compiler/rustc_middle/src/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::{Field, ProjectionKind};
   7 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeSuperFoldable};
   8 use crate::ty::print::{with_no_trimmed_paths, FmtPrinter, Printer};
   9 use crate::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
  10 use crate::ty::{self, InferConst, Lift, Term, TermKind, Ty, TyCtxt};
  11 use rustc_data_structures::functor::IdFunctor;
  12 use rustc_hir::def::Namespace;
  13 use rustc_index::vec::{Idx, IndexVec};
  14
  15 use std::fmt;
  16 use std::mem::ManuallyDrop;
  17 use std::ops::ControlFlow;
  18 use std::rc::Rc;
  19 use std::sync::Arc;
  20
  21 impl fmt::Debug for ty::TraitDef {
  22     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  23         ty::tls::with(|tcx| {
  24             with_no_trimmed_paths!({
  25                 f.write_str(
  26                     &FmtPrinter::new(tcx, Namespace::TypeNS)
  27                         .print_def_path(self.def_id, &[])?
  28                         .into_buffer(),
  29                 )
  30             })
  31         })
  32     }
  33 }
  34
  35 impl<'tcx> fmt::Debug for ty::AdtDef<'tcx> {
  36     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  37         ty::tls::with(|tcx| {
  38             with_no_trimmed_paths!({
  39                 f.write_str(
  40                     &FmtPrinter::new(tcx, Namespace::TypeNS)
  41                         .print_def_path(self.did(), &[])?
  42                         .into_buffer(),
  43                 )
  44             })
  45         })
  46     }
  47 }
  48
  49 impl fmt::Debug for ty::UpvarId {
  50     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  51         let name = ty::tls::with(|tcx| tcx.hir().name(self.var_path.hir_id));
  52         write!(f, "UpvarId({:?};`{}`;{:?})", self.var_path.hir_id, name, self.closure_expr_id)
  53     }
  54 }
  55
  56 impl<'tcx> fmt::Debug for ty::ExistentialTraitRef<'tcx> {
  57     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  58         with_no_trimmed_paths!(fmt::Display::fmt(self, f))
  59     }
  60 }
  61
  62 impl<'tcx> fmt::Debug for ty::adjustment::Adjustment<'tcx> {
  63     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  64         write!(f, "{:?} -> {}", self.kind, self.target)
  65     }
  66 }
  67
  68 impl fmt::Debug for ty::BoundRegionKind {
  69     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  70         match *self {
  71             ty::BrAnon(n, span) => write!(f, "BrAnon({n:?}, {span:?})"),
  72             ty::BrNamed(did, name) => {
  73                 if did.is_crate_root() {
  74                     write!(f, "BrNamed({})", name)
  75                 } else {
  76                     write!(f, "BrNamed({:?}, {})", did, name)
  77                 }
  78             }
  79             ty::BrEnv => write!(f, "BrEnv"),
  80         }
  81     }
  82 }
  83
  84 impl fmt::Debug for ty::FreeRegion {
  85     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  86         write!(f, "ReFree({:?}, {:?})", self.scope, self.bound_region)
  87     }
  88 }
  89
  90 impl<'tcx> fmt::Debug for ty::FnSig<'tcx> {
  91     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  92         write!(f, "({:?}; c_variadic: {})->{:?}", self.inputs(), self.c_variadic, self.output())
  93     }
  94 }
  95
  96 impl<'tcx> fmt::Debug for ty::ConstVid<'tcx> {
  97     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  98         write!(f, "_#{}c", self.index)
  99     }
 100 }
 101
 102 impl fmt::Debug for ty::RegionVid {
