src/librustc/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::hir::def::Namespace;
   6 use crate::mir::ProjectionKind;
   7 use crate::mir::interpret;
   8 use crate::ty::{self, Lift, Ty, TyCtxt, InferConst};
   9 use crate::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
  10 use crate::ty::print::{FmtPrinter, Printer};
  11
  12 use rustc_index::vec::{IndexVec, Idx};
  13 use smallvec::SmallVec;
  14
  15 use std::fmt;
  16 use std::rc::Rc;
  17 use std::sync::Arc;
  18
  19 impl fmt::Debug for ty::GenericParamDef {
  20     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  21         let type_name = match self.kind {
  22             ty::GenericParamDefKind::Lifetime => "Lifetime",
  23             ty::GenericParamDefKind::Type {..} => "Type",
  24             ty::GenericParamDefKind::Const => "Const",
  25         };
  26         write!(f, "{}({}, {:?}, {})",
  27                type_name,
  28                self.name,
  29                self.def_id,
  30                self.index)
  31     }
  32 }
  33
  34 impl fmt::Debug for ty::TraitDef {
  35     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  36         ty::tls::with(|tcx| {
  37             FmtPrinter::new(tcx, f, Namespace::TypeNS)
  38                 .print_def_path(self.def_id, &[])?;
  39             Ok(())
  40         })
  41     }
  42 }
  43
  44 impl fmt::Debug for ty::AdtDef {
  45     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  46         ty::tls::with(|tcx| {
  47             FmtPrinter::new(tcx, f, Namespace::TypeNS)
  48                 .print_def_path(self.did, &[])?;
  49             Ok(())
  50         })
  51     }
  52 }
  53
  54 impl fmt::Debug for ty::ClosureUpvar<'tcx> {
  55     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  56         write!(f, "ClosureUpvar({:?},{:?})",
  57                self.res,
  58                self.ty)
  59     }
  60 }
  61
  62 impl fmt::Debug for ty::UpvarId {
  63     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  64         let name = ty::tls::with(|tcx| {
  65             tcx.hir().name(self.var_path.hir_id)
  66         });
  67         write!(f, "UpvarId({:?};`{}`;{:?})",
  68             self.var_path.hir_id,
  69             name,
  70             self.closure_expr_id)
  71     }
  72 }
  73
  74 impl fmt::Debug for ty::UpvarBorrow<'tcx> {
  75     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  76         write!(f, "UpvarBorrow({:?}, {:?})",
  77                self.kind, self.region)
  78     }
  79 }
  80
  81 impl fmt::Debug for ty::ExistentialTraitRef<'tcx> {
  82     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  83         fmt::Display::fmt(self, f)
  84     }
  85 }
  86
  87 impl fmt::Debug for ty::adjustment::Adjustment<'tcx> {
  88     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  89         write!(f, "{:?} -> {}", self.kind, self.target)
  90     }
  91 }
  92
  93 impl fmt::Debug for ty::BoundRegion {
  94     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  95         match *self {
  96             ty::BrAnon(n) => write!(f, "BrAnon({:?})", n),
  97             ty::BrNamed(did, name) => {
  98                 write!(f, "BrNamed({:?}:{:?}, {})",
  99                         did.krate, did.index, name)
 100             }
 101             ty::BrEnv => write!(f, "BrEnv"),
 102         }
 103     }
 104 }
 105
 106 impl fmt::Debug for ty::RegionKind {
 107     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 108         match *self {
 109             ty::ReEarlyBound(ref data) => {
 110                 write!(f, "ReEarlyBound({}, {})",
 111                         data.index,
 112                         data.name)
 113             }
 114
 115             ty::ReClosureBound(ref vid) => {
 116                 write!(f, "ReClosureBound({:?})", vid)
 117             }
 118
 119             ty::ReLateBound(binder_id, ref bound_region) => {
 120                 write!(f, "ReLateBound({:?}, {:?})", binder_id, bound_region)
 121             }
 122
 123             ty::ReFree(ref fr) => fr.fmt(f),
 124
 125             ty::ReScope(id) => write!(f, "ReScope({:?})", id),
 126
 127             ty::ReStatic => write!(f, "ReStatic"),
 128
 129             ty::ReVar(ref vid) => vid.fmt(f),
 130
 131             ty::RePlaceholder(placeholder) => {
 132                 write!(f, "RePlaceholder({:?})", placeholder)
 133             }
 134
 135             ty::ReEmpty => write!(f, "ReEmpty"),
 136
 137             ty::ReErased => write!(f, "ReErased"),
 138         }
 139     }
 140 }
 141
 142 impl fmt::Debug for ty::FreeRegion {
 143     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 144         write!(f, "ReFree({:?}, {:?})", self.scope, self.bound_region)
 145     }
 146 }
 147
 148 impl fmt::Debug for ty::Variance {
 149     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 150         f.write_str(match *self {
 151             ty::Covariant => "+",
 152             ty::Contravariant => "-",
 153             ty::Invariant => "o",
 154             ty::Bivariant => "*",
 155         })
 156     }
 157 }
 158
 159 impl fmt::Debug for ty::FnSig<'tcx> {
 160     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 161         write!(f, "({:?}; c_variadic: {})->{:?}",
 162                 self.inputs(), self.c_variadic, self.output())
 163     }
 164 }
 165
 166 impl fmt::Debug for ty::TyVid {
