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 use rustc_target::abi::TyAndLayout;
  15
  16 use std::fmt;
  17 use std::mem::ManuallyDrop;
  18 use std::ops::ControlFlow;
  19 use std::rc::Rc;
  20 use std::sync::Arc;
  21
  22 impl fmt::Debug for ty::TraitDef {
  23     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  24         ty::tls::with(|tcx| {
  25             with_no_trimmed_paths!({
  26                 f.write_str(
  27                     &FmtPrinter::new(tcx, Namespace::TypeNS)
  28                         .print_def_path(self.def_id, &[])?
  29                         .into_buffer(),
  30                 )
  31             })
  32         })
  33     }
  34 }
  35
  36 impl<'tcx> fmt::Debug for ty::AdtDef<'tcx> {
  37     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  38         ty::tls::with(|tcx| {
  39             with_no_trimmed_paths!({
  40                 f.write_str(
  41                     &FmtPrinter::new(tcx, Namespace::TypeNS)
  42                         .print_def_path(self.did(), &[])?
  43                         .into_buffer(),
  44                 )
  45             })
  46         })
  47     }
  48 }
  49
  50 impl fmt::Debug for ty::UpvarId {
  51     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  52         let name = ty::tls::with(|tcx| tcx.hir().name(self.var_path.hir_id));
  53         write!(f, "UpvarId({:?};`{}`;{:?})", self.var_path.hir_id, name, self.closure_expr_id)
  54     }
  55 }
  56
  57 impl<'tcx> fmt::Debug for ty::ExistentialTraitRef<'tcx> {
  58     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  59         with_no_trimmed_paths!(fmt::Display::fmt(self, f))
  60     }
  61 }
  62
  63 impl<'tcx> fmt::Debug for ty::adjustment::Adjustment<'tcx> {
  64     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  65         write!(f, "{:?} -> {}", self.kind, self.target)
  66     }
  67 }
  68
  69 impl fmt::Debug for ty::BoundRegionKind {
  70     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  71         match *self {
  72             ty::BrAnon(n, span) => write!(f, "BrAnon({n:?}, {span:?})"),
  73             ty::BrNamed(did, name) => {
  74                 if did.is_crate_root() {
  75                     write!(f, "BrNamed({})", name)
  76                 } else {
  77                     write!(f, "BrNamed({:?}, {})", did, name)
  78                 }
  79             }
  80             ty::BrEnv => write!(f, "BrEnv"),
  81         }
  82     }
  83 }
  84
  85 impl fmt::Debug for ty::FreeRegion {
  86     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  87         write!(f, "ReFree({:?}, {:?})", self.scope, self.bound_region)
  88     }
  89 }
  90
  91 impl<'tcx> fmt::Debug for ty::FnSig<'tcx> {
  92     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  93         write!(f, "({:?}; c_variadic: {})->{:?}", self.inputs(), self.c_variadic, self.output())
  94     }
  95 }
  96
  97 impl<'tcx> fmt::Debug for ty::ConstVid<'tcx> {
  98     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  99         write!(f, "_#{}c", self.index)
 100     }
 101 }
 102
 103 impl<'tcx> fmt::Debug for ty::TraitRef<'tcx> {
 104     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 105         with_no_trimmed_paths!(fmt::Display::fmt(self, f))
 106     }
 107 }
 108
 109 impl<'tcx> fmt::Debug for Ty<'tcx> {
 110     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 111         with_no_trimmed_paths!(fmt::Display::fmt(self, f))
 112     }
 113 }
 114
 115 impl fmt::Debug for ty::ParamTy {
 116     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 117         write!(f, "{}/#{}", self.name, self.index)
 118     }
 119 }
 120
 121 impl fmt::Debug for ty::ParamConst {
 122     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 123         write!(f, "{}/#{}", self.name, self.index)
 124     }
 125 }
 126
 127 impl<'tcx> fmt::Debug for ty::TraitPredicate<'tcx> {
 128     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 129         if let ty::BoundConstness::ConstIfConst = self.constness {
 130             write!(f, "~const ")?;
 131         }
 132         write!(f, "TraitPredicate({:?}, polarity:{:?})", self.trait_ref, self.polarity)