 103     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 104         write!(f, "'_#{}r", self.index())
 105     }
 106 }
 107
 108 impl<'tcx> fmt::Debug for ty::TraitRef<'tcx> {
 109     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 110         with_no_trimmed_paths!(fmt::Display::fmt(self, f))
 111     }
 112 }
 113
 114 impl<'tcx> fmt::Debug for Ty<'tcx> {
 115     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 116         with_no_trimmed_paths!(fmt::Display::fmt(self, f))
 117     }
 118 }
 119
 120 impl fmt::Debug for ty::ParamTy {
 121     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 122         write!(f, "{}/#{}", self.name, self.index)
 123     }
 124 }
 125
 126 impl fmt::Debug for ty::ParamConst {
 127     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 128         write!(f, "{}/#{}", self.name, self.index)
 129     }
 130 }
 131
 132 impl<'tcx> fmt::Debug for ty::TraitPredicate<'tcx> {
 133     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 134         if let ty::BoundConstness::ConstIfConst = self.constness {
 135             write!(f, "~const ")?;
 136         }
 137         write!(f, "TraitPredicate({:?}, polarity:{:?})", self.trait_ref, self.polarity)
 138     }
 139 }
 140
 141 impl<'tcx> fmt::Debug for ty::ProjectionPredicate<'tcx> {
 142     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 143         write!(f, "ProjectionPredicate({:?}, {:?})", self.projection_ty, self.term)
 144     }
 145 }
 146
 147 impl<'tcx> fmt::Debug for ty::Predicate<'tcx> {
 148     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 149         write!(f, "{:?}", self.kind())
 150     }
 151 }
 152
 153 impl<'tcx> fmt::Debug for ty::Clause<'tcx> {
 154     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 155         match *self {
 156             ty::Clause::Trait(ref a) => a.fmt(f),
 157             ty::Clause::RegionOutlives(ref pair) => pair.fmt(f),
 158             ty::Clause::TypeOutlives(ref pair) => pair.fmt(f),
 159             ty::Clause::Projection(ref pair) => pair.fmt(f),
 160         }
 161     }
 162 }
 163
 164 impl<'tcx> fmt::Debug for ty::PredicateKind<'tcx> {
 165     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 166         match *self {
 167             ty::PredicateKind::Clause(ref a) => a.fmt(f),
 168             ty::PredicateKind::Subtype(ref pair) => pair.fmt(f),
 169             ty::PredicateKind::Coerce(ref pair) => pair.fmt(f),
 170             ty::PredicateKind::WellFormed(data) => write!(f, "WellFormed({:?})", data),
 171             ty::PredicateKind::ObjectSafe(trait_def_id) => {
 172                 write!(f, "ObjectSafe({:?})", trait_def_id)
 173             }
 174             ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
 175                 write!(f, "ClosureKind({:?}, {:?}, {:?})", closure_def_id, closure_substs, kind)
 176             }
 177             ty::PredicateKind::ConstEvaluatable(ct) => {
 178                 write!(f, "ConstEvaluatable({ct:?})")
 179             }
 180             ty::PredicateKind::ConstEquate(c1, c2) => write!(f, "ConstEquate({:?}, {:?})", c1, c2),
 181             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
 182                 write!(f, "TypeWellFormedFromEnv({:?})", ty)
 183             }
 184             ty::PredicateKind::Ambiguous => write!(f, "Ambiguous"),
 185         }
 186     }
 187 }
 188
 189 ///////////////////////////////////////////////////////////////////////////
 190 // Atomic structs
 191 //
 192 // For things that don't carry any arena-allocated data (and are
 193 // copy...), just add them to this list.