 167     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 168         write!(f, "_#{}t", self.index)
 169     }
 170 }
 171
 172 impl<'tcx> fmt::Debug for ty::ConstVid<'tcx> {
 173     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 174         write!(f, "_#{}c", self.index)
 175     }
 176 }
 177
 178 impl fmt::Debug for ty::IntVid {
 179     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 180         write!(f, "_#{}i", self.index)
 181     }
 182 }
 183
 184 impl fmt::Debug for ty::FloatVid {
 185     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 186         write!(f, "_#{}f", self.index)
 187     }
 188 }
 189
 190 impl fmt::Debug for ty::RegionVid {
 191     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 192         write!(f, "'_#{}r", self.index())
 193     }
 194 }
 195
 196 impl fmt::Debug for ty::InferTy {
 197     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 198         match *self {
 199             ty::TyVar(ref v) => v.fmt(f),
 200             ty::IntVar(ref v) => v.fmt(f),
 201             ty::FloatVar(ref v) => v.fmt(f),
 202             ty::FreshTy(v) => write!(f, "FreshTy({:?})", v),
 203             ty::FreshIntTy(v) => write!(f, "FreshIntTy({:?})", v),
 204             ty::FreshFloatTy(v) => write!(f, "FreshFloatTy({:?})", v),
 205         }
 206     }
 207 }
 208
 209 impl fmt::Debug for ty::IntVarValue {
 210     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 211         match *self {
 212             ty::IntType(ref v) => v.fmt(f),
 213             ty::UintType(ref v) => v.fmt(f),
 214         }
 215     }
 216 }
 217
 218 impl fmt::Debug for ty::FloatVarValue {
 219     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 220         self.0.fmt(f)
 221     }
 222 }
 223
 224 impl fmt::Debug for ty::TraitRef<'tcx> {
 225     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 226         // FIXME(#59188) this is used across the compiler to print
 227         // a `TraitRef` qualified (with the Self type explicit),
 228         // instead of having a different way to make that choice.
 229         write!(f, "<{} as {}>", self.self_ty(), self)
 230     }
 231 }
 232
 233 impl fmt::Debug for Ty<'tcx> {
 234     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 235         fmt::Display::fmt(self, f)
 236     }
 237 }
 238
 239 impl fmt::Debug for ty::ParamTy {
 240     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 241         write!(f, "{}/#{}", self.name, self.index)
 242     }
 243 }
 244
 245 impl fmt::Debug for ty::ParamConst {
 246     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 247         write!(f, "{}/#{}", self.name, self.index)
 248     }
 249 }
 250
 251 impl fmt::Debug for ty::TraitPredicate<'tcx> {
 252     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 253         write!(f, "TraitPredicate({:?})", self.trait_ref)
 254     }
 255 }
 256
 257 impl fmt::Debug for ty::ProjectionPredicate<'tcx> {
 258     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 259         write!(f, "ProjectionPredicate({:?}, {:?})", self.projection_ty, self.ty)
 260     }
 261 }
 262
 263 impl fmt::Debug for ty::Predicate<'tcx> {
 264     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 265         match *self {
 266             ty::Predicate::Trait(ref a) => a.fmt(f),
 267             ty::Predicate::Subtype(ref pair) => pair.fmt(f),
 268             ty::Predicate::RegionOutlives(ref pair) => pair.fmt(f),
 269             ty::Predicate::TypeOutlives(ref pair) => pair.fmt(f),
 270             ty::Predicate::Projection(ref pair) => pair.fmt(f),
 271             ty::Predicate::WellFormed(ty) => write!(f, "WellFormed({:?})", ty),
 272             ty::Predicate::ObjectSafe(trait_def_id) => {
 273                 write!(f, "ObjectSafe({:?})", trait_def_id)
 274             }
 275             ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind) => {
 276                 write!(f, "ClosureKind({:?}, {:?}, {:?})",
 277                     closure_def_id, closure_substs, kind)
 278             }
 279             ty::Predicate::ConstEvaluatable(def_id, substs) => {
 280                 write!(f, "ConstEvaluatable({:?}, {:?})", def_id, substs)
 281             }
 282         }
 283     }
 284 }
 285
 286 ///////////////////////////////////////////////////////////////////////////
 287 // Atomic structs
 288 //
 289 // For things that don't carry any arena-allocated data (and are
 290 // copy...), just add them to this list.
 291
 292 CloneTypeFoldableAndLiftImpls! {
 293     (),
 294     bool,
 295     usize,
 296     crate::ty::layout::VariantIdx,
 297     u64,
 298     String,
 299     crate::middle::region::Scope,
 300     ::syntax::ast::FloatTy,
 301     ::syntax::ast::NodeId,
 302     ::syntax_pos::symbol::Symbol,
 303     crate::hir::def::Res,
 304     crate::hir::def_id::DefId,
 305     crate::hir::InlineAsmInner,
 306     crate::hir::MatchSource,
 307     crate::hir::Mutability,
 308     crate::hir::Unsafety,
 309     ::rustc_target::spec::abi::Abi,
 310     crate::mir::Local,
 311     crate::mir::Promoted,
 312     crate::traits::Reveal,
 313     crate::ty::adjustment::AutoBorrowMutability,
 314     crate::ty::AdtKind,
 315     // Including `BoundRegion` is a *bit* dubious, but direct
 316     // references to bound region appear in `ty::Error`, and aren't
 317     // really meant to be folded. In general, we can only fold a fully
 318     // general `Region`.
