src/librustc_middle/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::ReLateBound(binder_id, ref bound_region) => {
  85                 write!(f, "ReLateBound({:?}, {:?})", binder_id, bound_region)
  86             }
  87
  88             ty::ReFree(ref fr) => fr.fmt(f),
  89
  90             ty::ReStatic => write!(f, "ReStatic"),
  91
  92             ty::ReVar(ref vid) => vid.fmt(f),
  93
  94             ty::RePlaceholder(placeholder) => write!(f, "RePlaceholder({:?})", placeholder),
  95
  96             ty::ReEmpty(ui) => write!(f, "ReEmpty({:?})", ui),
  97
  98             ty::ReErased => write!(f, "ReErased"),
  99         }
 100     }
 101 }
 102
 103 impl fmt::Debug for ty::FreeRegion {
 104     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 105         write!(f, "ReFree({:?}, {:?})", self.scope, self.bound_region)
 106     }
 107 }
 108
 109 impl fmt::Debug for ty::Variance {
 110     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 111         f.write_str(match *self {
 112             ty::Covariant => "+",
 113             ty::Contravariant => "-",
 114             ty::Invariant => "o",
 115             ty::Bivariant => "*",
 116         })
 117     }
 118 }
 119
 120 impl fmt::Debug for ty::FnSig<'tcx> {
 121     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 122         write!(f, "({:?}; c_variadic: {})->{:?}", self.inputs(), self.c_variadic, self.output())
 123     }
 124 }
 125
 126 impl fmt::Debug for ty::TyVid {
 127     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 128         write!(f, "_#{}t", self.index)
 129     }
 130 }
 131
 132 impl<'tcx> fmt::Debug for ty::ConstVid<'tcx> {
 133     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 134         write!(f, "_#{}c", self.index)
 135     }
 136 }
 137
 138 impl fmt::Debug for ty::IntVid {
 139     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 140         write!(f, "_#{}i", self.index)
 141     }
 142 }
 143
 144 impl fmt::Debug for ty::FloatVid {
 145     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 146         write!(f, "_#{}f", self.index)
 147     }
 148 }
 149
 150 impl fmt::Debug for ty::RegionVid {
 151     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 152         write!(f, "'_#{}r", self.index())
 153     }
 154 }
 155
 156 impl fmt::Debug for ty::InferTy {
 157     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 158         match *self {
 159             ty::TyVar(ref v) => v.fmt(f),
 160             ty::IntVar(ref v) => v.fmt(f),
 161             ty::FloatVar(ref v) => v.fmt(f),
 162             ty::FreshTy(v) => write!(f, "FreshTy({:?})", v),
 163             ty::FreshIntTy(v) => write!(f, "FreshIntTy({:?})", v),
 164             ty::FreshFloatTy(v) => write!(f, "FreshFloatTy({:?})", v),
 165         }
 166     }
 167 }
 168
 169 impl fmt::Debug for ty::IntVarValue {
 170     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 171         match *self {
 172             ty::IntType(ref v) => v.fmt(f),
 173             ty::UintType(ref v) => v.fmt(f),
 174         }
 175     }
 176 }
 177
 178 impl fmt::Debug for ty::FloatVarValue {
 179     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 180         self.0.fmt(f)
 181     }
 182 }
 183
 184 impl fmt::Debug for ty::TraitRef<'tcx> {
 185     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 186         fmt::Display::fmt(self, f)
 187     }
 188 }
 189
 190 impl fmt::Debug for Ty<'tcx> {
 191     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 192         fmt::Display::fmt(self, f)
 193     }
 194 }
 195
 196 impl fmt::Debug for ty::ParamTy {
 197     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 198         write!(f, "{}/#{}", self.name, self.index)
 199     }
 200 }
 201
 202 impl fmt::Debug for ty::ParamConst {
 203     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 204         write!(f, "{}/#{}", self.name, self.index)
 205     }
 206 }
 207
 208 impl fmt::Debug for ty::TraitPredicate<'tcx> {
