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 use syntax::ast;
  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::UpvarId {
  50     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  51         let name = ty::tls::with(|tcx| tcx.hir().name(self.var_path.hir_id));
  52         write!(f, "UpvarId({:?};`{}`;{:?})", self.var_path.hir_id, name, self.closure_expr_id)
  53     }
  54 }
  55
  56 impl fmt::Debug for ty::UpvarBorrow<'tcx> {
  57     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  58         write!(f, "UpvarBorrow({:?}, {:?})", self.kind, self.region)
  59     }
  60 }
  61
  62 impl fmt::Debug for ty::ExistentialTraitRef<'tcx> {
  63     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  64         fmt::Display::fmt(self, f)
  65     }
  66 }
  67
  68 impl fmt::Debug for ty::adjustment::Adjustment<'tcx> {
  69     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  70         write!(f, "{:?} -> {}", self.kind, self.target)
  71     }
  72 }
  73
  74 impl fmt::Debug for ty::BoundRegion {
  75     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  76         match *self {
  77             ty::BrAnon(n) => write!(f, "BrAnon({:?})", n),
  78             ty::BrNamed(did, name) => {
  79                 if did.index == CRATE_DEF_INDEX {
  80                     write!(f, "BrNamed({})", name)
  81                 } else {
  82                     write!(f, "BrNamed({:?}, {})", did, name)
  83                 }
  84             }
  85             ty::BrEnv => write!(f, "BrEnv"),
  86         }
  87     }
  88 }
  89
  90 impl fmt::Debug for ty::RegionKind {
  91     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  92         match *self {
  93             ty::ReEarlyBound(ref data) => write!(f, "ReEarlyBound({}, {})", data.index, data.name),
  94
  95             ty::ReClosureBound(ref vid) => write!(f, "ReClosureBound({:?})", vid),
  96
  97             ty::ReLateBound(binder_id, ref bound_region) => {
  98                 write!(f, "ReLateBound({:?}, {:?})", binder_id, bound_region)
  99             }
 100
 101             ty::ReFree(ref fr) => fr.fmt(f),
 102
 103             ty::ReScope(id) => write!(f, "ReScope({:?})", id),
 104
 105             ty::ReStatic => write!(f, "ReStatic"),
 106
 107             ty::ReVar(ref vid) => vid.fmt(f),
 108
 109             ty::RePlaceholder(placeholder) => write!(f, "RePlaceholder({:?})", placeholder),
 110
 111             ty::ReEmpty => write!(f, "ReEmpty"),
 112
 113             ty::ReErased => write!(f, "ReErased"),
 114         }
 115     }
 116 }
 117
 118 impl fmt::Debug for ty::FreeRegion {
 119     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 120         write!(f, "ReFree({:?}, {:?})", self.scope, self.bound_region)
 121     }
 122 }
 123
 124 impl fmt::Debug for ty::Variance {
 125     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 126         f.write_str(match *self {
 127             ty::Covariant => "+",
 128             ty::Contravariant => "-",
 129             ty::Invariant => "o",
 130             ty::Bivariant => "*",
 131         })
 132     }
 133 }
 134
 135 impl fmt::Debug for ty::FnSig<'tcx> {
 136     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 137         write!(f, "({:?}; c_variadic: {})->{:?}", self.inputs(), self.c_variadic, self.output())
 138     }
 139 }
 140
 141 impl fmt::Debug for ty::TyVid {
 142     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 143         write!(f, "_#{}t", self.index)
 144     }
 145 }
 146
 147 impl<'tcx> fmt::Debug for ty::ConstVid<'tcx> {
 148     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 149         write!(f, "_#{}c", self.index)
 150     }
 151 }
 152
 153 impl fmt::Debug for ty::IntVid {
 154     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 155         write!(f, "_#{}i", self.index)
 156     }
 157 }
 158
 159 impl fmt::Debug for ty::FloatVid {
 160     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 161         write!(f, "_#{}f", self.index)
 162     }
 163 }
 164
 165 impl fmt::Debug for ty::RegionVid {
 166     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 167         write!(f, "'_#{}r", self.index())