 319     crate::ty::BoundRegion,
 320     crate::ty::Placeholder<crate::ty::BoundRegion>,
 321     crate::ty::ClosureKind,
 322     crate::ty::FreeRegion,
 323     crate::ty::InferTy,
 324     crate::ty::IntVarValue,
 325     crate::ty::ParamConst,
 326     crate::ty::ParamTy,
 327     crate::ty::adjustment::PointerCast,
 328     crate::ty::RegionVid,
 329     crate::ty::UniverseIndex,
 330     crate::ty::Variance,
 331     ::syntax_pos::Span,
 332 }
 333
 334 ///////////////////////////////////////////////////////////////////////////
 335 // Lift implementations
 336
 337 // FIXME(eddyb) replace all the uses of `Option::map` with `?`.
 338 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>> Lift<'tcx> for (A, B) {
 339     type Lifted = (A::Lifted, B::Lifted);
 340     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 341         tcx.lift(&self.0).and_then(|a| tcx.lift(&self.1).map(|b| (a, b)))
 342     }
 343 }
 344
 345 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>, C: Lift<'tcx>> Lift<'tcx> for (A, B, C) {
 346     type Lifted = (A::Lifted, B::Lifted, C::Lifted);
 347     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 348         tcx.lift(&self.0).and_then(|a| {
 349             tcx.lift(&self.1).and_then(|b| tcx.lift(&self.2).map(|c| (a, b, c)))
 350         })
 351    }
 352 }
 353
 354 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Option<T> {
 355     type Lifted = Option<T::Lifted>;
 356     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 357         match *self {
 358             Some(ref x) => tcx.lift(x).map(Some),
 359             None => Some(None)
 360         }
 361     }
 362 }
 363
 364 impl<'tcx, T: Lift<'tcx>, E: Lift<'tcx>> Lift<'tcx> for Result<T, E> {
 365     type Lifted = Result<T::Lifted, E::Lifted>;
 366     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 367         match *self {
 368             Ok(ref x) => tcx.lift(x).map(Ok),
 369             Err(ref e) => tcx.lift(e).map(Err)
 370         }
 371     }
 372 }
 373
 374 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Box<T> {
 375     type Lifted = Box<T::Lifted>;
 376     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 377         tcx.lift(&**self).map(Box::new)
 378     }
 379 }
 380
 381 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Rc<T> {
 382     type Lifted = Rc<T::Lifted>;
 383     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 384         tcx.lift(&**self).map(Rc::new)
 385     }
 386 }
 387
 388 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Arc<T> {
 389     type Lifted = Arc<T::Lifted>;
 390     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 391         tcx.lift(&**self).map(Arc::new)
 392     }
 393 }
 394
 395 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for [T] {
 396     type Lifted = Vec<T::Lifted>;
 397     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 398         // type annotation needed to inform `projection_must_outlive`
 399         let mut result : Vec<<T as Lift<'tcx>>::Lifted>
 400             = Vec::with_capacity(self.len());
 401         for x in self {
 402             if let Some(value) = tcx.lift(x) {
 403                 result.push(value);
 404             } else {
 405                 return None;
 406             }
 407         }
 408         Some(result)
 409     }
 410 }
 411
 412 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Vec<T> {
 413     type Lifted = Vec<T::Lifted>;
 414     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 415         tcx.lift(&self[..])
 416     }
 417 }
 418
 419 impl<'tcx, I: Idx, T: Lift<'tcx>> Lift<'tcx> for IndexVec<I, T> {
 420     type Lifted = IndexVec<I, T::Lifted>;
 421     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 422         self.iter()
 423             .map(|e| tcx.lift(e))
 424             .collect()
 425     }
 426 }
 427
 428 impl<'a, 'tcx> Lift<'tcx> for ty::TraitRef<'a> {
 429     type Lifted = ty::TraitRef<'tcx>;
 430     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 431         tcx.lift(&self.substs).map(|substs| ty::TraitRef {
 432             def_id: self.def_id,
 433             substs,
 434         })
 435     }
 436 }
 437
 438 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialTraitRef<'a> {
 439     type Lifted = ty::ExistentialTraitRef<'tcx>;
 440     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 441         tcx.lift(&self.substs).map(|substs| ty::ExistentialTraitRef {
 442             def_id: self.def_id,
 443             substs,
 444         })
 445     }
 446 }
 447
 448 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialPredicate<'a> {
 449     type Lifted = ty::ExistentialPredicate<'tcx>;
 450     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 451         match self {
 452             ty::ExistentialPredicate::Trait(x) => {
 453                 tcx.lift(x).map(ty::ExistentialPredicate::Trait)
 454             }
 455             ty::ExistentialPredicate::Projection(x) => {
 456                 tcx.lift(x).map(ty::ExistentialPredicate::Projection)
 457             }
 458             ty::ExistentialPredicate::AutoTrait(def_id) => {
 459                 Some(ty::ExistentialPredicate::AutoTrait(*def_id))
 460             }
 461         }
 462     }
 463 }
 464
 465 impl<'a, 'tcx> Lift<'tcx> for ty::TraitPredicate<'a> {
 466     type Lifted = ty::TraitPredicate<'tcx>;
 467     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::TraitPredicate<'tcx>> {
 468         tcx.lift(&self.trait_ref).map(|trait_ref| ty::TraitPredicate {
 469             trait_ref,
 470         })
 471     }
 472 }
 473
 474 impl<'a, 'tcx> Lift<'tcx> for ty::SubtypePredicate<'a> {
 475     type Lifted = ty::SubtypePredicate<'tcx>;
