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, AliasTy, 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<'tcx> fmt::Debug for ty::TraitRef<'tcx> {
 103     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 104         with_no_trimmed_paths!(fmt::Display::fmt(self, f))
 105     }
 106 }
 107
 108 impl<'tcx> fmt::Debug for Ty<'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 fmt::Debug for ty::ParamTy {
 115     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 116         write!(f, "{}/#{}", self.name, self.index)
 117     }
 118 }
 119
 120 impl fmt::Debug for ty::ParamConst {
 121     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 122         write!(f, "{}/#{}", self.name, self.index)
 123     }
 124 }
 125
 126 impl<'tcx> fmt::Debug for ty::TraitPredicate<'tcx> {
 127     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 128         if let ty::BoundConstness::ConstIfConst = self.constness {
 129             write!(f, "~const ")?;
 130         }
 131         write!(f, "TraitPredicate({:?}, polarity:{:?})", self.trait_ref, self.polarity)
 132     }
 133 }
 134
 135 impl<'tcx> fmt::Debug for ty::ProjectionPredicate<'tcx> {
 136     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 137         write!(f, "ProjectionPredicate({:?}, {:?})", self.projection_ty, self.term)
 138     }
 139 }
 140
 141 impl<'tcx> fmt::Debug for ty::Predicate<'tcx> {
 142     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 143         write!(f, "{:?}", self.kind())
 144     }
 145 }
 146
 147 impl<'tcx> fmt::Debug for ty::Clause<'tcx> {
 148     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 149         match *self {
 150             ty::Clause::Trait(ref a) => a.fmt(f),
 151             ty::Clause::RegionOutlives(ref pair) => pair.fmt(f),
 152             ty::Clause::TypeOutlives(ref pair) => pair.fmt(f),
 153             ty::Clause::Projection(ref pair) => pair.fmt(f),
 154         }
 155     }
 156 }
 157
 158 impl<'tcx> fmt::Debug for ty::PredicateKind<'tcx> {
 159     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 160         match *self {
 161             ty::PredicateKind::Clause(ref a) => a.fmt(f),
 162             ty::PredicateKind::Subtype(ref pair) => pair.fmt(f),
 163             ty::PredicateKind::Coerce(ref pair) => pair.fmt(f),
 164             ty::PredicateKind::WellFormed(data) => write!(f, "WellFormed({:?})", data),
 165             ty::PredicateKind::ObjectSafe(trait_def_id) => {
 166                 write!(f, "ObjectSafe({:?})", trait_def_id)
 167             }
 168             ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
 169                 write!(f, "ClosureKind({:?}, {:?}, {:?})", closure_def_id, closure_substs, kind)
 170             }
 171             ty::PredicateKind::ConstEvaluatable(ct) => {
 172                 write!(f, "ConstEvaluatable({ct:?})")
 173             }
 174             ty::PredicateKind::ConstEquate(c1, c2) => write!(f, "ConstEquate({:?}, {:?})", c1, c2),
 175             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
 176                 write!(f, "TypeWellFormedFromEnv({:?})", ty)
 177             }
 178             ty::PredicateKind::Ambiguous => write!(f, "Ambiguous"),
 179         }
 180     }
 181 }
 182
 183 impl<'tcx> fmt::Debug for AliasTy<'tcx> {
 184     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 185         f.debug_struct("AliasTy")
 186             .field("substs", &self.substs)
 187             .field("def_id", &self.def_id)
 188             .finish()
 189     }
 190 }
 191
 192 ///////////////////////////////////////////////////////////////////////////
 193 // Atomic structs
 194 //
 195 // For things that don't carry any arena-allocated data (and are
 196 // copy...), just add them to this list.