 168     }
 169 }
 170
 171 impl fmt::Debug for ty::InferTy {
 172     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 173         match *self {
 174             ty::TyVar(ref v) => v.fmt(f),
 175             ty::IntVar(ref v) => v.fmt(f),
 176             ty::FloatVar(ref v) => v.fmt(f),
 177             ty::FreshTy(v) => write!(f, "FreshTy({:?})", v),
 178             ty::FreshIntTy(v) => write!(f, "FreshIntTy({:?})", v),
 179             ty::FreshFloatTy(v) => write!(f, "FreshFloatTy({:?})", v),
 180         }
 181     }
 182 }
 183
 184 impl fmt::Debug for ty::IntVarValue {
 185     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 186         match *self {
 187             ty::IntType(ref v) => v.fmt(f),
 188             ty::UintType(ref v) => v.fmt(f),
 189         }
 190     }
 191 }
 192
 193 impl fmt::Debug for ty::FloatVarValue {
 194     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 195         self.0.fmt(f)
 196     }
 197 }
 198
 199 impl fmt::Debug for ty::TraitRef<'tcx> {
 200     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 201         fmt::Display::fmt(self, f)
 202     }
 203 }
 204
 205 impl fmt::Debug for Ty<'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::ParamTy {
 212     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 213         write!(f, "{}/#{}", self.name, self.index)
 214     }
 215 }
 216
 217 impl fmt::Debug for ty::ParamConst {
 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::TraitPredicate<'tcx> {
 224     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 225         write!(f, "TraitPredicate({:?})", self.trait_ref)
 226     }
 227 }
 228
 229 impl fmt::Debug for ty::ProjectionPredicate<'tcx> {
 230     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 231         write!(f, "ProjectionPredicate({:?}, {:?})", self.projection_ty, self.ty)
 232     }
 233 }
 234
 235 impl fmt::Debug for ty::Predicate<'tcx> {
 236     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 237         match *self {
 238             ty::Predicate::Trait(ref a, constness) => {
 239                 if let ast::Constness::Const = constness {
 240                     write!(f, "const ")?;
 241                 }
 242                 a.fmt(f)
 243             }
 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, constness) => {
 484                 tcx.lift(binder).map(|binder| ty::Predicate::Trait(binder, constness))
 485             }
 486             ty::Predicate::Subtype(ref binder) => tcx.lift(binder).map(ty::Predicate::Subtype),
 487             ty::Predicate::RegionOutlives(ref binder) => {
 488                 tcx.lift(binder).map(ty::Predicate::RegionOutlives)
 489             }
 490             ty::Predicate::TypeOutlives(ref binder) => {
 491                 tcx.lift(binder).map(ty::Predicate::TypeOutlives)
 492             }
 493             ty::Predicate::Projection(ref binder) => {
 494                 tcx.lift(binder).map(ty::Predicate::Projection)
 495             }
 496             ty::Predicate::WellFormed(ty) => tcx.lift(&ty).map(ty::Predicate::WellFormed),
 497             ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind) => {
 498                 tcx.lift(&closure_substs).map(|closure_substs| {
 499                     ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind)
 500                 })
 501             }
 502             ty::Predicate::ObjectSafe(trait_def_id) => {
 503                 Some(ty::Predicate::ObjectSafe(trait_def_id))
 504             }
 505             ty::Predicate::ConstEvaluatable(def_id, substs) => {
 506                 tcx.lift(&substs).map(|substs| ty::Predicate::ConstEvaluatable(def_id, substs))
 507             }
 508         }
 509     }
 510 }
 511
 512 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::Binder<T> {
 513     type Lifted = ty::Binder<T::Lifted>;
 514     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 515         tcx.lift(self.skip_binder()).map(ty::Binder::bind)
 516     }
 517 }
 518
 519 impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
 520     type Lifted = ty::ParamEnv<'tcx>;
