1 //! Defines how the compiler represents types internally.
3 //! Two important entities in this module are:
5 //! - [`rustc_middle::ty::Ty`], used to represent the semantics of a type.
6 //! - [`rustc_middle::ty::TyCtxt`], the central data structure in the compiler.
8 //! For more information, see ["The `ty` module: representing types"] in the rustc-dev-guide.
10 //! ["The `ty` module: representing types"]: https://rustc-dev-guide.rust-lang.org/ty.html
12 pub use self::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeVisitor};
13 pub use self::AssocItemContainer::*;
14 pub use self::BorrowKind::*;
15 pub use self::IntVarValue::*;
16 pub use self::Variance::*;
20 use rustc_data_structures::fingerprint::Fingerprint;
23 use crate::metadata::ModChild;
24 use crate::middle::privacy::AccessLevels;
25 use crate::mir::{Body, GeneratorLayout};
26 use crate::traits::{self, Reveal};
28 use crate::ty::fast_reject::SimplifiedType;
29 use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
30 use crate::ty::util::Discr;
32 use rustc_attr as attr;
33 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
34 use rustc_data_structures::intern::{Interned, WithStableHash};
35 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
36 use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
38 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
39 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LocalDefIdMap, CRATE_DEF_INDEX};
41 use rustc_macros::HashStable;
42 use rustc_query_system::ich::StableHashingContext;
43 use rustc_session::cstore::CrateStoreDyn;
44 use rustc_span::symbol::{kw, Ident, Symbol};
46 use rustc_target::abi::Align;
50 use std::ops::ControlFlow;
53 pub use crate::ty::diagnostics::*;
54 pub use rustc_type_ir::InferTy::*;
55 pub use rustc_type_ir::*;
57 pub use self::binding::BindingMode;
58 pub use self::binding::BindingMode::*;
59 pub use self::closure::{
60 is_ancestor_or_same_capture, place_to_string_for_capture, BorrowKind, CaptureInfo,
61 CapturedPlace, ClosureKind, MinCaptureInformationMap, MinCaptureList,
62 RootVariableMinCaptureList, UpvarCapture, UpvarCaptureMap, UpvarId, UpvarListMap, UpvarPath,
65 pub use self::consts::{
66 Const, ConstInt, ConstKind, ConstS, InferConst, ScalarInt, Unevaluated, ValTree,
68 pub use self::context::{
69 tls, CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations,
70 CtxtInterners, DelaySpanBugEmitted, FreeRegionInfo, GeneratorInteriorTypeCause, GlobalCtxt,
71 Lift, OnDiskCache, TyCtxt, TypeckResults, UserType, UserTypeAnnotationIndex,
73 pub use self::instance::{Instance, InstanceDef};
74 pub use self::list::List;
75 pub use self::sty::BoundRegionKind::*;
76 pub use self::sty::RegionKind::*;
77 pub use self::sty::TyKind::*;
79 Binder, BoundRegion, BoundRegionKind, BoundTy, BoundTyKind, BoundVar, BoundVariableKind,
80 CanonicalPolyFnSig, ClosureSubsts, ClosureSubstsParts, ConstVid, EarlyBoundRegion,
81 ExistentialPredicate, ExistentialProjection, ExistentialTraitRef, FnSig, FreeRegion, GenSig,
82 GeneratorSubsts, GeneratorSubstsParts, InlineConstSubsts, InlineConstSubstsParts, ParamConst,
83 ParamTy, PolyExistentialProjection, PolyExistentialTraitRef, PolyFnSig, PolyGenSig,
84 PolyTraitRef, ProjectionTy, Region, RegionKind, RegionVid, TraitRef, TyKind, TypeAndMut,
85 UpvarSubsts, VarianceDiagInfo,
87 pub use self::trait_def::TraitDef;
98 pub mod inhabitedness;
100 pub mod normalize_erasing_regions;
121 mod structural_impls;
126 pub type RegisteredTools = FxHashSet<Ident>;
129 pub struct ResolverOutputs {
130 pub definitions: rustc_hir::definitions::Definitions,
131 pub cstore: Box<CrateStoreDyn>,
132 pub visibilities: FxHashMap<LocalDefId, Visibility>,
133 pub access_levels: AccessLevels,
134 pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
135 pub maybe_unused_trait_imports: FxHashSet<LocalDefId>,
136 pub maybe_unused_extern_crates: Vec<(LocalDefId, Span)>,
137 pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>,
138 pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
139 /// Extern prelude entries. The value is `true` if the entry was introduced
140 /// via `extern crate` item and not `--extern` option or compiler built-in.
141 pub extern_prelude: FxHashMap<Symbol, bool>,
142 pub main_def: Option<MainDefinition>,
143 pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,
144 /// A list of proc macro LocalDefIds, written out in the order in which
145 /// they are declared in the static array generated by proc_macro_harness.
