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     u32,
 266     u64,
 267     String,
 268     crate::middle::region::Scope,
 269     ::rustc_ast::ast::FloatTy,
 270     ::rustc_ast::ast::InlineAsmOptions,
 271     ::rustc_ast::ast::InlineAsmTemplatePiece,
 272     ::rustc_ast::ast::NodeId,
 273     ::rustc_span::symbol::Symbol,
 274     ::rustc_hir::def::Res,
 275     ::rustc_hir::def_id::DefId,
 276     ::rustc_hir::LlvmInlineAsmInner,
 277     ::rustc_hir::MatchSource,
 278     ::rustc_hir::Mutability,
 279     ::rustc_hir::Unsafety,
 280     ::rustc_target::asm::InlineAsmRegOrRegClass,
 281     ::rustc_target::spec::abi::Abi,
 282     crate::mir::Local,
 283     crate::mir::Promoted,
 284     crate::traits::Reveal,
 285     crate::ty::adjustment::AutoBorrowMutability,
 286     crate::ty::AdtKind,
 287     // Including `BoundRegion` is a *bit* dubious, but direct
 288     // references to bound region appear in `ty::Error`, and aren't
 289     // really meant to be folded. In general, we can only fold a fully
 290     // general `Region`.
 291     crate::ty::BoundRegion,
 292     crate::ty::Placeholder<crate::ty::BoundRegion>,
 293     crate::ty::ClosureKind,
 294     crate::ty::FreeRegion,
 295     crate::ty::InferTy,
 296     crate::ty::IntVarValue,
 297     crate::ty::ParamConst,
 298     crate::ty::ParamTy,
 299     crate::ty::adjustment::PointerCast,
 300     crate::ty::RegionVid,
 301     crate::ty::UniverseIndex,
 302     crate::ty::Variance,
 303     ::rustc_span::Span,
 304 }
 305
 306 ///////////////////////////////////////////////////////////////////////////
 307 // Lift implementations
 308
 309 // FIXME(eddyb) replace all the uses of `Option::map` with `?`.
 310 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>> Lift<'tcx> for (A, B) {
 311     type Lifted = (A::Lifted, B::Lifted);
 312     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 313         tcx.lift(&self.0).and_then(|a| tcx.lift(&self.1).map(|b| (a, b)))
 314     }
 315 }
 316
 317 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>, C: Lift<'tcx>> Lift<'tcx> for (A, B, C) {
 318     type Lifted = (A::Lifted, B::Lifted, C::Lifted);
 319     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 320         tcx.lift(&self.0)
 321             .and_then(|a| tcx.lift(&self.1).and_then(|b| tcx.lift(&self.2).map(|c| (a, b, c))))
 322     }
 323 }
 324
 325 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Option<T> {
 326     type Lifted = Option<T::Lifted>;
 327     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 328         match *self {
 329             Some(ref x) => tcx.lift(x).map(Some),
 330             None => Some(None),
 331         }
 332     }
 333 }
 334
 335 impl<'tcx, T: Lift<'tcx>, E: Lift<'tcx>> Lift<'tcx> for Result<T, E> {
 336     type Lifted = Result<T::Lifted, E::Lifted>;
 337     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 338         match *self {
 339             Ok(ref x) => tcx.lift(x).map(Ok),
 340             Err(ref e) => tcx.lift(e).map(Err),
 341         }
 342     }
 343 }
 344
 345 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Box<T> {
 346     type Lifted = Box<T::Lifted>;
 347     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 348         tcx.lift(&**self).map(Box::new)
 349     }
 350 }
 351
 352 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Rc<T> {
 353     type Lifted = Rc<T::Lifted>;
 354     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 355         tcx.lift(&**self).map(Rc::new)
 356     }
 357 }
 358
 359 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Arc<T> {
 360     type Lifted = Arc<T::Lifted>;
 361     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 362         tcx.lift(&**self).map(Arc::new)
 363     }
 364 }
 365
 366 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for [T] {
 367     type Lifted = Vec<T::Lifted>;
 368     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 369         // type annotation needed to inform `projection_must_outlive`
 370         let mut result: Vec<<T as Lift<'tcx>>::Lifted> = Vec::with_capacity(self.len());
 371         for x in self {
 372             if let Some(value) = tcx.lift(x) {
 373                 result.push(value);
 374             } else {
 375                 return None;
 376             }
 377         }
 378         Some(result)
 379     }
 380 }
 381
 382 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Vec<T> {
 383     type Lifted = Vec<T::Lifted>;
 384     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 385         tcx.lift(&self[..])