 521     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 522         tcx.lift(&self.caller_bounds).map(|caller_bounds| ty::ParamEnv {
 523             reveal: self.reveal,
 524             caller_bounds,
 525             def_id: self.def_id,
 526         })
 527     }
 528 }
 529
 530 impl<'a, 'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::ParamEnvAnd<'a, T> {
 531     type Lifted = ty::ParamEnvAnd<'tcx, T::Lifted>;
 532     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 533         tcx.lift(&self.param_env).and_then(|param_env| {
 534             tcx.lift(&self.value).map(|value| ty::ParamEnvAnd { param_env, value })
 535         })
 536     }
 537 }
 538
 539 impl<'a, 'tcx> Lift<'tcx> for ty::ClosureSubsts<'a> {
 540     type Lifted = ty::ClosureSubsts<'tcx>;
 541     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 542         tcx.lift(&self.substs).map(|substs| ty::ClosureSubsts { substs })
 543     }
 544 }
 545
 546 impl<'a, 'tcx> Lift<'tcx> for ty::GeneratorSubsts<'a> {
 547     type Lifted = ty::GeneratorSubsts<'tcx>;
 548     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 549         tcx.lift(&self.substs).map(|substs| ty::GeneratorSubsts { substs })
 550     }
 551 }
 552
 553 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjustment<'a> {
 554     type Lifted = ty::adjustment::Adjustment<'tcx>;
 555     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 556         tcx.lift(&self.kind).and_then(|kind| {
 557             tcx.lift(&self.target).map(|target| ty::adjustment::Adjustment { kind, target })
 558         })
 559     }
 560 }
 561
 562 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjust<'a> {
 563     type Lifted = ty::adjustment::Adjust<'tcx>;
 564     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 565         match *self {
 566             ty::adjustment::Adjust::NeverToAny => Some(ty::adjustment::Adjust::NeverToAny),
 567             ty::adjustment::Adjust::Pointer(ptr) => Some(ty::adjustment::Adjust::Pointer(ptr)),
 568             ty::adjustment::Adjust::Deref(ref overloaded) => {
 569                 tcx.lift(overloaded).map(ty::adjustment::Adjust::Deref)
 570             }
 571             ty::adjustment::Adjust::Borrow(ref autoref) => {
 572                 tcx.lift(autoref).map(ty::adjustment::Adjust::Borrow)
 573             }
 574         }
 575     }
 576 }
 577
 578 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::OverloadedDeref<'a> {
 579     type Lifted = ty::adjustment::OverloadedDeref<'tcx>;
 580     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 581         tcx.lift(&self.region)
 582             .map(|region| ty::adjustment::OverloadedDeref { region, mutbl: self.mutbl })
 583     }
 584 }
 585
 586 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::AutoBorrow<'a> {
 587     type Lifted = ty::adjustment::AutoBorrow<'tcx>;
 588     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 589         match *self {
 590             ty::adjustment::AutoBorrow::Ref(r, m) => {
 591                 tcx.lift(&r).map(|r| ty::adjustment::AutoBorrow::Ref(r, m))
 592             }
 593             ty::adjustment::AutoBorrow::RawPtr(m) => Some(ty::adjustment::AutoBorrow::RawPtr(m)),
 594         }
 595     }
 596 }
 597
 598 impl<'a, 'tcx> Lift<'tcx> for ty::GenSig<'a> {
 599     type Lifted = ty::GenSig<'tcx>;
 600     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 601         tcx.lift(&(self.yield_ty, self.return_ty))
 602             .map(|(yield_ty, return_ty)| ty::GenSig { yield_ty, return_ty })
 603     }
 604 }
 605
 606 impl<'a, 'tcx> Lift<'tcx> for ty::FnSig<'a> {
 607     type Lifted = ty::FnSig<'tcx>;
 608     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 609         tcx.lift(&self.inputs_and_output).map(|x| ty::FnSig {
 610             inputs_and_output: x,
 611             c_variadic: self.c_variadic,
 612             unsafety: self.unsafety,
 613             abi: self.abi,
 614         })
 615     }
 616 }
 617
 618 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::error::ExpectedFound<T> {
 619     type Lifted = ty::error::ExpectedFound<T::Lifted>;