 476     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::SubtypePredicate<'tcx>> {
 477         tcx.lift(&(self.a, self.b)).map(|(a, b)| ty::SubtypePredicate {
 478             a_is_expected: self.a_is_expected,
 479             a,
 480             b,
 481         })
 482     }
 483 }
 484
 485 impl<'tcx, A: Copy + Lift<'tcx>, B: Copy + Lift<'tcx>> Lift<'tcx> for ty::OutlivesPredicate<A, B> {
 486     type Lifted = ty::OutlivesPredicate<A::Lifted, B::Lifted>;
 487     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 488         tcx.lift(&(self.0, self.1)).map(|(a, b)| ty::OutlivesPredicate(a, b))
 489     }
 490 }
 491
 492 impl<'a, 'tcx> Lift<'tcx> for ty::ProjectionTy<'a> {
 493     type Lifted = ty::ProjectionTy<'tcx>;
 494     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::ProjectionTy<'tcx>> {
 495         tcx.lift(&self.substs).map(|substs| {
 496             ty::ProjectionTy {
 497                 item_def_id: self.item_def_id,
 498                 substs,
 499             }
 500         })
 501     }
 502 }
 503
 504 impl<'a, 'tcx> Lift<'tcx> for ty::ProjectionPredicate<'a> {
 505     type Lifted = ty::ProjectionPredicate<'tcx>;
 506     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::ProjectionPredicate<'tcx>> {
 507         tcx.lift(&(self.projection_ty, self.ty)).map(|(projection_ty, ty)| {
 508             ty::ProjectionPredicate {
 509                 projection_ty,
 510                 ty,
 511             }
 512         })
 513     }
 514 }
 515
 516 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialProjection<'a> {
 517     type Lifted = ty::ExistentialProjection<'tcx>;
 518     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 519         tcx.lift(&self.substs).map(|substs| {
 520             ty::ExistentialProjection {
 521                 substs,
 522                 ty: tcx.lift(&self.ty).expect("type must lift when substs do"),
 523                 item_def_id: self.item_def_id,
 524             }
 525         })
 526     }
 527 }
 528
 529 impl<'a, 'tcx> Lift<'tcx> for ty::Predicate<'a> {
 530     type Lifted = ty::Predicate<'tcx>;
 531     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 532         match *self {
 533             ty::Predicate::Trait(ref binder) => {
 534                 tcx.lift(binder).map(ty::Predicate::Trait)
 535             }
 536             ty::Predicate::Subtype(ref binder) => {
 537                 tcx.lift(binder).map(ty::Predicate::Subtype)
 538             }
 539             ty::Predicate::RegionOutlives(ref binder) => {
 540                 tcx.lift(binder).map(ty::Predicate::RegionOutlives)
 541             }
 542             ty::Predicate::TypeOutlives(ref binder) => {
 543                 tcx.lift(binder).map(ty::Predicate::TypeOutlives)
 544             }
 545             ty::Predicate::Projection(ref binder) => {
 546                 tcx.lift(binder).map(ty::Predicate::Projection)
 547             }
 548             ty::Predicate::WellFormed(ty) => {
 549                 tcx.lift(&ty).map(ty::Predicate::WellFormed)
 550             }
 551             ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind) => {
 552                 tcx.lift(&closure_substs)
 553                    .map(|closure_substs| ty::Predicate::ClosureKind(closure_def_id,
 554                                                                     closure_substs,
 555                                                                     kind))
 556             }
 557             ty::Predicate::ObjectSafe(trait_def_id) => {
 558                 Some(ty::Predicate::ObjectSafe(trait_def_id))
 559             }
 560             ty::Predicate::ConstEvaluatable(def_id, substs) => {
 561                 tcx.lift(&substs).map(|substs| {
 562                     ty::Predicate::ConstEvaluatable(def_id, substs)
 563                 })
 564             }
 565         }
 566     }
 567 }
 568
 569 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::Binder<T> {
 570     type Lifted = ty::Binder<T::Lifted>;
 571     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 572         tcx.lift(self.skip_binder()).map(ty::Binder::bind)
 573     }
 574 }
 575
 576 impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
 577     type Lifted = ty::ParamEnv<'tcx>;
 578     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 579         tcx.lift(&self.caller_bounds).map(|caller_bounds| {
 580             ty::ParamEnv {
 581                 reveal: self.reveal,
 582                 caller_bounds,
 583                 def_id: self.def_id,
 584             }
 585         })
 586     }
 587 }
 588
 589 impl<'a, 'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::ParamEnvAnd<'a, T> {
 590     type Lifted = ty::ParamEnvAnd<'tcx, T::Lifted>;
 591     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 592         tcx.lift(&self.param_env).and_then(|param_env| {
 593             tcx.lift(&self.value).map(|value| {
 594                 ty::ParamEnvAnd {
 595                     param_env,
 596                     value,
 597                 }
 598             })
 599         })
 600     }
 601 }
 602
 603 impl<'a, 'tcx> Lift<'tcx> for ty::ClosureSubsts<'a> {
 604     type Lifted = ty::ClosureSubsts<'tcx>;
 605     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 606         tcx.lift(&self.substs).map(|substs| {
 607             ty::ClosureSubsts { substs }
 608         })
 609     }
 610 }
 611
 612 impl<'a, 'tcx> Lift<'tcx> for ty::GeneratorSubsts<'a> {
 613     type Lifted = ty::GeneratorSubsts<'tcx>;
 614     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 615         tcx.lift(&self.substs).map(|substs| {
 616             ty::GeneratorSubsts { substs }
 617         })
 618     }
 619 }
 620
