compiler/rustc_middle/src/ty/structural_impls.rs

   1 //! This module contains implements of the `Lift` and `TypeFoldable`
   2 //! traits for various types in the Rust compiler. Most are written by
   3 //! hand, though we've recently added some macros and proc-macros to help with the tedium.
   4
   5 use crate::mir::interpret;
   6 use crate::mir::ProjectionKind;
   7 use crate::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
   8 use crate::ty::print::{with_no_trimmed_paths, FmtPrinter, Printer};
   9 use crate::ty::{self, InferConst, Lift, Ty, TyCtxt};
  10 use rustc_data_structures::functor::IdFunctor;
  11 use rustc_hir as hir;
  12 use rustc_hir::def::Namespace;
  13 use rustc_hir::def_id::CRATE_DEF_INDEX;
  14 use rustc_index::vec::{Idx, IndexVec};
  15
  16 use std::fmt;
  17 use std::ops::ControlFlow;
  18 use std::rc::Rc;
  19 use std::sync::Arc;
  20
  21 impl fmt::Debug for ty::TraitDef {
  22     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  23         ty::tls::with(|tcx| {
  24             with_no_trimmed_paths(|| {
  25                 FmtPrinter::new(tcx, f, Namespace::TypeNS).print_def_path(self.def_id, &[])
  26             })?;
  27             Ok(())
  28         })
  29     }
  30 }
  31
  32 impl fmt::Debug for ty::AdtDef {
  33     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  34         ty::tls::with(|tcx| {
  35             with_no_trimmed_paths(|| {
  36                 FmtPrinter::new(tcx, f, Namespace::TypeNS).print_def_path(self.did, &[])
  37             })?;
  38             Ok(())
  39         })
  40     }
  41 }
  42
  43 impl fmt::Debug for ty::UpvarId {
  44     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  45         let name = ty::tls::with(|tcx| tcx.hir().name(self.var_path.hir_id));
  46         write!(f, "UpvarId({:?};`{}`;{:?})", self.var_path.hir_id, name, self.closure_expr_id)
  47     }
  48 }
  49
  50 impl fmt::Debug for ty::UpvarBorrow<'tcx> {
  51     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  52         write!(f, "UpvarBorrow({:?}, {:?})", self.kind, self.region)
  53     }
  54 }
  55
  56 impl fmt::Debug for ty::ExistentialTraitRef<'tcx> {
  57     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  58         with_no_trimmed_paths(|| fmt::Display::fmt(self, f))
  59     }
  60 }
  61
  62 impl fmt::Debug for ty::adjustment::Adjustment<'tcx> {
  63     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  64         write!(f, "{:?} -> {}", self.kind, self.target)
  65     }
  66 }
  67
  68 impl fmt::Debug for ty::BoundRegionKind {
  69     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  70         match *self {
  71             ty::BrAnon(n) => write!(f, "BrAnon({:?})", n),
  72             ty::BrNamed(did, name) => {
  73                 if did.index == CRATE_DEF_INDEX {
  74                     write!(f, "BrNamed({})", name)
  75                 } else {
  76                     write!(f, "BrNamed({:?}, {})", did, name)
  77                 }
  78             }
  79             ty::BrEnv => write!(f, "BrEnv"),
  80         }
  81     }
  82 }
  83
  84 impl fmt::Debug for ty::RegionKind {
  85     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  86         match *self {
  87             ty::ReEarlyBound(ref data) => write!(f, "ReEarlyBound({}, {})", data.index, data.name),
  88
  89             ty::ReLateBound(binder_id, ref bound_region) => {
  90                 write!(f, "ReLateBound({:?}, {:?})", binder_id, bound_region)
  91             }
  92
  93             ty::ReFree(ref fr) => fr.fmt(f),
  94
  95             ty::ReStatic => write!(f, "ReStatic"),
  96
  97             ty::ReVar(ref vid) => vid.fmt(f),
  98
  99             ty::RePlaceholder(placeholder) => write!(f, "RePlaceholder({:?})", placeholder),
 100
 101             ty::ReEmpty(ui) => write!(f, "ReEmpty({:?})", ui),
 102
 103             ty::ReErased => write!(f, "ReErased"),
 104         }
 105     }
 106 }
 107
 108 impl fmt::Debug for ty::FreeRegion {
 109     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 110         write!(f, "ReFree({:?}, {:?})", self.scope, self.bound_region)
 111     }
 112 }
 113
 114 impl fmt::Debug for ty::FnSig<'tcx> {
 115     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 116         write!(f, "({:?}; c_variadic: {})->{:?}", self.inputs(), self.c_variadic, self.output())
 117     }
 118 }
 119
 120 impl<'tcx> fmt::Debug for ty::ConstVid<'tcx> {
 121     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 122         write!(f, "_#{}c", self.index)
 123     }
 124 }
 125
 126 impl fmt::Debug for ty::RegionVid {
 127     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 128         write!(f, "'_#{}r", self.index())
 129     }
 130 }
 131
 132 impl fmt::Debug for ty::TraitRef<'tcx> {
 133     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 134         with_no_trimmed_paths(|| fmt::Display::fmt(self, f))
 135     }
 136 }
 137
 138 impl fmt::Debug for Ty<'tcx> {