 620     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 621         tcx.lift(&self.expected).and_then(|expected| {
 622             tcx.lift(&self.found).map(|found| ty::error::ExpectedFound { expected, found })
 623         })
 624     }
 625 }
 626
 627 impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
 628     type Lifted = ty::error::TypeError<'tcx>;
 629     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 630         use crate::ty::error::TypeError::*;
 631
 632         Some(match *self {
 633             Mismatch => Mismatch,
 634             UnsafetyMismatch(x) => UnsafetyMismatch(x),
 635             AbiMismatch(x) => AbiMismatch(x),
 636             Mutability => Mutability,
 637             TupleSize(x) => TupleSize(x),
 638             FixedArraySize(x) => FixedArraySize(x),
 639             ArgCount => ArgCount,
 640             RegionsDoesNotOutlive(a, b) => {
 641                 return tcx.lift(&(a, b)).map(|(a, b)| RegionsDoesNotOutlive(a, b));
 642             }
 643             RegionsInsufficientlyPolymorphic(a, b) => {
 644                 return tcx.lift(&b).map(|b| RegionsInsufficientlyPolymorphic(a, b));
 645             }
 646             RegionsOverlyPolymorphic(a, b) => {
 647                 return tcx.lift(&b).map(|b| RegionsOverlyPolymorphic(a, b));
 648             }
 649             RegionsPlaceholderMismatch => RegionsPlaceholderMismatch,
 650             IntMismatch(x) => IntMismatch(x),
 651             FloatMismatch(x) => FloatMismatch(x),
 652             Traits(x) => Traits(x),
 653             VariadicMismatch(x) => VariadicMismatch(x),
 654             CyclicTy(t) => return tcx.lift(&t).map(|t| CyclicTy(t)),
 655             ProjectionMismatched(x) => ProjectionMismatched(x),
 656             ProjectionBoundsLength(x) => ProjectionBoundsLength(x),
 657             Sorts(ref x) => return tcx.lift(x).map(Sorts),
 658             ExistentialMismatch(ref x) => return tcx.lift(x).map(ExistentialMismatch),
 659             ConstMismatch(ref x) => return tcx.lift(x).map(ConstMismatch),
 660             IntrinsicCast => IntrinsicCast,
 661             ObjectUnsafeCoercion(ref x) => return tcx.lift(x).map(ObjectUnsafeCoercion),
 662         })
 663     }
 664 }
 665
 666 impl<'a, 'tcx> Lift<'tcx> for ty::InstanceDef<'a> {
 667     type Lifted = ty::InstanceDef<'tcx>;
 668     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 669         match *self {
 670             ty::InstanceDef::Item(def_id) => Some(ty::InstanceDef::Item(def_id)),
 671             ty::InstanceDef::VtableShim(def_id) => Some(ty::InstanceDef::VtableShim(def_id)),
 672             ty::InstanceDef::ReifyShim(def_id) => Some(ty::InstanceDef::ReifyShim(def_id)),
 673             ty::InstanceDef::Intrinsic(def_id) => Some(ty::InstanceDef::Intrinsic(def_id)),
 674             ty::InstanceDef::FnPtrShim(def_id, ref ty) => {
 675                 Some(ty::InstanceDef::FnPtrShim(def_id, tcx.lift(ty)?))
 676             }
 677             ty::InstanceDef::Virtual(def_id, n) => Some(ty::InstanceDef::Virtual(def_id, n)),
 678             ty::InstanceDef::ClosureOnceShim { call_once } => {
 679                 Some(ty::InstanceDef::ClosureOnceShim { call_once })
 680             }
 681             ty::InstanceDef::DropGlue(def_id, ref ty) => {
 682                 Some(ty::InstanceDef::DropGlue(def_id, tcx.lift(ty)?))
 683             }
 684             ty::InstanceDef::CloneShim(def_id, ref ty) => {
 685                 Some(ty::InstanceDef::CloneShim(def_id, tcx.lift(ty)?))
 686             }
 687         }
 688     }
 689 }
 690
 691 ///////////////////////////////////////////////////////////////////////////
 692 // TypeFoldable implementations.
 693 //
 694 // Ideally, each type should invoke `folder.fold_foo(self)` and
 695 // nothing else. In some cases, though, we haven't gotten around to
 696 // adding methods on the `folder` yet, and thus the folding is
 697 // hard-coded here. This is less-flexible, because folders cannot
 698 // override the behavior, but there are a lot of random types and one
 699 // can easily refactor the folding into the TypeFolder trait as
 700 // needed.
