compiler/rustc_traits/src/chalk/lowering.rs

   1 //! Contains the logic to lower rustc types into Chalk types
   2 //!
   3 //! In many cases there is a 1:1 relationship between a rustc type and a Chalk type.
   4 //! For example, a `SubstsRef` maps almost directly to a `Substitution`. In some
   5 //! other cases, such as `Param`s, there is no Chalk type, so we have to handle
   6 //! accordingly.
   7 //!
   8 //! ## `Ty` lowering
   9 //! Much of the `Ty` lowering is 1:1 with Chalk. (Or will be eventually). A
  10 //! helpful table for what types lower to what can be found in the
  11 //! [Chalk book](https://rust-lang.github.io/chalk/book/types/rust_types.html).
  12 //! The most notable difference lies with `Param`s. To convert from rustc to
  13 //! Chalk, we eagerly and deeply convert `Param`s to placeholders (in goals) or
  14 //! bound variables (for clause generation through functions in `db`).
  15 //!
  16 //! ## `Region` lowering
  17 //! Regions are handled in rustc and Chalk is quite differently. In rustc, there
  18 //! is a difference between "early bound" and "late bound" regions, where only
  19 //! the late bound regions have a `DebruijnIndex`. Moreover, in Chalk all
  20 //! regions (Lifetimes) have an associated index. In rustc, only `BrAnon`s have
  21 //! an index, whereas `BrNamed` don't. In order to lower regions to Chalk, we
  22 //! convert all regions into `BrAnon` late-bound regions.
  23 //!
  24 //! ## `Const` lowering
  25 //! Chalk doesn't handle consts currently, so consts are currently lowered to
  26 //! an empty tuple.
  27 //!
  28 //! ## Bound variable collection
  29 //! Another difference between rustc and Chalk lies in the handling of binders.
  30 //! Chalk requires that we store the bound parameter kinds, whereas rustc does
  31 //! not. To lower anything wrapped in a `Binder`, we first deeply find any bound
  32 //! variables from the current `Binder`.
  33
  34 use rustc_ast::ast;
  35 use rustc_middle::traits::{ChalkEnvironmentAndGoal, ChalkRustInterner as RustInterner};
  36 use rustc_middle::ty::fold::TypeFolder;
  37 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
  38 use rustc_middle::ty::{self, Binder, Region, RegionKind, Ty, TyCtxt, TypeFoldable, TypeVisitor};
  39 use rustc_span::def_id::DefId;
  40
  41 use chalk_ir::{FnSig, ForeignDefId};
  42 use rustc_hir::Unsafety;
  43 use std::collections::btree_map::{BTreeMap, Entry};
  44 use std::ops::ControlFlow;
  45
  46 /// Essentially an `Into` with a `&RustInterner` parameter
  47 crate trait LowerInto<'tcx, T> {
  48     /// Lower a rustc construct (e.g., `ty::TraitPredicate`) to a chalk type, consuming `self`.
  49     fn lower_into(self, interner: RustInterner<'tcx>) -> T;
  50 }
  51
  52 impl<'tcx> LowerInto<'tcx, chalk_ir::Substitution<RustInterner<'tcx>>> for SubstsRef<'tcx> {
  53     fn lower_into(
  54         self,
  55         interner: RustInterner<'tcx>,
  56     ) -> chalk_ir::Substitution<RustInterner<'tcx>> {
  57         chalk_ir::Substitution::from_iter(interner, self.iter().map(|s| s.lower_into(interner)))
  58     }
  59 }
  60
  61 impl<'tcx> LowerInto<'tcx, SubstsRef<'tcx>> for &chalk_ir::Substitution<RustInterner<'tcx>> {
  62     fn lower_into(self, interner: RustInterner<'tcx>) -> SubstsRef<'tcx> {
  63         interner.tcx.mk_substs(self.iter(interner).map(|subst| subst.lower_into(interner)))
  64     }
  65 }
  66
  67 impl<'tcx> LowerInto<'tcx, chalk_ir::AliasTy<RustInterner<'tcx>>> for ty::ProjectionTy<'tcx> {
  68     fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::AliasTy<RustInterner<'tcx>> {
  69         chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy {
  70             associated_ty_id: chalk_ir::AssocTypeId(self.item_def_id),
  71             substitution: self.substs.lower_into(interner),
  72         })
  73     }
  74 }
  75
  76 impl<'tcx> LowerInto<'tcx, chalk_ir::InEnvironment<chalk_ir::Goal<RustInterner<'tcx>>>>
  77     for ChalkEnvironmentAndGoal<'tcx>
  78 {
  79     fn lower_into(
  80         self,
  81         interner: RustInterner<'tcx>,
  82     ) -> chalk_ir::InEnvironment<chalk_ir::Goal<RustInterner<'tcx>>> {
  83         let clauses = self.environment.into_iter().map(|predicate| {
  84             let (predicate, binders, _named_regions) =
  85                 collect_bound_vars(interner, interner.tcx, predicate.kind());
  86             let consequence = match predicate {
  87                 ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
  88                     chalk_ir::DomainGoal::FromEnv(chalk_ir::FromEnv::Ty(ty.lower_into(interner)))
  89                 }
  90                 ty::PredicateKind::Trait(predicate) => chalk_ir::DomainGoal::FromEnv(
  91                     chalk_ir::FromEnv::Trait(predicate.trait_ref.lower_into(interner)),
  92                 ),
  93                 ty::PredicateKind::RegionOutlives(predicate) => chalk_ir::DomainGoal::Holds(
  94                     chalk_ir::WhereClause::LifetimeOutlives(chalk_ir::LifetimeOutlives {
  95                         a: predicate.0.lower_into(interner),
  96                         b: predicate.1.lower_into(interner),
  97                     }),
  98                 ),
  99                 ty::PredicateKind::TypeOutlives(predicate) => chalk_ir::DomainGoal::Holds(
 100                     chalk_ir::WhereClause::TypeOutlives(chalk_ir::TypeOutlives {
 101                         ty: predicate.0.lower_into(interner),
 102                         lifetime: predicate.1.lower_into(interner),
 103                     }),
 104                 ),
 105                 ty::PredicateKind::Projection(predicate) => chalk_ir::DomainGoal::Holds(
 106                     chalk_ir::WhereClause::AliasEq(predicate.lower_into(interner)),
 107                 ),
 108                 ty::PredicateKind::WellFormed(..)
 109                 | ty::PredicateKind::ObjectSafe(..)
 110                 | ty::PredicateKind::ClosureKind(..)
 111                 | ty::PredicateKind::Subtype(..)
 112                 | ty::PredicateKind::Coerce(..)
 113                 | ty::PredicateKind::ConstEvaluatable(..)