 139     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 140         with_no_trimmed_paths(|| fmt::Display::fmt(self, f))
 141     }
 142 }
 143
 144 impl fmt::Debug for ty::ParamTy {
 145     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 146         write!(f, "{}/#{}", self.name, self.index)
 147     }
 148 }
 149
 150 impl fmt::Debug for ty::ParamConst {
 151     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 152         write!(f, "{}/#{}", self.name, self.index)
 153     }
 154 }
 155
 156 impl fmt::Debug for ty::TraitPredicate<'tcx> {
 157     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 158         write!(f, "TraitPredicate({:?})", self.trait_ref)
 159     }
 160 }
 161
 162 impl fmt::Debug for ty::ProjectionPredicate<'tcx> {
 163     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 164         write!(f, "ProjectionPredicate({:?}, {:?})", self.projection_ty, self.ty)
 165     }
 166 }
 167
 168 impl fmt::Debug for ty::Predicate<'tcx> {
 169     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 170         write!(f, "{:?}", self.kind())
 171     }
 172 }
 173
 174 impl fmt::Debug for ty::PredicateKind<'tcx> {
 175     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 176         match *self {
 177             ty::PredicateKind::Trait(ref a, constness) => {
 178                 if let hir::Constness::Const = constness {
 179                     write!(f, "const ")?;
 180                 }
 181                 a.fmt(f)
 182             }
 183             ty::PredicateKind::Subtype(ref pair) => pair.fmt(f),
 184             ty::PredicateKind::RegionOutlives(ref pair) => pair.fmt(f),
 185             ty::PredicateKind::TypeOutlives(ref pair) => pair.fmt(f),
 186             ty::PredicateKind::Projection(ref pair) => pair.fmt(f),
 187             ty::PredicateKind::WellFormed(data) => write!(f, "WellFormed({:?})", data),
 188             ty::PredicateKind::ObjectSafe(trait_def_id) => {
 189                 write!(f, "ObjectSafe({:?})", trait_def_id)
 190             }
 191             ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
 192                 write!(f, "ClosureKind({:?}, {:?}, {:?})", closure_def_id, closure_substs, kind)
 193             }
 194             ty::PredicateKind::ConstEvaluatable(def_id, substs) => {
 195                 write!(f, "ConstEvaluatable({:?}, {:?})", def_id, substs)
 196             }
 197             ty::PredicateKind::ConstEquate(c1, c2) => write!(f, "ConstEquate({:?}, {:?})", c1, c2),
 198             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
 199                 write!(f, "TypeWellFormedFromEnv({:?})", ty)
 200             }
 201         }
 202     }
 203 }
 204
 205 ///////////////////////////////////////////////////////////////////////////
 206 // Atomic structs
 207 //
 208 // For things that don't carry any arena-allocated data (and are
 209 // copy...), just add them to this list.
 210
 211 TrivialTypeFoldableAndLiftImpls! {
 212     (),
 213     bool,
 214     usize,
 215     ::rustc_target::abi::VariantIdx,
 216     u32,
 217     u64,
 218     String,
 219     crate::middle::region::Scope,
 220     crate::ty::FloatTy,
 221     ::rustc_ast::InlineAsmOptions,
 222     ::rustc_ast::InlineAsmTemplatePiece,
 223     ::rustc_ast::NodeId,
 224     ::rustc_span::symbol::Symbol,
 225     ::rustc_hir::def::Res,
 226     ::rustc_hir::def_id::DefId,
 227     ::rustc_hir::def_id::LocalDefId,
 228     ::rustc_hir::HirId,
 229     ::rustc_hir::LlvmInlineAsmInner,
 230     ::rustc_hir::MatchSource,
 231     ::rustc_hir::Mutability,
 232     ::rustc_hir::Unsafety,
 233     ::rustc_target::asm::InlineAsmRegOrRegClass,
 234     ::rustc_target::spec::abi::Abi,
 235     crate::mir::coverage::ExpressionOperandId,
 236     crate::mir::coverage::CounterValueReference,
 237     crate::mir::coverage::InjectedExpressionId,
 238     crate::mir::coverage::InjectedExpressionIndex,
 239     crate::mir::coverage::MappedExpressionIndex,
 240     crate::mir::Local,
 241     crate::mir::Promoted,
 242     crate::traits::Reveal,
 243     crate::ty::adjustment::AutoBorrowMutability,
 244     crate::ty::AdtKind,
 245     // Including `BoundRegionKind` is a *bit* dubious, but direct
 246     // references to bound region appear in `ty::Error`, and aren't
 247     // really meant to be folded. In general, we can only fold a fully
 248     // general `Region`.
 249     crate::ty::BoundRegionKind,
 250     crate::ty::AssocItem,
 251     crate::ty::Placeholder<crate::ty::BoundRegionKind>,
 252     crate::ty::ClosureKind,
 253     crate::ty::FreeRegion,
 254     crate::ty::InferTy,
 255     crate::ty::IntVarValue,
 256     crate::ty::ParamConst,
 257     crate::ty::ParamTy,
 258     crate::ty::adjustment::PointerCast,
 259     crate::ty::RegionVid,
 260     crate::ty::UniverseIndex,
 261     crate::ty::Variance,
 262     ::rustc_span::Span,
 263 }
 264
 265 ///////////////////////////////////////////////////////////////////////////
 266 // Lift implementations
 267
 268 // FIXME(eddyb) replace all the uses of `Option::map` with `?`.
