, own_substs) = self.projection_ty.trait_ref_and_own_substs(interner.tcx); + chalk_solve::rust_ir::AliasEqBound { + trait_bound: trait_ref.lower_into(interner), + associated_ty_id: chalk_ir::AssocTypeId(self.projection_ty.item_def_id), + parameters: own_substs.iter().map(|arg| arg.lower_into(interner)).collect(), + value: self.term.ty().unwrap().lower_into(interner), + } + } +} + +/// To collect bound vars, we have to do two passes. In the first pass, we +/// collect all `BoundRegionKind`s and `ty::Bound`s. In the second pass, we then +/// replace `BrNamed` into `BrAnon`. The two separate passes are important, +/// since we can only replace `BrNamed` with `BrAnon`s with indices *after* all +/// "real" `BrAnon`s. +/// +/// It's important to note that because of prior substitution, we may have +/// late-bound regions, even outside of fn contexts, since this is the best way +/// to prep types for chalk lowering. +pub(crate) fn collect_bound_vars<'tcx, T: TypeFoldable<'tcx>>( + interner: RustInterner<'tcx>, + tcx: TyCtxt<'tcx>, + ty: Binder<'tcx, T>, +) -> (T, chalk_ir::VariableKinds<RustInterner<'tcx>>, BTreeMap<DefId, u32>) { + let mut bound_vars_collector = BoundVarsCollector::new(); + ty.as_ref().skip_binder().visit_with(&mut bound_vars_collector); + let mut parameters = bound_vars_collector.parameters; + let named_parameters: BTreeMap<DefId, u32> = bound_vars_collector + .named_parameters + .into_iter() + .enumerate() + .map(|(i, def_id)| (def_id, (i + parameters.len()) as u32)) + .collect(); + + let mut bound_var_substitutor = NamedBoundVarSubstitutor::new(tcx, &named_parameters); + let new_ty = ty.skip_binder().fold_with(&mut bound_var_substitutor); + + for var in named_parameters.values() { + parameters.insert(*var, chalk_ir::VariableKind::Lifetime); + } + + (0..parameters.len()).for_each(|i| { + parameters + .get(&(i as u32)) + .or_else(|| bug!("Skipped bound var index: parameters={:?}", parameters)); + }); + + let binders = + chalk_ir::VariableKinds::from_iter(interner, parameters.into_iter().map(|(_, v)| v)); + + (new_ty, binders, named_parameters) +} + +pub(crate) struct BoundVarsCollector<'tcx> { + binder_index: ty::DebruijnIndex, + pub(crate) parameters: BTreeMap<u32, chalk_ir::VariableKind<RustInterner<'tcx>>>, + pub(crate) named_parameters: Vec<DefId>, +} + +impl<'tcx> BoundVarsCollector<'tcx> { + pub(crate) fn new() -> Self { + BoundVarsCollector { + binder_index: ty::INNERMOST, + parameters: BTreeMap::new(), + named_parameters: vec![], + } + } +} + +impl<'tcx> TypeVisitor<'tcx> for BoundVarsCollector<'tcx> { + fn visit_binder<T: TypeVisitable<'tcx>>( + &mut self, + t: &Binder<'tcx, T>, + ) -> ControlFlow<Self::BreakTy> { + self.binder_index.shift_in(1); + let result = t.super_visit_with(self); + self.binder_index.shift_out(1); + result + } + + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { + match *t.kind() { + ty::Bound(debruijn, bound_ty) if debruijn == self.binder_index => { + match self.parameters.entry(bound_ty.var.as_u32()) { + Entry::Vacant(entry) => { + entry.insert(chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General)); + } + Entry::Occupied(entry) => match entry.get() { + chalk_ir::VariableKind::Ty(_) => {} + _ => panic!