 386     }
 387 }
 388
 389 impl<'tcx, I: Idx, T: Lift<'tcx>> Lift<'tcx> for IndexVec<I, T> {
 390     type Lifted = IndexVec<I, T::Lifted>;
 391     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 392         self.iter().map(|e| tcx.lift(e)).collect()
 393     }
 394 }
 395
 396 impl<'a, 'tcx> Lift<'tcx> for ty::TraitRef<'a> {
 397     type Lifted = ty::TraitRef<'tcx>;
 398     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 399         tcx.lift(&self.substs).map(|substs| ty::TraitRef { def_id: self.def_id, substs })
 400     }
 401 }
 402
 403 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialTraitRef<'a> {
 404     type Lifted = ty::ExistentialTraitRef<'tcx>;
 405     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 406         tcx.lift(&self.substs).map(|substs| ty::ExistentialTraitRef { def_id: self.def_id, substs })
 407     }
 408 }
 409
 410 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialPredicate<'a> {
 411     type Lifted = ty::ExistentialPredicate<'tcx>;
 412     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 413         match self {
 414             ty::ExistentialPredicate::Trait(x) => tcx.lift(x).map(ty::ExistentialPredicate::Trait),
 415             ty::ExistentialPredicate::Projection(x) => {
 416                 tcx.lift(x).map(ty::ExistentialPredicate::Projection)
 417             }
 418             ty::ExistentialPredicate::AutoTrait(def_id) => {
 419                 Some(ty::ExistentialPredicate::AutoTrait(*def_id))
 420             }
 421         }
 422     }
 423 }
 424
 425 impl<'a, 'tcx> Lift<'tcx> for ty::TraitPredicate<'a> {
 426     type Lifted = ty::TraitPredicate<'tcx>;
 427     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::TraitPredicate<'tcx>> {
 428         tcx.lift(&self.trait_ref).map(|trait_ref| ty::TraitPredicate { trait_ref })
 429     }
 430 }
 431
 432 impl<'a, 'tcx> Lift<'tcx> for ty::SubtypePredicate<'a> {
 433     type Lifted = ty::SubtypePredicate<'tcx>;
 434     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::SubtypePredicate<'tcx>> {
 435         tcx.lift(&(self.a, self.b)).map(|(a, b)| ty::SubtypePredicate {
 436             a_is_expected: self.a_is_expected,
 437             a,
 438             b,
 439         })
 440     }
 441 }
 442
 443 impl<'tcx, A: Copy + Lift<'tcx>, B: Copy + Lift<'tcx>> Lift<'tcx> for ty::OutlivesPredicate<A, B> {
 444     type Lifted = ty::OutlivesPredicate<A::Lifted, B::Lifted>;
 445     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 446         tcx.lift(&(self.0, self.1)).map(|(a, b)| ty::OutlivesPredicate(a, b))
 447     }
 448 }
 449
 450 impl<'a, 'tcx> Lift<'tcx> for ty::ProjectionTy<'a> {
 451     type Lifted = ty::ProjectionTy<'tcx>;
 452     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::ProjectionTy<'tcx>> {
 453         tcx.lift(&self.substs)
 454             .map(|substs| ty::ProjectionTy { item_def_id: self.item_def_id, substs })
 455     }
 456 }
 457
 458 impl<'a, 'tcx> Lift<'tcx> for ty::ProjectionPredicate<'a> {
 459     type Lifted = ty::ProjectionPredicate<'tcx>;
 460     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<ty::ProjectionPredicate<'tcx>> {
 461         tcx.lift(&(self.projection_ty, self.ty))
 462             .map(|(projection_ty, ty)| ty::ProjectionPredicate { projection_ty, ty })
 463     }
 464 }
 465
 466 impl<'a, 'tcx> Lift<'tcx> for ty::ExistentialProjection<'a> {
 467     type Lifted = ty::ExistentialProjection<'tcx>;
 468     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 469         tcx.lift(&self.substs).map(|substs| ty::ExistentialProjection {
 470             substs,