 269 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>> Lift<'tcx> for (A, B) {
 270     type Lifted = (A::Lifted, B::Lifted);
 271     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 272         Some((tcx.lift(self.0)?, tcx.lift(self.1)?))
 273     }
 274 }
 275
 276 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>, C: Lift<'tcx>> Lift<'tcx> for (A, B, C) {
 277     type Lifted = (A::Lifted, B::Lifted, C::Lifted);
 278     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 279         Some((tcx.lift(self.0)?, tcx.lift(self.1)?, tcx.lift(self.2)?))
 280     }
 281 }
 282
 283 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Option<T> {
 284     type Lifted = Option<T::Lifted>;
 285     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 286         match self {
 287             Some(x) => tcx.lift(x).map(Some),
 288             None => Some(None),
 289         }
 290     }
 291 }
 292
 293 impl<'tcx, T: Lift<'tcx>, E: Lift<'tcx>> Lift<'tcx> for Result<T, E> {
 294     type Lifted = Result<T::Lifted, E::Lifted>;
 295     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 296         match self {
 297             Ok(x) => tcx.lift(x).map(Ok),
 298             Err(e) => tcx.lift(e).map(Err),
 299         }
 300     }
 301 }
 302
 303 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Box<T> {
 304     type Lifted = Box<T::Lifted>;
 305     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 306         tcx.lift(*self).map(Box::new)
 307     }
 308 }
 309
 310 impl<'tcx, T: Lift<'tcx> + Clone> Lift<'tcx> for Rc<T> {
 311     type Lifted = Rc<T::Lifted>;
 312     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 313         tcx.lift(self.as_ref().clone()).map(Rc::new)
 314     }
 315 }
 316
 317 impl<'tcx, T: Lift<'tcx> + Clone> Lift<'tcx> for Arc<T> {
 318     type Lifted = Arc<T::Lifted>;
 319     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 320         tcx.lift(self.as_ref().clone()).map(Arc::new)
 321     }
 322 }
 323 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Vec<T> {
 324     type Lifted = Vec<T::Lifted>;
 325     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 326         self.into_iter().map(|v| tcx.lift(v)).collect()
 327     }
 328 }
 329
 330 impl<'tcx, I: Idx, T: Lift<'tcx>> Lift<'tcx> for IndexVec<I, T> {
 331     type Lifted = IndexVec<I, T::Lifted>;
 332     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 333         self.into_iter().map(|e| tcx.lift(e)).collect()
 334     }
 335 }
 336
 337 impl<'a, 'tcx> Lift<'tcx> for ty::TraitRef<'a> {
 338     type Lifted = ty::TraitRef<'tcx>;
 339     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 340         tcx.lift(self.substs).map(|substs| ty::TraitRef { def_id: self.def_id, substs })
 341     }
 342 }
 343
 344 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialTraitRef<'a> {
 345     type Lifted = ty::ExistentialTraitRef<'tcx>;
 346     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 347         tcx.lift(self.substs).map(|substs| ty::ExistentialTraitRef { def_id: self.def_id, substs })
 348     }
 349 }
 350
 351 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialPredicate<'a> {
 352     type Lifted = ty::ExistentialPredicate<'tcx>;
 353     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 354         match self {
 355             ty::ExistentialPredicate::Trait(x) => tcx.lift(x).map(ty::ExistentialPredicate::Trait),
 356             ty::ExistentialPredicate::Projection(x) => {
 357                 tcx.lift(x).map(ty::ExistentialPredicate::Projection)
 358             }
 359             ty::ExistentialPredicate::AutoTrait(def_id) => {
 360                 Some(ty::ExistentialPredicate::AutoTrait(def_id))
 361             }
 362         }
 363     }
 364 }
 365
 366 impl<'a, 'tcx> Lift<'tcx> for ty::TraitPredicate<'a> {
 367     type Lifted = ty::TraitPredicate<'tcx>;
 368     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<ty::TraitPredicate<'tcx>> {
 369         tcx.lift(self.trait_ref).map(|trait_ref| ty::TraitPredicate { trait_ref })
 370     }
 371 }
 372
 373 impl<'a, 'tcx> Lift<'tcx> for ty::SubtypePredicate<'a> {
 374     type Lifted = ty::SubtypePredicate<'tcx>;
 375     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<ty::SubtypePredicate<'tcx>> {
 376         tcx.lift((self.a, self.b)).map(|(a, b)| ty::SubtypePredicate {
 377             a_is_expected: self.a_is_expected,
 378             a,
 379             b,
 380         })
 381     }
 382 }
 383
 384 impl<'tcx, A: Copy + Lift<'tcx>, B: Copy + Lift<'tcx>> Lift<'tcx> for ty::OutlivesPredicate<A, B> {
 385     type Lifted = ty::OutlivesPredicate<A::Lifted, B::Lifted>;
 386     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 387         tcx.lift((self.0, self.1)).map(|(a, b)| ty::OutlivesPredicate(a, b))
 388     }
 389 }
 390
 391 impl<'a, 'tcx> Lift<'tcx> for ty::ProjectionTy<'a> {
 392     type Lifted = ty::ProjectionTy<'tcx>;
 393     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<ty::ProjectionTy<'tcx>> {
 394         tcx.lift(self.substs)
 395             .map(|substs| ty::ProjectionTy { item_def_id: self.item_def_id, substs })
 396     }
 397 }
 398
 399 impl<'a, 'tcx> Lift<'tcx> for ty::ProjectionPredicate<'a> {