 209     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 210         write!(f, "TraitPredicate({:?})", self.trait_ref)
 211     }
 212 }
 213
 214 impl fmt::Debug for ty::ProjectionPredicate<'tcx> {
 215     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 216         write!(f, "ProjectionPredicate({:?}, {:?})", self.projection_ty, self.ty)
 217     }
 218 }
 219
 220 impl fmt::Debug for ty::Predicate<'tcx> {
 221     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 222         write!(f, "{:?}", self.kind())
 223     }
 224 }
 225
 226 impl fmt::Debug for ty::PredicateKind<'tcx> {
 227     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 228         match *self {
 229             ty::PredicateKind::Trait(ref a, constness) => {
 230                 if let hir::Constness::Const = constness {
 231                     write!(f, "const ")?;
 232                 }
 233                 a.fmt(f)
 234             }
 235             ty::PredicateKind::Subtype(ref pair) => pair.fmt(f),
 236             ty::PredicateKind::RegionOutlives(ref pair) => pair.fmt(f),
 237             ty::PredicateKind::TypeOutlives(ref pair) => pair.fmt(f),
 238             ty::PredicateKind::Projection(ref pair) => pair.fmt(f),
 239             ty::PredicateKind::WellFormed(data) => write!(f, "WellFormed({:?})", data),
 240             ty::PredicateKind::ObjectSafe(trait_def_id) => {
 241                 write!(f, "ObjectSafe({:?})", trait_def_id)
 242             }
 243             ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
 244                 write!(f, "ClosureKind({:?}, {:?}, {:?})", closure_def_id, closure_substs, kind)
 245             }
 246             ty::PredicateKind::ConstEvaluatable(def_id, substs) => {
 247                 write!(f, "ConstEvaluatable({:?}, {:?})", def_id, substs)
 248             }
 249             ty::PredicateKind::ConstEquate(c1, c2) => write!(f, "ConstEquate({:?}, {:?})", c1, c2),
 250         }
 251     }
 252 }
 253
 254 ///////////////////////////////////////////////////////////////////////////
 255 // Atomic structs
 256 //
 257 // For things that don't carry any arena-allocated data (and are
 258 // copy...), just add them to this list.
 259
 260 CloneTypeFoldableAndLiftImpls! {
 261     (),
 262     bool,
 263     usize,
 264     ::rustc_target::abi::VariantIdx,
 265     u64,
 266     String,
 267     crate::middle::region::Scope,
 268     ::rustc_ast::ast::FloatTy,
 269     ::rustc_ast::ast::InlineAsmOptions,
 270     ::rustc_ast::ast::InlineAsmTemplatePiece,
 271     ::rustc_ast::ast::NodeId,
 272     ::rustc_span::symbol::Symbol,
 273     ::rustc_hir::def::Res,
 274     ::rustc_hir::def_id::DefId,
 275     ::rustc_hir::LlvmInlineAsmInner,
 276     ::rustc_hir::MatchSource,
 277     ::rustc_hir::Mutability,
 278     ::rustc_hir::Unsafety,
 279     ::rustc_target::asm::InlineAsmRegOrRegClass,
 280     ::rustc_target::spec::abi::Abi,
 281     crate::mir::Local,
 282     crate::mir::Promoted,
 283     crate::traits::Reveal,
 284     crate::ty::adjustment::AutoBorrowMutability,
 285     crate::ty::AdtKind,
 286     // Including `BoundRegion` is a *bit* dubious, but direct
 287     // references to bound region appear in `ty::Error`, and aren't
 288     // really meant to be folded. In general, we can only fold a fully
 289     // general `Region`.
 290     crate::ty::BoundRegion,
 291     crate::ty::Placeholder<crate::ty::BoundRegion>,
 292     crate::ty::ClosureKind,
 293     crate::ty::FreeRegion,
 294     crate::ty::InferTy,
 295     crate::ty::IntVarValue,
 296     crate::ty::ParamConst,
 297     crate::ty::ParamTy,
 298     crate::ty::adjustment::PointerCast,
 299     crate::ty::RegionVid,
 300     crate::ty::UniverseIndex,
 301     crate::ty::Variance,
 302     ::rustc_span::Span,
 303 }
 304
 305 ///////////////////////////////////////////////////////////////////////////
 306 // Lift implementations
 307
 308 // FIXME(eddyb) replace all the uses of `Option::map` with `?`.