146 pub proc_macros: Vec<LocalDefId>,
147 /// Mapping from ident span to path span for paths that don't exist as written, but that
148 /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`.
149 pub confused_type_with_std_module: FxHashMap<Span, Span>,
150 pub registered_tools: RegisteredTools,
153 #[derive(Clone, Copy, Debug)]
154 pub struct MainDefinition {
155 pub res: Res<ast::NodeId>,
160 impl MainDefinition {
161 pub fn opt_fn_def_id(self) -> Option<DefId> {
162 if let Res::Def(DefKind::Fn, def_id) = self.res { Some(def_id) } else { None }
166 /// The "header" of an impl is everything outside the body: a Self type, a trait
167 /// ref (in the case of a trait impl), and a set of predicates (from the
168 /// bounds / where-clauses).
169 #[derive(Clone, Debug, TypeFoldable)]
170 pub struct ImplHeader<'tcx> {
171 pub impl_def_id: DefId,
172 pub self_ty: Ty<'tcx>,
173 pub trait_ref: Option<TraitRef<'tcx>>,
174 pub predicates: Vec<Predicate<'tcx>>,
177 #[derive(Copy, Clone, Debug, TypeFoldable)]
178 pub enum ImplSubject<'tcx> {
179 Trait(TraitRef<'tcx>),
195 pub enum ImplPolarity {
196 /// `impl Trait for Type`
198 /// `impl !Trait for Type`
200 /// `#[rustc_reservation_impl] impl Trait for Type`
202 /// This is a "stability hack", not a real Rust feature.
203 /// See #64631 for details.
208 /// Flips polarity by turning `Positive` into `Negative` and `Negative` into `Positive`.
209 pub fn flip(&self) -> Option<ImplPolarity> {
211 ImplPolarity::Positive => Some(ImplPolarity::Negative),
212 ImplPolarity::Negative => Some(ImplPolarity::Positive),
213 ImplPolarity::Reservation => None,
218 impl fmt::Display for ImplPolarity {
219 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
221 Self::Positive => f.write_str("positive"),
222 Self::Negative => f.write_str("negative"),
223 Self::Reservation => f.write_str("reservation"),
228 #[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, TyEncodable, TyDecodable, HashStable)]
229 pub enum Visibility {
230 /// Visible everywhere (including in other crates).
232 /// Visible only in the given crate-local module.
234 /// Not visible anywhere in the local crate. This is the visibility of private external items.
238 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
239 pub enum BoundConstness {
242 /// `T: ~const Trait`
244 /// Requires resolving to const only when we are in a const context.
248 impl BoundConstness {
249 /// Reduce `self` and `constness` to two possible combined states instead of four.
250 pub fn and(&mut self, constness: hir::Constness) -> hir::Constness {
251 match (constness, self) {
252 (hir::Constness::Const, BoundConstness::ConstIfConst) => hir::Constness::Const,
254 *this = BoundConstness::NotConst;
255 hir::Constness::NotConst
261 impl fmt::Display for BoundConstness {
262 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
264 Self::NotConst => f.write_str("normal"),
265 Self::ConstIfConst => f.write_str("`~const`"),
282 pub struct ClosureSizeProfileData<'tcx> {
283 /// Tuple containing the types of closure captures before the feature `capture_disjoint_fields`
284 pub before_feature_tys: Ty<'tcx>,
285 /// Tuple containing the types of closure captures after the feature `capture_disjoint_fields`
286 pub after_feature_tys: Ty<'tcx>,
289 pub trait DefIdTree: Copy {
290 fn parent(self, id: DefId) -> Option<DefId>;
292 fn is_descendant_of(self, mut descendant: DefId, ancestor: DefId) -> bool {
293 if descendant.krate != ancestor.krate {
297 while descendant != ancestor {
298 match self.parent(descendant) {
299 Some(parent) => descendant = parent,
300 None => return false,
307 impl<'tcx> DefIdTree for TyCtxt<'tcx> {
308 fn parent(self, id: DefId) -> Option<DefId> {
309 self.def_key(id).parent.map(|index| DefId { index, ..id })
314 pub fn from_hir(visibility: &hir::Visibility<'_>, id: hir::HirId, tcx: TyCtxt<'_>) -> Self {
315 match visibility.node {
316 hir::VisibilityKind::Public => Visibility::Public,
317 hir::VisibilityKind::Crate(_) => Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
318 hir::VisibilityKind::Restricted { ref path, .. } => match path.res {
319 // If there is no resolution, `resolve` will have already reported an error, so
320 // assume that the visibility is public to avoid reporting more privacy errors.
321 Res::Err => Visibility::Public,
322 def => Visibility::Restricted(def.def_id()),
324 hir::VisibilityKind::Inherited => {
325 Visibility::Restricted(tcx.parent_module(id).to_def_id())
330 /// Returns `true` if an item with this visibility is accessible from the given block.