 194
 195 TrivialTypeTraversalAndLiftImpls! {
 196     (),
 197     bool,
 198     usize,
 199     ::rustc_target::abi::VariantIdx,
 200     u32,
 201     u64,
 202     String,
 203     crate::middle::region::Scope,
 204     crate::ty::FloatTy,
 205     ::rustc_ast::InlineAsmOptions,
 206     ::rustc_ast::InlineAsmTemplatePiece,
 207     ::rustc_ast::NodeId,
 208     ::rustc_span::symbol::Symbol,
 209     ::rustc_hir::def::Res,
 210     ::rustc_hir::def_id::DefId,
 211     ::rustc_hir::def_id::LocalDefId,
 212     ::rustc_hir::HirId,
 213     ::rustc_hir::MatchSource,
 214     ::rustc_hir::Mutability,
 215     ::rustc_hir::Unsafety,
 216     ::rustc_target::asm::InlineAsmRegOrRegClass,
 217     ::rustc_target::spec::abi::Abi,
 218     crate::mir::coverage::ExpressionOperandId,
 219     crate::mir::coverage::CounterValueReference,
 220     crate::mir::coverage::InjectedExpressionId,
 221     crate::mir::coverage::InjectedExpressionIndex,
 222     crate::mir::coverage::MappedExpressionIndex,
 223     crate::mir::Local,
 224     crate::mir::Promoted,
 225     crate::traits::Reveal,
 226     crate::ty::adjustment::AutoBorrowMutability,
 227     crate::ty::AdtKind,
 228     crate::ty::BoundConstness,
 229     // Including `BoundRegionKind` is a *bit* dubious, but direct
 230     // references to bound region appear in `ty::Error`, and aren't
 231     // really meant to be folded. In general, we can only fold a fully
 232     // general `Region`.
 233     crate::ty::BoundRegionKind,
 234     crate::ty::AssocItem,
 235     crate::ty::AssocKind,
 236     crate::ty::Placeholder<crate::ty::BoundRegionKind>,
 237     crate::ty::ClosureKind,
 238     crate::ty::FreeRegion,
 239     crate::ty::InferTy,
 240     crate::ty::IntVarValue,
 241     crate::ty::ParamConst,
 242     crate::ty::ParamTy,
 243     crate::ty::adjustment::PointerCast,
 244     crate::ty::RegionVid,
 245     crate::ty::UniverseIndex,
 246     crate::ty::Variance,
 247     ::rustc_span::Span,
 248     ::rustc_errors::ErrorGuaranteed,
 249     Field,
 250     interpret::Scalar,
 251     rustc_target::abi::Size,
 252     rustc_type_ir::DebruijnIndex,
 253     ty::BoundVar,
 254     ty::Placeholder<ty::BoundVar>,
 255 }
 256
 257 TrivialTypeTraversalAndLiftImpls! {
 258     for<'tcx> {
 259         ty::ValTree<'tcx>,
 260     }
 261 }
 262
 263 ///////////////////////////////////////////////////////////////////////////
 264 // Lift implementations
 265
 266 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>> Lift<'tcx> for (A, B) {
 267     type Lifted = (A::Lifted, B::Lifted);
 268     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 269         Some((tcx.lift(self.0)?, tcx.lift(self.1)?))
 270     }
 271 }
 272
 273 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>, C: Lift<'tcx>> Lift<'tcx> for (A, B, C) {
 274     type Lifted = (A::Lifted, B::Lifted, C::Lifted);
 275     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 276         Some((tcx.lift(self.0)?, tcx.lift(self.1)?, tcx.lift(self.2)?))
 277     }
 278 }
 279
 280 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Option<T> {
 281     type Lifted = Option<T::Lifted>;
 282     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 283         Some(match self {
 284             Some(x) => Some(tcx.lift(x)?),
 285             None => None,
 286         })
 287     }
 288 }
 289
 290 impl<'tcx, T: Lift<'tcx>, E: Lift<'tcx>> Lift<'tcx> for Result<T, E> {
 291     type Lifted = Result<T::Lifted, E::Lifted>;
 292     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 293         match self {
 294             Ok(x) => tcx.lift(x).map(Ok),
 295             Err(e) => tcx.lift(e).map(Err),
 296         }
 297     }
 298 }
 299
 300 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Box<T> {
 301     type Lifted = Box<T::Lifted>;
 302     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 303         Some(Box::new(tcx.lift(*self)?))
