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