 471             ty: tcx.lift(&self.ty).expect("type must lift when substs do"),
 472             item_def_id: self.item_def_id,
 473         })
 474     }
 475 }
 476
 477 impl<'a, 'tcx> Lift<'tcx> for ty::PredicateKind<'a> {
 478     type Lifted = ty::PredicateKind<'tcx>;
 479     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 480         match *self {
 481             ty::PredicateKind::Trait(ref binder, constness) => {
 482                 tcx.lift(binder).map(|binder| ty::PredicateKind::Trait(binder, constness))
 483             }
 484             ty::PredicateKind::Subtype(ref binder) => {
 485                 tcx.lift(binder).map(ty::PredicateKind::Subtype)
 486             }
 487             ty::PredicateKind::RegionOutlives(ref binder) => {
 488                 tcx.lift(binder).map(ty::PredicateKind::RegionOutlives)
 489             }
 490             ty::PredicateKind::TypeOutlives(ref binder) => {
 491                 tcx.lift(binder).map(ty::PredicateKind::TypeOutlives)
 492             }
 493             ty::PredicateKind::Projection(ref binder) => {
 494                 tcx.lift(binder).map(ty::PredicateKind::Projection)
 495             }
 496             ty::PredicateKind::WellFormed(ty) => tcx.lift(&ty).map(ty::PredicateKind::WellFormed),
 497             ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
 498                 tcx.lift(&closure_substs).map(|closure_substs| {
 499                     ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind)
 500                 })
 501             }
 502             ty::PredicateKind::ObjectSafe(trait_def_id) => {
 503                 Some(ty::PredicateKind::ObjectSafe(trait_def_id))
 504             }
 505             ty::PredicateKind::ConstEvaluatable(def_id, substs) => {
 506                 tcx.lift(&substs).map(|substs| ty::PredicateKind::ConstEvaluatable(def_id, substs))
 507             }
 508             ty::PredicateKind::ConstEquate(c1, c2) => {
 509                 tcx.lift(&(c1, c2)).map(|(c1, c2)| ty::PredicateKind::ConstEquate(c1, c2))
 510             }
 511         }
 512     }
 513 }
 514
 515 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::Binder<T> {
 516     type Lifted = ty::Binder<T::Lifted>;
 517     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 518         tcx.lift(self.skip_binder()).map(ty::Binder::bind)
 519     }
 520 }
 521
 522 impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
 523     type Lifted = ty::ParamEnv<'tcx>;
 524     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 525         tcx.lift(&self.caller_bounds).map(|caller_bounds| ty::ParamEnv {
 526             reveal: self.reveal,
 527             caller_bounds,
 528             def_id: self.def_id,
 529         })
 530     }
 531 }
 532
 533 impl<'a, 'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::ParamEnvAnd<'a, T> {
 534     type Lifted = ty::ParamEnvAnd<'tcx, T::Lifted>;
 535     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 536         tcx.lift(&self.param_env).and_then(|param_env| {
 537             tcx.lift(&self.value).map(|value| ty::ParamEnvAnd { param_env, value })
 538         })
 539     }
 540 }
 541
 542 impl<'a, 'tcx> Lift<'tcx> for ty::ClosureSubsts<'a> {
 543     type Lifted = ty::ClosureSubsts<'tcx>;
 544     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 545         tcx.lift(&self.substs).map(|substs| ty::ClosureSubsts { substs })
 546     }
 547 }
 548
 549 impl<'a, 'tcx> Lift<'tcx> for ty::GeneratorSubsts<'a> {
 550     type Lifted = ty::GeneratorSubsts<'tcx>;
 551     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 552         tcx.lift(&self.substs).map(|substs| ty::GeneratorSubsts { substs })