 304     }
 305 }
 306
 307 impl<'tcx, T: Lift<'tcx> + Clone> Lift<'tcx> for Rc<T> {
 308     type Lifted = Rc<T::Lifted>;
 309     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 310         Some(Rc::new(tcx.lift(self.as_ref().clone())?))
 311     }
 312 }
 313
 314 impl<'tcx, T: Lift<'tcx> + Clone> Lift<'tcx> for Arc<T> {
 315     type Lifted = Arc<T::Lifted>;
 316     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 317         Some(Arc::new(tcx.lift(self.as_ref().clone())?))
 318     }
 319 }
 320 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Vec<T> {
 321     type Lifted = Vec<T::Lifted>;
 322     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 323         self.into_iter().map(|v| tcx.lift(v)).collect()
 324     }
 325 }
 326
 327 impl<'tcx, I: Idx, T: Lift<'tcx>> Lift<'tcx> for IndexVec<I, T> {
 328     type Lifted = IndexVec<I, T::Lifted>;
 329     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 330         self.into_iter().map(|e| tcx.lift(e)).collect()
 331     }
 332 }
 333
 334 impl<'a, 'tcx> Lift<'tcx> for Term<'a> {
 335     type Lifted = ty::Term<'tcx>;
 336     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 337         Some(
 338             match self.unpack() {
 339                 TermKind::Ty(ty) => TermKind::Ty(tcx.lift(ty)?),
 340                 TermKind::Const(c) => TermKind::Const(tcx.lift(c)?),
 341             }
 342             .pack(),
 343         )
 344     }
 345 }
 346 impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
 347     type Lifted = ty::ParamEnv<'tcx>;
 348     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 349         tcx.lift(self.caller_bounds())
 350             .map(|caller_bounds| ty::ParamEnv::new(caller_bounds, self.reveal(), self.constness()))
 351     }
 352 }
 353
 354 ///////////////////////////////////////////////////////////////////////////
 355 // TypeFoldable implementations.
 356
 357 /// AdtDefs are basically the same as a DefId.
 358 impl<'tcx> TypeFoldable<'tcx> for ty::AdtDef<'tcx> {
 359     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
 360         Ok(self)
 361     }
 362 }
 363
 364 impl<'tcx> TypeVisitable<'tcx> for ty::AdtDef<'tcx> {
 365     fn visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 366         ControlFlow::CONTINUE
 367     }
 368 }
 369
 370 impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
 371     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 372         self,
 373         folder: &mut F,
 374     ) -> Result<(T, U), F::Error> {
 375         Ok((self.0.try_fold_with(folder)?, self.1.try_fold_with(folder)?))
 376     }
 377 }
 378
 379 impl<'tcx, T: TypeVisitable<'tcx>, U: TypeVisitable<'tcx>> TypeVisitable<'tcx> for (T, U) {
 380     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 381         self.0.visit_with(visitor)?;
 382         self.1.visit_with(visitor)
 383     }
 384 }
 385
 386 impl<'tcx, A: TypeFoldable<'tcx>, B: TypeFoldable<'tcx>, C: TypeFoldable<'tcx>> TypeFoldable<'tcx>
 387     for (A, B, C)
 388 {
 389     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 390         self,
 391         folder: &mut F,
 392     ) -> Result<(A, B, C), F::Error> {
 393         Ok((
 394             self.0.try_fold_with(folder)?,
 395             self.1.try_fold_with(folder)?,
 396             self.2.try_fold_with(folder)?,
 397         ))
 398     }
 399 }
 400
 401 impl<'tcx, A: TypeVisitable<'tcx>, B: TypeVisitable<'tcx>, C: TypeVisitable<'tcx>>
 402     TypeVisitable<'tcx> for (A, B, C)
 403 {
 404     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 405         self.0.visit_with(visitor)?;
 406         self.1.visit_with(visitor)?;
 407         self.2.visit_with(visitor)
 408     }
 409 }
 410
 411 EnumTypeTraversalImpl! {
 412     impl<'tcx, T> TypeFoldable<'tcx> for Option<T> {
 413         (Some)(a),
 414         (None),
 415     } where T: TypeFoldable<'tcx>
 416 }
 417 EnumTypeTraversalImpl! {
 418     impl<'tcx, T> TypeVisitable<'tcx> for Option<T> {
 419         (Some)(a),