 197
 198 TrivialTypeTraversalAndLiftImpls! {
 199     (),
 200     bool,
 201     usize,
 202     ::rustc_target::abi::VariantIdx,
 203     u32,
 204     u64,
 205     String,
 206     crate::middle::region::Scope,
 207     crate::ty::FloatTy,
 208     ::rustc_ast::InlineAsmOptions,
 209     ::rustc_ast::InlineAsmTemplatePiece,
 210     ::rustc_ast::NodeId,
 211     ::rustc_span::symbol::Symbol,
 212     ::rustc_hir::def::Res,
 213     ::rustc_hir::def_id::DefId,
 214     ::rustc_hir::def_id::LocalDefId,
 215     ::rustc_hir::HirId,
 216     ::rustc_hir::MatchSource,
 217     ::rustc_hir::Mutability,
 218     ::rustc_hir::Unsafety,
 219     ::rustc_target::asm::InlineAsmRegOrRegClass,
 220     ::rustc_target::spec::abi::Abi,
 221     crate::mir::coverage::ExpressionOperandId,
 222     crate::mir::coverage::CounterValueReference,
 223     crate::mir::coverage::InjectedExpressionId,
 224     crate::mir::coverage::InjectedExpressionIndex,
 225     crate::mir::coverage::MappedExpressionIndex,
 226     crate::mir::Local,
 227     crate::mir::Promoted,
 228     crate::traits::Reveal,
 229     crate::ty::adjustment::AutoBorrowMutability,
 230     crate::ty::AdtKind,
 231     crate::ty::BoundConstness,
 232     // Including `BoundRegionKind` is a *bit* dubious, but direct
 233     // references to bound region appear in `ty::Error`, and aren't
 234     // really meant to be folded. In general, we can only fold a fully
 235     // general `Region`.
 236     crate::ty::BoundRegionKind,
 237     crate::ty::AssocItem,
 238     crate::ty::AssocKind,
 239     crate::ty::AliasKind,
 240     crate::ty::Placeholder<crate::ty::BoundRegionKind>,
 241     crate::ty::ClosureKind,
 242     crate::ty::FreeRegion,
 243     crate::ty::InferTy,
 244     crate::ty::IntVarValue,
 245     crate::ty::ParamConst,
 246     crate::ty::ParamTy,
 247     crate::ty::adjustment::PointerCast,
 248     crate::ty::RegionVid,
 249     crate::ty::UniverseIndex,
 250     crate::ty::Variance,
 251     ::rustc_span::Span,
 252     ::rustc_errors::ErrorGuaranteed,
 253     Field,
 254     interpret::Scalar,
 255     rustc_target::abi::Size,
 256     rustc_type_ir::DebruijnIndex,
 257     ty::BoundVar,
 258     ty::Placeholder<ty::BoundVar>,
 259 }
 260
 261 TrivialTypeTraversalAndLiftImpls! {
 262     for<'tcx> {
 263         ty::ValTree<'tcx>,
 264     }
 265 }
 266
 267 ///////////////////////////////////////////////////////////////////////////
 268 // Lift implementations
 269
 270 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>> Lift<'tcx> for (A, B) {
 271     type Lifted = (A::Lifted, B::Lifted);
 272     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 273         Some((tcx.lift(self.0)?, tcx.lift(self.1)?))
 274     }
 275 }
 276
 277 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>, C: Lift<'tcx>> Lift<'tcx> for (A, B, C) {
 278     type Lifted = (A::Lifted, B::Lifted, C::Lifted);
 279     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 280         Some((tcx.lift(self.0)?, tcx.lift(self.1)?, tcx.lift(self.2)?))
 281     }
 282 }
 283
 284 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Option<T> {
 285     type Lifted = Option<T::Lifted>;
 286     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 287         Some(match self {
 288             Some(x) => Some(tcx.lift(x)?),
 289             None => None,
 290         })
 291     }
 292 }
 293
 294 impl<'tcx, T: Lift<'tcx>, E: Lift<'tcx>> Lift<'tcx> for Result<T, E> {
 295     type Lifted = Result<T::Lifted, E::Lifted>;
 296     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 297         match self {
 298             Ok(x) => tcx.lift(x).map(Ok),
 299             Err(e) => tcx.lift(e).map(Err),
 300         }
 301     }
 302 }
 303
 304 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Box<T> {
 305     type Lifted = Box<T::Lifted>;
 306     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 307         Some(Box::new(tcx.lift(*self)?))