331 pub fn is_accessible_from<T: DefIdTree>(self, module: DefId, tree: T) -> bool {
332 let restriction = match self {
333 // Public items are visible everywhere.
334 Visibility::Public => return true,
335 // Private items from other crates are visible nowhere.
336 Visibility::Invisible => return false,
337 // Restricted items are visible in an arbitrary local module.
338 Visibility::Restricted(other) if other.krate != module.krate => return false,
339 Visibility::Restricted(module) => module,
342 tree.is_descendant_of(module, restriction)
345 /// Returns `true` if this visibility is at least as accessible as the given visibility
346 pub fn is_at_least<T: DefIdTree>(self, vis: Visibility, tree: T) -> bool {
347 let vis_restriction = match vis {
348 Visibility::Public => return self == Visibility::Public,
349 Visibility::Invisible => return true,
350 Visibility::Restricted(module) => module,
353 self.is_accessible_from(vis_restriction, tree)
356 // Returns `true` if this item is visible anywhere in the local crate.
357 pub fn is_visible_locally(self) -> bool {
359 Visibility::Public => true,
360 Visibility::Restricted(def_id) => def_id.is_local(),
361 Visibility::Invisible => false,
365 pub fn is_public(self) -> bool {
366 matches!(self, Visibility::Public)
370 /// The crate variances map is computed during typeck and contains the
371 /// variance of every item in the local crate. You should not use it
372 /// directly, because to do so will make your pass dependent on the
373 /// HIR of every item in the local crate. Instead, use
374 /// `tcx.variances_of()` to get the variance for a *particular*
376 #[derive(HashStable, Debug)]
377 pub struct CrateVariancesMap<'tcx> {
378 /// For each item with generics, maps to a vector of the variance
379 /// of its generics. If an item has no generics, it will have no
381 pub variances: FxHashMap<DefId, &'tcx [ty::Variance]>,
384 // Contains information needed to resolve types and (in the future) look up
385 // the types of AST nodes.
386 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
387 pub struct CReaderCacheKey {
388 pub cnum: Option<CrateNum>,
392 /// Represents a type.
395 /// - This is a very "dumb" struct (with no derives and no `impls`).
396 /// - Values of this type are always interned and thus unique, and are stored
397 /// as an `Interned<TyS>`.
398 /// - `Ty` (which contains a reference to a `Interned<TyS>`) or `Interned<TyS>`
399 /// should be used everywhere instead of `TyS`. In particular, `Ty` has most
400 /// of the relevant methods.
401 #[derive(PartialEq, Eq, PartialOrd, Ord)]
402 #[allow(rustc::usage_of_ty_tykind)]
403 crate struct TyS<'tcx> {
404 /// This field shouldn't be used directly and may be removed in the future.
405 /// Use `Ty::kind()` instead.
408 /// This field provides fast access to information that is also contained
411 /// This field shouldn't be used directly and may be removed in the future.
412 /// Use `Ty::flags()` instead.
415 /// This field provides fast access to information that is also contained
418 /// This is a kind of confusing thing: it stores the smallest
421 /// (a) the binder itself captures nothing but
422 /// (b) all the late-bound things within the type are captured
423 /// by some sub-binder.
425 /// So, for a type without any late-bound things, like `u32`, this
426 /// will be *innermost*, because that is the innermost binder that
427 /// captures nothing. But for a type `&'D u32`, where `'D` is a
428 /// late-bound region with De Bruijn index `D`, this would be `D + 1`
429 /// -- the binder itself does not capture `D`, but `D` is captured
430 /// by an inner binder.
432 /// We call this concept an "exclusive" binder `D` because all
433 /// De Bruijn indices within the type are contained within `0..D`
435 outer_exclusive_binder: ty::DebruijnIndex,
438 // `TyS` is used a lot. Make sure it doesn't unintentionally get bigger.
439 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
440 static_assert_size!(TyS<'_>, 40);
442 // We are actually storing a stable hash cache next to the type, so let's
443 // also check the full size
444 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
445 static_assert_size!(WithStableHash<TyS<'_>>, 56);
447 /// Use this rather than `TyS`, whenever possible.
448 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
449 #[rustc_diagnostic_item = "Ty"]
450 #[rustc_pass_by_value]
451 pub struct Ty<'tcx>(Interned<'tcx, WithStableHash<TyS<'tcx>>>);
453 // Statics only used for internal testing.
454 pub static BOOL_TY: Ty<'static> = Ty(Interned::new_unchecked(&WithStableHash {
456 stable_hash: Fingerprint::ZERO,
458 const BOOL_TYS: TyS<'static> = TyS {
460 flags: TypeFlags::empty(),
461 outer_exclusive_binder: DebruijnIndex::from_usize(0),
464 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for TyS<'tcx> {
466 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
470 // The other fields just provide fast access to information that is
471 // also contained in `kind`, so no need to hash them.