 114                 | ty::PredicateKind::ConstEquate(..) => bug!("unexpected predicate {}", predicate),
 115             };
 116             let value = chalk_ir::ProgramClauseImplication {
 117                 consequence,
 118                 conditions: chalk_ir::Goals::empty(interner),
 119                 priority: chalk_ir::ClausePriority::High,
 120                 constraints: chalk_ir::Constraints::empty(interner),
 121             };
 122             chalk_ir::ProgramClauseData(chalk_ir::Binders::new(binders, value)).intern(interner)
 123         });
 124
 125         let goal: chalk_ir::GoalData<RustInterner<'tcx>> = self.goal.lower_into(interner);
 126         chalk_ir::InEnvironment {
 127             environment: chalk_ir::Environment {
 128                 clauses: chalk_ir::ProgramClauses::from_iter(interner, clauses),
 129             },
 130             goal: goal.intern(interner),
 131         }
 132     }
 133 }
 134
 135 impl<'tcx> LowerInto<'tcx, chalk_ir::GoalData<RustInterner<'tcx>>> for ty::Predicate<'tcx> {
 136     fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::GoalData<RustInterner<'tcx>> {
 137         let (predicate, binders, _named_regions) =
 138             collect_bound_vars(interner, interner.tcx, self.kind());
 139
 140         let value = match predicate {
 141             ty::PredicateKind::Trait(predicate) => {
 142                 chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
 143                     chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner)),
 144                 ))
 145             }
 146             ty::PredicateKind::RegionOutlives(predicate) => {
 147                 chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
 148                     chalk_ir::WhereClause::LifetimeOutlives(chalk_ir::LifetimeOutlives {
 149                         a: predicate.0.lower_into(interner),
 150                         b: predicate.1.lower_into(interner),
 151                     }),
 152                 ))
 153             }
 154             ty::PredicateKind::TypeOutlives(predicate) => {
 155                 chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
 156                     chalk_ir::WhereClause::TypeOutlives(chalk_ir::TypeOutlives {
 157                         ty: predicate.0.lower_into(interner),
 158                         lifetime: predicate.1.lower_into(interner),
 159                     }),
 160                 ))
 161             }
 162             ty::PredicateKind::Projection(predicate) => {
 163                 chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::Holds(
 164                     chalk_ir::WhereClause::AliasEq(predicate.lower_into(interner)),
 165                 ))
 166             }
 167             ty::PredicateKind::WellFormed(arg) => match arg.unpack() {
 168                 GenericArgKind::Type(ty) => match ty.kind() {
 169                     // FIXME(chalk): In Chalk, a placeholder is WellFormed if it
 170                     // `FromEnv`. However, when we "lower" Params, we don't update
 171                     // the environment.
 172                     ty::Placeholder(..) => {
 173                         chalk_ir::GoalData::All(chalk_ir::Goals::empty(interner))
 174                     }
 175
 176                     _ => chalk_ir::GoalData::DomainGoal(chalk_ir::DomainGoal::WellFormed(
 177                         chalk_ir::WellFormed::Ty(ty.lower_into(interner)),
 178                     )),
 179                 },
 180                 // FIXME(chalk): handle well formed consts
 181                 GenericArgKind::Const(..) => {
 182                     chalk_ir::GoalData::All(chalk_ir::Goals::empty(interner))
 183                 }
 184                 GenericArgKind::Lifetime(lt) => bug!("unexpect well formed predicate: {:?}", lt),
 185             },
 186
 187             ty::PredicateKind::ObjectSafe(t) => chalk_ir::GoalData::DomainGoal(
 188                 chalk_ir::DomainGoal::ObjectSafe(chalk_ir::TraitId(t)),
 189             ),
 190
 191             // FIXME(chalk): other predicates
 192             //
 193             // We can defer this, but ultimately we'll want to express
 194             // some of these in terms of chalk operations.
 195             ty::PredicateKind::ClosureKind(..)
 196             | ty::PredicateKind::Subtype(..)
 197             | ty::PredicateKind::Coerce(..)
 198             | ty::PredicateKind::ConstEvaluatable(..)
 199             | ty::PredicateKind::ConstEquate(..) => {
 200                 chalk_ir::GoalData::All(chalk_ir::Goals::empty(interner))
 201             }
 202             ty::PredicateKind::TypeWellFormedFromEnv(ty) => chalk_ir::GoalData::DomainGoal(
 203                 chalk_ir::DomainGoal::FromEnv(chalk_ir::FromEnv::Ty(ty.lower_into(interner))),
 204             ),
 205         };
 206
 207         chalk_ir::GoalData::Quantified(
 208             chalk_ir::QuantifierKind::ForAll,
 209             chalk_ir::Binders::new(binders, value.intern(interner)),
 210         )
 211     }
 212 }
 213
 214 impl<'tcx> LowerInto<'tcx, chalk_ir::TraitRef<RustInterner<'tcx>>>
 215     for rustc_middle::ty::TraitRef<'tcx>
 216 {
 217     fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::TraitRef<RustInterner<'tcx>> {
 218         chalk_ir::TraitRef {
 219             trait_id: chalk_ir::TraitId(self.def_id),
 220             substitution: self.substs.lower_into(interner),
 221         }
 222     }
 223 }
 224
 225 impl<'tcx> LowerInto<'tcx, chalk_ir::AliasEq<RustInterner<'tcx>>>
 226     for rustc_middle::ty::ProjectionPredicate<'tcx>
 227 {
 228     fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::AliasEq<RustInterner<'tcx>> {
 229         chalk_ir::AliasEq {
 230             ty: self.ty.lower_into(interner),
 231             alias: self.projection_ty.lower_into(interner),
 232         }
 233     }
 234 }
 235
 236 impl<'tcx> LowerInto<'tcx, chalk_ir::Ty<RustInterner<'tcx>>> for Ty<'tcx> {
 237     fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Ty<RustInterner<'tcx>> {
 238         let int = |i| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Int(i));
 239         let uint = |i| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Uint(i));
 240         let float = |f| chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Float(f));
 241
 242         match *self.kind() {
 243             ty::Bool => chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Bool),
 244             ty::Char => chalk_ir::TyKind::Scalar(chalk_ir::Scalar::Char),
 245             ty::Int(ty) => match ty {
 246                 ty::IntTy::Isize => int(chalk_ir::IntTy::Isize),
 247                 ty::IntTy::I8 => int(chalk_ir::IntTy::I8),
 248                 ty::IntTy::I16 => int(chalk_ir::IntTy::I16),
 249                 ty::IntTy::I32 => int(chalk_ir::IntTy::I32),
 250                 ty::IntTy::I64 => int(chalk_ir::IntTy::I64),
 251                 ty::IntTy::I128 => int(chalk_ir::IntTy::I128),
 252             },
 253             ty::Uint(ty) => match ty {
 254                 ty::UintTy::Usize => uint(chalk_ir::UintTy::Usize),
 255                 ty::UintTy::U8 => uint(chalk_ir::UintTy::U8),