 420         (None),
 421     } where T: TypeVisitable<'tcx>
 422 }
 423
 424 EnumTypeTraversalImpl! {
 425     impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
 426         (Ok)(a),
 427         (Err)(a),
 428     } where T: TypeFoldable<'tcx>, E: TypeFoldable<'tcx>,
 429 }
 430 EnumTypeTraversalImpl! {
 431     impl<'tcx, T, E> TypeVisitable<'tcx> for Result<T, E> {
 432         (Ok)(a),
 433         (Err)(a),
 434     } where T: TypeVisitable<'tcx>, E: TypeVisitable<'tcx>,
 435 }
 436
 437 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
 438     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 439         mut self,
 440         folder: &mut F,
 441     ) -> Result<Self, F::Error> {
 442         // We merely want to replace the contained `T`, if at all possible,
 443         // so that we don't needlessly allocate a new `Rc` or indeed clone
 444         // the contained type.
 445         unsafe {
 446             // First step is to ensure that we have a unique reference to
 447             // the contained type, which `Rc::make_mut` will accomplish (by
 448             // allocating a new `Rc` and cloning the `T` only if required).
 449             // This is done *before* casting to `Rc<ManuallyDrop<T>>` so that
 450             // panicking during `make_mut` does not leak the `T`.
 451             Rc::make_mut(&mut self);
 452
 453             // Casting to `Rc<ManuallyDrop<T>>` is safe because `ManuallyDrop`
 454             // is `repr(transparent)`.
 455             let ptr = Rc::into_raw(self).cast::<ManuallyDrop<T>>();
 456             let mut unique = Rc::from_raw(ptr);
 457
 458             // Call to `Rc::make_mut` above guarantees that `unique` is the
 459             // sole reference to the contained value, so we can avoid doing
 460             // a checked `get_mut` here.
 461             let slot = Rc::get_mut_unchecked(&mut unique);
 462
 463             // Semantically move the contained type out from `unique`, fold
 464             // it, then move the folded value back into `unique`.  Should
 465             // folding fail, `ManuallyDrop` ensures that the "moved-out"
 466             // value is not re-dropped.
 467             let owned = ManuallyDrop::take(slot);
 468             let folded = owned.try_fold_with(folder)?;
 469             *slot = ManuallyDrop::new(folded);
 470
 471             // Cast back to `Rc<T>`.
 472             Ok(Rc::from_raw(Rc::into_raw(unique).cast()))
 473         }
 474     }
 475 }
 476
 477 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Rc<T> {
 478     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 479         (**self).visit_with(visitor)
 480     }
 481 }
 482
 483 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
 484     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 485         mut self,
 486         folder: &mut F,
 487     ) -> Result<Self, F::Error> {
 488         // We merely want to replace the contained `T`, if at all possible,
 489         // so that we don't needlessly allocate a new `Arc` or indeed clone
 490         // the contained type.
 491         unsafe {
 492             // First step is to ensure that we have a unique reference to
 493             // the contained type, which `Arc::make_mut` will accomplish (by
 494             // allocating a new `Arc` and cloning the `T` only if required).
 495             // This is done *before* casting to `Arc<ManuallyDrop<T>>` so that
 496             // panicking during `make_mut` does not leak the `T`.
 497             Arc::make_mut(&mut self);
 498
 499             // Casting to `Arc<ManuallyDrop<T>>` is safe because `ManuallyDrop`
 500             // is `repr(transparent)`.
 501             let ptr = Arc::into_raw(self).cast::<ManuallyDrop<T>>();
 502             let mut unique = Arc::from_raw(ptr);
 503
 504             // Call to `Arc::make_mut` above guarantees that `unique` is the
 505             // sole reference to the contained value, so we can avoid doing
 506             // a checked `get_mut` here.