 553     }
 554 }
 555
 556 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjustment<'a> {
 557     type Lifted = ty::adjustment::Adjustment<'tcx>;
 558     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 559         tcx.lift(&self.kind).and_then(|kind| {
 560             tcx.lift(&self.target).map(|target| ty::adjustment::Adjustment { kind, target })
 561         })
 562     }
 563 }
 564
 565 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::Adjust<'a> {
 566     type Lifted = ty::adjustment::Adjust<'tcx>;
 567     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 568         match *self {
 569             ty::adjustment::Adjust::NeverToAny => Some(ty::adjustment::Adjust::NeverToAny),
 570             ty::adjustment::Adjust::Pointer(ptr) => Some(ty::adjustment::Adjust::Pointer(ptr)),
 571             ty::adjustment::Adjust::Deref(ref overloaded) => {
 572                 tcx.lift(overloaded).map(ty::adjustment::Adjust::Deref)
 573             }
 574             ty::adjustment::Adjust::Borrow(ref autoref) => {
 575                 tcx.lift(autoref).map(ty::adjustment::Adjust::Borrow)
 576             }
 577         }
 578     }
 579 }
 580
 581 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::OverloadedDeref<'a> {
 582     type Lifted = ty::adjustment::OverloadedDeref<'tcx>;
 583     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 584         tcx.lift(&self.region)
 585             .map(|region| ty::adjustment::OverloadedDeref { region, mutbl: self.mutbl })
 586     }
 587 }
 588
 589 impl<'a, 'tcx> Lift<'tcx> for ty::adjustment::AutoBorrow<'a> {
 590     type Lifted = ty::adjustment::AutoBorrow<'tcx>;
 591     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 592         match *self {
 593             ty::adjustment::AutoBorrow::Ref(r, m) => {
 594                 tcx.lift(&r).map(|r| ty::adjustment::AutoBorrow::Ref(r, m))
 595             }
 596             ty::adjustment::AutoBorrow::RawPtr(m) => Some(ty::adjustment::AutoBorrow::RawPtr(m)),
 597         }
 598     }
 599 }
 600
 601 impl<'a, 'tcx> Lift<'tcx> for ty::GenSig<'a> {
 602     type Lifted = ty::GenSig<'tcx>;
 603     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 604         tcx.lift(&(self.resume_ty, self.yield_ty, self.return_ty))
 605             .map(|(resume_ty, yield_ty, return_ty)| ty::GenSig { resume_ty, yield_ty, return_ty })
 606     }
 607 }
 608
 609 impl<'a, 'tcx> Lift<'tcx> for ty::FnSig<'a> {
 610     type Lifted = ty::FnSig<'tcx>;
 611     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 612         tcx.lift(&self.inputs_and_output).map(|x| ty::FnSig {
 613             inputs_and_output: x,
 614             c_variadic: self.c_variadic,
 615             unsafety: self.unsafety,
 616             abi: self.abi,
 617         })
 618     }
 619 }
 620
 621 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for ty::error::ExpectedFound<T> {
 622     type Lifted = ty::error::ExpectedFound<T::Lifted>;
 623     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 624         tcx.lift(&self.expected).and_then(|expected| {
 625             tcx.lift(&self.found).map(|found| ty::error::ExpectedFound { expected, found })
 626         })
 627     }
 628 }
 629
 630 impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
 631     type Lifted = ty::error::TypeError<'tcx>;
 632     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 633         use crate::ty::error::TypeError::*;
 634
 635         Some(match *self {
 636             Mismatch => Mismatch,
 637             UnsafetyMismatch(x) => UnsafetyMismatch(x),
 638             AbiMismatch(x) => AbiMismatch(x),