 621 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjustment<'a> {
 622     type Lifted = ty::adjustment::Adjustment<'tcx>;
 623     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 624         tcx.lift(&self.kind).and_then(|kind| {
 625             tcx.lift(&self.target).map(|target| {
 626                 ty::adjustment::Adjustment { kind, target }
 627             })
 628         })
 629     }
 630 }
 631
 632 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjust<'a> {
 633     type Lifted = ty::adjustment::Adjust<'tcx>;
 634     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 635         match *self {
 636             ty::adjustment::Adjust::NeverToAny =>
 637                 Some(ty::adjustment::Adjust::NeverToAny),
 638             ty::adjustment::Adjust::Pointer(ptr) =>
 639                 Some(ty::adjustment::Adjust::Pointer(ptr)),
 640             ty::adjustment::Adjust::Deref(ref overloaded) => {
 641                 tcx.lift(overloaded).map(ty::adjustment::Adjust::Deref)
 642             }
 643             ty::adjustment::Adjust::Borrow(ref autoref) => {
 644                 tcx.lift(autoref).map(ty::adjustment::Adjust::Borrow)
 645             }
 646         }
 647     }
 648 }
 649
 650 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::OverloadedDeref<'a> {
 651     type Lifted = ty::adjustment::OverloadedDeref<'tcx>;
 652     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 653         tcx.lift(&self.region).map(|region| {
 654             ty::adjustment::OverloadedDeref {
 655                 region,
 656                 mutbl: self.mutbl,
 657             }
 658         })
 659     }
 660 }
 661
 662 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::AutoBorrow<'a> {
 663     type Lifted = ty::adjustment::AutoBorrow<'tcx>;
 664     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 665         match *self {
 666             ty::adjustment::AutoBorrow::Ref(r, m) => {
 667                 tcx.lift(&r).map(|r| ty::adjustment::AutoBorrow::Ref(r, m))
 668             }
 669             ty::adjustment::AutoBorrow::RawPtr(m) => {
 670                 Some(ty::adjustment::AutoBorrow::RawPtr(m))
 671             }
 672         }
 673     }
 674 }
 675
 676 impl<'a, 'tcx> Lift<'tcx> for ty::GenSig<'a> {
 677     type Lifted = ty::GenSig<'tcx>;
 678     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 679         tcx.lift(&(self.yield_ty, self.return_ty))
 680            .map(|(yield_ty, return_ty)| {
 681                ty::GenSig {
 682                    yield_ty,
 683                    return_ty,
 684                }
 685            })
 686     }
 687 }
 688
 689 impl<'a, 'tcx> Lift<'tcx> for ty::FnSig<'a> {
 690     type Lifted = ty::FnSig<'tcx>;
 691     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 692         tcx.lift(&self.inputs_and_output).map(|x| {
 693             ty::FnSig {
 694                 inputs_and_output: x,
 695                 c_variadic: self.c_variadic,
 696                 unsafety: self.unsafety,
 697                 abi: self.abi,
 698             }
 699         })
 700     }
 701 }
 702
 703 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::error::ExpectedFound<T> {
 704     type Lifted = ty::error::ExpectedFound<T::Lifted>;
 705     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 706         tcx.lift(&self.expected).and_then(|expected| {
 707             tcx.lift(&self.found).map(|found| {
 708                 ty::error::ExpectedFound {
 709                     expected,
 710                     found,
 711                 }
 712             })
 713         })
 714     }
 715 }
 716
 717 impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
 718     type Lifted = ty::error::TypeError<'tcx>;
 719     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 720         use crate::ty::error::TypeError::*;
 721
 722         Some(match *self {
 723             Mismatch => Mismatch,
 724             UnsafetyMismatch(x) => UnsafetyMismatch(x),
 725             AbiMismatch(x) => AbiMismatch(x),
 726             Mutability => Mutability,
 727             TupleSize(x) => TupleSize(x),
 728             FixedArraySize(x) => FixedArraySize(x),
 729             ArgCount => ArgCount,
 730             RegionsDoesNotOutlive(a, b) => {
 731                 return tcx.lift(&(a, b)).map(|(a, b)| RegionsDoesNotOutlive(a, b))
 732             }
 733             RegionsInsufficientlyPolymorphic(a, b) => {
 734                 return tcx.lift(&b).map(|b| RegionsInsufficientlyPolymorphic(a, b))
 735             }
 736             RegionsOverlyPolymorphic(a, b) => {
 737                 return tcx.lift(&b).map(|b| RegionsOverlyPolymorphic(a, b))
 738             }
 739             RegionsPlaceholderMismatch => RegionsPlaceholderMismatch,
 740             IntMismatch(x) => IntMismatch(x),
 741             FloatMismatch(x) => FloatMismatch(x),
 742             Traits(x) => Traits(x),
 743             VariadicMismatch(x) => VariadicMismatch(x),
 744             CyclicTy(t) => return tcx.lift(&t).map(|t| CyclicTy(t)),
 745             ProjectionMismatched(x) => ProjectionMismatched(x),
 746             ProjectionBoundsLength(x) => ProjectionBoundsLength(x),
 747             Sorts(ref x) => return tcx.lift(x).map(Sorts),
 748             ExistentialMismatch(ref x) => return tcx.lift(x).map(ExistentialMismatch),
 749             ConstMismatch(ref x) => return tcx.lift(x).map(ConstMismatch),
 750             IntrinsicCast => IntrinsicCast,
 751             ObjectUnsafeCoercion(ref x) => return tcx.lift(x).map(ObjectUnsafeCoercion),
 752         })
 753     }
 754 }
 755
 756 impl<'a, 'tcx> Lift<'tcx> for ty::InstanceDef<'a> {
 757     type Lifted = ty::InstanceDef<'tcx>;