 400     type Lifted = ty::ProjectionPredicate<'tcx>;
 401     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<ty::ProjectionPredicate<'tcx>> {
 402         tcx.lift((self.projection_ty, self.ty))
 403             .map(|(projection_ty, ty)| ty::ProjectionPredicate { projection_ty, ty })
 404     }
 405 }
 406
 407 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialProjection<'a> {
 408     type Lifted = ty::ExistentialProjection<'tcx>;
 409     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 410         tcx.lift(self.substs).map(|substs| ty::ExistentialProjection {
 411             substs,
 412             ty: tcx.lift(self.ty).expect("type must lift when substs do"),
 413             item_def_id: self.item_def_id,
 414         })
 415     }
 416 }
 417
 418 impl<'a, 'tcx> Lift<'tcx> for ty::PredicateKind<'a> {
 419     type Lifted = ty::PredicateKind<'tcx>;
 420     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 421         match self {
 422             ty::PredicateKind::Trait(data, constness) => {
 423                 tcx.lift(data).map(|data| ty::PredicateKind::Trait(data, constness))
 424             }
 425             ty::PredicateKind::Subtype(data) => tcx.lift(data).map(ty::PredicateKind::Subtype),
 426             ty::PredicateKind::RegionOutlives(data) => {
 427                 tcx.lift(data).map(ty::PredicateKind::RegionOutlives)
 428             }
 429             ty::PredicateKind::TypeOutlives(data) => {
 430                 tcx.lift(data).map(ty::PredicateKind::TypeOutlives)
 431             }
 432             ty::PredicateKind::Projection(data) => {
 433                 tcx.lift(data).map(ty::PredicateKind::Projection)
 434             }
 435             ty::PredicateKind::WellFormed(ty) => tcx.lift(ty).map(ty::PredicateKind::WellFormed),
 436             ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
 437                 tcx.lift(closure_substs).map(|closure_substs| {
 438                     ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind)
 439                 })
 440             }
 441             ty::PredicateKind::ObjectSafe(trait_def_id) => {
 442                 Some(ty::PredicateKind::ObjectSafe(trait_def_id))
 443             }
 444             ty::PredicateKind::ConstEvaluatable(def_id, substs) => {
 445                 tcx.lift(substs).map(|substs| ty::PredicateKind::ConstEvaluatable(def_id, substs))
 446             }
 447             ty::PredicateKind::ConstEquate(c1, c2) => {
 448                 tcx.lift((c1, c2)).map(|(c1, c2)| ty::PredicateKind::ConstEquate(c1, c2))
 449             }
 450             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
 451                 tcx.lift(ty).map(ty::PredicateKind::TypeWellFormedFromEnv)
 452             }
 453         }
 454     }
 455 }
 456
 457 impl<'a, 'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::Binder<'a, T>
 458 where
 459     <T as Lift<'tcx>>::Lifted: TypeFoldable<'tcx>,
 460 {
 461     type Lifted = ty::Binder<'tcx, T::Lifted>;
 462     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 463         let bound_vars = tcx.lift(self.bound_vars());
 464         tcx.lift(self.skip_binder())
 465             .zip(bound_vars)
 466             .map(|(value, vars)| ty::Binder::bind_with_vars(value, vars))
 467     }
 468 }
 469
 470 impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
 471     type Lifted = ty::ParamEnv<'tcx>;
 472     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 473         tcx.lift(self.caller_bounds())
 474             .map(|caller_bounds| ty::ParamEnv::new(caller_bounds, self.reveal()))
 475     }
 476 }
 477
 478 impl<'a, 'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::ParamEnvAnd<'a, T> {
 479     type Lifted = ty::ParamEnvAnd<'tcx, T::Lifted>;
 480     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 481         tcx.lift(self.param_env).and_then(|param_env| {
 482             tcx.lift(self.value).map(|value| ty::ParamEnvAnd { param_env, value })
 483         })
 484     }
 485 }
 486
 487 impl<'a, 'tcx> Lift<'tcx> for ty::ClosureSubsts<'a> {
 488     type Lifted = ty::ClosureSubsts<'tcx>;
 489     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 490         tcx.lift(self.substs).map(|substs| ty::ClosureSubsts { substs })
 491     }
 492 }
 493
 494 impl<'a, 'tcx> Lift<'tcx> for ty::GeneratorSubsts<'a> {
 495     type Lifted = ty::GeneratorSubsts<'tcx>;
 496     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 497         tcx.lift(self.substs).map(|substs| ty::GeneratorSubsts { substs })
 498     }
 499 }
 500
 501 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjustment<'a> {
 502     type Lifted = ty::adjustment::Adjustment<'tcx>;
 503     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 504         let ty::adjustment::Adjustment { kind, target } = self;
 505         tcx.lift(kind).and_then(|kind| {
 506             tcx.lift(target).map(|target| ty::adjustment::Adjustment { kind, target })
 507         })
 508     }
 509 }
 510
 511 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjust<'a> {
 512     type Lifted = ty::adjustment::Adjust<'tcx>;
 513     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 514         match self {
 515             ty::adjustment::Adjust::NeverToAny => Some(ty::adjustment::Adjust::NeverToAny),
