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