 507             let slot = Arc::get_mut_unchecked(&mut unique);
 508
 509             // Semantically move the contained type out from `unique`, fold
 510             // it, then move the folded value back into `unique`.  Should
 511             // folding fail, `ManuallyDrop` ensures that the "moved-out"
 512             // value is not re-dropped.
 513             let owned = ManuallyDrop::take(slot);
 514             let folded = owned.try_fold_with(folder)?;
 515             *slot = ManuallyDrop::new(folded);
 516
 517             // Cast back to `Arc<T>`.
 518             Ok(Arc::from_raw(Arc::into_raw(unique).cast()))
 519         }
 520     }
 521 }
 522
 523 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Arc<T> {
 524     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 525         (**self).visit_with(visitor)
 526     }
 527 }
 528
 529 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
 530     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 531         self.try_map_id(|value| value.try_fold_with(folder))
 532     }
 533 }
 534
 535 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Box<T> {
 536     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 537         (**self).visit_with(visitor)
 538     }
 539 }
 540
 541 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
 542     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 543         self.try_map_id(|t| t.try_fold_with(folder))
 544     }
 545 }
 546
 547 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Vec<T> {
 548     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 549         self.iter().try_for_each(|t| t.visit_with(visitor))
 550     }
 551 }
 552
 553 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for &[T] {
 554     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 555         self.iter().try_for_each(|t| t.visit_with(visitor))
 556     }
 557 }
 558
 559 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
 560     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 561         self.try_map_id(|t| t.try_fold_with(folder))
 562     }
 563 }
 564
 565 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Box<[T]> {
 566     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 567         self.iter().try_for_each(|t| t.visit_with(visitor))
 568     }
 569 }
 570
 571 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<'tcx, T> {
 572     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 573         folder.try_fold_binder(self)
 574     }
 575 }
 576
 577 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for ty::Binder<'tcx, T> {
 578     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 579         visitor.visit_binder(self)
 580     }
 581 }
 582
 583 impl<'tcx, T: TypeFoldable<'tcx>> TypeSuperFoldable<'tcx> for ty::Binder<'tcx, T> {
 584     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 585         self,
 586         folder: &mut F,
 587     ) -> Result<Self, F::Error> {
 588         self.try_map_bound(|ty| ty.try_fold_with(folder))
 589     }
 590 }
 591
 592 impl<'tcx, T: TypeVisitable<'tcx>> TypeSuperVisitable<'tcx> for ty::Binder<'tcx, T> {
 593     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 594         self.as_ref().skip_binder().visit_with(visitor)
 595     }
 596 }
 597
 598 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
 599     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 600         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_poly_existential_predicates(v))
 601     }
 602 }
 603
 604 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Const<'tcx>> {
 605     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 606         ty::util::fold_list(self, folder, |tcx, v| tcx.mk_const_list(v.iter()))
 607     }
 608 }
 609
 610 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
 611     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 612         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_projs(v))
 613     }
 614 }
 615
 616 impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
 617     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 618         folder.try_fold_ty(self)