 701
 702 /// AdtDefs are basically the same as a DefId.
 703 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::AdtDef {
 704     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
 705         *self
 706     }
 707
 708     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
 709         false
 710     }
 711 }
 712
 713 impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
 714     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> (T, U) {
 715         (self.0.fold_with(folder), self.1.fold_with(folder))
 716     }
 717
 718     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 719         self.0.visit_with(visitor) || self.1.visit_with(visitor)
 720     }
 721 }
 722
 723 EnumTypeFoldableImpl! {
 724     impl<'tcx, T> TypeFoldable<'tcx> for Option<T> {
 725         (Some)(a),
 726         (None),
 727     } where T: TypeFoldable<'tcx>
 728 }
 729
 730 EnumTypeFoldableImpl! {
 731     impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
 732         (Ok)(a),
 733         (Err)(a),
 734     } where T: TypeFoldable<'tcx>, E: TypeFoldable<'tcx>,
 735 }
 736
 737 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
 738     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 739         Rc::new((**self).fold_with(folder))
 740     }
 741
 742     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 743         (**self).visit_with(visitor)
 744     }
 745 }
 746
 747 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
 748     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 749         Arc::new((**self).fold_with(folder))
 750     }
 751
 752     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 753         (**self).visit_with(visitor)
 754     }
 755 }
 756
 757 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
 758     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 759         let content: T = (**self).fold_with(folder);
 760         box content
 761     }
 762
 763     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 764         (**self).visit_with(visitor)
 765     }
 766 }
 767
 768 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
 769     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 770         self.iter().map(|t| t.fold_with(folder)).collect()
 771     }
 772
 773     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 774         self.iter().any(|t| t.visit_with(visitor))
 775     }
 776 }
 777
 778 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
 779     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 780         self.iter().map(|t| t.fold_with(folder)).collect::<Vec<_>>().into_boxed_slice()
 781     }
 782
 783     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 784         self.iter().any(|t| t.visit_with(visitor))
 785     }
 786 }
 787
 788 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<T> {
 789     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 790         self.map_bound_ref(|ty| ty.fold_with(folder))
 791     }
 792
 793     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 794         folder.fold_binder(self)
 795     }
 796
 797     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 798         self.skip_binder().visit_with(visitor)
 799     }
 800
 801     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 802         visitor.visit_binder(self)
 803     }
 804 }
 805
 806 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::ExistentialPredicate<'tcx>> {
 807     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 808         let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
 809         folder.tcx().intern_existential_predicates(&v)
 810     }
 811
 812     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 813         self.iter().any(|p| p.visit_with(visitor))
 814     }
 815 }
 816
 817 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
 818     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 819         let v = self.iter().map(|t| t.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
 820         folder.tcx().intern_type_list(&v)
 821     }
 822
 823     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 824         self.iter().any(|t| t.visit_with(visitor))
 825     }
 826 }
 827
 828 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
 829     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 830         let v = self.iter().map(|t| t.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