 256                 ty::UintTy::U16 => uint(chalk_ir::UintTy::U16),
 257                 ty::UintTy::U32 => uint(chalk_ir::UintTy::U32),
 258                 ty::UintTy::U64 => uint(chalk_ir::UintTy::U64),
 259                 ty::UintTy::U128 => uint(chalk_ir::UintTy::U128),
 260             },
 261             ty::Float(ty) => match ty {
 262                 ty::FloatTy::F32 => float(chalk_ir::FloatTy::F32),
 263                 ty::FloatTy::F64 => float(chalk_ir::FloatTy::F64),
 264             },
 265             ty::Adt(def, substs) => {
 266                 chalk_ir::TyKind::Adt(chalk_ir::AdtId(def), substs.lower_into(interner))
 267             }
 268             ty::Foreign(def_id) => chalk_ir::TyKind::Foreign(ForeignDefId(def_id)),
 269             ty::Str => chalk_ir::TyKind::Str,
 270             ty::Array(ty, len) => {
 271                 chalk_ir::TyKind::Array(ty.lower_into(interner), len.lower_into(interner))
 272             }
 273             ty::Slice(ty) => chalk_ir::TyKind::Slice(ty.lower_into(interner)),
 274
 275             ty::RawPtr(ptr) => {
 276                 chalk_ir::TyKind::Raw(ptr.mutbl.lower_into(interner), ptr.ty.lower_into(interner))
 277             }
 278             ty::Ref(region, ty, mutability) => chalk_ir::TyKind::Ref(
 279                 mutability.lower_into(interner),
 280                 region.lower_into(interner),
 281                 ty.lower_into(interner),
 282             ),
 283             ty::FnDef(def_id, substs) => {
 284                 chalk_ir::TyKind::FnDef(chalk_ir::FnDefId(def_id), substs.lower_into(interner))
 285             }
 286             ty::FnPtr(sig) => {
 287                 let (inputs_and_outputs, binders, _named_regions) =
 288                     collect_bound_vars(interner, interner.tcx, sig.inputs_and_output());
 289                 chalk_ir::TyKind::Function(chalk_ir::FnPointer {
 290                     num_binders: binders.len(interner),
 291                     sig: sig.lower_into(interner),
 292                     substitution: chalk_ir::FnSubst(chalk_ir::Substitution::from_iter(
 293                         interner,
 294                         inputs_and_outputs.iter().map(|ty| {
 295                             chalk_ir::GenericArgData::Ty(ty.lower_into(interner)).intern(interner)
 296                         }),
 297                     )),
 298                 })
 299             }
 300             ty::Dynamic(predicates, region) => chalk_ir::TyKind::Dyn(chalk_ir::DynTy {
 301                 bounds: predicates.lower_into(interner),
 302                 lifetime: region.lower_into(interner),
 303             }),
 304             ty::Closure(def_id, substs) => {
 305                 chalk_ir::TyKind::Closure(chalk_ir::ClosureId(def_id), substs.lower_into(interner))
 306             }
 307             ty::Generator(_def_id, _substs, _) => unimplemented!(),
 308             ty::GeneratorWitness(_) => unimplemented!(),
 309             ty::Never => chalk_ir::TyKind::Never,
 310             ty::Tuple(substs) => chalk_ir::TyKind::Tuple(substs.len(), substs.lower_into(interner)),
 311             ty::Projection(proj) => chalk_ir::TyKind::Alias(proj.lower_into(interner)),
 312             ty::Opaque(def_id, substs) => {
 313                 chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Opaque(chalk_ir::OpaqueTy {
 314                     opaque_ty_id: chalk_ir::OpaqueTyId(def_id),
 315                     substitution: substs.lower_into(interner),
 316                 }))
 317             }
 318             // This should have been done eagerly prior to this, and all Params
 319             // should have been substituted to placeholders
 320             ty::Param(_) => panic!("Lowering Param when not expected."),
 321             ty::Bound(db, bound) => chalk_ir::TyKind::BoundVar(chalk_ir::BoundVar::new(
 322                 chalk_ir::DebruijnIndex::new(db.as_u32()),
 323                 bound.var.index(),
 324             )),
 325             ty::Placeholder(_placeholder) => {
 326                 chalk_ir::TyKind::Placeholder(chalk_ir::PlaceholderIndex {
 327                     ui: chalk_ir::UniverseIndex { counter: _placeholder.universe.as_usize() },
 328                     idx: _placeholder.name.as_usize(),
 329                 })
 330             }
 331             ty::Infer(_infer) => unimplemented!(),
 332             ty::Error(_) => chalk_ir::TyKind::Error,
 333         }
 334         .intern(interner)
 335     }
 336 }
 337
 338 impl<'tcx> LowerInto<'tcx, Ty<'tcx>> for &chalk_ir::Ty<RustInterner<'tcx>> {
 339     fn lower_into(self, interner: RustInterner<'tcx>) -> Ty<'tcx> {
 340         use chalk_ir::TyKind;
 341
 342         let kind = match self.kind(interner) {
 343             TyKind::Adt(struct_id, substitution) => {
 344                 ty::Adt(struct_id.0, substitution.lower_into(interner))
 345             }
 346             TyKind::Scalar(scalar) => match scalar {
 347                 chalk_ir::Scalar::Bool => ty::Bool,
 348                 chalk_ir::Scalar::Char => ty::Char,
 349                 chalk_ir::Scalar::Int(int_ty) => match int_ty {
 350                     chalk_ir::IntTy::Isize => ty::Int(ty::IntTy::Isize),
 351                     chalk_ir::IntTy::I8 => ty::Int(ty::IntTy::I8),
 352                     chalk_ir::IntTy::I16 => ty::Int(ty::IntTy::I16),
 353                     chalk_ir::IntTy::I32 => ty::Int(ty::IntTy::I32),
 354                     chalk_ir::IntTy::I64 => ty::Int(ty::IntTy::I64),
 355                     chalk_ir::IntTy::I128 => ty::Int(ty::IntTy::I128),
 356                 },
 357                 chalk_ir::Scalar::Uint(int_ty) => match int_ty {
 358                     chalk_ir::UintTy::Usize => ty::Uint(ty::UintTy::Usize),
 359                     chalk_ir::UintTy::U8 => ty::Uint(ty::UintTy::U8),
 360                     chalk_ir::UintTy::U16 => ty::Uint(ty::UintTy::U16),
 361                     chalk_ir::UintTy::U32 => ty::Uint(ty::UintTy::U32),
 362                     chalk_ir::UintTy::U64 => ty::Uint(ty::UintTy::U64),
 363                     chalk_ir::UintTy::U128 => ty::Uint(ty::UintTy::U128),
 364                 },
 365                 chalk_ir::Scalar::Float(float_ty) => match float_ty {
 366                     chalk_ir::FloatTy::F32 => ty::Float(ty::FloatTy::F32),
 367                     chalk_ir::FloatTy::F64 => ty::Float(ty::FloatTy::F64),
 368                 },
 369             },
 370             TyKind::Array(ty, c) => {
 371                 let ty = ty.lower_into(interner);
 372                 let c = c.lower_into(interner);
 373                 ty::Array(ty, interner.tcx.mk_const(c))
 374             }
 375             TyKind::FnDef(id, substitution) => ty::FnDef(id.0, substitution.lower_into(interner)),
 376             TyKind::Closure(closure, substitution) => {
 377                 ty::Closure(closure.0, substitution.lower_into(interner))
 378             }
 379             TyKind::Generator(..) => unimplemented!(),
 380             TyKind::GeneratorWitness(..) => unimplemented!(),
 381             TyKind::Never => ty::Never,
 382             TyKind::Tuple(_len, substitution) => ty::Tuple(substitution.lower_into(interner)),