 309 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>> Lift<'tcx> for (A, B) {
 310     type Lifted = (A::Lifted, B::Lifted);
 311     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 312         tcx.lift(&self.0).and_then(|a| tcx.lift(&self.1).map(|b| (a, b)))
 313     }
 314 }
 315
 316 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>, C: Lift<'tcx>> Lift<'tcx> for (A, B, C) {
 317     type Lifted = (A::Lifted, B::Lifted, C::Lifted);
 318     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 319         tcx.lift(&self.0)
 320             .and_then(|a| tcx.lift(&self.1).and_then(|b| tcx.lift(&self.2).map(|c| (a, b, c))))
 321     }
 322 }
 323
 324 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Option<T> {
 325     type Lifted = Option<T::Lifted>;
 326     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 327         match *self {
 328             Some(ref x) => tcx.lift(x).map(Some),
 329             None => Some(None),
 330         }
 331     }
 332 }
 333
 334 impl<'tcx, T: Lift<'tcx>, E: Lift<'tcx>> Lift<'tcx> for Result<T, E> {
 335     type Lifted = Result<T::Lifted, E::Lifted>;
 336     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 337         match *self {
 338             Ok(ref x) => tcx.lift(x).map(Ok),
 339             Err(ref e) => tcx.lift(e).map(Err),
 340         }
 341     }
 342 }
 343
 344 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Box<T> {
 345     type Lifted = Box<T::Lifted>;
 346     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 347         tcx.lift(&**self).map(Box::new)
 348     }
 349 }
 350
 351 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Rc<T> {
 352     type Lifted = Rc<T::Lifted>;
 353     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 354         tcx.lift(&**self).map(Rc::new)
 355     }
 356 }
 357
 358 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Arc<T> {
 359     type Lifted = Arc<T::Lifted>;
 360     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 361         tcx.lift(&**self).map(Arc::new)
 362     }
 363 }
 364
 365 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for [T] {
 366     type Lifted = Vec<T::Lifted>;
 367     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 368         // type annotation needed to inform `projection_must_outlive`
 369         let mut result: Vec<<T as Lift<'tcx>>::Lifted> = Vec::with_capacity(self.len());
 370         for x in self {
 371             if let Some(value) = tcx.lift(x) {
 372                 result.push(value);
 373             } else {
 374                 return None;
 375             }
 376         }
 377         Some(result)
 378     }
 379 }
 380
 381 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Vec<T> {
 382     type Lifted = Vec<T::Lifted>;
 383     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 384         tcx.lift(&self[..])
 385     }
 386 }
 387
 388 impl<'tcx, I: Idx, T: Lift<'tcx>> Lift<'tcx> for IndexVec<I, T> {
 389     type Lifted = IndexVec<I, T::Lifted>;
 390     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 391         self.iter().map(|e| tcx.lift(e)).collect()
 392     }
 393 }
 394
 395 impl<'a, 'tcx> Lift<'tcx> for ty::TraitRef<'a> {
 396     type Lifted = ty::TraitRef<'tcx>;
 397     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 398         tcx.lift(&self.substs).map(|substs| ty::TraitRef { def_id: self.def_id, substs })
 399     }
 400 }
 401
 402 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialTraitRef<'a> {
 403     type Lifted = ty::ExistentialTraitRef<'tcx>;
 404     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 405         tcx.lift(&self.substs).map(|substs| ty::ExistentialTraitRef { def_id: self.def_id, substs })
 406     }
 407 }
 408
 409 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialPredicate<'a> {
 410     type Lifted = ty::ExistentialPredicate<'tcx>;
 411     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 412         match self {
 413             ty::ExistentialPredicate::Trait(x) => tcx.lift(x).map(ty::ExistentialPredicate::Trait),
 414             ty::ExistentialPredicate::Projection(x) => {
 415                 tcx.lift(x).map(ty::ExistentialPredicate::Projection)
 416             }
 417             ty::ExistentialPredicate::AutoTrait(def_id) => {
 418                 Some(ty::ExistentialPredicate::AutoTrait(*def_id))