 758     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 759         match *self {
 760             ty::InstanceDef::Item(def_id) =>
 761                 Some(ty::InstanceDef::Item(def_id)),
 762             ty::InstanceDef::VtableShim(def_id) =>
 763                 Some(ty::InstanceDef::VtableShim(def_id)),
 764             ty::InstanceDef::ReifyShim(def_id) =>
 765                 Some(ty::InstanceDef::ReifyShim(def_id)),
 766             ty::InstanceDef::Intrinsic(def_id) =>
 767                 Some(ty::InstanceDef::Intrinsic(def_id)),
 768             ty::InstanceDef::FnPtrShim(def_id, ref ty) =>
 769                 Some(ty::InstanceDef::FnPtrShim(def_id, tcx.lift(ty)?)),
 770             ty::InstanceDef::Virtual(def_id, n) =>
 771                 Some(ty::InstanceDef::Virtual(def_id, n)),
 772             ty::InstanceDef::ClosureOnceShim { call_once } =>
 773                 Some(ty::InstanceDef::ClosureOnceShim { call_once }),
 774             ty::InstanceDef::DropGlue(def_id, ref ty) =>
 775                 Some(ty::InstanceDef::DropGlue(def_id, tcx.lift(ty)?)),
 776             ty::InstanceDef::CloneShim(def_id, ref ty) =>
 777                 Some(ty::InstanceDef::CloneShim(def_id, tcx.lift(ty)?)),
 778         }
 779     }
 780 }
 781
 782 ///////////////////////////////////////////////////////////////////////////
 783 // TypeFoldable implementations.
 784 //
 785 // Ideally, each type should invoke `folder.fold_foo(self)` and
 786 // nothing else. In some cases, though, we haven't gotten around to
 787 // adding methods on the `folder` yet, and thus the folding is
 788 // hard-coded here. This is less-flexible, because folders cannot
 789 // override the behavior, but there are a lot of random types and one
 790 // can easily refactor the folding into the TypeFolder trait as
 791 // needed.
 792
 793 /// AdtDefs are basically the same as a DefId.
 794 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::AdtDef {
 795     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
 796         *self
 797     }
 798
 799     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
 800         false
 801     }
 802 }
 803
 804 impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
 805     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> (T, U) {
 806         (self.0.fold_with(folder), self.1.fold_with(folder))
 807     }
 808
 809     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 810         self.0.visit_with(visitor) || self.1.visit_with(visitor)
 811     }
 812 }
 813
 814 EnumTypeFoldableImpl! {
 815     impl<'tcx, T> TypeFoldable<'tcx> for Option<T> {
 816         (Some)(a),
 817         (None),
 818     } where T: TypeFoldable<'tcx>
 819 }
 820
 821 EnumTypeFoldableImpl! {
 822     impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
 823         (Ok)(a),
 824         (Err)(a),
 825     } where T: TypeFoldable<'tcx>, E: TypeFoldable<'tcx>,
 826 }
 827
 828 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
 829     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 830         Rc::new((**self).fold_with(folder))
 831     }
 832
 833     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 834         (**self).visit_with(visitor)
 835     }
 836 }
 837
 838 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
 839     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 840         Arc::new((**self).fold_with(folder))
 841     }
 842
 843     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 844         (**self).visit_with(visitor)
 845     }
 846 }
 847
 848 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
 849     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 850         let content: T = (**self).fold_with(folder);
 851         box content
 852     }
 853
 854     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 855         (**self).visit_with(visitor)
 856     }
 857 }
 858
 859 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
 860     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 861         self.iter().map(|t| t.fold_with(folder)).collect()
 862     }
 863
 864     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 865         self.iter().any(|t| t.visit_with(visitor))
 866     }
 867 }
 868
 869 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
 870     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 871         self.iter().map(|t| t.fold_with(folder)).collect::<Vec<_>>().into_boxed_slice()
 872     }
 873
 874     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 875         self.iter().any(|t| t.visit_with(visitor))
 876     }
 877 }
 878
 879 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<T> {
 880     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 881         self.map_bound_ref(|ty| ty.fold_with(folder))
 882     }
 883
 884     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 885         folder.fold_binder(self)
 886     }
 887
 888     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 889         self.skip_binder().visit_with(visitor)
 890     }
 891
 892     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 893         visitor.visit_binder(self)
 894     }
 895 }
 896
 897 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::ExistentialPredicate<'tcx>> {
 898     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 899         let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
 900         folder.tcx().intern_existential_predicates(&v)
 901     }
 902
 903     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 904         self.iter().any(|p| p.visit_with(visitor))
 905     }
 906 }
 907
 908 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