 308     }
 309 }
 310
 311 impl<'tcx, T: Lift<'tcx> + Clone> Lift<'tcx> for Rc<T> {
 312     type Lifted = Rc<T::Lifted>;
 313     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 314         Some(Rc::new(tcx.lift(self.as_ref().clone())?))
 315     }
 316 }
 317
 318 impl<'tcx, T: Lift<'tcx> + Clone> Lift<'tcx> for Arc<T> {
 319     type Lifted = Arc<T::Lifted>;
 320     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 321         Some(Arc::new(tcx.lift(self.as_ref().clone())?))
 322     }
 323 }
 324 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Vec<T> {
 325     type Lifted = Vec<T::Lifted>;
 326     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 327         self.into_iter().map(|v| tcx.lift(v)).collect()
 328     }
 329 }
 330
 331 impl<'tcx, I: Idx, T: Lift<'tcx>> Lift<'tcx> for IndexVec<I, T> {
 332     type Lifted = IndexVec<I, T::Lifted>;
 333     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 334         self.into_iter().map(|e| tcx.lift(e)).collect()
 335     }
 336 }
 337
 338 impl<'a, 'tcx> Lift<'tcx> for Term<'a> {
 339     type Lifted = ty::Term<'tcx>;
 340     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 341         Some(
 342             match self.unpack() {
 343                 TermKind::Ty(ty) => TermKind::Ty(tcx.lift(ty)?),
 344                 TermKind::Const(c) => TermKind::Const(tcx.lift(c)?),
 345             }
 346             .pack(),
 347         )
 348     }
 349 }
 350 impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
 351     type Lifted = ty::ParamEnv<'tcx>;
 352     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 353         tcx.lift(self.caller_bounds())
 354             .map(|caller_bounds| ty::ParamEnv::new(caller_bounds, self.reveal(), self.constness()))
 355     }
 356 }
 357
 358 ///////////////////////////////////////////////////////////////////////////
 359 // TypeFoldable implementations.
 360
 361 /// AdtDefs are basically the same as a DefId.
 362 impl<'tcx> TypeFoldable<'tcx> for ty::AdtDef<'tcx> {
 363     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
 364         Ok(self)
 365     }
 366 }
 367
 368 impl<'tcx> TypeVisitable<'tcx> for ty::AdtDef<'tcx> {
 369     fn visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 370         ControlFlow::Continue(())