 419             }
 420         }
 421     }
 422 }
 423
 424 impl<'a, 'tcx> Lift<'tcx> for ty::TraitPredicate<'a> {
 425     type Lifted = ty::TraitPredicate<'tcx>;
 426     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::TraitPredicate<'tcx>> {
 427         tcx.lift(&self.trait_ref).map(|trait_ref| ty::TraitPredicate { trait_ref })
 428     }
 429 }
 430
 431 impl<'a, 'tcx> Lift<'tcx> for ty::SubtypePredicate<'a> {
 432     type Lifted = ty::SubtypePredicate<'tcx>;
 433     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::SubtypePredicate<'tcx>> {
 434         tcx.lift(&(self.a, self.b)).map(|(a, b)| ty::SubtypePredicate {
 435             a_is_expected: self.a_is_expected,
 436             a,
 437             b,
 438         })
 439     }
 440 }
 441
 442 impl<'tcx, A: Copy + Lift<'tcx>, B: Copy + Lift<'tcx>> Lift<'tcx> for ty::OutlivesPredicate<A, B> {
 443     type Lifted = ty::OutlivesPredicate<A::Lifted, B::Lifted>;
 444     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 445         tcx.lift(&(self.0, self.1)).map(|(a, b)| ty::OutlivesPredicate(a, b))
 446     }
 447 }
 448
 449 impl<'a, 'tcx> Lift<'tcx> for ty::ProjectionTy<'a> {
 450     type Lifted = ty::ProjectionTy<'tcx>;
 451     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::ProjectionTy<'tcx>> {
 452         tcx.lift(&self.substs)
 453             .map(|substs| ty::ProjectionTy { item_def_id: self.item_def_id, substs })
 454     }
 455 }
 456
 457 impl<'a, 'tcx> Lift<'tcx> for ty::ProjectionPredicate<'a> {
 458     type Lifted = ty::ProjectionPredicate<'tcx>;
 459     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::ProjectionPredicate<'tcx>> {
 460         tcx.lift(&(self.projection_ty, self.ty))
 461             .map(|(projection_ty, ty)| ty::ProjectionPredicate { projection_ty, ty })
 462     }
 463 }
 464
 465 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialProjection<'a> {
 466     type Lifted = ty::ExistentialProjection<'tcx>;
 467     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 468         tcx.lift(&self.substs).map(|substs| ty::ExistentialProjection {
 469             substs,
 470             ty: tcx.lift(&self.ty).expect("type must lift when substs do"),
 471             item_def_id: self.item_def_id,
 472         })
 473     }
 474 }
 475
 476 impl<'a, 'tcx> Lift<'tcx> for ty::PredicateKind<'a> {
 477     type Lifted = ty::PredicateKind<'tcx>;
 478     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 479         match *self {
 480             ty::PredicateKind::Trait(ref binder, constness) => {
 481                 tcx.lift(binder).map(|binder| ty::PredicateKind::Trait(binder, constness))
 482             }
 483             ty::PredicateKind::Subtype(ref binder) => {
 484                 tcx.lift(binder).map(ty::PredicateKind::Subtype)
 485             }
 486             ty::PredicateKind::RegionOutlives(ref binder) => {
 487                 tcx.lift(binder).map(ty::PredicateKind::RegionOutlives)
 488             }
 489             ty::PredicateKind::TypeOutlives(ref binder) => {
 490                 tcx.lift(binder).map(ty::PredicateKind::TypeOutlives)
 491             }
 492             ty::PredicateKind::Projection(ref binder) => {
 493                 tcx.lift(binder).map(ty::PredicateKind::Projection)
 494             }
 495             ty::PredicateKind::WellFormed(ty) => tcx.lift(&ty).map(ty::PredicateKind::WellFormed),
 496             ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
 497                 tcx.lift(&closure_substs).map(|closure_substs| {
 498                     ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind)
 499                 })
 500             }
 501             ty::PredicateKind::ObjectSafe(trait_def_id) => {
 502                 Some(ty::PredicateKind::ObjectSafe(trait_def_id))
 503             }
 504             ty::PredicateKind::ConstEvaluatable(def_id, substs) => {
 505                 tcx.lift(&substs).map(|substs| ty::PredicateKind::ConstEvaluatable(def_id, substs))
 506             }
 507             ty::PredicateKind::ConstEquate(c1, c2) => {
 508                 tcx.lift(&(c1, c2)).map(|(c1, c2)| ty::PredicateKind::ConstEquate(c1, c2))
 509             }
 510         }
 511     }
 512 }
 513
 514 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::Binder<T> {
 515     type Lifted = ty::Binder<T::Lifted>;