 133     }
 134 }
 135
 136 impl<'tcx> fmt::Debug for ty::ProjectionPredicate<'tcx> {
 137     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 138         write!(f, "ProjectionPredicate({:?}, {:?})", self.projection_ty, self.term)
 139     }
 140 }
 141
 142 impl<'tcx> fmt::Debug for ty::Predicate<'tcx> {
 143     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 144         write!(f, "{:?}", self.kind())
 145     }
 146 }
 147
 148 impl<'tcx> fmt::Debug for ty::Clause<'tcx> {
 149     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 150         match *self {
 151             ty::Clause::Trait(ref a) => a.fmt(f),
 152             ty::Clause::RegionOutlives(ref pair) => pair.fmt(f),
 153             ty::Clause::TypeOutlives(ref pair) => pair.fmt(f),
 154             ty::Clause::Projection(ref pair) => pair.fmt(f),
 155         }
 156     }
 157 }
 158
 159 impl<'tcx> fmt::Debug for ty::PredicateKind<'tcx> {
 160     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 161         match *self {
 162             ty::PredicateKind::Clause(ref a) => a.fmt(f),
 163             ty::PredicateKind::Subtype(ref pair) => pair.fmt(f),
 164             ty::PredicateKind::Coerce(ref pair) => pair.fmt(f),
 165             ty::PredicateKind::WellFormed(data) => write!(f, "WellFormed({:?})", data),
 166             ty::PredicateKind::ObjectSafe(trait_def_id) => {
 167                 write!(f, "ObjectSafe({:?})", trait_def_id)
 168             }
 169             ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
 170                 write!(f, "ClosureKind({:?}, {:?}, {:?})", closure_def_id, closure_substs, kind)
 171             }
 172             ty::PredicateKind::ConstEvaluatable(ct) => {
 173                 write!(f, "ConstEvaluatable({ct:?})")
 174             }
 175             ty::PredicateKind::ConstEquate(c1, c2) => write!(f, "ConstEquate({:?}, {:?})", c1, c2),
 176             ty::PredicateKind::TypeWellFormedFromEnv(ty) => {
 177                 write!(f, "TypeWellFormedFromEnv({:?})", ty)
 178             }
 179             ty::PredicateKind::Ambiguous => write!(f, "Ambiguous"),
 180         }
 181     }
 182 }
 183
 184 impl<'tcx> fmt::Debug for AliasTy<'tcx> {
 185     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 186         f.debug_struct("AliasTy")
 187             .field("substs", &self.substs)
 188             .field("def_id", &self.def_id)
 189             .finish()
 190     }
 191 }
 192
 193 ///////////////////////////////////////////////////////////////////////////
 194 // Atomic structs
 195 //
 196 // For things that don't carry any arena-allocated data (and are
 197 // copy...), just add them to this list.
 198
 199 TrivialTypeTraversalAndLiftImpls! {
 200     (),
 201     bool,
 202     usize,
 203     ::rustc_target::abi::VariantIdx,
 204     u16,
 205     u32,
 206     u64,
 207     String,
 208     crate::middle::region::Scope,
 209     crate::ty::FloatTy,
 210     ::rustc_ast::InlineAsmOptions,
 211     ::rustc_ast::InlineAsmTemplatePiece,
 212     ::rustc_ast::NodeId,
 213     ::rustc_span::symbol::Symbol,
 214     ::rustc_hir::def::Res,
 215     ::rustc_hir::def_id::DefId,
 216     ::rustc_hir::def_id::LocalDefId,
 217     ::rustc_hir::HirId,
 218     ::rustc_hir::MatchSource,
 219     ::rustc_hir::Mutability,
 220     ::rustc_hir::Unsafety,
 221     ::rustc_target::asm::InlineAsmRegOrRegClass,
 222     ::rustc_target::spec::abi::Abi,
 223     crate::mir::coverage::ExpressionOperandId,
 224     crate::mir::coverage::CounterValueReference,
 225     crate::mir::coverage::InjectedExpressionId,
 226     crate::mir::coverage::InjectedExpressionIndex,
 227     crate::mir::coverage::MappedExpressionIndex,
 228     crate::mir::Local,
 229     crate::mir::Promoted,
 230     crate::traits::Reveal,
 231     crate::ty::adjustment::AutoBorrowMutability,
 232     crate::ty::AdtKind,
 233     crate::ty::BoundConstness,
 234     // Including `BoundRegionKind` is a *bit* dubious, but direct
 235     // references to bound region appear in `ty::Error`, and aren't
 236     // really meant to be folded. In general, we can only fold a fully
 237     // general `Region`.