 383             TyKind::Slice(ty) => ty::Slice(ty.lower_into(interner)),
 384             TyKind::Raw(mutbl, ty) => ty::RawPtr(ty::TypeAndMut {
 385                 ty: ty.lower_into(interner),
 386                 mutbl: mutbl.lower_into(interner),
 387             }),
 388             TyKind::Ref(mutbl, lifetime, ty) => ty::Ref(
 389                 lifetime.lower_into(interner),
 390                 ty.lower_into(interner),
 391                 mutbl.lower_into(interner),
 392             ),
 393             TyKind::Str => ty::Str,
 394             TyKind::OpaqueType(opaque_ty, substitution) => {
 395                 ty::Opaque(opaque_ty.0, substitution.lower_into(interner))
 396             }
 397             TyKind::AssociatedType(assoc_ty, substitution) => ty::Projection(ty::ProjectionTy {
 398                 substs: substitution.lower_into(interner),
 399                 item_def_id: assoc_ty.0,
 400             }),
 401             TyKind::Foreign(def_id) => ty::Foreign(def_id.0),
 402             TyKind::Error => return interner.tcx.ty_error(),
 403             TyKind::Placeholder(placeholder) => ty::Placeholder(ty::Placeholder {
 404                 universe: ty::UniverseIndex::from_usize(placeholder.ui.counter),
 405                 name: ty::BoundVar::from_usize(placeholder.idx),
 406             }),
 407             TyKind::Alias(alias_ty) => match alias_ty {
 408                 chalk_ir::AliasTy::Projection(projection) => ty::Projection(ty::ProjectionTy {
 409                     item_def_id: projection.associated_ty_id.0,
 410                     substs: projection.substitution.lower_into(interner),
 411                 }),
 412                 chalk_ir::AliasTy::Opaque(opaque) => {
 413                     ty::Opaque(opaque.opaque_ty_id.0, opaque.substitution.lower_into(interner))
 414                 }
 415             },
 416             TyKind::Function(_quantified_ty) => unimplemented!(),
 417             TyKind::BoundVar(_bound) => ty::Bound(
 418                 ty::DebruijnIndex::from_usize(_bound.debruijn.depth() as usize),
 419                 ty::BoundTy {
 420                     var: ty::BoundVar::from_usize(_bound.index),
 421                     kind: ty::BoundTyKind::Anon,
 422                 },
 423             ),
 424             TyKind::InferenceVar(_, _) => unimplemented!(),
 425             TyKind::Dyn(_) => unimplemented!(),
 426         };
 427         interner.tcx.mk_ty(kind)
 428     }
 429 }
 430
 431 impl<'tcx> LowerInto<'tcx, chalk_ir::Lifetime<RustInterner<'tcx>>> for Region<'tcx> {
 432     fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Lifetime<RustInterner<'tcx>> {
 433         use rustc_middle::ty::RegionKind::*;
 434
 435         match self {
 436             ReEarlyBound(_) => {
 437                 panic!("Should have already been substituted.");
 438             }
 439             ReLateBound(db, br) => chalk_ir::LifetimeData::BoundVar(chalk_ir::BoundVar::new(
 440                 chalk_ir::DebruijnIndex::new(db.as_u32()),
 441                 br.var.as_usize(),
 442             ))
 443             .intern(interner),
 444             ReFree(_) => unimplemented!(),
 445             ReStatic => chalk_ir::LifetimeData::Static.intern(interner),
 446             ReVar(_) => unimplemented!(),
 447             RePlaceholder(placeholder_region) => {
 448                 chalk_ir::LifetimeData::Placeholder(chalk_ir::PlaceholderIndex {
 449                     ui: chalk_ir::UniverseIndex { counter: placeholder_region.universe.index() },
 450                     idx: 0,
 451                 })
 452                 .intern(interner)
 453             }
 454             ReEmpty(_) => unimplemented!(),
 455             // FIXME(chalk): need to handle ReErased
 456             ReErased => unimplemented!(),
 457         }
 458     }
 459 }
 460
 461 impl<'tcx> LowerInto<'tcx, Region<'tcx>> for &chalk_ir::Lifetime<RustInterner<'tcx>> {
 462     fn lower_into(self, interner: RustInterner<'tcx>) -> Region<'tcx> {
 463         let kind = match self.data(interner) {
 464             chalk_ir::LifetimeData::BoundVar(var) => ty::RegionKind::ReLateBound(
 465                 ty::DebruijnIndex::from_u32(var.debruijn.depth()),
 466                 ty::BoundRegion {
 467                     var: ty::BoundVar::from_usize(var.index),
 468                     kind: ty::BrAnon(var.index as u32),
 469                 },
 470             ),
 471             chalk_ir::LifetimeData::InferenceVar(_var) => unimplemented!(),
 472             chalk_ir::LifetimeData::Placeholder(p) => {
 473                 ty::RegionKind::RePlaceholder(ty::Placeholder {
 474                     universe: ty::UniverseIndex::from_usize(p.ui.counter),
 475                     name: ty::BoundRegionKind::BrAnon(p.idx as u32),
 476                 })
 477             }
 478             chalk_ir::LifetimeData::Static => ty::RegionKind::ReStatic,
 479             chalk_ir::LifetimeData::Phantom(_, _) => unimplemented!(),
 480             chalk_ir::LifetimeData::Empty(ui) => {
 481                 ty::RegionKind::ReEmpty(ty::UniverseIndex::from_usize(ui.counter))
 482             }
 483             chalk_ir::LifetimeData::Erased => ty::RegionKind::ReErased,
 484         };
 485         interner.tcx.mk_region(kind)
 486     }
 487 }
 488
 489 impl<'tcx> LowerInto<'tcx, chalk_ir::Const<RustInterner<'tcx>>> for ty::Const<'tcx> {
 490     fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::Const<RustInterner<'tcx>> {
 491         let ty = self.ty.lower_into(interner);
 492         let value = match self.val {
 493             ty::ConstKind::Value(val) => {
 494                 chalk_ir::ConstValue::Concrete(chalk_ir::ConcreteConst { interned: val })
 495             }
 496             ty::ConstKind::Bound(db, bound) => chalk_ir::ConstValue::BoundVar(
 497                 chalk_ir::BoundVar::new(chalk_ir::DebruijnIndex::new(db.as_u32()), bound.index()),
 498             ),
 499             _ => unimplemented!("Const not implemented. {:?}", self),
 500         };
 501         chalk_ir::ConstData { ty, value }.intern(interner)
 502     }
 503 }
 504
 505 impl<'tcx> LowerInto<'tcx, ty::Const<'tcx>> for &chalk_ir::Const<RustInterner<'tcx>> {
 506     fn lower_into(self, interner: RustInterner<'tcx>) -> ty::Const<'tcx> {
 507         let data = self.data(interner);
 508         let ty = data.ty.lower_into(interner);
 509         let val = match data.value {
 510             chalk_ir::ConstValue::BoundVar(var) => ty::ConstKind::Bound(
 511                 ty::DebruijnIndex::from_u32(var.debruijn.depth()),
 512                 ty::BoundVar::from_u32(var.index as u32),
 513             ),
 514             chalk_ir::ConstValue::InferenceVar(_var) => unimplemented!(),
 515             chalk_ir::ConstValue::Placeholder(_p) => unimplemented!(),
 516             chalk_ir::ConstValue::Concrete(c) => ty::ConstKind::Value(c.interned),
 517         };
 518         ty::Const { ty, val }
 519     }
 520 }
 521
 522 impl<'tcx> LowerInto<'tcx, chalk_ir::GenericArg<RustInterner<'tcx>>> for GenericArg<'tcx> {
 523     fn lower_into(self, interner: RustInterner<'tcx>) -> chalk_ir::GenericArg<RustInterner<'tcx>> {
 524         match self.unpack() {
