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