 238     crate::ty::BoundRegionKind,
 239     crate::ty::AssocItem,
 240     crate::ty::AssocKind,
 241     crate::ty::AliasKind,
 242     crate::ty::Placeholder<crate::ty::BoundRegionKind>,
 243     crate::ty::ClosureKind,
 244     crate::ty::FreeRegion,
 245     crate::ty::InferTy,
 246     crate::ty::IntVarValue,
 247     crate::ty::ParamConst,
 248     crate::ty::ParamTy,
 249     crate::ty::adjustment::PointerCast,
 250     crate::ty::RegionVid,
 251     crate::ty::UniverseIndex,
 252     crate::ty::Variance,
 253     ::rustc_span::Span,
 254     ::rustc_errors::ErrorGuaranteed,
 255     Field,
 256     interpret::Scalar,
 257     rustc_target::abi::Size,
 258     rustc_type_ir::DebruijnIndex,
 259     ty::BoundVar,
 260     ty::Placeholder<ty::BoundVar>,
 261 }
 262
 263 TrivialTypeTraversalAndLiftImpls! {
 264     for<'tcx> {
 265         ty::ValTree<'tcx>,
 266     }
 267 }
 268
 269 ///////////////////////////////////////////////////////////////////////////
 270 // Lift implementations
 271
 272 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>> Lift<'tcx> for (A, B) {
 273     type Lifted = (A::Lifted, B::Lifted);
 274     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 275         Some((tcx.lift(self.0)?, tcx.lift(self.1)?))
 276     }
 277 }
 278
 279 impl<'tcx, A: Lift<'tcx>, B: Lift<'tcx>, C: Lift<'tcx>> Lift<'tcx> for (A, B, C) {
 280     type Lifted = (A::Lifted, B::Lifted, C::Lifted);
 281     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 282         Some((tcx.lift(self.0)?, tcx.lift(self.1)?, tcx.lift(self.2)?))
 283     }
 284 }
 285
 286 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Option<T> {
 287     type Lifted = Option<T::Lifted>;
 288     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 289         Some(match self {
 290             Some(x) => Some(tcx.lift(x)?),
 291             None => None,
 292         })
 293     }
 294 }
 295
 296 impl<'tcx, T: Lift<'tcx>, E: Lift<'tcx>> Lift<'tcx> for Result<T, E> {
 297     type Lifted = Result<T::Lifted, E::Lifted>;
 298     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 299         match self {
 300             Ok(x) => tcx.lift(x).map(Ok),
 301             Err(e) => tcx.lift(e).map(Err),
 302         }
 303     }
 304 }
 305
 306 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Box<T> {
 307     type Lifted = Box<T::Lifted>;
 308     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 309         Some(Box::new(tcx.lift(*self)?))
 310     }
 311 }
 312
 313 impl<'tcx, T: Lift<'tcx> + Clone> Lift<'tcx> for Rc<T> {
 314     type Lifted = Rc<T::Lifted>;
 315     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 316         Some(Rc::new(tcx.lift(self.as_ref().clone())?))
 317     }
 318 }
 319
 320 impl<'tcx, T: Lift<'tcx> + Clone> Lift<'tcx> for Arc<T> {
 321     type Lifted = Arc<T::Lifted>;
 322     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 323         Some(Arc::new(tcx.lift(self.as_ref().clone())?))