 516     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 517         tcx.lift(self.skip_binder()).map(ty::Binder::bind)
 518     }
 519 }
 520
 521 impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
 522     type Lifted = ty::ParamEnv<'tcx>;
 523     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 524         tcx.lift(&self.caller_bounds).map(|caller_bounds| ty::ParamEnv {
 525             reveal: self.reveal,
 526             caller_bounds,
 527             def_id: self.def_id,
 528         })
 529     }
 530 }
 531
 532 impl<'a, 'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::ParamEnvAnd<'a, T> {
 533     type Lifted = ty::ParamEnvAnd<'tcx, T::Lifted>;
 534     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 535         tcx.lift(&self.param_env).and_then(|param_env| {
 536             tcx.lift(&self.value).map(|value| ty::ParamEnvAnd { param_env, value })
 537         })
 538     }
 539 }
 540
 541 impl<'a, 'tcx> Lift<'tcx> for ty::ClosureSubsts<'a> {
 542     type Lifted = ty::ClosureSubsts<'tcx>;
 543     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 544         tcx.lift(&self.substs).map(|substs| ty::ClosureSubsts { substs })
 545     }
 546 }
 547
 548 impl<'a, 'tcx> Lift<'tcx> for ty::GeneratorSubsts<'a> {
 549     type Lifted = ty::GeneratorSubsts<'tcx>;
 550     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 551         tcx.lift(&self.substs).map(|substs| ty::GeneratorSubsts { substs })
 552     }
 553 }
 554
 555 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjustment<'a> {
 556     type Lifted = ty::adjustment::Adjustment<'tcx>;
 557     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 558         tcx.lift(&self.kind).and_then(|kind| {
 559             tcx.lift(&self.target).map(|target| ty::adjustment::Adjustment { kind, target })
 560         })
 561     }
 562 }
 563
 564 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjust<'a> {
 565     type Lifted = ty::adjustment::Adjust<'tcx>;
 566     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 567         match *self {
 568             ty::adjustment::Adjust::NeverToAny => Some(ty::adjustment::Adjust::NeverToAny),
 569             ty::adjustment::Adjust::Pointer(ptr) => Some(ty::adjustment::Adjust::Pointer(ptr)),
 570             ty::adjustment::Adjust::Deref(ref overloaded) => {
 571                 tcx.lift(overloaded).map(ty::adjustment::Adjust::Deref)
 572             }
 573             ty::adjustment::Adjust::Borrow(ref autoref) => {
 574                 tcx.lift(autoref).map(ty::adjustment::Adjust::Borrow)
 575             }
 576         }
 577     }
 578 }
 579
 580 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::OverloadedDeref<'a> {
 581     type Lifted = ty::adjustment::OverloadedDeref<'tcx>;
 582     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 583         tcx.lift(&self.region)
 584             .map(|region| ty::adjustment::OverloadedDeref { region, mutbl: self.mutbl })
 585     }
 586 }
 587
 588 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::AutoBorrow<'a> {
 589     type Lifted = ty::adjustment::AutoBorrow<'tcx>;
 590     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 591         match *self {
 592             ty::adjustment::AutoBorrow::Ref(r, m) => {
 593                 tcx.lift(&r).map(|r| ty::adjustment::AutoBorrow::Ref(r, m))
 594             }
 595             ty::adjustment::AutoBorrow::RawPtr(m) => Some(ty::adjustment::AutoBorrow::RawPtr(m)),
 596         }
 597     }
 598 }
 599
 600 impl<'a, 'tcx> Lift<'tcx> for ty::GenSig<'a> {
 601     type Lifted = ty::GenSig<'tcx>;
 602     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 603         tcx.lift(&(self.resume_ty, self.yield_ty, self.return_ty))
 604             .map(|(resume_ty, yield_ty, return_ty)| ty::GenSig { resume_ty, yield_ty, return_ty })
 605     }
 606 }
 607
 608 impl<'a, 'tcx> Lift<'tcx> for ty::FnSig<'a> {
 609     type Lifted = ty::FnSig<'tcx>;
 610     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 611         tcx.lift(&self.inputs_and_output).map(|x| ty::FnSig {
 612             inputs_and_output: x,
 613             c_variadic: self.c_variadic,
 614             unsafety: self.unsafety,
 615             abi: self.abi,
 616         })
 617     }
 618 }
 619
 620 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::error::ExpectedFound<T> {