 831         folder.tcx().intern_projs(&v)
 832     }
 833
 834     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 835         self.iter().any(|t| t.visit_with(visitor))
 836     }
 837 }
 838
 839 impl<'tcx> TypeFoldable<'tcx> for ty::instance::Instance<'tcx> {
 840     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 841         use crate::ty::InstanceDef::*;
 842         Self {
 843             substs: self.substs.fold_with(folder),
 844             def: match self.def {
 845                 Item(did) => Item(did.fold_with(folder)),
 846                 VtableShim(did) => VtableShim(did.fold_with(folder)),
 847                 ReifyShim(did) => ReifyShim(did.fold_with(folder)),
 848                 Intrinsic(did) => Intrinsic(did.fold_with(folder)),
 849                 FnPtrShim(did, ty) => FnPtrShim(did.fold_with(folder), ty.fold_with(folder)),
 850                 Virtual(did, i) => Virtual(did.fold_with(folder), i),
 851                 ClosureOnceShim { call_once } => {
 852                     ClosureOnceShim { call_once: call_once.fold_with(folder) }
 853                 }
 854                 DropGlue(did, ty) => DropGlue(did.fold_with(folder), ty.fold_with(folder)),
 855                 CloneShim(did, ty) => CloneShim(did.fold_with(folder), ty.fold_with(folder)),
 856             },
 857         }
 858     }
 859
 860     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 861         use crate::ty::InstanceDef::*;
 862         self.substs.visit_with(visitor)
 863             || match self.def {
 864                 Item(did) | VtableShim(did) | ReifyShim(did) | Intrinsic(did) | Virtual(did, _) => {
 865                     did.visit_with(visitor)
 866                 }
 867                 FnPtrShim(did, ty) | CloneShim(did, ty) => {
 868                     did.visit_with(visitor) || ty.visit_with(visitor)
 869                 }
 870                 DropGlue(did, ty) => did.visit_with(visitor) || ty.visit_with(visitor),
 871                 ClosureOnceShim { call_once } => call_once.visit_with(visitor),
 872             }
 873     }
 874 }
 875
 876 impl<'tcx> TypeFoldable<'tcx> for interpret::GlobalId<'tcx> {
 877     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 878         Self { instance: self.instance.fold_with(folder), promoted: self.promoted }
 879     }
 880
 881     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 882         self.instance.visit_with(visitor)
 883     }
 884 }
 885
 886 impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
 887     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 888         let kind = match self.kind {
 889             ty::RawPtr(tm) => ty::RawPtr(tm.fold_with(folder)),
 890             ty::Array(typ, sz) => ty::Array(typ.fold_with(folder), sz.fold_with(folder)),
 891             ty::Slice(typ) => ty::Slice(typ.fold_with(folder)),
 892             ty::Adt(tid, substs) => ty::Adt(tid, substs.fold_with(folder)),
 893             ty::Dynamic(ref trait_ty, ref region) => {
 894                 ty::Dynamic(trait_ty.fold_with(folder), region.fold_with(folder))
 895             }
 896             ty::Tuple(ts) => ty::Tuple(ts.fold_with(folder)),
 897             ty::FnDef(def_id, substs) => ty::FnDef(def_id, substs.fold_with(folder)),
 898             ty::FnPtr(f) => ty::FnPtr(f.fold_with(folder)),
 899             ty::Ref(ref r, ty, mutbl) => ty::Ref(r.fold_with(folder), ty.fold_with(folder), mutbl),
 900             ty::Generator(did, substs, movability) => {
 901                 ty::Generator(did, substs.fold_with(folder), movability)
 902             }
 903             ty::GeneratorWitness(types) => ty::GeneratorWitness(types.fold_with(folder)),
 904             ty::Closure(did, substs) => ty::Closure(did, substs.fold_with(folder)),
 905             ty::Projection(ref data) => ty::Projection(data.fold_with(folder)),
 906             ty::UnnormalizedProjection(ref data) => {
 907                 ty::UnnormalizedProjection(data.fold_with(folder))
 908             }
 909             ty::Opaque(did, substs) => ty::Opaque(did, substs.fold_with(folder)),
 910
 911             ty::Bool
 912             | ty::Char
 913             | ty::Str
 914             | ty::Int(_)
 915             | ty::Uint(_)
 916             | ty::Float(_)
 917             | ty::Error
 918             | ty::Infer(_)
 919             | ty::Param(..)
 920             | ty::Bound(..)
 921             | ty::Placeholder(..)