 371     }
 372 }
 373
 374 impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
 375     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 376         self,
 377         folder: &mut F,
 378     ) -> Result<(T, U), F::Error> {
 379         Ok((self.0.try_fold_with(folder)?, self.1.try_fold_with(folder)?))
 380     }
 381 }
 382
 383 impl<'tcx, T: TypeVisitable<'tcx>, U: TypeVisitable<'tcx>> TypeVisitable<'tcx> for (T, U) {
 384     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 385         self.0.visit_with(visitor)?;
 386         self.1.visit_with(visitor)
 387     }
 388 }
 389
 390 impl<'tcx, A: TypeFoldable<'tcx>, B: TypeFoldable<'tcx>, C: TypeFoldable<'tcx>> TypeFoldable<'tcx>
 391     for (A, B, C)
 392 {
 393     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 394         self,
 395         folder: &mut F,
 396     ) -> Result<(A, B, C), F::Error> {
 397         Ok((
 398             self.0.try_fold_with(folder)?,
 399             self.1.try_fold_with(folder)?,
 400             self.2.try_fold_with(folder)?,
 401         ))
 402     }
 403 }
 404
 405 impl<'tcx, A: TypeVisitable<'tcx>, B: TypeVisitable<'tcx>, C: TypeVisitable<'tcx>>
 406     TypeVisitable<'tcx> for (A, B, C)
 407 {
 408     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 409         self.0.visit_with(visitor)?;
 410         self.1.visit_with(visitor)?;
 411         self.2.visit_with(visitor)
 412     }
 413 }
 414
 415 EnumTypeTraversalImpl! {
 416     impl<'tcx, T> TypeFoldable<'tcx> for Option<T> {
 417         (Some)(a),
 418         (None),
 419     } where T: TypeFoldable<'tcx>
 420 }
 421 EnumTypeTraversalImpl! {
 422     impl<'tcx, T> TypeVisitable<'tcx> for Option<T> {
 423         (Some)(a),
 424         (None),
 425     } where T: TypeVisitable<'tcx>
 426 }
 427
 428 EnumTypeTraversalImpl! {
 429     impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
 430         (Ok)(a),
 431         (Err)(a),
 432     } where T: TypeFoldable<'tcx>, E: TypeFoldable<'tcx>,
 433 }
 434 EnumTypeTraversalImpl! {
 435     impl<'tcx, T, E> TypeVisitable<'tcx> for Result<T, E> {
 436         (Ok)(a),
 437         (Err)(a),
 438     } where T: TypeVisitable<'tcx>, E: TypeVisitable<'tcx>,
 439 }
 440
 441 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
 442     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 443         mut self,
 444         folder: &mut F,
 445     ) -> Result<Self, F::Error> {
 446         // We merely want to replace the contained `T`, if at all possible,
 447         // so that we don't needlessly allocate a new `Rc` or indeed clone
 448         // the contained type.
 449         unsafe {
 450             // First step is to ensure that we have a unique reference to
 451             // the contained type, which `Rc::make_mut` will accomplish (by
 452             // allocating a new `Rc` and cloning the `T` only if required).
 453             // This is done *before* casting to `Rc<ManuallyDrop<T>>` so that
 454             // panicking during `make_mut` does not leak the `T`.
 455             Rc::make_mut(&mut self);
 456
 457             // Casting to `Rc<ManuallyDrop<T>>` is safe because `ManuallyDrop`
 458             // is `repr(transparent)`.
 459             let ptr = Rc::into_raw(self).cast::<ManuallyDrop<T>>();
 460             let mut unique = Rc::from_raw(ptr);
 461
 462             // Call to `Rc::make_mut` above guarantees that `unique` is the
 463             // sole reference to the contained value, so we can avoid doing
 464             // a checked `get_mut` here.
 465             let slot = Rc::get_mut_unchecked(&mut unique);
 466
 467             // Semantically move the contained type out from `unique`, fold
 468             // it, then move the folded value back into `unique`. Should
 469             // folding fail, `ManuallyDrop` ensures that the "moved-out"
 470             // value is not re-dropped.
 471             let owned = ManuallyDrop::take(slot);
 472             let folded = owned.try_fold_with(folder)?;
 473             *slot = ManuallyDrop::new(folded);
 474
 475             // Cast back to `Rc<T>`.
 476             Ok(Rc::from_raw(Rc::into_raw(unique).cast()))
 477         }
 478     }
 479 }
 480
 481 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Rc<T> {
 482     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 483         (**self).visit_with(visitor)
 484     }
 485 }
 486
 487 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
 488     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 489         mut self,
 490         folder: &mut F,
 491     ) -> Result<Self, F::Error> {
 492         // We merely want to replace the contained `T`, if at all possible,
 493         // so that we don't needlessly allocate a new `Arc` or indeed clone
 494         // the contained type.
 495         unsafe {
 496             // First step is to ensure that we have a unique reference to
 497             // the contained type, which `Arc::make_mut` will accomplish (by
 498             // allocating a new `Arc` and cloning the `T` only if required).
 499             // This is done *before* casting to `Arc<ManuallyDrop<T>>` so that
 500             // panicking during `make_mut` does not leak the `T`.
 501             Arc::make_mut(&mut self);
 502
 503             // Casting to `Arc<ManuallyDrop<T>>` is safe because `ManuallyDrop`
 504             // is `repr(transparent)`.