 525             ty::subst::GenericArgKind::Type(ty) => {
 526                 chalk_ir::GenericArgData::Ty(ty.lower_into(interner))
 527             }
 528             ty::subst::GenericArgKind::Lifetime(lifetime) => {
 529                 chalk_ir::GenericArgData::Lifetime(lifetime.lower_into(interner))
 530             }
 531             ty::subst::GenericArgKind::Const(c) => {
 532                 chalk_ir::GenericArgData::Const(c.lower_into(interner))
 533             }
 534         }
 535         .intern(interner)
 536     }
 537 }
 538
 539 impl<'tcx> LowerInto<'tcx, ty::subst::GenericArg<'tcx>>
 540     for &chalk_ir::GenericArg<RustInterner<'tcx>>
 541 {
 542     fn lower_into(self, interner: RustInterner<'tcx>) -> ty::subst::GenericArg<'tcx> {
 543         match self.data(interner) {
 544             chalk_ir::GenericArgData::Ty(ty) => {
 545                 let t: Ty<'tcx> = ty.lower_into(interner);
 546                 t.into()
 547             }
 548             chalk_ir::GenericArgData::Lifetime(lifetime) => {
 549                 let r: Region<'tcx> = lifetime.lower_into(interner);
 550                 r.into()
 551             }
 552             chalk_ir::GenericArgData::Const(c) => {
 553                 let c: ty::Const<'tcx> = c.lower_into(interner);
 554                 interner.tcx.mk_const(c).into()
 555             }
 556         }
 557     }
 558 }
 559
 560 // We lower into an Option here since there are some predicates which Chalk
 561 // doesn't have a representation for yet (as a `WhereClause`), but are so common
 562 // that we just are accepting the unsoundness for now. The `Option` will
 563 // eventually be removed.
 564 impl<'tcx> LowerInto<'tcx, Option<chalk_ir::QuantifiedWhereClause<RustInterner<'tcx>>>>
 565     for ty::Predicate<'tcx>
 566 {
 567     fn lower_into(
 568         self,
 569         interner: RustInterner<'tcx>,
 570     ) -> Option<chalk_ir::QuantifiedWhereClause<RustInterner<'tcx>>> {
 571         let (predicate, binders, _named_regions) =
 572             collect_bound_vars(interner, interner.tcx, self.kind());
 573         let value = match predicate {
 574             ty::PredicateKind::Trait(predicate) => {
 575                 Some(chalk_ir::WhereClause::Implemented(predicate.trait_ref.lower_into(interner)))
 576             }
 577             ty::PredicateKind::RegionOutlives(predicate) => {
 578                 Some(chalk_ir::WhereClause::LifetimeOutlives(chalk_ir::LifetimeOutlives {
 579                     a: predicate.0.lower_into(interner),
 580                     b: predicate.1.lower_into(interner),
 581                 }))
 582             }
 583             ty::PredicateKind::TypeOutlives(predicate) => {
 584                 Some(chalk_ir::WhereClause::TypeOutlives(chalk_ir::TypeOutlives {
 585                     ty: predicate.0.lower_into(interner),
 586                     lifetime: predicate.1.lower_into(interner),
 587                 }))
 588             }
 589             ty::PredicateKind::Projection(predicate) => {
 590                 Some(chalk_ir::WhereClause::AliasEq(predicate.lower_into(interner)))
 591             }
 592             ty::PredicateKind::WellFormed(_ty) => None,
 593
 594             ty::PredicateKind::ObjectSafe(..)
 595             | ty::PredicateKind::ClosureKind(..)
 596             | ty::PredicateKind::Subtype(..)
 597             | ty::PredicateKind::Coerce(..)
 598             | ty::PredicateKind::ConstEvaluatable(..)
 599             | ty::PredicateKind::ConstEquate(..)
 600             | ty::PredicateKind::TypeWellFormedFromEnv(..) => {
 601                 bug!("unexpected predicate {}", &self)
 602             }
 603         };
 604         value.map(|value| chalk_ir::Binders::new(binders, value))
 605     }
 606 }
 607
 608 impl<'tcx> LowerInto<'tcx, chalk_ir::Binders<chalk_ir::QuantifiedWhereClauses<RustInterner<'tcx>>>>
 609     for &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>
 610 {
 611     fn lower_into(
 612         self,
 613         interner: RustInterner<'tcx>,
 614     ) -> chalk_ir::Binders<chalk_ir::QuantifiedWhereClauses<RustInterner<'tcx>>> {
 615         // `Self` has one binder:
 616         // Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>
 617         // The return type has two:
 618         // Binders<&[Binders<WhereClause<I>>]>
 619         // This means that any variables that are escaping `self` need to be
 620         // shifted in by one so that they are still escaping.
 621         let predicates = ty::fold::shift_vars(interner.tcx, self, 1);
 622
 623         let self_ty = interner.tcx.mk_ty(ty::Bound(
 624             // This is going to be wrapped in a binder
 625             ty::DebruijnIndex::from_usize(1),
 626             ty::BoundTy { var: ty::BoundVar::from_usize(0), kind: ty::BoundTyKind::Anon },
 627         ));
 628         let where_clauses = predicates.into_iter().map(|predicate| {
 629             let (predicate, binders, _named_regions) =
 630                 collect_bound_vars(interner, interner.tcx, predicate);
 631             match predicate {
 632                 ty::ExistentialPredicate::Trait(ty::ExistentialTraitRef { def_id, substs }) => {
 633                     chalk_ir::Binders::new(
 634                         binders.clone(),
 635                         chalk_ir::WhereClause::Implemented(chalk_ir::TraitRef {
 636                             trait_id: chalk_ir::TraitId(def_id),
 637                             substitution: interner
 638                                 .tcx
 639                                 .mk_substs_trait(self_ty, substs)
 640                                 .lower_into(interner),
 641                         }),
 642                     )
 643                 }
 644                 ty::ExistentialPredicate::Projection(predicate) => chalk_ir::Binders::new(
 645                     binders.clone(),
 646                     chalk_ir::WhereClause::AliasEq(chalk_ir::AliasEq {
 647                         alias: chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy {
 648                             associated_ty_id: chalk_ir::AssocTypeId(predicate.item_def_id),
 649                             substitution: interner
 650                                 .tcx
 651                                 .mk_substs_trait(self_ty, predicate.substs)
 652                                 .lower_into(interner),
 653                         }),
 654                         ty: predicate.ty.lower_into(interner),
 655                     }),
 656                 ),
 657                 ty::ExistentialPredicate::AutoTrait(def_id) => chalk_ir::Binders::new(
 658                     binders.clone(),
 659                     chalk_ir::WhereClause::Implemented(chalk_ir::TraitRef {
 660                         trait_id: chalk_ir::TraitId(def_id),
 661                         substitution: interner
 662                             .tcx
 663                             .mk_substs_trait(self_ty, &[])
 664                             .lower_into(interner),
 665                     }),
 666                 ),
 667             }
 668         });
 669
 670         // Binder for the bound variable representing the concrete underlying type.