474 outer_exclusive_binder: _,
477 kind.hash_stable(hcx, hasher)
481 impl ty::EarlyBoundRegion {
482 /// Does this early bound region have a name? Early bound regions normally
483 /// always have names except when using anonymous lifetimes (`'_`).
484 pub fn has_name(&self) -> bool {
485 self.name != kw::UnderscoreLifetime
489 /// Represents a predicate.
491 /// See comments on `TyS`, which apply here too (albeit for
492 /// `PredicateS`/`Predicate` rather than `TyS`/`Ty`).
494 crate struct PredicateS<'tcx> {
495 kind: Binder<'tcx, PredicateKind<'tcx>>,
497 /// See the comment for the corresponding field of [TyS].
498 outer_exclusive_binder: ty::DebruijnIndex,
501 // This type is used a lot. Make sure it doesn't unintentionally get bigger.
502 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
503 static_assert_size!(PredicateS<'_>, 56);
505 /// Use this rather than `PredicateS`, whenever possible.
506 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
507 #[rustc_pass_by_value]
508 pub struct Predicate<'tcx>(Interned<'tcx, PredicateS<'tcx>>);
510 impl<'tcx> Predicate<'tcx> {
511 /// Gets the inner `Binder<'tcx, PredicateKind<'tcx>>`.
513 pub fn kind(self) -> Binder<'tcx, PredicateKind<'tcx>> {
518 pub fn flags(self) -> TypeFlags {
523 pub fn outer_exclusive_binder(self) -> DebruijnIndex {
524 self.0.outer_exclusive_binder
527 /// Flips the polarity of a Predicate.
529 /// Given `T: Trait` predicate it returns `T: !Trait` and given `T: !Trait` returns `T: Trait`.
530 pub fn flip_polarity(self, tcx: TyCtxt<'tcx>) -> Option<Predicate<'tcx>> {
533 .map_bound(|kind| match kind {
534 PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) => {
535 Some(PredicateKind::Trait(TraitPredicate {
538 polarity: polarity.flip()?,
546 Some(tcx.mk_predicate(kind))
550 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> {
551 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
555 // The other fields just provide fast access to information that is
556 // also contained in `kind`, so no need to hash them.
558 outer_exclusive_binder: _,
561 kind.hash_stable(hcx, hasher);
565 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
566 #[derive(HashStable, TypeFoldable)]
567 pub enum PredicateKind<'tcx> {
568 /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
569 /// the `Self` type of the trait reference and `A`, `B`, and `C`
570 /// would be the type parameters.
571 Trait(TraitPredicate<'tcx>),
574 RegionOutlives(RegionOutlivesPredicate<'tcx>),
577 TypeOutlives(TypeOutlivesPredicate<'tcx>),
579 /// `where <T as TraitRef>::Name == X`, approximately.
580 /// See the `ProjectionPredicate` struct for details.
581 Projection(ProjectionPredicate<'tcx>),
583 /// No syntax: `T` well-formed.
584 WellFormed(GenericArg<'tcx>),
586 /// Trait must be object-safe.
589 /// No direct syntax. May be thought of as `where T: FnFoo<...>`
590 /// for some substitutions `...` and `T` being a closure type.
591 /// Satisfied (or refuted) once we know the closure's kind.
592 ClosureKind(DefId, SubstsRef<'tcx>, ClosureKind),
596 /// This obligation is created most often when we have two
597 /// unresolved type variables and hence don't have enough
598 /// information to process the subtyping obligation yet.
599 Subtype(SubtypePredicate<'tcx>),
601 /// `T1` coerced to `T2`
603 /// Like a subtyping obligation, this is created most often
604 /// when we have two unresolved type variables and hence
605 /// don't have enough information to process the coercion
606 /// obligation yet. At the moment, we actually process coercions
607 /// very much like subtyping and don't handle the full coercion
609 Coerce(CoercePredicate<'tcx>),
611 /// Constant initializer must evaluate successfully.
612 ConstEvaluatable(ty::Unevaluated<'tcx, ()>),
614 /// Constants must be equal. The first component is the const that is expected.
615 ConstEquate(Const<'tcx>, Const<'tcx>),
617 /// Represents a type found in the environment that we can use for implied bounds.
619 /// Only used for Chalk.
620 TypeWellFormedFromEnv(Ty<'tcx>),
623 /// The crate outlives map is computed during typeck and contains the
624 /// outlives of every item in the local crate. You should not use it
625 /// directly, because to do so will make your pass dependent on the
626 /// HIR of every item in the local crate. Instead, use
627 /// `tcx.inferred_outlives_of()` to get the outlives for a *particular*
629 #[derive(HashStable, Debug)]
630 pub struct CratePredicatesMap<'tcx> {
631 /// For each struct with outlive bounds, maps to a vector of the
632 /// predicate of its outlive bounds. If an item has no outlives
633 /// bounds, it will have no entry.