 909     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 910         let v = self.iter().map(|t| t.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
 911         folder.tcx().intern_type_list(&v)
 912     }
 913
 914     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 915         self.iter().any(|t| t.visit_with(visitor))
 916     }
 917 }
 918
 919 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
 920     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 921         let v = self.iter().map(|t| t.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
 922         folder.tcx().intern_projs(&v)
 923     }
 924
 925     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 926         self.iter().any(|t| t.visit_with(visitor))
 927     }
 928 }
 929
 930 impl<'tcx> TypeFoldable<'tcx> for ty::instance::Instance<'tcx> {
 931     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 932         use crate::ty::InstanceDef::*;
 933         Self {
 934             substs: self.substs.fold_with(folder),
 935             def: match self.def {
 936                 Item(did) => Item(did.fold_with(folder)),
 937                 VtableShim(did) => VtableShim(did.fold_with(folder)),
 938                 ReifyShim(did) => ReifyShim(did.fold_with(folder)),
 939                 Intrinsic(did) => Intrinsic(did.fold_with(folder)),
 940                 FnPtrShim(did, ty) => FnPtrShim(
 941                     did.fold_with(folder),
 942                     ty.fold_with(folder),
 943                 ),
 944                 Virtual(did, i) => Virtual(
 945                     did.fold_with(folder),
 946                     i,
 947                 ),
 948                 ClosureOnceShim { call_once } => ClosureOnceShim {
 949                     call_once: call_once.fold_with(folder),
 950                 },
 951                 DropGlue(did, ty) => DropGlue(
 952                     did.fold_with(folder),
 953                     ty.fold_with(folder),
 954                 ),
 955                 CloneShim(did, ty) => CloneShim(
 956                     did.fold_with(folder),
 957                     ty.fold_with(folder),
 958                 ),
 959             },
 960         }
 961     }
 962
 963     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 964         use crate::ty::InstanceDef::*;
 965         self.substs.visit_with(visitor) ||
 966         match self.def {
 967             Item(did) | VtableShim(did) | ReifyShim(did) | Intrinsic(did) | Virtual(did, _) => {
 968                 did.visit_with(visitor)
 969             },
 970             FnPtrShim(did, ty) | CloneShim(did, ty) => {
 971                 did.visit_with(visitor) || ty.visit_with(visitor)
 972             },
 973             DropGlue(did, ty) => {
 974                 did.visit_with(visitor) || ty.visit_with(visitor)
 975             },
 976             ClosureOnceShim { call_once } => call_once.visit_with(visitor),
 977         }
 978     }
 979 }
 980
 981 impl<'tcx> TypeFoldable<'tcx> for interpret::GlobalId<'tcx> {
 982     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 983         Self {
 984             instance: self.instance.fold_with(folder),
 985             promoted: self.promoted
 986         }
 987     }
 988
 989     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 990         self.instance.visit_with(visitor)
 991     }
 992 }
 993
 994 impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
 995     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 996         let kind = match self.kind {
 997             ty::RawPtr(tm) => ty::RawPtr(tm.fold_with(folder)),
 998             ty::Array(typ, sz) => ty::Array(typ.fold_with(folder), sz.fold_with(folder)),
 999             ty::Slice(typ) => ty::Slice(typ.fold_with(folder)),
1000             ty::Adt(tid, substs) => ty::Adt(tid, substs.fold_with(folder)),
1001             ty::Dynamic(ref trait_ty, ref region) =>
1002                 ty::Dynamic(trait_ty.fold_with(folder), region.fold_with(folder)),
1003             ty::Tuple(ts) => ty::Tuple(ts.fold_with(folder)),
1004             ty::FnDef(def_id, substs) => {
1005                 ty::FnDef(def_id, substs.fold_with(folder))
1006             }
1007             ty::FnPtr(f) => ty::FnPtr(f.fold_with(folder)),
1008             ty::Ref(ref r, ty, mutbl) => {
1009                 ty::Ref(r.fold_with(folder), ty.fold_with(folder), mutbl)
1010             }
1011             ty::Generator(did, substs, movability) => {
1012                 ty::Generator(
1013                     did,
1014                     substs.fold_with(folder),
1015                     movability)
1016             }
1017             ty::GeneratorWitness(types) => ty::GeneratorWitness(types.fold_with(folder)),
1018             ty::Closure(did, substs) => ty::Closure(did, substs.fold_with(folder)),
1019             ty::Projection(ref data) => ty::Projection(data.fold_with(folder)),
1020             ty::UnnormalizedProjection(ref data) => {
1021                 ty::UnnormalizedProjection(data.fold_with(folder))
1022             }
1023             ty::Opaque(did, substs) => ty::Opaque(did, substs.fold_with(folder)),
1024
1025             ty::Bool |
1026             ty::Char |
1027             ty::Str |
1028             ty::Int(_) |
1029             ty::Uint(_) |
1030             ty::Float(_) |
1031             ty::Error |
1032             ty::Infer(_) |
1033             ty::Param(..) |
1034             ty::Bound(..) |
1035             ty::Placeholder(..) |
1036             ty::Never |
1037             ty::Foreign(..) => return self,
1038         };
1039
1040         if self.kind == kind {
1041             self
1042         } else {
1043             folder.tcx().mk_ty(kind)
1044         }
1045     }
1046
1047     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1048         folder.fold_ty(*self)