 671         let existential_binder = chalk_ir::VariableKinds::from1(
 672             interner,
 673             chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
 674         );
 675         let value = chalk_ir::QuantifiedWhereClauses::from_iter(interner, where_clauses);
 676         chalk_ir::Binders::new(existential_binder, value)
 677     }
 678 }
 679
 680 impl<'tcx> LowerInto<'tcx, chalk_ir::FnSig<RustInterner<'tcx>>>
 681     for ty::Binder<'tcx, ty::FnSig<'tcx>>
 682 {
 683     fn lower_into(self, _interner: RustInterner<'_>) -> FnSig<RustInterner<'tcx>> {
 684         chalk_ir::FnSig {
 685             abi: self.abi(),
 686             safety: match self.unsafety() {
 687                 Unsafety::Normal => chalk_ir::Safety::Safe,
 688                 Unsafety::Unsafe => chalk_ir::Safety::Unsafe,
 689             },
 690             variadic: self.c_variadic(),
 691         }
 692     }
 693 }
 694
 695 // We lower into an Option here since there are some predicates which Chalk
 696 // doesn't have a representation for yet (as an `InlineBound`). The `Option` will
 697 // eventually be removed.
 698 impl<'tcx> LowerInto<'tcx, Option<chalk_solve::rust_ir::QuantifiedInlineBound<RustInterner<'tcx>>>>
 699     for ty::Predicate<'tcx>
 700 {
 701     fn lower_into(
 702         self,
 703         interner: RustInterner<'tcx>,
 704     ) -> Option<chalk_solve::rust_ir::QuantifiedInlineBound<RustInterner<'tcx>>> {
 705         let (predicate, binders, _named_regions) =
 706             collect_bound_vars(interner, interner.tcx, self.kind());
 707         match predicate {
 708             ty::PredicateKind::Trait(predicate) => Some(chalk_ir::Binders::new(
 709                 binders,
 710                 chalk_solve::rust_ir::InlineBound::TraitBound(
 711                     predicate.trait_ref.lower_into(interner),
 712                 ),
 713             )),
 714             ty::PredicateKind::Projection(predicate) => Some(chalk_ir::Binders::new(
 715                 binders,
 716                 chalk_solve::rust_ir::InlineBound::AliasEqBound(predicate.lower_into(interner)),
 717             )),
 718             ty::PredicateKind::TypeOutlives(_predicate) => None,
 719             ty::PredicateKind::WellFormed(_ty) => None,
 720
 721             ty::PredicateKind::RegionOutlives(..)
 722             | ty::PredicateKind::ObjectSafe(..)
 723             | ty::PredicateKind::ClosureKind(..)
 724             | ty::PredicateKind::Subtype(..)
 725             | ty::PredicateKind::Coerce(..)
 726             | ty::PredicateKind::ConstEvaluatable(..)
 727             | ty::PredicateKind::ConstEquate(..)
 728             | ty::PredicateKind::TypeWellFormedFromEnv(..) => {
 729                 bug!("unexpected predicate {}", &self)
 730             }
 731         }
 732     }
 733 }
 734
 735 impl<'tcx> LowerInto<'tcx, chalk_solve::rust_ir::TraitBound<RustInterner<'tcx>>>
 736     for ty::TraitRef<'tcx>
 737 {
 738     fn lower_into(
 739         self,
 740         interner: RustInterner<'tcx>,
 741     ) -> chalk_solve::rust_ir::TraitBound<RustInterner<'tcx>> {
 742         chalk_solve::rust_ir::TraitBound {
 743             trait_id: chalk_ir::TraitId(self.def_id),
 744             args_no_self: self.substs[1..].iter().map(|arg| arg.lower_into(interner)).collect(),
 745         }
 746     }
 747 }
 748
 749 impl<'tcx> LowerInto<'tcx, chalk_ir::Mutability> for ast::Mutability {
 750     fn lower_into(self, _interner: RustInterner<'tcx>) -> chalk_ir::Mutability {
 751         match self {
 752             rustc_ast::Mutability::Mut => chalk_ir::Mutability::Mut,
 753             rustc_ast::Mutability::Not => chalk_ir::Mutability::Not,
 754         }
 755     }
 756 }
 757
 758 impl<'tcx> LowerInto<'tcx, ast::Mutability> for chalk_ir::Mutability {
 759     fn lower_into(self, _interner: RustInterner<'tcx>) -> ast::Mutability {
 760         match self {
 761             chalk_ir::Mutability::Mut => ast::Mutability::Mut,
 762             chalk_ir::Mutability::Not => ast::Mutability::Not,
 763         }
 764     }
 765 }
 766
 767 impl<'tcx> LowerInto<'tcx, chalk_solve::rust_ir::Polarity> for ty::ImplPolarity {
 768     fn lower_into(self, _interner: RustInterner<'tcx>) -> chalk_solve::rust_ir::Polarity {
 769         match self {
 770             ty::ImplPolarity::Positive => chalk_solve::rust_ir::Polarity::Positive,
 771             ty::ImplPolarity::Negative => chalk_solve::rust_ir::Polarity::Negative,
 772             // FIXME(chalk) reservation impls
 773             ty::ImplPolarity::Reservation => chalk_solve::rust_ir::Polarity::Negative,
 774         }
 775     }
 776 }
 777
 778 impl<'tcx> LowerInto<'tcx, chalk_solve::rust_ir::AliasEqBound<RustInterner<'tcx>>>
 779     for ty::ProjectionPredicate<'tcx>
 780 {
 781     fn lower_into(
 782         self,
 783         interner: RustInterner<'tcx>,
 784     ) -> chalk_solve::rust_ir::AliasEqBound<RustInterner<'tcx>> {
 785         let (trait_ref, own_substs) = self.projection_ty.trait_ref_and_own_substs(interner.tcx);
 786         chalk_solve::rust_ir::AliasEqBound {
 787             trait_bound: trait_ref.lower_into(interner),
 788             associated_ty_id: chalk_ir::AssocTypeId(self.projection_ty.item_def_id),
 789             parameters: own_substs.iter().map(|arg| arg.lower_into(interner)).collect(),
 790             value: self.ty.lower_into(interner),
 791         }
 792     }
 793 }
 794
 795 /// To collect bound vars, we have to do two passes. In the first pass, we
 796 /// collect all `BoundRegionKind`s and `ty::Bound`s. In the second pass, we then
 797 /// replace `BrNamed` into `BrAnon`. The two separate passes are important,
 798 /// since we can only replace `BrNamed` with `BrAnon`s with indices *after* all
 799 /// "real" `BrAnon`s.