634 pub predicates: FxHashMap<DefId, &'tcx [(Predicate<'tcx>, Span)]>,
637 impl<'tcx> Predicate<'tcx> {
638 /// Performs a substitution suitable for going from a
639 /// poly-trait-ref to supertraits that must hold if that
640 /// poly-trait-ref holds. This is slightly different from a normal
641 /// substitution in terms of what happens with bound regions. See
642 /// lengthy comment below for details.
643 pub fn subst_supertrait(
646 trait_ref: &ty::PolyTraitRef<'tcx>,
647 ) -> Predicate<'tcx> {
648 // The interaction between HRTB and supertraits is not entirely
649 // obvious. Let me walk you (and myself) through an example.
651 // Let's start with an easy case. Consider two traits:
653 // trait Foo<'a>: Bar<'a,'a> { }
654 // trait Bar<'b,'c> { }
656 // Now, if we have a trait reference `for<'x> T: Foo<'x>`, then
657 // we can deduce that `for<'x> T: Bar<'x,'x>`. Basically, if we
658 // knew that `Foo<'x>` (for any 'x) then we also know that
659 // `Bar<'x,'x>` (for any 'x). This more-or-less falls out from
660 // normal substitution.
662 // In terms of why this is sound, the idea is that whenever there
663 // is an impl of `T:Foo<'a>`, it must show that `T:Bar<'a,'a>`
664 // holds. So if there is an impl of `T:Foo<'a>` that applies to
665 // all `'a`, then we must know that `T:Bar<'a,'a>` holds for all
668 // Another example to be careful of is this:
670 // trait Foo1<'a>: for<'b> Bar1<'a,'b> { }
671 // trait Bar1<'b,'c> { }
673 // Here, if we have `for<'x> T: Foo1<'x>`, then what do we know?
674 // The answer is that we know `for<'x,'b> T: Bar1<'x,'b>`. The
675 // reason is similar to the previous example: any impl of
676 // `T:Foo1<'x>` must show that `for<'b> T: Bar1<'x, 'b>`. So
677 // basically we would want to collapse the bound lifetimes from
678 // the input (`trait_ref`) and the supertraits.
680 // To achieve this in practice is fairly straightforward. Let's
681 // consider the more complicated scenario:
683 // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x`
684 // has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`,
685 // where both `'x` and `'b` would have a DB index of 1.
686 // The substitution from the input trait-ref is therefore going to be
687 // `'a => 'x` (where `'x` has a DB index of 1).
688 // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an
689 // early-bound parameter and `'b' is a late-bound parameter with a
691 // - If we replace `'a` with `'x` from the input, it too will have
692 // a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>`
693 // just as we wanted.
695 // There is only one catch. If we just apply the substitution `'a
696 // => 'x` to `for<'b> Bar1<'a,'b>`, the substitution code will
697 // adjust the DB index because we substituting into a binder (it
698 // tries to be so smart...) resulting in `for<'x> for<'b>
699 // Bar1<'x,'b>` (we have no syntax for this, so use your
700 // imagination). Basically the 'x will have DB index of 2 and 'b
701 // will have DB index of 1. Not quite what we want. So we apply
702 // the substitution to the *contents* of the trait reference,
703 // rather than the trait reference itself (put another way, the
704 // substitution code expects equal binding levels in the values
705 // from the substitution and the value being substituted into, and
706 // this trick achieves that).
708 // Working through the second example:
709 // trait_ref: for<'x> T: Foo1<'^0.0>; substs: [T, '^0.0]
710 // predicate: for<'b> Self: Bar1<'a, '^0.0>; substs: [Self, 'a, '^0.0]
711 // We want to end up with:
712 // for<'x, 'b> T: Bar1<'^0.0, '^0.1>
714 // 1) We must shift all bound vars in predicate by the length
715 // of trait ref's bound vars. So, we would end up with predicate like
716 // Self: Bar1<'a, '^0.1>
717 // 2) We can then apply the trait substs to this, ending up with
718 // T: Bar1<'^0.0, '^0.1>
719 // 3) Finally, to create the final bound vars, we concatenate the bound
720 // vars of the trait ref with those of the predicate:
722 let bound_pred = self.kind();
723 let pred_bound_vars = bound_pred.bound_vars();
724 let trait_bound_vars = trait_ref.bound_vars();
725 // 1) Self: Bar1<'a, '^0.0> -> Self: Bar1<'a, '^0.1>
727 tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
728 // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
729 let new = shifted_pred.subst(tcx, trait_ref.skip_binder().substs);
730 // 3) ['x] + ['b] -> ['x, 'b]
732 tcx.mk_bound_variable_kinds(trait_bound_vars.iter().chain(pred_bound_vars));
733 tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars))
737 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
738 #[derive(HashStable, TypeFoldable)]
739 pub struct TraitPredicate<'tcx> {
740 pub trait_ref: TraitRef<'tcx>,
742 pub constness: BoundConstness,
744 /// If polarity is Positive: we are proving that the trait is implemented.