 619     }
 620 }
 621
 622 impl<'tcx> TypeVisitable<'tcx> for Ty<'tcx> {
 623     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 624         visitor.visit_ty(*self)
 625     }
 626 }
 627
 628 impl<'tcx> TypeSuperFoldable<'tcx> for Ty<'tcx> {
 629     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 630         self,
 631         folder: &mut F,
 632     ) -> Result<Self, F::Error> {
 633         let kind = match *self.kind() {
 634             ty::RawPtr(tm) => ty::RawPtr(tm.try_fold_with(folder)?),
 635             ty::Array(typ, sz) => ty::Array(typ.try_fold_with(folder)?, sz.try_fold_with(folder)?),
 636             ty::Slice(typ) => ty::Slice(typ.try_fold_with(folder)?),
 637             ty::Adt(tid, substs) => ty::Adt(tid, substs.try_fold_with(folder)?),
 638             ty::Dynamic(trait_ty, region, representation) => ty::Dynamic(
 639                 trait_ty.try_fold_with(folder)?,
 640                 region.try_fold_with(folder)?,
 641                 representation,
 642             ),
 643             ty::Tuple(ts) => ty::Tuple(ts.try_fold_with(folder)?),
 644             ty::FnDef(def_id, substs) => ty::FnDef(def_id, substs.try_fold_with(folder)?),
 645             ty::FnPtr(f) => ty::FnPtr(f.try_fold_with(folder)?),
 646             ty::Ref(r, ty, mutbl) => {
 647                 ty::Ref(r.try_fold_with(folder)?, ty.try_fold_with(folder)?, mutbl)
 648             }
 649             ty::Generator(did, substs, movability) => {
 650                 ty::Generator(did, substs.try_fold_with(folder)?, movability)
 651             }
 652             ty::GeneratorWitness(types) => ty::GeneratorWitness(types.try_fold_with(folder)?),
 653             ty::Closure(did, substs) => ty::Closure(did, substs.try_fold_with(folder)?),
 654             ty::Alias(kind, data) => ty::Alias(kind, data.try_fold_with(folder)?),
 655
 656             ty::Bool
 657             | ty::Char
 658             | ty::Str
 659             | ty::Int(_)
 660             | ty::Uint(_)
 661             | ty::Float(_)
 662             | ty::Error(_)
 663             | ty::Infer(_)
 664             | ty::Param(..)
 665             | ty::Bound(..)
 666             | ty::Placeholder(..)
 667             | ty::Never
 668             | ty::Foreign(..) => return Ok(self),
 669         };
 670
 671         Ok(if *self.kind() == kind { self } else { folder.tcx().mk_ty(kind) })
 672     }
 673 }
 674
 675 impl<'tcx> TypeSuperVisitable<'tcx> for Ty<'tcx> {
 676     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 677         match self.kind() {
 678             ty::RawPtr(ref tm) => tm.visit_with(visitor),
 679             ty::Array(typ, sz) => {
 680                 typ.visit_with(visitor)?;
 681                 sz.visit_with(visitor)
 682             }
 683             ty::Slice(typ) => typ.visit_with(visitor),
 684             ty::Adt(_, substs) => substs.visit_with(visitor),
 685             ty::Dynamic(ref trait_ty, ref reg, _) => {
 686                 trait_ty.visit_with(visitor)?;
 687                 reg.visit_with(visitor)
 688             }
 689             ty::Tuple(ts) => ts.visit_with(visitor),
 690             ty::FnDef(_, substs) => substs.visit_with(visitor),
 691             ty::FnPtr(ref f) => f.visit_with(visitor),
 692             ty::Ref(r, ty, _) => {
 693                 r.visit_with(visitor)?;
 694                 ty.visit_with(visitor)
 695             }
 696             ty::Generator(_did, ref substs, _) => substs.visit_with(visitor),
 697             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
 698             ty::Closure(_did, ref substs) => substs.visit_with(visitor),
 699             ty::Alias(_, ref data) => data.visit_with(visitor),
 700
 701             ty::Bool
 702             | ty::Char
 703             | ty::Str
 704             | ty::Int(_)
 705             | ty::Uint(_)
 706             | ty::Float(_)
 707             | ty::Error(_)
 708             | ty::Infer(_)
 709             | ty::Bound(..)
 710             | ty::Placeholder(..)
 711             | ty::Param(..)