 800 ///
 801 /// It's important to note that because of prior substitution, we may have
 802 /// late-bound regions, even outside of fn contexts, since this is the best way
 803 /// to prep types for chalk lowering.
 804 crate fn collect_bound_vars<'tcx, T: TypeFoldable<'tcx>>(
 805     interner: RustInterner<'tcx>,
 806     tcx: TyCtxt<'tcx>,
 807     ty: Binder<'tcx, T>,
 808 ) -> (T, chalk_ir::VariableKinds<RustInterner<'tcx>>, BTreeMap<DefId, u32>) {
 809     let mut bound_vars_collector = BoundVarsCollector::new(tcx);
 810     ty.as_ref().skip_binder().visit_with(&mut bound_vars_collector);
 811     let mut parameters = bound_vars_collector.parameters;
 812     let named_parameters: BTreeMap<DefId, u32> = bound_vars_collector
 813         .named_parameters
 814         .into_iter()
 815         .enumerate()
 816         .map(|(i, def_id)| (def_id, (i + parameters.len()) as u32))
 817         .collect();
 818
 819     let mut bound_var_substitutor = NamedBoundVarSubstitutor::new(tcx, &named_parameters);
 820     let new_ty = ty.skip_binder().fold_with(&mut bound_var_substitutor);
 821
 822     for var in named_parameters.values() {
 823         parameters.insert(*var, chalk_ir::VariableKind::Lifetime);
 824     }
 825
 826     (0..parameters.len()).for_each(|i| {
 827         parameters
 828             .get(&(i as u32))
 829             .or_else(|| bug!("Skipped bound var index: parameters={:?}", parameters));
 830     });
 831
 832     let binders =
 833         chalk_ir::VariableKinds::from_iter(interner, parameters.into_iter().map(|(_, v)| v));
 834
 835     (new_ty, binders, named_parameters)
 836 }
 837
 838 crate struct BoundVarsCollector<'tcx> {
 839     tcx: TyCtxt<'tcx>,
 840     binder_index: ty::DebruijnIndex,
 841     crate parameters: BTreeMap<u32, chalk_ir::VariableKind<RustInterner<'tcx>>>,
 842     crate named_parameters: Vec<DefId>,
 843 }
 844
 845 impl<'tcx> BoundVarsCollector<'tcx> {
 846     crate fn new(tcx: TyCtxt<'tcx>) -> Self {
 847         BoundVarsCollector {
 848             tcx,
 849             binder_index: ty::INNERMOST,
 850             parameters: BTreeMap::new(),
 851             named_parameters: vec![],
 852         }
 853     }
 854 }
 855
 856 impl<'tcx> TypeVisitor<'tcx> for BoundVarsCollector<'tcx> {
 857     fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
 858         Some(self.tcx)
 859     }
 860
 861     fn visit_binder<T: TypeFoldable<'tcx>>(
 862         &mut self,
 863         t: &Binder<'tcx, T>,
 864     ) -> ControlFlow<Self::BreakTy> {
 865         self.binder_index.shift_in(1);
 866         let result = t.super_visit_with(self);
 867         self.binder_index.shift_out(1);
 868         result
 869     }
 870
 871     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
 872         match *t.kind() {
 873             ty::Bound(debruijn, bound_ty) if debruijn == self.binder_index => {
 874                 match self.parameters.entry(bound_ty.var.as_u32()) {
 875                     Entry::Vacant(entry) => {
 876                         entry.insert(chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General));
 877                     }
 878                     Entry::Occupied(entry) => match entry.get() {
 879                         chalk_ir::VariableKind::Ty(_) => {}
 880                         _ => panic!(),
 881                     },
 882                 }
 883             }
 884
 885             _ => (),
 886         };
 887
 888         t.super_visit_with(self)
 889     }
 890
 891     fn visit_region(&mut self, r: Region<'tcx>) -> ControlFlow<Self::BreakTy> {
 892         match r {
 893             ty::ReLateBound(index, br) if *index == self.binder_index => match br.kind {
 894                 ty::BoundRegionKind::BrNamed(def_id, _name) => {
 895                     if !self.named_parameters.iter().any(|d| *d == def_id) {
 896                         self.named_parameters.push(def_id);
 897                     }
 898                 }
 899
 900                 ty::BoundRegionKind::BrAnon(var) => match self.parameters.entry(var) {
 901                     Entry::Vacant(entry) => {
 902                         entry.insert(chalk_ir::VariableKind::Lifetime);
 903                     }
 904                     Entry::Occupied(entry) => match entry.get() {
 905                         chalk_ir::VariableKind::Lifetime => {}
 906                         _ => panic!(),
 907                     },
 908                 },
 909
 910                 ty::BoundRegionKind::BrEnv => unimplemented!(),
 911             },
 912
 913             ty::ReEarlyBound(_re) => {
 914                 // FIXME(chalk): jackh726 - I think we should always have already
 915                 // substituted away `ReEarlyBound`s for `ReLateBound`s, but need to confirm.
 916                 unimplemented!();
 917             }
 918
 919             _ => (),
 920         };
 921
 922         r.super_visit_with(self)
 923     }
 924 }
 925
 926 /// This is used to replace `BoundRegionKind::BrNamed` with `BoundRegionKind::BrAnon`.
 927 /// Note: we assume that we will always have room for more bound vars. (i.e. we
 928 /// won't ever hit the `u32` limit in `BrAnon`s).
 929 struct NamedBoundVarSubstitutor<'a, 'tcx> {
 930     tcx: TyCtxt<'tcx>,
 931     binder_index: ty::DebruijnIndex,
 932     named_parameters: &'a BTreeMap<DefId, u32>,
 933 }
 934
 935 impl<'a, 'tcx> NamedBoundVarSubstitutor<'a, 'tcx> {
 936     fn new(tcx: TyCtxt<'tcx>, named_parameters: &'a BTreeMap<DefId, u32>) -> Self {
 937         NamedBoundVarSubstitutor { tcx, binder_index: ty::INNERMOST, named_parameters }
 938     }
 939 }
 940
 941 impl<'a, 'tcx> TypeFolder<'tcx> for NamedBoundVarSubstitutor<'a, 'tcx> {
 942     fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
 943         self.tcx
 944     }
 945
 946     fn fold_binder<T: TypeFoldable<'tcx>>(&mut self, t: Binder<'tcx, T>) -> Binder<'tcx, T> {
 947         self.binder_index.shift_in(1);
 948         let result = t.super_fold_with(self);
 949         self.binder_index.shift_out(1);
 950         result
 951     }
 952
 953     fn fold_region(&mut self, r: Region<'tcx>) -> Region<'tcx> {
 954         match r {
 955             ty::ReLateBound(index, br) if *index == self.binder_index => match br.kind {
 956                 ty::BrNamed(def_id, _name) => match self.named_parameters.get(&def_id) {
 957                     Some(idx) => {
 958                         let new_br = ty::BoundRegion { var: br.var, kind: ty::BrAnon(*idx) };
 959                         return self.tcx.mk_region(RegionKind::ReLateBound(*index, new_br));
 960                     }
 961                     None => panic!("Missing `BrNamed`."),
 962                 },
 963                 ty::BrEnv => unimplemented!(),
 964                 ty::BrAnon(_) => {}
 965             },
 966             _ => (),
 967         };
 968
 969         r.super_fold_with(self)
 970     }
 971 }
 972
 973 /// Used to substitute `Param`s with placeholders. We do this since Chalk
 974 /// have a notion of `Param`s.