 324     }
 325 }
 326 impl<'tcx, T: Lift<'tcx>> Lift<'tcx> for Vec<T> {
 327     type Lifted = Vec<T::Lifted>;
 328     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 329         self.into_iter().map(|v| tcx.lift(v)).collect()
 330     }
 331 }
 332
 333 impl<'tcx, I: Idx, T: Lift<'tcx>> Lift<'tcx> for IndexVec<I, T> {
 334     type Lifted = IndexVec<I, T::Lifted>;
 335     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 336         self.into_iter().map(|e| tcx.lift(e)).collect()
 337     }
 338 }
 339
 340 impl<'a, 'tcx> Lift<'tcx> for Term<'a> {
 341     type Lifted = ty::Term<'tcx>;
 342     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 343         Some(
 344             match self.unpack() {
 345                 TermKind::Ty(ty) => TermKind::Ty(tcx.lift(ty)?),
 346                 TermKind::Const(c) => TermKind::Const(tcx.lift(c)?),
 347             }
 348             .pack(),
 349         )
 350     }
 351 }
 352 impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
 353     type Lifted = ty::ParamEnv<'tcx>;
 354     fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
 355         tcx.lift(self.caller_bounds())
 356             .map(|caller_bounds| ty::ParamEnv::new(caller_bounds, self.reveal(), self.constness()))
 357     }
 358 }
 359
 360 ///////////////////////////////////////////////////////////////////////////
 361 // TypeFoldable implementations.
 362
 363 /// AdtDefs are basically the same as a DefId.
 364 impl<'tcx> TypeFoldable<'tcx> for ty::AdtDef<'tcx> {
 365     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
 366         Ok(self)
 367     }
 368 }
 369
 370 impl<'tcx> TypeVisitable<'tcx> for ty::AdtDef<'tcx> {
 371     fn visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 372         ControlFlow::Continue(())
 373     }
 374 }
 375
 376 impl<'tcx, T: TypeFoldable<'tcx>, U: TypeFoldable<'tcx>> TypeFoldable<'tcx> for (T, U) {
 377     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 378         self,
 379         folder: &mut F,
 380     ) -> Result<(T, U), F::Error> {
 381         Ok((self.0.try_fold_with(folder)?, self.1.try_fold_with(folder)?))
 382     }
 383 }
 384
 385 impl<'tcx, T: TypeVisitable<'tcx>, U: TypeVisitable<'tcx>> TypeVisitable<'tcx> for (T, U) {
 386     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 387         self.0.visit_with(visitor)?;
 388         self.1.visit_with(visitor)
 389     }
 390 }
 391
 392 impl<'tcx, A: TypeFoldable<'tcx>, B: TypeFoldable<'tcx>, C: TypeFoldable<'tcx>> TypeFoldable<'tcx>
 393     for (A, B, C)
 394 {
 395     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 396         self,
 397         folder: &mut F,
 398     ) -> Result<(A, B, C), F::Error> {
 399         Ok((
 400             self.0.try_fold_with(folder)?,
 401             self.1.try_fold_with(folder)?,
 402             self.2.try_fold_with(folder)?,
 403         ))
 404     }
 405 }
 406
 407 impl<'tcx, A: TypeVisitable<'tcx>, B: TypeVisitable<'tcx>, C: TypeVisitable<'tcx>>
 408     TypeVisitable<'tcx> for (A, B, C)
 409 {
 410     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 411         self.0.visit_with(visitor)?;
 412         self.1.visit_with(visitor)?;
 413         self.2.visit_with(visitor)
 414     }
 415 }
 416
 417 EnumTypeTraversalImpl! {
 418     impl<'tcx, T> TypeFoldable<'tcx> for Option<T> {
 419         (Some)(a),
 420         (None),
 421     } where T: TypeFoldable<'tcx>
 422 }
 423 EnumTypeTraversalImpl! {
 424     impl<'tcx, T> TypeVisitable<'tcx> for Option<T> {
 425         (Some)(a),
 426         (None),
 427     } where T: TypeVisitable<'tcx>
 428 }
 429
 430 EnumTypeTraversalImpl! {
 431     impl<'tcx, T, E> TypeFoldable<'tcx> for Result<T, E> {
 432         (Ok)(a),
 433         (Err)(a),
 434     } where T: TypeFoldable<'tcx>, E: TypeFoldable<'tcx>,
 435 }
 436 EnumTypeTraversalImpl! {
 437     impl<'tcx, T, E> TypeVisitable<'tcx> for Result<T, E> {
 438         (Ok)(a),
 439         (Err)(a),
 440     } where T: TypeVisitable<'tcx>, E: TypeVisitable<'tcx>,
 441 }
 442
 443 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Rc<T> {
 444     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 445         mut self,
 446         folder: &mut F,
 447     ) -> Result<Self, F::Error> {
 448         // We merely want to replace the contained `T`, if at all possible,
 449         // so that we don't needlessly allocate a new `Rc` or indeed clone
 450         // the contained type.