 516             ty::adjustment::Adjust::Pointer(ptr) => Some(ty::adjustment::Adjust::Pointer(ptr)),
 517             ty::adjustment::Adjust::Deref(overloaded) => {
 518                 tcx.lift(overloaded).map(ty::adjustment::Adjust::Deref)
 519             }
 520             ty::adjustment::Adjust::Borrow(autoref) => {
 521                 tcx.lift(autoref).map(ty::adjustment::Adjust::Borrow)
 522             }
 523         }
 524     }
 525 }
 526
 527 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::OverloadedDeref<'a> {
 528     type Lifted = ty::adjustment::OverloadedDeref<'tcx>;
 529     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 530         tcx.lift(self.region).map(|region| ty::adjustment::OverloadedDeref {
 531             region,
 532             mutbl: self.mutbl,
 533             span: self.span,
 534         })
 535     }
 536 }
 537
 538 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::AutoBorrow<'a> {
 539     type Lifted = ty::adjustment::AutoBorrow<'tcx>;
 540     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 541         match self {
 542             ty::adjustment::AutoBorrow::Ref(r, m) => {
 543                 tcx.lift(r).map(|r| ty::adjustment::AutoBorrow::Ref(r, m))
 544             }
 545             ty::adjustment::AutoBorrow::RawPtr(m) => Some(ty::adjustment::AutoBorrow::RawPtr(m)),
 546         }
 547     }
 548 }
 549
 550 impl<'a, 'tcx> Lift<'tcx> for ty::GenSig<'a> {
 551     type Lifted = ty::GenSig<'tcx>;
 552     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 553         tcx.lift((self.resume_ty, self.yield_ty, self.return_ty))
 554             .map(|(resume_ty, yield_ty, return_ty)| ty::GenSig { resume_ty, yield_ty, return_ty })
 555     }
 556 }
 557
 558 impl<'a, 'tcx> Lift<'tcx> for ty::FnSig<'a> {
 559     type Lifted = ty::FnSig<'tcx>;
 560     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 561         tcx.lift(self.inputs_and_output).map(|x| ty::FnSig {
 562             inputs_and_output: x,
 563             c_variadic: self.c_variadic,
 564             unsafety: self.unsafety,
 565             abi: self.abi,
 566         })
 567     }
 568 }
 569
 570 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::error::ExpectedFound<T> {
 571     type Lifted = ty::error::ExpectedFound<T::Lifted>;
 572     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 573         let ty::error::ExpectedFound { expected, found } = self;
 574         tcx.lift(expected).and_then(|expected| {
 575             tcx.lift(found).map(|found| ty::error::ExpectedFound { expected, found })
 576         })
 577     }
 578 }
 579
 580 impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
 581     type Lifted = ty::error::TypeError<'tcx>;
 582     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 583         use crate::ty::error::TypeError::*;
 584
 585         Some(match self {
 586             Mismatch => Mismatch,
 587             UnsafetyMismatch(x) => UnsafetyMismatch(x),
 588             AbiMismatch(x) => AbiMismatch(x),
 589             Mutability => Mutability,
 590             TupleSize(x) => TupleSize(x),
 591             FixedArraySize(x) => FixedArraySize(x),
 592             ArgCount => ArgCount,
 593             RegionsDoesNotOutlive(a, b) => {
 594                 return tcx.lift((a, b)).map(|(a, b)| RegionsDoesNotOutlive(a, b));
 595             }
 596             RegionsInsufficientlyPolymorphic(a, b) => {
 597                 return tcx.lift(b).map(|b| RegionsInsufficientlyPolymorphic(a, b));
 598             }
 599             RegionsOverlyPolymorphic(a, b) => {
 600                 return tcx.lift(b).map(|b| RegionsOverlyPolymorphic(a, b));
 601             }
 602             RegionsPlaceholderMismatch => RegionsPlaceholderMismatch,
 603             IntMismatch(x) => IntMismatch(x),
 604             FloatMismatch(x) => FloatMismatch(x),
 605             Traits(x) => Traits(x),
 606             VariadicMismatch(x) => VariadicMismatch(x),
 607             CyclicTy(t) => return tcx.lift(t).map(|t| CyclicTy(t)),
 608             CyclicConst(ct) => return tcx.lift(ct).map(|ct| CyclicConst(ct)),
 609             ProjectionMismatched(x) => ProjectionMismatched(x),
 610             Sorts(x) => return tcx.lift(x).map(Sorts),
 611             ExistentialMismatch(x) => return tcx.lift(x).map(ExistentialMismatch),
 612             ConstMismatch(x) => return tcx.lift(x).map(ConstMismatch),
 613             IntrinsicCast => IntrinsicCast,
 614             TargetFeatureCast(x) => TargetFeatureCast(x),
 615             ObjectUnsafeCoercion(x) => return tcx.lift(x).map(ObjectUnsafeCoercion),
 616         })
 617     }
 618 }
 619
 620 impl<'a, 'tcx> Lift<'tcx> for ty::InstanceDef<'a> {
 621     type Lifted = ty::InstanceDef<'tcx>;
 622     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 623         match self {
 624             ty::InstanceDef::Item(def_id) => Some(ty::InstanceDef::Item(def_id)),
 625             ty::InstanceDef::VtableShim(def_id) => Some(ty::InstanceDef::VtableShim(def_id)),
 626             ty::InstanceDef::ReifyShim(def_id) => Some(ty::InstanceDef::ReifyShim(def_id)),
 627             ty::InstanceDef::Intrinsic(def_id) => Some(ty::InstanceDef::Intrinsic(def_id)),