(), + }, + } + } + + _ => (), + }; + + t.super_visit_with(self) + } + + fn visit_region(&mut self, r: Region<'tcx>) -> ControlFlow<Self::BreakTy> { + match *r { + ty::ReLateBound(index, br) if index == self.binder_index => match br.kind { + ty::BoundRegionKind::BrNamed(def_id, _name) => { + if !self.named_parameters.iter().any(|d| *d == def_id) { + self.named_parameters.push(def_id); + } + } + + ty::BoundRegionKind::BrAnon(var) => match self.parameters.entry(var) { + Entry::Vacant(entry) => { + entry.insert(chalk_ir::VariableKind::Lifetime); + } + Entry::Occupied(entry) => match entry.get() { + chalk_ir::VariableKind::Lifetime => {} + _ => panic!(), + }, + }, + + ty::BoundRegionKind::BrEnv => unimplemented!(), + }, + + ty::ReEarlyBound(_re) => { + // FIXME(chalk): jackh726 - I think we should always have already + // substituted away `ReEarlyBound`s for `ReLateBound`s, but need to confirm. + unimplemented!(); + } + + _ => (), + }; + + r.super_visit_with(self) + } +} + +/// This is used to replace `BoundRegionKind::BrNamed` with `BoundRegionKind::BrAnon`. +/// Note: we assume that we will always have room for more bound vars. (i.e. we +/// won't ever hit the `u32` limit in `BrAnon`s). +struct NamedBoundVarSubstitutor<'a, 'tcx> { + tcx: TyCtxt<'tcx>, + binder_index: ty::DebruijnIndex, + named_parameters: &'a BTreeMap<DefId, u32>, +} + +impl<'a, 'tcx> NamedBoundVarSubstitutor<'a, 'tcx> { + fn new(tcx: TyCtxt<'tcx>, named_parameters: &'a BTreeMap<DefId, u32>) -> Self { + NamedBoundVarSubstitutor { tcx, binder_index: ty::INNERMOST, named_parameters } + } +} + +impl<'a, 'tcx> TypeFolder<'tcx> for NamedBoundVarSubstitutor<'a, 'tcx> { + fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { + self.tcx + } + + fn fold_binder<T: TypeFoldable<'tcx>>(&mut self, t: Binder<'tcx, T>) -> Binder<'tcx, T> { + self.binder_index.shift_in(1); + let result = t.super_fold_with(self); + self.binder_index.shift_out(1); + result + } + + fn fold_region(&mut self, r: Region<'tcx>) -> Region<'tcx> { + match *r { + ty::ReLateBound(index, br) if index == self.binder_index => match br.kind { + ty::BrNamed(def_id, _name) => match self.named_parameters.get(&def_id) { + Some(idx) => { + let new_br = ty::BoundRegion { var: br.var, kind: ty::BrAnon(*idx) }; + return self.tcx.mk_region(ty::ReLateBound(index, new_br)); + } + None => panic!("Missing `BrNamed`."), + }, + ty::BrEnv => unimplemented!(), + ty::BrAnon(_) => {} + }, + _ => (), + }; + + r.super_fold_with(self) + } +} + +/// Used to substitute `Param`s with placeholders. We do this since Chalk +/// have a notion of `Param`s. +pub(crate) struct ParamsSubstitutor<'tcx> { + tcx: TyCtxt<'tcx>, + binder_index: ty::DebruijnIndex, + list: Vec<rustc_middle::ty::ParamTy>, + next_ty_placeholder: usize, + pub(crate) params: rustc_data_structures::fx::FxHashMap<usize, rustc_middle::ty::ParamTy>, + pub(crate) named_regions: BTreeMap<DefId, u32>, +} + +impl<'tcx> ParamsSubstitutor<'tcx> { + pub(crate) fn new(tcx: TyCtxt<'tcx>, next_ty_placeholder: usize) -> Self { + ParamsSubstitutor { + tcx, + binder_index: ty::INNERMOST, + list: vec![], + next_ty_placeholder, + params: rustc_data_structures::fx::FxHashMap::default(), + named_regions: BTreeMap::default(), + } + } +} + +impl<'tcx> TypeFolder<'tcx> for ParamsSubstitutor<'tcx> { + fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { + self.tcx + } + + fn fold_binder<T: TypeFoldable<'tcx>>(&mut self, t: Binder<'tcx, T>) -> Binder<'tcx, T> { + self.binder_index.shift_in(1); + let result = t.super_fold_with(self); + self.binder_index.shift_out(1); + result + } + + fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { + match *t.kind() { + ty::Param(param) => match self.list.iter().position(|r| r == ¶m) { + Some(idx) => self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType { + universe: ty::UniverseIndex::from_usize(0), + name: ty::BoundVar::from_usize(idx), + })), + None => { + self.list.push(param); + let idx = self.list.len() - 1 + self.next_ty_placeholder; + self.params.insert(idx, param); + self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType { + universe: ty::UniverseIndex::from_usize(0), + name: ty::BoundVar::from_usize(idx), + })) + } + }, + _ => t.super_fold_with(self), + } + } + + fn fold_region(&mut self, r: Region<'tcx>) -> Region<'tcx> { + match *r { + // FIXME(chalk) - jackh726 - this currently isn't hit in any tests, + // since canonicalization will already change these to canonical + // variables (ty::ReLateBound). + ty::ReEarlyBound(_re) => match self.named_regions.get(&_re.def_id) { + Some(idx) => { + let br = ty::BoundRegion { + var: ty::BoundVar::from_u32(*idx), + kind: ty::BrAnon(*idx), + }; + self.tcx.mk_region(ty::ReLateBound(self.binder_index, br)) + } + None => { + let idx = self.named_regions.len() as u32; + let br = + ty::BoundRegion { var: ty::BoundVar::from_u32(idx), kind: ty::BrAnon(idx) }; + self.named_regions.insert(_re.def_id, idx); + self.tcx.mk_region(ty::ReLateBound(self.binder_index, br)) + } + }, + + _ => r.super_fold_with(self), + } + } +} + +pub(crate) struct ReverseParamsSubstitutor<'tcx> { + tcx: TyCtxt<'tcx>, + params: rustc_data_structures::fx::FxHashMap<usize, rustc_middle::ty::ParamTy>, +} + +impl<'tcx> ReverseParamsSubstitutor<'tcx> { + pub(crate) fn new( + tcx: TyCtxt<'tcx>, + params: rustc_data_structures::fx::FxHashMap<usize, rustc_middle::ty::ParamTy>, + ) -> Self { + Self { tcx, params } + } +} + +impl<'tcx> TypeFolder<'tcx> for ReverseParamsSubstitutor<'tcx> { + fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { + self.tcx + } + + fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { + match *t.kind() { + ty::Placeholder(ty::PlaceholderType { universe: ty::UniverseIndex::ROOT, name }) => { + match self.params.get(&name.as_usize()) { + Some(param) => self.tcx.mk_ty(ty::Param(*param)), + None => t, + } + } + + _ => t.super_fold_with(self), + } + } +} + +/// Used to collect `Placeholder`s. +pub(crate) struct PlaceholdersCollector { + universe_index: ty::UniverseIndex, + pub(crate) next_ty_placeholder: usize, + pub(crate) next_anon_region_placeholder: u32, +} + +impl PlaceholdersCollector { + pub(crate) fn new() -> Self { + PlaceholdersCollector { + universe_index: ty::UniverseIndex::ROOT, + next_ty_placeholder: 0, + next_anon_region_placeholder: 0, + } + } +} + +impl<'tcx> TypeVisitor<'tcx> for PlaceholdersCollector { + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { + match t.kind() { + ty::Placeholder(p) if p.universe == self.universe_index => { + self.next_ty_placeholder = self.next_ty_placeholder.max(p.name.as_usize() + 1); + } + + _ => (), + }; + + t.super_visit_with(self) + } + + fn visit_region(&mut self, r: Region<'tcx>) -> ControlFlow<Self::BreakTy> { + match *r { + ty::RePlaceholder(p) if p.universe == self.universe_index => { + if let ty::BoundRegionKind::BrAnon(anon) = p.name { + self.next_anon_region_placeholder = self.next_anon_region_placeholder.max(anon); + } + } + + _ => (), + }; + + r.super_visit_with(self) + } +} |