 639             Mutability => Mutability,
 640             TupleSize(x) => TupleSize(x),
 641             FixedArraySize(x) => FixedArraySize(x),
 642             ArgCount => ArgCount,
 643             RegionsDoesNotOutlive(a, b) => {
 644                 return tcx.lift(&(a, b)).map(|(a, b)| RegionsDoesNotOutlive(a, b));
 645             }
 646             RegionsInsufficientlyPolymorphic(a, b) => {
 647                 return tcx.lift(&b).map(|b| RegionsInsufficientlyPolymorphic(a, b));
 648             }
 649             RegionsOverlyPolymorphic(a, b) => {
 650                 return tcx.lift(&b).map(|b| RegionsOverlyPolymorphic(a, b));
 651             }
 652             RegionsPlaceholderMismatch => RegionsPlaceholderMismatch,
 653             IntMismatch(x) => IntMismatch(x),
 654             FloatMismatch(x) => FloatMismatch(x),
 655             Traits(x) => Traits(x),
 656             VariadicMismatch(x) => VariadicMismatch(x),
 657             CyclicTy(t) => return tcx.lift(&t).map(|t| CyclicTy(t)),
 658             ProjectionMismatched(x) => ProjectionMismatched(x),
 659             ProjectionBoundsLength(x) => ProjectionBoundsLength(x),
 660             Sorts(ref x) => return tcx.lift(x).map(Sorts),
 661             ExistentialMismatch(ref x) => return tcx.lift(x).map(ExistentialMismatch),
 662             ConstMismatch(ref x) => return tcx.lift(x).map(ConstMismatch),
 663             IntrinsicCast => IntrinsicCast,
 664             TargetFeatureCast(ref x) => TargetFeatureCast(*x),
 665             ObjectUnsafeCoercion(ref x) => return tcx.lift(x).map(ObjectUnsafeCoercion),
 666         })
 667     }
 668 }
 669
 670 impl<'a, 'tcx> Lift<'tcx> for ty::InstanceDef<'a> {
 671     type Lifted = ty::InstanceDef<'tcx>;
 672     fn lift_to_tcx(&self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 673         match *self {
 674             ty::InstanceDef::Item(def_id) => Some(ty::InstanceDef::Item(def_id)),
 675             ty::InstanceDef::VtableShim(def_id) => Some(ty::InstanceDef::VtableShim(def_id)),
 676             ty::InstanceDef::ReifyShim(def_id) => Some(ty::InstanceDef::ReifyShim(def_id)),
 677             ty::InstanceDef::Intrinsic(def_id) => Some(ty::InstanceDef::Intrinsic(def_id)),
 678             ty::InstanceDef::FnPtrShim(def_id, ref ty) => {
 679                 Some(ty::InstanceDef::FnPtrShim(def_id, tcx.lift(ty)?))
 680             }
 681             ty::InstanceDef::Virtual(def_id, n) => Some(ty::InstanceDef::Virtual(def_id, n)),
 682             ty::InstanceDef::ClosureOnceShim { call_once } => {
 683                 Some(ty::InstanceDef::ClosureOnceShim { call_once })
 684             }
 685             ty::InstanceDef::DropGlue(def_id, ref ty) => {
 686                 Some(ty::InstanceDef::DropGlue(def_id, tcx.lift(ty)?))
 687             }
 688             ty::InstanceDef::CloneShim(def_id, ref ty) => {
 689                 Some(ty::InstanceDef::CloneShim(def_id, tcx.lift(ty)?))
 690             }
 691         }
 692     }
 693 }
 694
 695 ///////////////////////////////////////////////////////////////////////////
 696 // TypeFoldable implementations.
 697 //
 698 // Ideally, each type should invoke `folder.fold_foo(self)` and
 699 // nothing else. In some cases, though, we haven't gotten around to
 700 // adding methods on the `folder` yet, and thus the folding is
 701 // hard-coded here. This is less-flexible, because folders cannot
 702 // override the behavior, but there are a lot of random types and one
 703 // can easily refactor the folding into the TypeFolder trait as
 704 // needed.
 705
 706 /// AdtDefs are basically the same as a DefId.