 628             ty::InstanceDef::FnPtrShim(def_id, ty) => {
 629                 Some(ty::InstanceDef::FnPtrShim(def_id, tcx.lift(ty)?))
 630             }
 631             ty::InstanceDef::Virtual(def_id, n) => Some(ty::InstanceDef::Virtual(def_id, n)),
 632             ty::InstanceDef::ClosureOnceShim { call_once } => {
 633                 Some(ty::InstanceDef::ClosureOnceShim { call_once })
 634             }
 635             ty::InstanceDef::DropGlue(def_id, ty) => {
 636                 Some(ty::InstanceDef::DropGlue(def_id, tcx.lift(ty)?))
 637             }
 638             ty::InstanceDef::CloneShim(def_id, ty) => {
 639                 Some(ty::InstanceDef::CloneShim(def_id, tcx.lift(ty)?))
 640             }
 641         }
 642     }
 643 }
 644
 645 ///////////////////////////////////////////////////////////////////////////
 646 // TypeFoldable implementations.
 647 //
 648 // Ideally, each type should invoke `folder.fold_foo(self)` and
 649 // nothing else. In some cases, though, we haven't gotten around to
 650 // adding methods on the `folder` yet, and thus the folding is
 651 // hard-coded here. This is less-flexible, because folders cannot
 652 // override the behavior, but there are a lot of random types and one
 653 // can easily refactor the folding into the TypeFolder trait as
 654 // needed.
 655
 656 /// AdtDefs are basically the same as a DefId.
 657 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::AdtDef {
 658     fn super_fold_with<F: TypeFolder<'tcx>>(self, _folder: &mut F) -> Self {
 659         self
 660     }
 661
 662     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 663         ControlFlow::CONTINUE
 664     }
 665 }
 666
 667 impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
 668     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> (T, U) {
 669         (self.0.fold_with(folder), self.1.fold_with(folder))
 670     }
 671
 672     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 673         self.0.visit_with(visitor)?;
 674         self.1.visit_with(visitor)
 675     }
 676 }
 677
 678 impl<'tcx, A: TypeFoldable<'tcx>, B: TypeFoldable<'tcx>, C: TypeFoldable<'tcx>> TypeFoldable<'tcx>
 679     for (A, B, C)
 680 {
 681     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> (A, B, C) {
 682         (self.0.fold_with(folder), self.1.fold_with(folder), self.2.fold_with(folder))
 683     }
 684
 685     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 686         self.0.visit_with(visitor)?;
 687         self.1.visit_with(visitor)?;
 688         self.2.visit_with(visitor)
 689     }
 690 }
 691
 692 EnumTypeFoldableImpl! {
 693     impl<'tcx, T> TypeFoldable<'tcx> for Option<T> {
 694         (Some)(a),
 695         (None),
 696     } where T: TypeFoldable<'tcx>
 697 }
 698
 699 EnumTypeFoldableImpl! {
 700     impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
 701         (Ok)(a),
 702         (Err)(a),
 703     } where T: TypeFoldable<'tcx>, E: TypeFoldable<'tcx>,
 704 }
 705
 706 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
 707     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 708         // FIXME: Reuse the `Rc` here.
 709         Rc::new((*self).clone().fold_with(folder))
 710     }
 711
 712     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 713         (**self).visit_with(visitor)
 714     }
 715 }
 716
 717 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
 718     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 719         // FIXME: Reuse the `Arc` here.