 505             let ptr = Arc::into_raw(self).cast::<ManuallyDrop<T>>();
 506             let mut unique = Arc::from_raw(ptr);
 507
 508             // Call to `Arc::make_mut` above guarantees that `unique` is the
 509             // sole reference to the contained value, so we can avoid doing
 510             // a checked `get_mut` here.
 511             let slot = Arc::get_mut_unchecked(&mut unique);
 512
 513             // Semantically move the contained type out from `unique`, fold
 514             // it, then move the folded value back into `unique`. Should
 515             // folding fail, `ManuallyDrop` ensures that the "moved-out"
 516             // value is not re-dropped.
 517             let owned = ManuallyDrop::take(slot);
 518             let folded = owned.try_fold_with(folder)?;
 519             *slot = ManuallyDrop::new(folded);
 520
 521             // Cast back to `Arc<T>`.
 522             Ok(Arc::from_raw(Arc::into_raw(unique).cast()))
 523         }
 524     }
 525 }
 526
 527 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Arc<T> {
 528     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 529         (**self).visit_with(visitor)
 530     }
 531 }
 532
 533 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
 534     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 535         self.try_map_id(|value| value.try_fold_with(folder))
 536     }
 537 }
 538
 539 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Box<T> {
 540     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 541         (**self).visit_with(visitor)
 542     }
 543 }
 544
 545 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
 546     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 547         self.try_map_id(|t| t.try_fold_with(folder))
 548     }
 549 }
 550
 551 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Vec<T> {
 552     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 553         self.iter().try_for_each(|t| t.visit_with(visitor))
 554     }
 555 }
 556
 557 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for &[T] {
 558     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 559         self.iter().try_for_each(|t| t.visit_with(visitor))
 560     }
 561 }
 562
 563 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
 564     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 565         self.try_map_id(|t| t.try_fold_with(folder))
 566     }
 567 }
 568
 569 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Box<[T]> {
 570     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 571         self.iter().try_for_each(|t| t.visit_with(visitor))
 572     }
 573 }
 574
 575 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<'tcx, T> {
 576     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 577         folder.try_fold_binder(self)
 578     }
 579 }
 580
 581 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for ty::Binder<'tcx, T> {
 582     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 583         visitor.visit_binder(self)
 584     }
 585 }
 586
 587 impl<'tcx, T: TypeFoldable<'tcx>> TypeSuperFoldable<'tcx> for ty::Binder<'tcx, T> {
 588     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 589         self,
 590         folder: &mut F,
 591     ) -> Result<Self, F::Error> {
 592         self.try_map_bound(|ty| ty.try_fold_with(folder))
 593     }
 594 }
 595
 596 impl<'tcx, T: TypeVisitable<'tcx>> TypeSuperVisitable<'tcx> for ty::Binder<'tcx, T> {
 597     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 598         self.as_ref().skip_binder().visit_with(visitor)
 599     }
 600 }
 601
 602 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
 603     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 604         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_poly_existential_predicates(v))
 605     }
 606 }
 607
 608 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Const<'tcx>> {
 609     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 610         ty::util::fold_list(self, folder, |tcx, v| tcx.mk_const_list(v.iter()))
 611     }
 612 }
 613
 614 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
 615     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 616         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_projs(v))