 922             | ty::Never
 923             | ty::Foreign(..) => return self,
 924         };
 925
 926         if self.kind == kind { self } else { folder.tcx().mk_ty(kind) }
 927     }
 928
 929     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 930         folder.fold_ty(*self)
 931     }
 932
 933     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 934         match self.kind {
 935             ty::RawPtr(ref tm) => tm.visit_with(visitor),
 936             ty::Array(typ, sz) => typ.visit_with(visitor) || sz.visit_with(visitor),
 937             ty::Slice(typ) => typ.visit_with(visitor),
 938             ty::Adt(_, substs) => substs.visit_with(visitor),
 939             ty::Dynamic(ref trait_ty, ref reg) => {
 940                 trait_ty.visit_with(visitor) || reg.visit_with(visitor)
 941             }
 942             ty::Tuple(ts) => ts.visit_with(visitor),
 943             ty::FnDef(_, substs) => substs.visit_with(visitor),
 944             ty::FnPtr(ref f) => f.visit_with(visitor),
 945             ty::Ref(r, ty, _) => r.visit_with(visitor) || ty.visit_with(visitor),
 946             ty::Generator(_did, ref substs, _) => substs.visit_with(visitor),
 947             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
 948             ty::Closure(_did, ref substs) => substs.visit_with(visitor),
 949             ty::Projection(ref data) | ty::UnnormalizedProjection(ref data) => {
 950                 data.visit_with(visitor)
 951             }
 952             ty::Opaque(_, ref substs) => substs.visit_with(visitor),
 953
 954             ty::Bool
 955             | ty::Char
 956             | ty::Str
 957             | ty::Int(_)
 958             | ty::Uint(_)
 959             | ty::Float(_)
 960             | ty::Error
 961             | ty::Infer(_)
 962             | ty::Bound(..)
 963             | ty::Placeholder(..)
 964             | ty::Param(..)
 965             | ty::Never
 966             | ty::Foreign(..) => false,
 967         }
 968     }
 969
 970     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 971         visitor.visit_ty(self)
 972     }
 973 }
 974
 975 impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
 976     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
 977         *self
 978     }
 979
 980     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 981         folder.fold_region(*self)
 982     }
 983
 984     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
 985         false
 986     }
 987
 988     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 989         visitor.visit_region(*self)
 990     }
 991 }
 992
 993 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
 994     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 995         // This code is hot enough that it's worth specializing for a list of
 996         // length 0. (No other length is common enough to be worth singling
 997         // out).
 998         if self.len() == 0 {
 999             self
1000         } else {
1001             // Don't bother interning if nothing changed, which is the common
1002             // case.
1003             let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
1004             if v[..] == self[..] { self } else { folder.tcx().intern_predicates(&v) }
1005         }
1006     }
1007
1008     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1009         self.iter().any(|p| p.visit_with(visitor))
1010     }
1011 }
1012
1013 impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
1014     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1015         self.iter().map(|x| x.fold_with(folder)).collect()
1016     }
1017
1018     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1019         self.iter().any(|t| t.visit_with(visitor))
1020     }
1021 }
1022
1023 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
1024     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1025         let ty = self.ty.fold_with(folder);
1026         let val = self.val.fold_with(folder);
1027         folder.tcx().mk_const(ty::Const { ty, val })
1028     }
1029
1030     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1031         folder.fold_const(*self)
1032     }
1033
1034     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1035         self.ty.visit_with(visitor) || self.val.visit_with(visitor)
1036     }
1037
1038     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1039         visitor.visit_const(self)
1040     }
1041 }
1042
1043 impl<'tcx> TypeFoldable<'tcx> for ty::ConstKind<'tcx> {
1044     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1045         match *self {
1046             ty::ConstKind::Infer(ic) => ty::ConstKind::Infer(ic.fold_with(folder)),
1047             ty::ConstKind::Param(p) => ty::ConstKind::Param(p.fold_with(folder)),
1048             ty::ConstKind::Unevaluated(did, substs, promoted) => {
1049                 ty::ConstKind::Unevaluated(did, substs.fold_with(folder), promoted)
1050             }
1051             ty::ConstKind::Value(_) | ty::ConstKind::Bound(..) | ty::ConstKind::Placeholder(..) => {
1052                 *self
1053             }
1054         }
1055     }
1056
1057     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1058         match *self {
1059             ty::ConstKind::Infer(ic) => ic.visit_with(visitor),
1060             ty::ConstKind::Param(p) => p.visit_with(visitor),
1061             ty::ConstKind::Unevaluated(_, substs, _) => substs.visit_with(visitor),
1062             ty::ConstKind::Value(_) | ty::ConstKind::Bound(..) | ty::ConstKind::Placeholder(_) => {
1063                 false
1064             }
1065         }
1066     }
1067 }
1068
1069 impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
1070     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
1071         *self
1072     }
1073
1074     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
1075         false
1076     }
1077 }