 720         Arc::new((*self).clone().fold_with(folder))
 721     }
 722
 723     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 724         (**self).visit_with(visitor)
 725     }
 726 }
 727
 728 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
 729     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 730         self.map_id(|value| value.fold_with(folder))
 731     }
 732
 733     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 734         (**self).visit_with(visitor)
 735     }
 736 }
 737
 738 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
 739     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 740         self.map_id(|t| t.fold_with(folder))
 741     }
 742
 743     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 744         self.iter().try_for_each(|t| t.visit_with(visitor))
 745     }
 746 }
 747
 748 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
 749     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 750         self.map_id(|t| t.fold_with(folder))
 751     }
 752
 753     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 754         self.iter().try_for_each(|t| t.visit_with(visitor))
 755     }
 756 }
 757
 758 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<'tcx, T> {
 759     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 760         self.map_bound(|ty| ty.fold_with(folder))
 761     }
 762
 763     fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 764         folder.fold_binder(self)
 765     }
 766
 767     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 768         self.as_ref().skip_binder().visit_with(visitor)
 769     }
 770
 771     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 772         visitor.visit_binder(self)
 773     }
 774 }
 775
 776 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>> {
 777     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 778         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_poly_existential_predicates(v))
 779     }
 780
 781     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 782         self.iter().try_for_each(|p| p.visit_with(visitor))
 783     }
 784 }
 785
 786 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
 787     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 788         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_type_list(v))
 789     }
 790
 791     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 792         self.iter().try_for_each(|t| t.visit_with(visitor))
 793     }
 794 }
 795
 796 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
 797     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 798         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_projs(v))
 799     }
 800
 801     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 802         self.iter().try_for_each(|t| t.visit_with(visitor))
 803     }
 804 }
 805
 806 impl<'tcx> TypeFoldable<'tcx> for ty::instance::Instance<'tcx> {
 807     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 808         use crate::ty::InstanceDef::*;
 809         Self {
 810             substs: self.substs.fold_with(folder),
 811             def: match self.def {
 812                 Item(def) => Item(def.fold_with(folder)),
 813                 VtableShim(did) => VtableShim(did.fold_with(folder)),
 814                 ReifyShim(did) => ReifyShim(did.fold_with(folder)),
 815                 Intrinsic(did) => Intrinsic(did.fold_with(folder)),
 816                 FnPtrShim(did, ty) => FnPtrShim(did.fold_with(folder), ty.fold_with(folder)),
 817                 Virtual(did, i) => Virtual(did.fold_with(folder), i),
 818                 ClosureOnceShim { call_once } => {
 819                     ClosureOnceShim { call_once: call_once.fold_with(folder) }
 820                 }
 821                 DropGlue(did, ty) => DropGlue(did.fold_with(folder), ty.fold_with(folder)),
 822                 CloneShim(did, ty) => CloneShim(did.fold_with(folder), ty.fold_with(folder)),
 823             },
 824         }
 825     }
 826
 827     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 828         use crate::ty::InstanceDef::*;
 829         self.substs.visit_with(visitor)?;
 830         match self.def {
 831             Item(def) => def.visit_with(visitor),
 832             VtableShim(did) | ReifyShim(did) | Intrinsic(did) | Virtual(did, _) => {
 833                 did.visit_with(visitor)
 834             }
 835             FnPtrShim(did, ty) | CloneShim(did, ty) => {
 836                 did.visit_with(visitor)?;
 837                 ty.visit_with(visitor)
 838             }
 839             DropGlue(did, ty) => {
 840                 did.visit_with(visitor)?;
 841                 ty.visit_with(visitor)
 842             }
 843             ClosureOnceShim { call_once } => call_once.visit_with(visitor),
 844         }
 845     }
 846 }
 847
 848 impl<'tcx> TypeFoldable<'tcx> for interpret::GlobalId<'tcx> {
 849     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 850         Self { instance: self.instance.fold_with(folder), promoted: self.promoted }
 851     }
 852
 853     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 854         self.instance.visit_with(visitor)
 855     }
 856 }
 857
 858 impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
 859     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 860         let kind = match *self.kind() {
 861             ty::RawPtr(tm) => ty::RawPtr(tm.fold_with(folder)),
 862             ty::Array(typ, sz) => ty::Array(typ.fold_with(folder), sz.fold_with(folder)),
 863             ty::Slice(typ) => ty::Slice(typ.fold_with(folder)),
 864             ty::Adt(tid, substs) => ty::Adt(tid, substs.fold_with(folder)),
 865             ty::Dynamic(trait_ty, region) => {
 866                 ty::Dynamic(trait_ty.fold_with(folder), region.fold_with(folder))
 867             }
 868             ty::Tuple(ts) => ty::Tuple(ts.fold_with(folder)),
 869             ty::FnDef(def_id, substs) => ty::FnDef(def_id, substs.fold_with(folder)),
 870             ty::FnPtr(f) => ty::FnPtr(f.fold_with(folder)),
 871             ty::Ref(r, ty, mutbl) => ty::Ref(r.fold_with(folder), ty.fold_with(folder), mutbl),
 872             ty::Generator(did, substs, movability) => {
 873                 ty::Generator(did, substs.fold_with(folder), movability)
 874             }
 875             ty::GeneratorWitness(types) => ty::GeneratorWitness(types.fold_with(folder)),
 876             ty::Closure(did, substs) => ty::Closure(did, substs.fold_with(folder)),
 877             ty::Projection(data) => ty::Projection(data.fold_with(folder)),
 878             ty::Opaque(did, substs) => ty::Opaque(did, substs.fold_with(folder)),
 879
 880             ty::Bool
 881             | ty::Char
 882             | ty::Str
 883             | ty::Int(_)
 884             | ty::Uint(_)
 885             | ty::Float(_)
 886             | ty::Error(_)
 887             | ty::Infer(_)
 888             | ty::Param(..)
 889             | ty::Bound(..)
 890             | ty::Placeholder(..)