 617     }
 618 }
 619
 620 impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
 621     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 622         folder.try_fold_ty(self)
 623     }
 624 }
 625
 626 impl<'tcx> TypeVisitable<'tcx> for Ty<'tcx> {
 627     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 628         visitor.visit_ty(*self)
 629     }
 630 }
 631
 632 impl<'tcx> TypeSuperFoldable<'tcx> for Ty<'tcx> {
 633     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 634         self,
 635         folder: &mut F,
 636     ) -> Result<Self, F::Error> {
 637         let kind = match *self.kind() {
 638             ty::RawPtr(tm) => ty::RawPtr(tm.try_fold_with(folder)?),
 639             ty::Array(typ, sz) => ty::Array(typ.try_fold_with(folder)?, sz.try_fold_with(folder)?),
 640             ty::Slice(typ) => ty::Slice(typ.try_fold_with(folder)?),
 641             ty::Adt(tid, substs) => ty::Adt(tid, substs.try_fold_with(folder)?),
 642             ty::Dynamic(trait_ty, region, representation) => ty::Dynamic(
 643                 trait_ty.try_fold_with(folder)?,
 644                 region.try_fold_with(folder)?,
 645                 representation,
 646             ),
 647             ty::Tuple(ts) => ty::Tuple(ts.try_fold_with(folder)?),
 648             ty::FnDef(def_id, substs) => ty::FnDef(def_id, substs.try_fold_with(folder)?),
 649             ty::FnPtr(f) => ty::FnPtr(f.try_fold_with(folder)?),
 650             ty::Ref(r, ty, mutbl) => {
 651                 ty::Ref(r.try_fold_with(folder)?, ty.try_fold_with(folder)?, mutbl)
 652             }
 653             ty::Generator(did, substs, movability) => {
 654                 ty::Generator(did, substs.try_fold_with(folder)?, movability)
 655             }
 656             ty::GeneratorWitness(types) => ty::GeneratorWitness(types.try_fold_with(folder)?),
 657             ty::Closure(did, substs) => ty::Closure(did, substs.try_fold_with(folder)?),
 658             ty::Alias(kind, data) => ty::Alias(kind, data.try_fold_with(folder)?),
 659
 660             ty::Bool
 661             | ty::Char
 662             | ty::Str
 663             | ty::Int(_)
 664             | ty::Uint(_)
 665             | ty::Float(_)
 666             | ty::Error(_)
 667             | ty::Infer(_)
 668             | ty::Param(..)
 669             | ty::Bound(..)
 670             | ty::Placeholder(..)
 671             | ty::Never
 672             | ty::Foreign(..) => return Ok(self),
 673         };
 674
 675         Ok(if *self.kind() == kind { self } else { folder.tcx().mk_ty(kind) })
 676     }
 677 }
 678
 679 impl<'tcx> TypeSuperVisitable<'tcx> for Ty<'tcx> {
 680     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 681         match self.kind() {
 682             ty::RawPtr(ref tm) => tm.visit_with(visitor),
 683             ty::Array(typ, sz) => {
 684                 typ.visit_with(visitor)?;
 685                 sz.visit_with(visitor)
 686             }
 687             ty::Slice(typ) => typ.visit_with(visitor),
 688             ty::Adt(_, substs) => substs.visit_with(visitor),
 689             ty::Dynamic(ref trait_ty, ref reg, _) => {
 690                 trait_ty.visit_with(visitor)?;
 691                 reg.visit_with(visitor)
 692             }
 693             ty::Tuple(ts) => ts.visit_with(visitor),
 694             ty::FnDef(_, substs) => substs.visit_with(visitor),
 695             ty::FnPtr(ref f) => f.visit_with(visitor),
 696             ty::Ref(r, ty, _) => {
 697                 r.visit_with(visitor)?;
 698                 ty.visit_with(visitor)
 699             }
 700             ty::Generator(_did, ref substs, _) => substs.visit_with(visitor),
 701             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
 702             ty::Closure(_did, ref substs) => substs.visit_with(visitor),
 703             ty::Alias(_, ref data) => data.visit_with(visitor),
 704
 705             ty::Bool
 706             | ty::Char
 707             | ty::Str
 708             | ty::Int(_)
 709             | ty::Uint(_)
 710             | ty::Float(_)
 711             | ty::Error(_)
 712             | ty::Infer(_)
 713             | ty::Bound(..)
 714             | ty::Placeholder(..)
 715             | ty::Param(..)