 707 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::AdtDef {
 708     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
 709         *self
 710     }
 711
 712     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
 713         false
 714     }
 715 }
 716
 717 impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
 718     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> (T, U) {
 719         (self.0.fold_with(folder), self.1.fold_with(folder))
 720     }
 721
 722     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 723         self.0.visit_with(visitor) || self.1.visit_with(visitor)
 724     }
 725 }
 726
 727 EnumTypeFoldableImpl! {
 728     impl<'tcx, T> TypeFoldable<'tcx> for Option<T> {
 729         (Some)(a),
 730         (None),
 731     } where T: TypeFoldable<'tcx>
 732 }
 733
 734 EnumTypeFoldableImpl! {
 735     impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
 736         (Ok)(a),
 737         (Err)(a),
 738     } where T: TypeFoldable<'tcx>, E: TypeFoldable<'tcx>,
 739 }
 740
 741 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
 742     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 743         Rc::new((**self).fold_with(folder))
 744     }
 745
 746     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 747         (**self).visit_with(visitor)
 748     }
 749 }
 750
 751 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
 752     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 753         Arc::new((**self).fold_with(folder))
 754     }
 755
 756     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 757         (**self).visit_with(visitor)
 758     }
 759 }
 760
 761 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
 762     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 763         let content: T = (**self).fold_with(folder);
 764         box content
 765     }
 766
 767     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 768         (**self).visit_with(visitor)
 769     }
 770 }
 771
 772 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
 773     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 774         self.iter().map(|t| t.fold_with(folder)).collect()
 775     }
 776
 777     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 778         self.iter().any(|t| t.visit_with(visitor))
 779     }
 780 }
 781
 782 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
 783     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 784         self.iter().map(|t| t.fold_with(folder)).collect::<Vec<_>>().into_boxed_slice()
 785     }
 786
 787     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 788         self.iter().any(|t| t.visit_with(visitor))
 789     }
 790 }
 791
 792 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<T> {
 793     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 794         self.map_bound_ref(|ty| ty.fold_with(folder))
 795     }
 796
 797     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 798         folder.fold_binder(self)
 799     }
 800
 801     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 802         self.skip_binder().visit_with(visitor)
 803     }
 804
 805     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 806         visitor.visit_binder(self)
 807     }
 808 }
 809
 810 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::ExistentialPredicate<'tcx>> {
 811     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 812         fold_list(*self, folder, |tcx, v| tcx.intern_existential_predicates(v))
 813     }
 814
 815     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 816         self.iter().any(|p| p.visit_with(visitor))
 817     }
 818 }
 819
 820 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<Ty<'tcx>> {
 821     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 822         fold_list(*self, folder, |tcx, v| tcx.intern_type_list(v))
 823     }
 824
 825     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 826         self.iter().any(|t| t.visit_with(visitor))
 827     }
 828 }
 829
 830 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
 831     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 832         fold_list(*self, folder, |tcx, v| tcx.intern_projs(v))
 833     }
 834
 835     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 836         self.iter().any(|t| t.visit_with(visitor))
 837     }
 838 }
 839
 840 impl<'tcx> TypeFoldable<'tcx> for ty::instance::Instance<'tcx> {
 841     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 842         use crate::ty::InstanceDef::*;
 843         Self {
 844             substs: self.substs.fold_with(folder),
 845             def: match self.def {
 846                 Item(did) => Item(did.fold_with(folder)),
 847                 VtableShim(did) => VtableShim(did.fold_with(folder)),
 848                 ReifyShim(did) => ReifyShim(did.fold_with(folder)),
 849                 Intrinsic(did) => Intrinsic(did.fold_with(folder)),
 850                 FnPtrShim(did, ty) => FnPtrShim(did.fold_with(folder), ty.fold_with(folder)),
 851                 Virtual(did, i) => Virtual(did.fold_with(folder), i),