 975 crate struct ParamsSubstitutor<'tcx> {
 976     tcx: TyCtxt<'tcx>,
 977     binder_index: ty::DebruijnIndex,
 978     list: Vec<rustc_middle::ty::ParamTy>,
 979     next_ty_placeholder: usize,
 980     crate params: rustc_data_structures::fx::FxHashMap<usize, rustc_middle::ty::ParamTy>,
 981     crate named_regions: BTreeMap<DefId, u32>,
 982 }
 983
 984 impl<'tcx> ParamsSubstitutor<'tcx> {
 985     crate fn new(tcx: TyCtxt<'tcx>, next_ty_placeholder: usize) -> Self {
 986         ParamsSubstitutor {
 987             tcx,
 988             binder_index: ty::INNERMOST,
 989             list: vec![],
 990             next_ty_placeholder,
 991             params: rustc_data_structures::fx::FxHashMap::default(),
 992             named_regions: BTreeMap::default(),
 993         }
 994     }
 995 }
 996
 997 impl<'tcx> TypeFolder<'tcx> for ParamsSubstitutor<'tcx> {
 998     fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
 999         self.tcx
1000     }
1001
1002     fn fold_binder<T: TypeFoldable<'tcx>>(&mut self, t: Binder<'tcx, T>) -> Binder<'tcx, T> {
1003         self.binder_index.shift_in(1);
1004         let result = t.super_fold_with(self);
1005         self.binder_index.shift_out(1);
1006         result
1007     }
1008
1009     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
1010         match *t.kind() {
1011             // FIXME(chalk): currently we convert params to placeholders starting at
1012             // index `0`. To support placeholders, we'll actually need to do a
1013             // first pass to collect placeholders. Then we can insert params after.
1014             ty::Placeholder(_) => unimplemented!(),
1015             ty::Param(param) => match self.list.iter().position(|r| r == &param) {
1016                 Some(idx) => self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
1017                     universe: ty::UniverseIndex::from_usize(0),
1018                     name: ty::BoundVar::from_usize(idx),
1019                 })),
1020                 None => {
1021                     self.list.push(param);
1022                     let idx = self.list.len() - 1 + self.next_ty_placeholder;
1023                     self.params.insert(idx, param);
1024                     self.tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
1025                         universe: ty::UniverseIndex::from_usize(0),
1026                         name: ty::BoundVar::from_usize(idx),
1027                     }))
1028                 }
1029             },
1030
1031             _ => t.super_fold_with(self),
1032         }
1033     }
1034
1035     fn fold_region(&mut self, r: Region<'tcx>) -> Region<'tcx> {
1036         match r {
1037             // FIXME(chalk) - jackh726 - this currently isn't hit in any tests.
1038             // This covers any region variables in a goal, right?
1039             ty::ReEarlyBound(_re) => match self.named_regions.get(&_re.def_id) {
1040                 Some(idx) => {
1041                     let br = ty::BoundRegion {
1042                         var: ty::BoundVar::from_u32(*idx),
1043                         kind: ty::BrAnon(*idx),
1044                     };
1045                     self.tcx.mk_region(RegionKind::ReLateBound(self.binder_index, br))
1046                 }
1047                 None => {
1048                     let idx = self.named_regions.len() as u32;
1049                     let br =
1050                         ty::BoundRegion { var: ty::BoundVar::from_u32(idx), kind: ty::BrAnon(idx) };
1051                     self.named_regions.insert(_re.def_id, idx);
1052                     self.tcx.mk_region(RegionKind::ReLateBound(self.binder_index, br))
1053                 }
1054             },
1055
1056             _ => r.super_fold_with(self),
1057         }
1058     }
1059 }
1060
1061 /// Used to collect `Placeholder`s.
1062 crate struct PlaceholdersCollector {
1063     universe_index: ty::UniverseIndex,
1064     crate next_ty_placeholder: usize,
1065     crate next_anon_region_placeholder: u32,
1066 }
1067
1068 impl PlaceholdersCollector {
1069     crate fn new() -> Self {
1070         PlaceholdersCollector {
1071             universe_index: ty::UniverseIndex::ROOT,
1072             next_ty_placeholder: 0,
1073             next_anon_region_placeholder: 0,
1074         }
1075     }
1076 }
1077
1078 impl<'tcx> TypeVisitor<'tcx> for PlaceholdersCollector {
1079     fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
1080         // Anon const substs do not contain placeholders by default.
1081         None
1082     }
1083
1084     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1085         match t.kind() {
1086             ty::Placeholder(p) if p.universe == self.universe_index => {
1087                 self.next_ty_placeholder = self.next_ty_placeholder.max(p.name.as_usize() + 1);
1088             }
1089
1090             _ => (),
1091         };
1092
1093         t.super_visit_with(self)
1094     }
1095
1096     fn visit_region(&mut self, r: Region<'tcx>) -> ControlFlow<Self::BreakTy> {
1097         match r {
1098             ty::RePlaceholder(p) if p.universe == self.universe_index => {
1099                 if let ty::BoundRegionKind::BrAnon(anon) = p.name {
1100                     self.next_anon_region_placeholder = self.next_anon_region_placeholder.max(anon);
1101                 }
1102             }
1103
1104             _ => (),
1105         };
1106
1107         r.super_visit_with(self)
1108     }
1109 }
1110
1111 /// Used to substitute specific `Regions`s with placeholders.
1112 crate struct RegionsSubstitutor<'tcx> {
1113     tcx: TyCtxt<'tcx>,
1114     reempty_placeholder: ty::Region<'tcx>,
1115 }
1116
1117 impl<'tcx> RegionsSubstitutor<'tcx> {
1118     crate fn new(tcx: TyCtxt<'tcx>, reempty_placeholder: ty::Region<'tcx>) -> Self {
1119         RegionsSubstitutor { tcx, reempty_placeholder }
1120     }
1121 }
1122
1123 impl<'tcx> TypeFolder<'tcx> for RegionsSubstitutor<'tcx> {
1124     fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
1125         self.tcx
1126     }
1127
1128     fn fold_region(&mut self, r: Region<'tcx>) -> Region<'tcx> {
1129         match r {
1130             ty::ReEmpty(ui) => {
1131                 assert_eq!(ui.as_usize(), 0);
1132                 self.reempty_placeholder
1133             }
1134
1135             _ => r.super_fold_with(self),
1136         }
1137     }
1138 }