 891             | ty::Never
 892             | ty::Foreign(..) => return self,
 893         };
 894
 895         if *self.kind() == kind { self } else { folder.tcx().mk_ty(kind) }
 896     }
 897
 898     fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 899         folder.fold_ty(self)
 900     }
 901
 902     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 903         match self.kind() {
 904             ty::RawPtr(ref tm) => tm.visit_with(visitor),
 905             ty::Array(typ, sz) => {
 906                 typ.visit_with(visitor)?;
 907                 sz.visit_with(visitor)
 908             }
 909             ty::Slice(typ) => typ.visit_with(visitor),
 910             ty::Adt(_, substs) => substs.visit_with(visitor),
 911             ty::Dynamic(ref trait_ty, ref reg) => {
 912                 trait_ty.visit_with(visitor)?;
 913                 reg.visit_with(visitor)
 914             }
 915             ty::Tuple(ts) => ts.visit_with(visitor),
 916             ty::FnDef(_, substs) => substs.visit_with(visitor),
 917             ty::FnPtr(ref f) => f.visit_with(visitor),
 918             ty::Ref(r, ty, _) => {
 919                 r.visit_with(visitor)?;
 920                 ty.visit_with(visitor)
 921             }
 922             ty::Generator(_did, ref substs, _) => substs.visit_with(visitor),
 923             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
 924             ty::Closure(_did, ref substs) => substs.visit_with(visitor),
 925             ty::Projection(ref data) => data.visit_with(visitor),
 926             ty::Opaque(_, ref substs) => substs.visit_with(visitor),
 927
 928             ty::Bool
 929             | ty::Char
 930             | ty::Str
 931             | ty::Int(_)
 932             | ty::Uint(_)
 933             | ty::Float(_)
 934             | ty::Error(_)
 935             | ty::Infer(_)
 936             | ty::Bound(..)
 937             | ty::Placeholder(..)
 938             | ty::Param(..)
 939             | ty::Never
 940             | ty::Foreign(..) => ControlFlow::CONTINUE,
 941         }
 942     }
 943
 944     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 945         visitor.visit_ty(self)
 946     }
 947 }
 948
 949 impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
 950     fn super_fold_with<F: TypeFolder<'tcx>>(self, _folder: &mut F) -> Self {
 951         self
 952     }
 953
 954     fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 955         folder.fold_region(self)
 956     }
 957
 958     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 959         ControlFlow::CONTINUE
 960     }
 961
 962     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 963         visitor.visit_region(*self)
 964     }
 965 }
 966
 967 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
 968     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 969         let new = self.inner.kind.fold_with(folder);
 970         folder.tcx().reuse_or_mk_predicate(self, new)
 971     }
 972
 973     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 974         self.inner.kind.visit_with(visitor)
 975     }
 976
 977     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 978         visitor.visit_predicate(*self)
 979     }
 980
 981     fn has_vars_bound_at_or_above(&self, binder: ty::DebruijnIndex) -> bool {
 982         self.inner.outer_exclusive_binder > binder
 983     }
 984
 985     fn has_type_flags(&self, flags: ty::TypeFlags) -> bool {
 986         self.inner.flags.intersects(flags)
 987     }
 988 }
 989
 990 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
 991     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
 992         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_predicates(v))
 993     }
 994
 995     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 996         self.iter().try_for_each(|p| p.visit_with(visitor))
 997     }
 998 }
 999
1000 impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
1001     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
1002         self.map_id(|x| x.fold_with(folder))
1003     }
1004
1005     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1006         self.iter().try_for_each(|t| t.visit_with(visitor))
1007     }
1008 }
1009
1010 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
1011     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
1012         let ty = self.ty.fold_with(folder);
1013         let val = self.val.fold_with(folder);
1014         if ty != self.ty || val != self.val {
1015             folder.tcx().mk_const(ty::Const { ty, val })
1016         } else {
1017             self
1018         }
1019     }
1020
1021     fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
1022         folder.fold_const(self)
1023     }
1024
1025     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1026         self.ty.visit_with(visitor)?;
1027         self.val.visit_with(visitor)
1028     }
1029
1030     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1031         visitor.visit_const(self)
1032     }
1033 }
1034
1035 impl<'tcx> TypeFoldable<'tcx> for ty::ConstKind<'tcx> {
1036     fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
1037         match self {
1038             ty::ConstKind::Infer(ic) => ty::ConstKind::Infer(ic.fold_with(folder)),
1039             ty::ConstKind::Param(p) => ty::ConstKind::Param(p.fold_with(folder)),
1040             ty::ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted }) => {
1041                 ty::ConstKind::Unevaluated(ty::Unevaluated {
1042                     def,
1043                     substs: substs.fold_with(folder),
1044                     promoted,
1045                 })
1046             }
1047             ty::ConstKind::Value(_)
1048             | ty::ConstKind::Bound(..)
1049             | ty::ConstKind::Placeholder(..)
1050             | ty::ConstKind::Error(_) => self,
1051         }
1052     }
1053
1054     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1055         match *self {
1056             ty::ConstKind::Infer(ic) => ic.visit_with(visitor),
1057             ty::ConstKind::Param(p) => p.visit_with(visitor),
1058             ty::ConstKind::Unevaluated(ct) => ct.substs.visit_with(visitor),
1059             ty::ConstKind::Value(_)
1060             | ty::ConstKind::Bound(..)
1061             | ty::ConstKind::Placeholder(_)
1062             | ty::ConstKind::Error(_) => ControlFlow::CONTINUE,
1063         }
1064     }
1065 }
1066
1067 impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
1068     fn super_fold_with<F: TypeFolder<'tcx>>(self, _folder: &mut F) -> Self {
1069         self
1070     }
1071
1072     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
1073         ControlFlow::CONTINUE
1074     }
1075 }