 852                 ClosureOnceShim { call_once } => {
 853                     ClosureOnceShim { call_once: call_once.fold_with(folder) }
 854                 }
 855                 DropGlue(did, ty) => DropGlue(did.fold_with(folder), ty.fold_with(folder)),
 856                 CloneShim(did, ty) => CloneShim(did.fold_with(folder), ty.fold_with(folder)),
 857             },
 858         }
 859     }
 860
 861     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 862         use crate::ty::InstanceDef::*;
 863         self.substs.visit_with(visitor)
 864             || match self.def {
 865                 Item(did) | VtableShim(did) | ReifyShim(did) | Intrinsic(did) | Virtual(did, _) => {
 866                     did.visit_with(visitor)
 867                 }
 868                 FnPtrShim(did, ty) | CloneShim(did, ty) => {
 869                     did.visit_with(visitor) || ty.visit_with(visitor)
 870                 }
 871                 DropGlue(did, ty) => did.visit_with(visitor) || ty.visit_with(visitor),
 872                 ClosureOnceShim { call_once } => call_once.visit_with(visitor),
 873             }
 874     }
 875 }
 876
 877 impl<'tcx> TypeFoldable<'tcx> for interpret::GlobalId<'tcx> {
 878     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 879         Self { instance: self.instance.fold_with(folder), promoted: self.promoted }
 880     }
 881
 882     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 883         self.instance.visit_with(visitor)
 884     }
 885 }
 886
 887 impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
 888     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 889         let kind = match self.kind {
 890             ty::RawPtr(tm) => ty::RawPtr(tm.fold_with(folder)),
 891             ty::Array(typ, sz) => ty::Array(typ.fold_with(folder), sz.fold_with(folder)),
 892             ty::Slice(typ) => ty::Slice(typ.fold_with(folder)),
 893             ty::Adt(tid, substs) => ty::Adt(tid, substs.fold_with(folder)),
 894             ty::Dynamic(ref trait_ty, ref region) => {
 895                 ty::Dynamic(trait_ty.fold_with(folder), region.fold_with(folder))
 896             }
 897             ty::Tuple(ts) => ty::Tuple(ts.fold_with(folder)),
 898             ty::FnDef(def_id, substs) => ty::FnDef(def_id, substs.fold_with(folder)),
 899             ty::FnPtr(f) => ty::FnPtr(f.fold_with(folder)),
 900             ty::Ref(ref r, ty, mutbl) => ty::Ref(r.fold_with(folder), ty.fold_with(folder), mutbl),
 901             ty::Generator(did, substs, movability) => {
 902                 ty::Generator(did, substs.fold_with(folder), movability)
 903             }
 904             ty::GeneratorWitness(types) => ty::GeneratorWitness(types.fold_with(folder)),
 905             ty::Closure(did, substs) => ty::Closure(did, substs.fold_with(folder)),
 906             ty::Projection(ref data) => ty::Projection(data.fold_with(folder)),
 907             ty::Opaque(did, substs) => ty::Opaque(did, substs.fold_with(folder)),
 908
 909             ty::Bool
 910             | ty::Char
 911             | ty::Str
 912             | ty::Int(_)
 913             | ty::Uint(_)
 914             | ty::Float(_)
 915             | ty::Error(_)
 916             | ty::Infer(_)
 917             | ty::Param(..)
 918             | ty::Bound(..)
 919             | ty::Placeholder(..)
 920             | ty::Never
 921             | ty::Foreign(..) => return self,
 922         };
 923
 924         if self.kind == kind { self } else { folder.tcx().mk_ty(kind) }
 925     }
 926
 927     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 928         folder.fold_ty(*self)
 929     }
 930
 931     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 932         match self.kind {
 933             ty::RawPtr(ref tm) => tm.visit_with(visitor),
 934             ty::Array(typ, sz) => typ.visit_with(visitor) || sz.visit_with(visitor),
 935             ty::Slice(typ) => typ.visit_with(visitor),
 936             ty::Adt(_, substs) => substs.visit_with(visitor),
 937             ty::Dynamic(ref trait_ty, ref reg) => {
 938                 trait_ty.visit_with(visitor) || reg.visit_with(visitor)
 939             }
 940             ty::Tuple(ts) => ts.visit_with(visitor),
 941             ty::FnDef(_, substs) => substs.visit_with(visitor),
 942             ty::FnPtr(ref f) => f.visit_with(visitor),
 943             ty::Ref(r, ty, _) => r.visit_with(visitor) || ty.visit_with(visitor),
 944             ty::Generator(_did, ref substs, _) => substs.visit_with(visitor),
 945             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
 946             ty::Closure(_did, ref substs) => substs.visit_with(visitor),
 947             ty::Projection(ref data) => data.visit_with(visitor),
 948             ty::Opaque(_, ref substs) => substs.visit_with(visitor),
 949
 950             ty::Bool
 951             | ty::Char
 952             | ty::Str
 953             | ty::Int(_)
 954             | ty::Uint(_)
 955             | ty::Float(_)
 956             | ty::Error(_)
 957             | ty::Infer(_)
 958             | ty::Bound(..)
 959             | ty::Placeholder(..)
 960             | ty::Param(..)