 712             | ty::Never
 713             | ty::Foreign(..) => ControlFlow::CONTINUE,
 714         }
 715     }
 716 }
 717
 718 impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
 719     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 720         folder.try_fold_region(self)
 721     }
 722 }
 723
 724 impl<'tcx> TypeVisitable<'tcx> for ty::Region<'tcx> {
 725     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 726         visitor.visit_region(*self)
 727     }
 728 }
 729
 730 impl<'tcx> TypeSuperFoldable<'tcx> for ty::Region<'tcx> {
 731     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 732         self,
 733         _folder: &mut F,
 734     ) -> Result<Self, F::Error> {
 735         Ok(self)
 736     }
 737 }
 738
 739 impl<'tcx> TypeSuperVisitable<'tcx> for ty::Region<'tcx> {
 740     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 741         ControlFlow::CONTINUE
 742     }
 743 }
 744
 745 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
 746     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 747         folder.try_fold_predicate(self)
 748     }
 749 }
 750
 751 impl<'tcx> TypeVisitable<'tcx> for ty::Predicate<'tcx> {
 752     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 753         visitor.visit_predicate(*self)
 754     }
 755
 756     #[inline]
 757     fn has_vars_bound_at_or_above(&self, binder: ty::DebruijnIndex) -> bool {
 758         self.outer_exclusive_binder() > binder
 759     }
 760
 761     #[inline]
 762     fn has_type_flags(&self, flags: ty::TypeFlags) -> bool {
 763         self.flags().intersects(flags)
 764     }
 765 }
 766
 767 impl<'tcx> TypeSuperFoldable<'tcx> for ty::Predicate<'tcx> {
 768     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 769         self,
 770         folder: &mut F,
 771     ) -> Result<Self, F::Error> {
 772         let new = self.kind().try_fold_with(folder)?;
 773         Ok(folder.tcx().reuse_or_mk_predicate(self, new))
 774     }
 775 }
 776
 777 impl<'tcx> TypeSuperVisitable<'tcx> for ty::Predicate<'tcx> {
 778     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 779         self.kind().visit_with(visitor)
 780     }
 781 }
 782
 783 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
 784     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 785         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_predicates(v))
 786     }
 787 }
 788
 789 impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
 790     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 791         self.try_map_id(|x| x.try_fold_with(folder))
 792     }
 793 }
 794
 795 impl<'tcx, T: TypeVisitable<'tcx>, I: Idx> TypeVisitable<'tcx> for IndexVec<I, T> {
 796     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 797         self.iter().try_for_each(|t| t.visit_with(visitor))
 798     }
 799 }
 800
 801 impl<'tcx> TypeFoldable<'tcx> for ty::Const<'tcx> {
 802     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 803         folder.try_fold_const(self)
 804     }
 805 }
 806
 807 impl<'tcx> TypeVisitable<'tcx> for ty::Const<'tcx> {
 808     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 809         visitor.visit_const(*self)
 810     }
 811 }
 812
 813 impl<'tcx> TypeSuperFoldable<'tcx> for ty::Const<'tcx> {
 814     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 815         self,
 816         folder: &mut F,
 817     ) -> Result<Self, F::Error> {
 818         let ty = self.ty().try_fold_with(folder)?;
 819         let kind = self.kind().try_fold_with(folder)?;
 820         if ty != self.ty() || kind != self.kind() {
 821             Ok(folder.tcx().mk_const(kind, ty))
 822         } else {
 823             Ok(self)
 824         }
 825     }
 826 }
 827
 828 impl<'tcx> TypeSuperVisitable<'tcx> for ty::Const<'tcx> {
 829     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 830         self.ty().visit_with(visitor)?;
 831         self.kind().visit_with(visitor)
 832     }
 833 }
 834
 835 impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
 836     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
 837         Ok(self)
 838     }
 839 }
 840
 841 impl<'tcx> TypeVisitable<'tcx> for InferConst<'tcx> {
 842     fn visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 843         ControlFlow::CONTINUE
 844     }
 845 }
 846
 847 impl<'tcx> TypeSuperVisitable<'tcx> for ty::UnevaluatedConst<'tcx> {
 848     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 849         self.substs.visit_with(visitor)
 850     }
 851 }