 451         unsafe {
 452             // First step is to ensure that we have a unique reference to
 453             // the contained type, which `Rc::make_mut` will accomplish (by
 454             // allocating a new `Rc` and cloning the `T` only if required).
 455             // This is done *before* casting to `Rc<ManuallyDrop<T>>` so that
 456             // panicking during `make_mut` does not leak the `T`.
 457             Rc::make_mut(&mut self);
 458
 459             // Casting to `Rc<ManuallyDrop<T>>` is safe because `ManuallyDrop`
 460             // is `repr(transparent)`.
 461             let ptr = Rc::into_raw(self).cast::<ManuallyDrop<T>>();
 462             let mut unique = Rc::from_raw(ptr);
 463
 464             // Call to `Rc::make_mut` above guarantees that `unique` is the
 465             // sole reference to the contained value, so we can avoid doing
 466             // a checked `get_mut` here.
 467             let slot = Rc::get_mut_unchecked(&mut unique);
 468
 469             // Semantically move the contained type out from `unique`, fold
 470             // it, then move the folded value back into `unique`. Should
 471             // folding fail, `ManuallyDrop` ensures that the "moved-out"
 472             // value is not re-dropped.
 473             let owned = ManuallyDrop::take(slot);
 474             let folded = owned.try_fold_with(folder)?;
 475             *slot = ManuallyDrop::new(folded);
 476
 477             // Cast back to `Rc<T>`.
 478             Ok(Rc::from_raw(Rc::into_raw(unique).cast()))
 479         }
 480     }
 481 }
 482
 483 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Rc<T> {
 484     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 485         (**self).visit_with(visitor)
 486     }
 487 }
 488
 489 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Arc<T> {
 490     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
 491         mut self,
 492         folder: &mut F,
 493     ) -> Result<Self, F::Error> {
 494         // We merely want to replace the contained `T`, if at all possible,
 495         // so that we don't needlessly allocate a new `Arc` or indeed clone
 496         // the contained type.
 497         unsafe {
 498             // First step is to ensure that we have a unique reference to
 499             // the contained type, which `Arc::make_mut` will accomplish (by
 500             // allocating a new `Arc` and cloning the `T` only if required).
 501             // This is done *before* casting to `Arc<ManuallyDrop<T>>` so that
 502             // panicking during `make_mut` does not leak the `T`.
 503             Arc::make_mut(&mut self);
 504
 505             // Casting to `Arc<ManuallyDrop<T>>` is safe because `ManuallyDrop`
 506             // is `repr(transparent)`.
 507             let ptr = Arc::into_raw(self).cast::<ManuallyDrop<T>>();
 508             let mut unique = Arc::from_raw(ptr);
 509
 510             // Call to `Arc::make_mut` above guarantees that `unique` is the
 511             // sole reference to the contained value, so we can avoid doing
 512             // a checked `get_mut` here.
 513             let slot = Arc::get_mut_unchecked(&mut unique);
 514
 515             // Semantically move the contained type out from `unique`, fold
 516             // it, then move the folded value back into `unique`. Should
 517             // folding fail, `ManuallyDrop` ensures that the "moved-out"
 518             // value is not re-dropped.
