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