 716             | ty::Never
 717             | ty::Foreign(..) => ControlFlow::Continue(()),
 718         }
 719     }
 720 }
 721
 722 impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
 723     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 724         folder.try_fold_region(self)
 725     }
 726 }
 727
 728 impl<'tcx> TypeVisitable<'tcx> for ty::Region<'tcx> {
 729     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 730         visitor.visit_region(*self)
 731     }
 732 }
 733
 734 impl<'tcx> TypeSuperFoldable<'tcx> for ty::Region<'tcx> {
 735     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 736         self,
 737         _folder: &mut F,
 738     ) -> Result<Self, F::Error> {
 739         Ok(self)
 740     }
 741 }
 742
 743 impl<'tcx> TypeSuperVisitable<'tcx> for ty::Region<'tcx> {
 744     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 745         ControlFlow::Continue(())
 746     }
 747 }
 748
 749 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
 750     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 751         folder.try_fold_predicate(self)
 752     }
 753 }
 754
 755 impl<'tcx> TypeVisitable<'tcx> for ty::Predicate<'tcx> {
 756     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 757         visitor.visit_predicate(*self)
 758     }
 759
 760     #[inline]
 761     fn has_vars_bound_at_or_above(&self, binder: ty::DebruijnIndex) -> bool {
 762         self.outer_exclusive_binder() > binder
 763     }
 764
 765     #[inline]
 766     fn has_type_flags(&self, flags: ty::TypeFlags) -> bool {
 767         self.flags().intersects(flags)
 768     }
 769 }
 770
 771 impl<'tcx> TypeSuperFoldable<'tcx> for ty::Predicate<'tcx> {
 772     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 773         self,
 774         folder: &mut F,
 775     ) -> Result<Self, F::Error> {
 776         let new = self.kind().try_fold_with(folder)?;
 777         Ok(folder.tcx().reuse_or_mk_predicate(self, new))
 778     }
 779 }
 780
 781 impl<'tcx> TypeSuperVisitable<'tcx> for ty::Predicate<'tcx> {
 782     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 783         self.kind().visit_with(visitor)
 784     }
 785 }
 786
 787 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
 788     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 789         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_predicates(v))
 790     }
 791 }
 792
 793 impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
 794     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 795         self.try_map_id(|x| x.try_fold_with(folder))
 796     }
 797 }
 798
 799 impl<'tcx, T: TypeVisitable<'tcx>, I: Idx> TypeVisitable<'tcx> for IndexVec<I, T> {
 800     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 801         self.iter().try_for_each(|t| t.visit_with(visitor))
 802     }
 803 }
 804
 805 impl<'tcx> TypeFoldable<'tcx> for ty::Const<'tcx> {
 806     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 807         folder.try_fold_const(self)
 808     }
 809 }
 810
 811 impl<'tcx> TypeVisitable<'tcx> for ty::Const<'tcx> {
 812     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 813         visitor.visit_const(*self)
 814     }
 815 }
 816
 817 impl<'tcx> TypeSuperFoldable<'tcx> for ty::Const<'tcx> {
 818     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 819         self,
 820         folder: &mut F,
 821     ) -> Result<Self, F::Error> {
 822         let ty = self.ty().try_fold_with(folder)?;
 823         let kind = self.kind().try_fold_with(folder)?;
 824         if ty != self.ty() || kind != self.kind() {
 825             Ok(folder.tcx().mk_const(kind, ty))
 826         } else {
 827             Ok(self)
 828         }
 829     }
 830 }
 831
 832 impl<'tcx> TypeSuperVisitable<'tcx> for ty::Const<'tcx> {
 833     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 834         self.ty().visit_with(visitor)?;
 835         self.kind().visit_with(visitor)
 836     }
 837 }
 838
 839 impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
 840     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
 841         Ok(self)
 842     }
 843 }
 844
 845 impl<'tcx> TypeVisitable<'tcx> for InferConst<'tcx> {
 846     fn visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 847         ControlFlow::Continue(())
 848     }
 849 }
 850
 851 impl<'tcx> TypeSuperVisitable<'tcx> for ty::UnevaluatedConst<'tcx> {
 852     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 853         self.substs.visit_with(visitor)
 854     }
 855 }