 519             let owned = ManuallyDrop::take(slot);
 520             let folded = owned.try_fold_with(folder)?;
 521             *slot = ManuallyDrop::new(folded);
 522
 523             // Cast back to `Arc<T>`.
 524             Ok(Arc::from_raw(Arc::into_raw(unique).cast()))
 525         }
 526     }
 527 }
 528
 529 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Arc<T> {
 530     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 531         (**self).visit_with(visitor)
 532     }
 533 }
 534
 535 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<T> {
 536     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 537         self.try_map_id(|value| value.try_fold_with(folder))
 538     }
 539 }
 540
 541 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Box<T> {
 542     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 543         (**self).visit_with(visitor)
 544     }
 545 }
 546
 547 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vec<T> {
 548     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 549         self.try_map_id(|t| t.try_fold_with(folder))
 550     }
 551 }
 552
 553 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Vec<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: TypeVisitable<'tcx>> TypeVisitable<'tcx> for &[T] {
 560     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 561         self.iter().try_for_each(|t| t.visit_with(visitor))
 562     }
 563 }
 564
 565 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Box<[T]> {
 566     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 567         self.try_map_id(|t| t.try_fold_with(folder))
 568     }
 569 }
 570
 571 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for Box<[T]> {
 572     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 573         self.iter().try_for_each(|t| t.visit_with(visitor))
 574     }
 575 }
 576
 577 impl<'tcx, T: TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<'tcx, T> {
 578     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 579         folder.try_fold_binder(self)
 580     }
 581 }
 582
 583 impl<'tcx, T: TypeVisitable<'tcx>> TypeVisitable<'tcx> for ty::Binder<'tcx, T> {
 584     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 585         visitor.visit_binder(self)
 586     }
 587 }
 588
 589 impl<'tcx, T: TypeFoldable<'tcx>> TypeSuperFoldable<'tcx> for ty::Binder<'tcx, T> {
 590     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 591         self,
 592         folder: &mut F,
 593     ) -> Result<Self, F::Error> {
 594         self.try_map_bound(|ty| ty.try_fold_with(folder))
 595     }
 596 }
 597
 598 impl<'tcx, T: TypeVisitable<'tcx>> TypeSuperVisitable<'tcx> for ty::Binder<'tcx, T> {
 599     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 600         self.as_ref().skip_binder().visit_with(visitor)
 601     }
 602 }
 603
 604 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::PolyExistentialPredicate<'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.intern_poly_existential_predicates(v))
 607     }
 608 }
 609
 610 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Const<'tcx>> {
 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.mk_const_list(v.iter()))
 613     }
 614 }
 615
 616 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ProjectionKind> {
 617     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 618         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_projs(v))
 619     }
 620 }
 621
 622 impl<'tcx> TypeFoldable<'tcx> for Ty<'tcx> {
 623     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 624         folder.try_fold_ty(self)
 625     }
 626 }
 627
 628 impl<'tcx> TypeVisitable<'tcx> for Ty<'tcx> {
 629     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 630         visitor.visit_ty(*self)
 631     }
 632 }
 633
 634 impl<'tcx> TypeSuperFoldable<'tcx> for Ty<'tcx> {
 635     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 636         self,
 637         folder: &mut F,
 638     ) -> Result<Self, F::Error> {
 639         let kind = match *self.kind() {
 640             ty::RawPtr(tm) => ty::RawPtr(tm.try_fold_with(folder)?),
 641             ty::Array(typ, sz) => ty::Array(typ.try_fold_with(folder)?, sz.try_fold_with(folder)?),
 642             ty::Slice(typ) => ty::Slice(typ.try_fold_with(folder)?),
 643             ty::Adt(tid, substs) => ty::Adt(tid, substs.try_fold_with(folder)?),
 644             ty::Dynamic(trait_ty, region, representation) => ty::Dynamic(
 645                 trait_ty.try_fold_with(folder)?,
 646                 region.try_fold_with(folder)?,
 647                 representation,
 648             ),
 649             ty::Tuple(ts) => ty::Tuple(ts.try_fold_with(folder)?),
 650             ty::FnDef(def_id, substs) => ty::FnDef(def_id, substs.try_fold_with(folder)?),
 651             ty::FnPtr(f) => ty::FnPtr(f.try_fold_with(folder)?),
 652             ty::Ref(r, ty, mutbl) => {
 653                 ty::Ref(r.try_fold_with(folder)?, ty.try_fold_with(folder)?, mutbl)
 654             }
 655             ty::Generator(did, substs, movability) => {
 656                 ty::Generator(did, substs.try_fold_with(folder)?, movability)
 657             }
 658             ty::GeneratorWitness(types) => ty::GeneratorWitness(types.try_fold_with(folder)?),
 659             ty::GeneratorWitnessMIR(did, substs) => {
 660                 ty::GeneratorWitnessMIR(did, substs.try_fold_with(folder)?)