746 /// If polarity is Negative: we are proving that a negative impl of this trait
747 /// exists. (Note that coherence also checks whether negative impls of supertraits
748 /// exist via a series of predicates.)
750 /// If polarity is Reserved: that's a bug.
751 pub polarity: ImplPolarity,
754 pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
756 impl<'tcx> TraitPredicate<'tcx> {
757 pub fn remap_constness(&mut self, tcx: TyCtxt<'tcx>, param_env: &mut ParamEnv<'tcx>) {
758 if unlikely!(Some(self.trait_ref.def_id) == tcx.lang_items().drop_trait()) {
759 // remap without changing constness of this predicate.
760 // this is because `T: ~const Drop` has a different meaning to `T: Drop`
761 // FIXME(fee1-dead): remove this logic after beta bump
762 param_env.remap_constness_with(self.constness)
764 *param_env = param_env.with_constness(self.constness.and(param_env.constness()))
768 /// Remap the constness of this predicate before emitting it for diagnostics.
769 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
770 // this is different to `remap_constness` that callees want to print this predicate
771 // in case of selection errors. `T: ~const Drop` bounds cannot end up here when the
772 // param_env is not const because we it is always satisfied in non-const contexts.
773 if let hir::Constness::NotConst = param_env.constness() {
774 self.constness = ty::BoundConstness::NotConst;
778 pub fn def_id(self) -> DefId {
779 self.trait_ref.def_id
782 pub fn self_ty(self) -> Ty<'tcx> {
783 self.trait_ref.self_ty()
787 pub fn is_const_if_const(self) -> bool {
788 self.constness == BoundConstness::ConstIfConst
792 impl<'tcx> PolyTraitPredicate<'tcx> {
793 pub fn def_id(self) -> DefId {
794 // Ok to skip binder since trait `DefId` does not care about regions.
795 self.skip_binder().def_id()
798 pub fn self_ty(self) -> ty::Binder<'tcx, Ty<'tcx>> {
799 self.map_bound(|trait_ref| trait_ref.self_ty())
802 /// Remap the constness of this predicate before emitting it for diagnostics.
803 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
804 *self = self.map_bound(|mut p| {
805 p.remap_constness_diag(param_env);
811 pub fn is_const_if_const(self) -> bool {
812 self.skip_binder().is_const_if_const()
816 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
817 #[derive(HashStable, TypeFoldable)]
818 pub struct OutlivesPredicate<A, B>(pub A, pub B); // `A: B`
819 pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>;
820 pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>;
821 pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>;
822 pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>;
824 /// Encodes that `a` must be a subtype of `b`. The `a_is_expected` flag indicates
825 /// whether the `a` type is the type that we should label as "expected" when
826 /// presenting user diagnostics.
827 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
828 #[derive(HashStable, TypeFoldable)]
829 pub struct SubtypePredicate<'tcx> {
830 pub a_is_expected: bool,
834 pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>;
836 /// Encodes that we have to coerce *from* the `a` type to the `b` type.
837 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
838 #[derive(HashStable, TypeFoldable)]
839 pub struct CoercePredicate<'tcx> {
843 pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
845 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, TyEncodable, TyDecodable)]
846 #[derive(HashStable, TypeFoldable)]
847 pub enum Term<'tcx> {
852 impl<'tcx> From<Ty<'tcx>> for Term<'tcx> {
853 fn from(ty: Ty<'tcx>) -> Self {
858 impl<'tcx> From<Const<'tcx>> for Term<'tcx> {
859 fn from(c: Const<'tcx>) -> Self {
864 impl<'tcx> Term<'tcx> {
865 pub fn ty(&self) -> Option<Ty<'tcx>> {
866 if let Term::Ty(ty) = self { Some(*ty) } else { None }
868 pub fn ct(&self) -> Option<Const<'tcx>> {
869 if let Term::Const(c) = self { Some(*c) } else { None }
873 /// This kind of predicate has no *direct* correspondent in the
874 /// syntax, but it roughly corresponds to the syntactic forms:
876 /// 1. `T: TraitRef<..., Item = Type>`
877 /// 2. `<T as TraitRef<...>>::Item == Type` (NYI)
879 /// In particular, form #1 is "desugared" to the combination of a
880 /// normal trait predicate (`T: TraitRef<...>`) and one of these
881 /// predicates. Form #2 is a broader form in that it also permits
882 /// equality between arbitrary types. Processing an instance of
883 /// Form #2 eventually yields one of these `ProjectionPredicate`
884 /// instances to normalize the LHS.
