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