 621     type Lifted = ty::error::ExpectedFound<T::Lifted>;
 622     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 623         tcx.lift(&self.expected).and_then(|expected| {
 624             tcx.lift(&self.found).map(|found| ty::error::ExpectedFound { expected, found })
 625         })
 626     }
 627 }
 628
 629 impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
 630     type Lifted = ty::error::TypeError<'tcx>;
 631     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 632         use crate::ty::error::TypeError::*;
 633
 634         Some(match *self {
 635             Mismatch => Mismatch,
 636             UnsafetyMismatch(x) => UnsafetyMismatch(x),
 637             AbiMismatch(x) => AbiMismatch(x),
 638             Mutability => Mutability,
 639             TupleSize(x) => TupleSize(x),
 640             FixedArraySize(x) => FixedArraySize(x),
 641             ArgCount => ArgCount,
 642             RegionsDoesNotOutlive(a, b) => {
 643                 return tcx.lift(&(a, b)).map(|(a, b)| RegionsDoesNotOutlive(a, b));
 644             }
 645             RegionsInsufficientlyPolymorphic(a, b) => {
 646                 return tcx.lift(&b).map(|b| RegionsInsufficientlyPolymorphic(a, b));
 647             }
 648             RegionsOverlyPolymorphic(a, b) => {
 649                 return tcx.lift(&b).map(|b| RegionsOverlyPolymorphic(a, b));
 650             }
 651             RegionsPlaceholderMismatch => RegionsPlaceholderMismatch,
 652             IntMismatch(x) => IntMismatch(x),
 653             FloatMismatch(x) => FloatMismatch(x),
 654             Traits(x) => Traits(x),
 655             VariadicMismatch(x) => VariadicMismatch(x),
 656             CyclicTy(t) => return tcx.lift(&t).map(|t| CyclicTy(t)),
 657             ProjectionMismatched(x) => ProjectionMismatched(x),
 658             ProjectionBoundsLength(x) => ProjectionBoundsLength(x),
 659             Sorts(ref x) => return tcx.lift(x).map(Sorts),
 660             ExistentialMismatch(ref x) => return tcx.lift(x).map(ExistentialMismatch),
 661             ConstMismatch(ref x) => return tcx.lift(x).map(ConstMismatch),
 662             IntrinsicCast => IntrinsicCast,
 663             TargetFeatureCast(ref x) => TargetFeatureCast(*x),
 664             ObjectUnsafeCoercion(ref x) => return tcx.lift(x).map(ObjectUnsafeCoercion),
 665         })
 666     }
 667 }
 668
 669 impl<'a, 'tcx> Lift<'tcx> for ty::InstanceDef<'a> {
 670     type Lifted = ty::InstanceDef<'tcx>;
 671     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 672         match *self {
 673             ty::InstanceDef::Item(def_id) => Some(ty::InstanceDef::Item(def_id)),
 674             ty::InstanceDef::VtableShim(def_id) => Some(ty::InstanceDef::VtableShim(def_id)),
 675             ty::InstanceDef::ReifyShim(def_id) => Some(ty::InstanceDef::ReifyShim(def_id)),
 676             ty::InstanceDef::Intrinsic(def_id) => Some(ty::InstanceDef::Intrinsic(def_id)),
 677             ty::InstanceDef::FnPtrShim(def_id, ref ty) => {
 678                 Some(ty::InstanceDef::FnPtrShim(def_id, tcx.lift(ty)?))
 679             }
 680             ty::InstanceDef::Virtual(def_id, n) => Some(ty::InstanceDef::Virtual(def_id, n)),
 681             ty::InstanceDef::ClosureOnceShim { call_once } => {
 682                 Some(ty::InstanceDef::ClosureOnceShim { call_once })
 683             }
 684             ty::InstanceDef::DropGlue(def_id, ref ty) => {
 685                 Some(ty::InstanceDef::DropGlue(def_id, tcx.lift(ty)?))
 686             }
 687             ty::InstanceDef::CloneShim(def_id, ref ty) => {
 688                 Some(ty::InstanceDef::CloneShim(def_id, tcx.lift(ty)?))
 689             }
 690         }
 691     }
 692 }
 693
 694 ///////////////////////////////////////////////////////////////////////////
 695 // TypeFoldable implementations.
 696 //
 697 // Ideally, each type should invoke `folder.fold_foo(self)` and
 698 // nothing else. In some cases, though, we haven't gotten around to
 699 // adding methods on the `folder` yet, and thus the folding is
 700 // hard-coded here. This is less-flexible, because folders cannot
 701 // override the behavior, but there are a lot of random types and one
 702 // can easily refactor the folding into the TypeFolder trait as
 703 // needed.
 704
 705 /// AdtDefs are basically the same as a DefId.