885 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
886 #[derive(HashStable, TypeFoldable)]
887 pub struct ProjectionPredicate<'tcx> {
888 pub projection_ty: ProjectionTy<'tcx>,
889 pub term: Term<'tcx>,
892 pub type PolyProjectionPredicate<'tcx> = Binder<'tcx, ProjectionPredicate<'tcx>>;
894 impl<'tcx> PolyProjectionPredicate<'tcx> {
895 /// Returns the `DefId` of the trait of the associated item being projected.
897 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
898 self.skip_binder().projection_ty.trait_def_id(tcx)
901 /// Get the [PolyTraitRef] required for this projection to be well formed.
902 /// Note that for generic associated types the predicates of the associated
903 /// type also need to be checked.
905 pub fn required_poly_trait_ref(&self, tcx: TyCtxt<'tcx>) -> PolyTraitRef<'tcx> {
906 // Note: unlike with `TraitRef::to_poly_trait_ref()`,
907 // `self.0.trait_ref` is permitted to have escaping regions.
908 // This is because here `self` has a `Binder` and so does our
909 // return value, so we are preserving the number of binding
911 self.map_bound(|predicate| predicate.projection_ty.trait_ref(tcx))
914 pub fn term(&self) -> Binder<'tcx, Term<'tcx>> {
915 self.map_bound(|predicate| predicate.term)
918 /// The `DefId` of the `TraitItem` for the associated type.
920 /// Note that this is not the `DefId` of the `TraitRef` containing this
921 /// associated type, which is in `tcx.associated_item(projection_def_id()).container`.
922 pub fn projection_def_id(&self) -> DefId {
923 // Ok to skip binder since trait `DefId` does not care about regions.
924 self.skip_binder().projection_ty.item_def_id
928 pub trait ToPolyTraitRef<'tcx> {
929 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx>;
932 impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
933 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> {
934 self.map_bound_ref(|trait_pred| trait_pred.trait_ref)
938 pub trait ToPredicate<'tcx> {
939 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx>;
942 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
944 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
945 tcx.mk_predicate(self)
949 impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
950 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
951 self.map_bound(PredicateKind::Trait).to_predicate(tcx)
955 impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
956 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
957 self.map_bound(PredicateKind::RegionOutlives).to_predicate(tcx)
961 impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> {
962 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
963 self.map_bound(PredicateKind::TypeOutlives).to_predicate(tcx)
967 impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
968 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
969 self.map_bound(PredicateKind::Projection).to_predicate(tcx)
973 impl<'tcx> Predicate<'tcx> {
974 pub fn to_opt_poly_trait_pred(self) -> Option<PolyTraitPredicate<'tcx>> {
975 let predicate = self.kind();
976 match predicate.skip_binder() {
977 PredicateKind::Trait(t) => Some(predicate.rebind(t)),
978 PredicateKind::Projection(..)
979 | PredicateKind::Subtype(..)
980 | PredicateKind::Coerce(..)
981 | PredicateKind::RegionOutlives(..)
982 | PredicateKind::WellFormed(..)
983 | PredicateKind::ObjectSafe(..)
984 | PredicateKind::ClosureKind(..)
985 | PredicateKind::TypeOutlives(..)
986 | PredicateKind::ConstEvaluatable(..)
987 | PredicateKind::ConstEquate(..)
988 | PredicateKind::TypeWellFormedFromEnv(..) => None,
992 pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> {
993 let predicate = self.kind();
994 match predicate.skip_binder() {
995 PredicateKind::TypeOutlives(data) => Some(predicate.rebind(data)),
996 PredicateKind::Trait(..)
997 | PredicateKind::Projection(..)
998 | PredicateKind::Subtype(..)
999 | PredicateKind::Coerce(..)
1000 | PredicateKind::RegionOutlives(..)
1001 | PredicateKind::WellFormed(..)
1002 | PredicateKind::ObjectSafe(..)
1003 | PredicateKind::ClosureKind(..)
1004 | PredicateKind::ConstEvaluatable(..)
1005 | PredicateKind::ConstEquate(..)
1006 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1011 /// Represents the bounds declared on a particular set of type
1012 /// parameters. Should eventually be generalized into a flag list of
1013 /// where-clauses. You can obtain an `InstantiatedPredicates` list from a
1014 /// `GenericPredicates` by using the `instantiate` method. Note that this method
1015 /// reflects an important semantic invariant of `InstantiatedPredicates`: while
1016 /// the `GenericPredicates` are expressed in terms of the bound type
1017 /// parameters of the impl/trait/whatever, an `InstantiatedPredicates` instance
1018 /// represented a set of bounds for some particular instantiation,
1019 /// meaning that the generic parameters have been substituted with
1024 /// struct Foo<T, U: Bar<T>> { ... }
1026 /// Here, the `GenericPredicates` for `Foo` would contain a list of bounds like
1027 /// `[[], [U:Bar<T>]]`. Now if there were some particular reference
1028 /// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[],
1029 /// [usize:Bar<isize>]]`.
