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