 706 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::AdtDef {
 707     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
 708         *self
 709     }
 710
 711     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
 712         false
 713     }
 714 }
 715
 716 impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
 717     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> (T, U) {
 718         (self.0.fold_with(folder), self.1.fold_with(folder))
 719     }
 720
 721     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 722         self.0.visit_with(visitor) || self.1.visit_with(visitor)
 723     }
 724 }
 725
 726 EnumTypeFoldableImpl! {
 727     impl<'tcx, T> TypeFoldable<'tcx> for Option<T> {
 728         (Some)(a),
 729         (None),
 730     } where T: TypeFoldable<'tcx>
 731 }
 732
 733 EnumTypeFoldableImpl! {
 734     impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
 735         (Ok)(a),
 736         (Err)(a),
 737     } where T: TypeFoldable<'tcx>, E: TypeFoldable<'tcx>,
 738 }
 739
 740 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
 741     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 742         Rc::new((**self).fold_with(folder))
 743     }
 744
 745     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 746         (**self).visit_with(visitor)
 747     }
 748 }
 749
 750 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
 751     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 752         Arc::new((**self).fold_with(folder))
 753     }
 754
 755     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 756         (**self).visit_with(visitor)
 757     }
 758 }
 759
 760 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
 761     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 762         let content: T = (**self).fold_with(folder);
 763         box content
 764     }
 765
 766     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 767         (**self).visit_with(visitor)
 768     }
 769 }
 770
 771 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
 772     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 773         self.iter().map(|t| t.fold_with(folder)).collect()
 774     }
 775
 776     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 777         self.iter().any(|t| t.visit_with(visitor))
 778     }
 779 }
 780
 781 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
 782     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 783         self.iter().map(|t| t.fold_with(folder)).collect::<Vec<_>>().into_boxed_slice()
 784     }
 785
 786     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 787         self.iter().any(|t| t.visit_with(visitor))
 788     }
 789 }
 790
 791 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<T> {
 792     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 793         self.map_bound_ref(|ty| ty.fold_with(folder))
 794     }
 795
 796     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 797         folder.fold_binder(self)
 798     }
 799
 800     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 801         self.skip_binder().visit_with(visitor)
 802     }
 803
 804     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 805         visitor.visit_binder(self)
 806     }
 807 }
 808
 809 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::ExistentialPredicate<'tcx>> {
 810     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 811         fold_list(*self, folder, |tcx, v| tcx.intern_existential_predicates(v))
 812     }
 813
 814     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 815         self.iter().any(|p| p.visit_with(visitor))
 816     }
 817 }
 818
 819 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
 820     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 821         fold_list(*self, folder, |tcx, v| tcx.intern_type_list(v))
 822     }
 823
 824     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 825         self.iter().any(|t| t.visit_with(visitor))
 826     }
 827 }
 828
 829 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
 830     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 831         fold_list(*self, folder, |tcx, v| 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::Opaque(did, substs) => ty::Opaque(did, substs.fold_with(folder)),
 907
 908             ty::Bool
 909             | ty::Char
 910             | ty::Str
 911             | ty::Int(_)
 912             | ty::Uint(_)
 913             | ty::Float(_)
 914             | ty::Error(_)
 915             | ty::Infer(_)
 916             | ty::Param(..)
 917             | ty::Bound(..)
 918             | ty::Placeholder(..)
 919             | ty::Never
 920             | ty::Foreign(..) => return self,
 921         };
 922
 923         if self.kind == kind { self } else { folder.tcx().mk_ty(kind) }
 924     }
 925
 926     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 927         folder.fold_ty(*self)
 928     }
 929
 930     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 931         match self.kind {
 932             ty::RawPtr(ref tm) => tm.visit_with(visitor),
 933             ty::Array(typ, sz) => typ.visit_with(visitor) || sz.visit_with(visitor),
 934             ty::Slice(typ) => typ.visit_with(visitor),
 935             ty::Adt(_, substs) => substs.visit_with(visitor),
 936             ty::Dynamic(ref trait_ty, ref reg) => {
 937                 trait_ty.visit_with(visitor) || reg.visit_with(visitor)
 938             }
 939             ty::Tuple(ts) => ts.visit_with(visitor),
 940             ty::FnDef(_, substs) => substs.visit_with(visitor),
 941             ty::FnPtr(ref f) => f.visit_with(visitor),
 942             ty::Ref(r, ty, _) => r.visit_with(visitor) || ty.visit_with(visitor),
 943             ty::Generator(_did, ref substs, _) => substs.visit_with(visitor),
 944             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
 945             ty::Closure(_did, ref substs) => substs.visit_with(visitor),
 946             ty::Projection(ref data) => data.visit_with(visitor),
 947             ty::Opaque(_, ref substs) => substs.visit_with(visitor),
 948
 949             ty::Bool
 950             | ty::Char
 951             | ty::Str
 952             | ty::Int(_)
 953             | ty::Uint(_)
 954             | ty::Float(_)
 955             | ty::Error(_)
 956             | ty::Infer(_)
 957             | ty::Bound(..)