 961             | ty::Never
 962             | ty::Foreign(..) => false,
 963         }
 964     }
 965
 966     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 967         visitor.visit_ty(self)
 968     }
 969 }
 970
 971 impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
 972     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
 973         *self
 974     }
 975
 976     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 977         folder.fold_region(*self)
 978     }
 979
 980     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
 981         false
 982     }
 983
 984     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 985         visitor.visit_region(*self)
 986     }
 987 }
 988
 989 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
 990     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
 991         let new = ty::PredicateKind::super_fold_with(self.kind, folder);
 992         if new != *self.kind { folder.tcx().mk_predicate(new) } else { *self }
 993     }
 994
 995     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
 996         ty::PredicateKind::super_visit_with(self.kind, visitor)
 997     }
 998 }
 999
1000 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
1001     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1002         fold_list(*self, folder, |tcx, v| tcx.intern_predicates(v))
1003     }
1004
1005     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1006         self.iter().any(|p| p.visit_with(visitor))
1007     }
1008 }
1009
1010 impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
1011     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1012         self.iter().map(|x| x.fold_with(folder)).collect()
1013     }
1014
1015     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1016         self.iter().any(|t| t.visit_with(visitor))
1017     }
1018 }
1019
1020 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
1021     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1022         let ty = self.ty.fold_with(folder);
1023         let val = self.val.fold_with(folder);
1024         if ty != self.ty || val != self.val {
1025             folder.tcx().mk_const(ty::Const { ty, val })
1026         } else {
1027             *self
1028         }
1029     }
1030
1031     fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1032         folder.fold_const(*self)
1033     }
1034
1035     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1036         self.ty.visit_with(visitor) || self.val.visit_with(visitor)
1037     }
1038
1039     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1040         visitor.visit_const(self)
1041     }
1042 }
1043
1044 impl<'tcx> TypeFoldable<'tcx> for ty::ConstKind<'tcx> {
1045     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
1046         match *self {
1047             ty::ConstKind::Infer(ic) => ty::ConstKind::Infer(ic.fold_with(folder)),
1048             ty::ConstKind::Param(p) => ty::ConstKind::Param(p.fold_with(folder)),
1049             ty::ConstKind::Unevaluated(did, substs, promoted) => {
1050                 ty::ConstKind::Unevaluated(did, substs.fold_with(folder), promoted)
1051             }
1052             ty::ConstKind::Value(_)
1053             | ty::ConstKind::Bound(..)
1054             | ty::ConstKind::Placeholder(..)
1055             | ty::ConstKind::Error(_) => *self,
1056         }
1057     }
1058
1059     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1060         match *self {
1061             ty::ConstKind::Infer(ic) => ic.visit_with(visitor),
1062             ty::ConstKind::Param(p) => p.visit_with(visitor),
1063             ty::ConstKind::Unevaluated(_, substs, _) => substs.visit_with(visitor),
1064             ty::ConstKind::Value(_)
1065             | ty::ConstKind::Bound(..)
1066             | ty::ConstKind::Placeholder(_)
1067             | ty::ConstKind::Error(_) => false,
1068         }
1069     }
1070 }
1071
1072 impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
1073     fn super_fold_with<F: TypeFolder<'tcx>>(&self, _folder: &mut F) -> Self {
1074         *self
1075     }
1076
1077     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
1078         false
1079     }
1080 }
1081
1082 // Does the equivalent of
1083 // ```
1084 // let v = self.iter().map(|p| p.fold_with(folder)).collect::<SmallVec<[_; 8]>>();
1085 // folder.tcx().intern_*(&v)
1086 // ```
1087 fn fold_list<'tcx, F, T>(
1088     list: &'tcx ty::List<T>,
1089     folder: &mut F,
1090     intern: impl FnOnce(TyCtxt<'tcx>, &[T]) -> &'tcx ty::List<T>,
1091 ) -> &'tcx ty::List<T>
1092 where
1093     F: TypeFolder<'tcx>,
1094     T: TypeFoldable<'tcx> + PartialEq + Copy,
1095 {
1096     let mut iter = list.iter();
1097     // Look for the first element that changed
1098     if let Some((i, new_t)) = iter.by_ref().enumerate().find_map(|(i, t)| {
1099         let new_t = t.fold_with(folder);
1100         if new_t == t { None } else { Some((i, new_t)) }
1101     }) {
1102         // An element changed, prepare to intern the resulting list
1103         let mut new_list = SmallVec::<[_; 8]>::with_capacity(list.len());
1104         new_list.extend_from_slice(&list[..i]);
1105         new_list.push(new_t);
1106         new_list.extend(iter.map(|t| t.fold_with(folder)));
1107         intern(folder.tcx(), &new_list)
1108     } else {
1109         list
1110     }
1111 }