 661             }
 662             ty::Closure(did, substs) => ty::Closure(did, substs.try_fold_with(folder)?),
 663             ty::Alias(kind, data) => ty::Alias(kind, data.try_fold_with(folder)?),
 664
 665             ty::Bool
 666             | ty::Char
 667             | ty::Str
 668             | ty::Int(_)
 669             | ty::Uint(_)
 670             | ty::Float(_)
 671             | ty::Error(_)
 672             | ty::Infer(_)
 673             | ty::Param(..)
 674             | ty::Bound(..)
 675             | ty::Placeholder(..)
 676             | ty::Never
 677             | ty::Foreign(..) => return Ok(self),
 678         };
 679
 680         Ok(if *self.kind() == kind { self } else { folder.tcx().mk_ty(kind) })
 681     }
 682 }
 683
 684 impl<'tcx> TypeSuperVisitable<'tcx> for Ty<'tcx> {
 685     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 686         match self.kind() {
 687             ty::RawPtr(ref tm) => tm.visit_with(visitor),
 688             ty::Array(typ, sz) => {
 689                 typ.visit_with(visitor)?;
 690                 sz.visit_with(visitor)
 691             }
 692             ty::Slice(typ) => typ.visit_with(visitor),
 693             ty::Adt(_, substs) => substs.visit_with(visitor),
 694             ty::Dynamic(ref trait_ty, ref reg, _) => {
 695                 trait_ty.visit_with(visitor)?;
 696                 reg.visit_with(visitor)
 697             }
 698             ty::Tuple(ts) => ts.visit_with(visitor),
 699             ty::FnDef(_, substs) => substs.visit_with(visitor),
 700             ty::FnPtr(ref f) => f.visit_with(visitor),
 701             ty::Ref(r, ty, _) => {
 702                 r.visit_with(visitor)?;
 703                 ty.visit_with(visitor)
 704             }
 705             ty::Generator(_did, ref substs, _) => substs.visit_with(visitor),
 706             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
 707             ty::GeneratorWitnessMIR(_did, ref substs) => substs.visit_with(visitor),
 708             ty::Closure(_did, ref substs) => substs.visit_with(visitor),
 709             ty::Alias(_, ref data) => data.visit_with(visitor),
 710
 711             ty::Bool
 712             | ty::Char
 713             | ty::Str
 714             | ty::Int(_)
 715             | ty::Uint(_)
 716             | ty::Float(_)
 717             | ty::Error(_)
 718             | ty::Infer(_)
 719             | ty::Bound(..)
 720             | ty::Placeholder(..)
 721             | ty::Param(..)