1049     }
1050
1051     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1052         match self.kind {
1053             ty::RawPtr(ref tm) => tm.visit_with(visitor),
1054             ty::Array(typ, sz) => typ.visit_with(visitor) || sz.visit_with(visitor),
1055             ty::Slice(typ) => typ.visit_with(visitor),
1056             ty::Adt(_, substs) => substs.visit_with(visitor),
1057             ty::Dynamic(ref trait_ty, ref reg) =>
1058                 trait_ty.visit_with(visitor) || reg.visit_with(visitor),
1059             ty::Tuple(ts) => ts.visit_with(visitor),
1060             ty::FnDef(_, substs) => substs.visit_with(visitor),
1061             ty::FnPtr(ref f) => f.visit_with(visitor),
1062             ty::Ref(r, ty, _) => r.visit_with(visitor) || ty.visit_with(visitor),
1063             ty::Generator(_did, ref substs, _) => {
1064                 substs.visit_with(visitor)
1065             }
1066             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
1067             ty::Closure(_did, ref substs) => substs.visit_with(visitor),
1068             ty::Projection(ref data) | ty::UnnormalizedProjection(ref data) => {
1069                 data.visit_with(visitor)
1070             }
1071             ty::Opaque(_, ref substs) => substs.visit_with(visitor),
1072
1073             ty::Bool |
1074             ty::Char |
1075             ty::Str |
1076             ty::Int(_) |
1077             ty::Uint(_) |
1078             ty::Float(_) |
1079             ty::Error |
1080             ty::Infer(_) |
1081             ty::Bound(..) |
1082             ty::Placeholder(..) |
1083             ty::Param(..) |
1084             ty::Never |
1085             ty::Foreign(..) => false,
1086         }
1087     }
1088
1089     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1090         visitor.visit_ty(self)
1091     }
1092 }
1093
1094 impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
1095     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
1096         *self
1097     }
1098
1099     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1100         folder.fold_region(*self)
1101     }
1102
1103     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
1104         false
1105     }
1106
1107     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1108         visitor.visit_region(*self)
1109     }
1110 }
1111
1112 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
1113     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1114         // This code is hot enough that it's worth specializing for a list of
1115         // length 0. (No other length is common enough to be worth singling
1116         // out).
1117         if self.len() == 0 {
1118             self
1119         } else {
1120             // Don't bother interning if nothing changed, which is the common
1121             // case.
1122             let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
1123             if v[..] == self[..] {
1124                 self
1125             } else {
1126                 folder.tcx().intern_predicates(&v)
1127             }
1128         }
1129     }
1130
1131     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1132         self.iter().any(|p| p.visit_with(visitor))
1133     }
1134 }
1135
1136 impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
1137     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1138         self.iter().map(|x| x.fold_with(folder)).collect()
1139     }
1140
1141     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1142         self.iter().any(|t| t.visit_with(visitor))
1143     }
1144 }
1145
1146 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
1147     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1148         let ty = self.ty.fold_with(folder);
1149         let val = self.val.fold_with(folder);
1150         folder.tcx().mk_const(ty::Const {
1151             ty,
1152             val
1153         })
1154     }
1155
1156     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1157         folder.fold_const(*self)
1158     }
1159
1160     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1161         self.ty.visit_with(visitor) || self.val.visit_with(visitor)
1162     }
1163
1164     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1165         visitor.visit_const(self)
1166     }
1167 }
1168
1169 impl<'tcx> TypeFoldable<'tcx> for ty::ConstKind<'tcx> {
1170     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1171         match *self {
1172             ty::ConstKind::Infer(ic) => ty::ConstKind::Infer(ic.fold_with(folder)),
1173             ty::ConstKind::Param(p) => ty::ConstKind::Param(p.fold_with(folder)),
1174             ty::ConstKind::Unevaluated(did, substs)
1175                 => ty::ConstKind::Unevaluated(did, substs.fold_with(folder)),
1176             ty::ConstKind::Value(_) | ty::ConstKind::Bound(..)
1177             | ty::ConstKind::Placeholder(..) => *self,
1178         }
1179     }
1180
1181     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1182         match *self {
1183             ty::ConstKind::Infer(ic) => ic.visit_with(visitor),
1184             ty::ConstKind::Param(p) => p.visit_with(visitor),
1185             ty::ConstKind::Unevaluated(_, substs) => substs.visit_with(visitor),
1186             ty::ConstKind::Value(_) | ty::ConstKind::Bound(..)
1187             | ty::ConstKind::Placeholder(_) => false,
1188         }
1189     }
1190 }
1191
1192 impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
1193     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
1194         *self
1195     }
1196
1197     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
1198         false
1199     }
1200 }