 958             | ty::Placeholder(..)
 959             | ty::Param(..)
 960             | ty::Never
 961             | ty::Foreign(..) => false,
 962         }
 963     }
 964
 965     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 966         visitor.visit_ty(self)
 967     }
 968 }
 969
 970 impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
 971     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
 972         *self
 973     }
 974
 975     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 976         folder.fold_region(*self)
 977     }
 978
 979     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
 980         false
 981     }
 982
 983     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 984         visitor.visit_region(*self)
 985     }
 986 }
 987
 988 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
 989     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 990         let new = ty::PredicateKind::super_fold_with(self.kind, folder);
 991         if new != *self.kind { folder.tcx().mk_predicate(new) } else { *self }
 992     }
 993
 994     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 995         ty::PredicateKind::super_visit_with(self.kind, visitor)
 996     }
 997 }
 998
 999 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
1000     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1001         fold_list(*self, folder, |tcx, v| tcx.intern_predicates(v))
1002     }
1003
1004     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1005         self.iter().any(|p| p.visit_with(visitor))
1006     }
1007 }
1008
1009 impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
1010     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1011         self.iter().map(|x| x.fold_with(folder)).collect()
1012     }
1013
1014     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1015         self.iter().any(|t| t.visit_with(visitor))
1016     }
1017 }
1018
1019 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
1020     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1021         let ty = self.ty.fold_with(folder);
1022         let val = self.val.fold_with(folder);
1023         if ty != self.ty || val != self.val {
1024             folder.tcx().mk_const(ty::Const { ty, val })
1025         } else {
1026             *self
1027         }
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(_)
1052             | ty::ConstKind::Bound(..)
1053             | ty::ConstKind::Placeholder(..)
1054             | ty::ConstKind::Error(_) => *self,
1055         }
1056     }
1057
1058     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1059         match *self {
1060             ty::ConstKind::Infer(ic) => ic.visit_with(visitor),
1061             ty::ConstKind::Param(p) => p.visit_with(visitor),
1062             ty::ConstKind::Unevaluated(_, substs, _) => substs.visit_with(visitor),
1063             ty::ConstKind::Value(_)
1064             | ty::ConstKind::Bound(..)
1065             | ty::ConstKind::Placeholder(_)
1066             | ty::ConstKind::Error(_) => false,
1067         }
1068     }
1069 }
1070
1071 impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
1072     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
1073         *self
1074     }
1075
1076     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
1077         false
1078     }
1079 }
1080
1081 // Does the equivalent of
1082 // ```
1083 // let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
1084 // folder.tcx().intern_*(&v)
1085 // ```
1086 fn fold_list<'tcx, F, T>(
1087     list: &'tcx ty::List<T>,
1088     folder: &mut F,
1089     intern: impl FnOnce(TyCtxt<'tcx>, &[T]) -> &'tcx ty::List<T>,
1090 ) -> &'tcx ty::List<T>
1091 where
1092     F: TypeFolder<'tcx>,
1093     T: TypeFoldable<'tcx> + PartialEq + Copy,
1094 {
1095     let mut iter = list.iter();
1096     // Look for the first element that changed
1097     if let Some((i, new_t)) = iter.by_ref().enumerate().find_map(|(i, t)| {
1098         let new_t = t.fold_with(folder);
1099         if new_t == t { None } else { Some((i, new_t)) }
1100     }) {
1101         // An element changed, prepare to intern the resulting list
1102         let mut new_list = SmallVec::<[_; 8]>::with_capacity(list.len());
1103         new_list.extend_from_slice(&list[..i]);
1104         new_list.push(new_t);
1105         new_list.extend(iter.map(|t| t.fold_with(folder)));
1106         intern(folder.tcx(), &new_list)
1107     } else {
1108         list
1109     }
1110 }