 722             | ty::Never
 723             | ty::Foreign(..) => ControlFlow::Continue(()),
 724         }
 725     }
 726 }
 727
 728 impl<'tcx> TypeFoldable<'tcx> for ty::Region<'tcx> {
 729     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 730         folder.try_fold_region(self)
 731     }
 732 }
 733
 734 impl<'tcx> TypeVisitable<'tcx> for ty::Region<'tcx> {
 735     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 736         visitor.visit_region(*self)
 737     }
 738 }
 739
 740 impl<'tcx> TypeSuperFoldable<'tcx> for ty::Region<'tcx> {
 741     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 742         self,
 743         _folder: &mut F,
 744     ) -> Result<Self, F::Error> {
 745         Ok(self)
 746     }
 747 }
 748
 749 impl<'tcx> TypeSuperVisitable<'tcx> for ty::Region<'tcx> {
 750     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 751         ControlFlow::Continue(())
 752     }
 753 }
 754
 755 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
 756     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 757         folder.try_fold_predicate(self)
 758     }
 759 }
 760
 761 impl<'tcx> TypeVisitable<'tcx> for ty::Predicate<'tcx> {
 762     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 763         visitor.visit_predicate(*self)
 764     }
 765
 766     #[inline]
 767     fn has_vars_bound_at_or_above(&self, binder: ty::DebruijnIndex) -> bool {
 768         self.outer_exclusive_binder() > binder
 769     }
 770
 771     #[inline]
 772     fn has_type_flags(&self, flags: ty::TypeFlags) -> bool {
 773         self.flags().intersects(flags)
 774     }
 775 }
 776
 777 impl<'tcx> TypeSuperFoldable<'tcx> for ty::Predicate<'tcx> {
 778     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 779         self,
 780         folder: &mut F,
 781     ) -> Result<Self, F::Error> {
 782         let new = self.kind().try_fold_with(folder)?;
 783         Ok(folder.tcx().reuse_or_mk_predicate(self, new))
 784     }
 785 }
 786
 787 impl<'tcx> TypeSuperVisitable<'tcx> for ty::Predicate<'tcx> {
 788     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 789         self.kind().visit_with(visitor)
 790     }
 791 }
 792
 793 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<ty::Predicate<'tcx>> {
 794     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 795         ty::util::fold_list(self, folder, |tcx, v| tcx.intern_predicates(v))
 796     }
 797 }
 798
 799 impl<'tcx, T: TypeFoldable<'tcx>, I: Idx> TypeFoldable<'tcx> for IndexVec<I, T> {
 800     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 801         self.try_map_id(|x| x.try_fold_with(folder))
 802     }
 803 }
 804
 805 impl<'tcx, T: TypeVisitable<'tcx>, I: Idx> TypeVisitable<'tcx> for IndexVec<I, T> {
 806     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 807         self.iter().try_for_each(|t| t.visit_with(visitor))
 808     }
 809 }
 810
 811 impl<'tcx> TypeFoldable<'tcx> for ty::Const<'tcx> {
 812     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
 813         folder.try_fold_const(self)
 814     }
 815 }
 816
 817 impl<'tcx> TypeVisitable<'tcx> for ty::Const<'tcx> {
 818     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 819         visitor.visit_const(*self)
 820     }
 821 }
 822
 823 impl<'tcx> TypeSuperFoldable<'tcx> for ty::Const<'tcx> {
 824     fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
 825         self,
 826         folder: &mut F,
 827     ) -> Result<Self, F::Error> {
 828         let ty = self.ty().try_fold_with(folder)?;
 829         let kind = self.kind().try_fold_with(folder)?;
 830         if ty != self.ty() || kind != self.kind() {
 831             Ok(folder.tcx().mk_const(kind, ty))
 832         } else {
 833             Ok(self)
 834         }
 835     }
 836 }
 837
 838 impl<'tcx> TypeSuperVisitable<'tcx> for ty::Const<'tcx> {
 839     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 840         self.ty().visit_with(visitor)?;
 841         self.kind().visit_with(visitor)
 842     }
 843 }
 844
 845 impl<'tcx> TypeFoldable<'tcx> for InferConst<'tcx> {
 846     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
 847         Ok(self)
 848     }
 849 }
 850
 851 impl<'tcx> TypeVisitable<'tcx> for InferConst<'tcx> {
 852     fn visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
 853         ControlFlow::Continue(())
 854     }
 855 }
 856
 857 impl<'tcx> TypeSuperVisitable<'tcx> for ty::UnevaluatedConst<'tcx> {
 858     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 859         self.substs.visit_with(visitor)
 860     }
 861 }
 862
 863 impl<'tcx> TypeVisitable<'tcx> for TyAndLayout<'tcx, Ty<'tcx>> {
 864     fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
 865         visitor.visit_ty(self.ty)
 866     }
 867 }