1030 #[derive(Clone, Debug, TypeFoldable)]
1031 pub struct InstantiatedPredicates<'tcx> {
1032 pub predicates: Vec<Predicate<'tcx>>,
1033 pub spans: Vec<Span>,
1036 impl<'tcx> InstantiatedPredicates<'tcx> {
1037 pub fn empty() -> InstantiatedPredicates<'tcx> {
1038 InstantiatedPredicates { predicates: vec![], spans: vec![] }
1041 pub fn is_empty(&self) -> bool {
1042 self.predicates.is_empty()
1058 pub struct OpaqueTypeKey<'tcx> {
1060 pub substs: SubstsRef<'tcx>,
1063 #[derive(Copy, Clone, Debug, TypeFoldable, HashStable, TyEncodable, TyDecodable)]
1064 pub struct OpaqueHiddenType<'tcx> {
1065 /// The span of this particular definition of the opaque type. So
1068 /// ```ignore (incomplete snippet)
1069 /// type Foo = impl Baz;
1070 /// fn bar() -> Foo {
1071 /// // ^^^ This is the span we are looking for!
1075 /// In cases where the fn returns `(impl Trait, impl Trait)` or
1076 /// other such combinations, the result is currently
1077 /// over-approximated, but better than nothing.
1080 /// The type variable that represents the value of the opaque type
1081 /// that we require. In other words, after we compile this function,
1082 /// we will be created a constraint like:
1086 /// where `?C` is the value of this type variable. =) It may
1087 /// naturally refer to the type and lifetime parameters in scope
1088 /// in this function, though ultimately it should only reference
1089 /// those that are arguments to `Foo` in the constraint above. (In
1090 /// other words, `?C` should not include `'b`, even though it's a
1091 /// lifetime parameter on `foo`.)
1095 rustc_index::newtype_index! {
1096 /// "Universes" are used during type- and trait-checking in the
1097 /// presence of `for<..>` binders to control what sets of names are
1098 /// visible. Universes are arranged into a tree: the root universe
1099 /// contains names that are always visible. Each child then adds a new
1100 /// set of names that are visible, in addition to those of its parent.
1101 /// We say that the child universe "extends" the parent universe with
1104 /// To make this more concrete, consider this program:
1108 /// fn bar<T>(x: T) {
1109 /// let y: for<'a> fn(&'a u8, Foo) = ...;
1113 /// The struct name `Foo` is in the root universe U0. But the type
1114 /// parameter `T`, introduced on `bar`, is in an extended universe U1
1115 /// -- i.e., within `bar`, we can name both `T` and `Foo`, but outside
1116 /// of `bar`, we cannot name `T`. Then, within the type of `y`, the
1117 /// region `'a` is in a universe U2 that extends U1, because we can
1118 /// name it inside the fn type but not outside.
1120 /// Universes are used to do type- and trait-checking around these
1121 /// "forall" binders (also called **universal quantification**). The
1122 /// idea is that when, in the body of `bar`, we refer to `T` as a
1123 /// type, we aren't referring to any type in particular, but rather a
1124 /// kind of "fresh" type that is distinct from all other types we have
1125 /// actually declared. This is called a **placeholder** type, and we
1126 /// use universes to talk about this. In other words, a type name in
1127 /// universe 0 always corresponds to some "ground" type that the user
1128 /// declared, but a type name in a non-zero universe is a placeholder
1129 /// type -- an idealized representative of "types in general" that we
1130 /// use for checking generic functions.
1131 pub struct UniverseIndex {
1133 DEBUG_FORMAT = "U{}",
1137 impl UniverseIndex {
1138 pub const ROOT: UniverseIndex = UniverseIndex::from_u32(0);
1140 /// Returns the "next" universe index in order -- this new index
1141 /// is considered to extend all previous universes. This
1142 /// corresponds to entering a `forall` quantifier. So, for
1143 /// example, suppose we have this type in universe `U`:
1146 /// for<'a> fn(&'a u32)
1149 /// Once we "enter" into this `for<'a>` quantifier, we are in a
1150 /// new universe that extends `U` -- in this new universe, we can
1151 /// name the region `'a`, but that region was not nameable from
1152 /// `U` because it was not in scope there.
1153 pub fn next_universe(self) -> UniverseIndex {
1154 UniverseIndex::from_u32(self.private.checked_add(1).unwrap())
1157 /// Returns `true` if `self` can name a name from `other` -- in other words,
1158 /// if the set of names in `self` is a superset of those in
1159 /// `other` (`self >= other`).
1160 pub fn can_name(self, other: UniverseIndex) -> bool {
1161 self.private >= other.private
1164 /// Returns `true` if `self` cannot name some names from `other` -- in other
1165 /// words, if the set of names in `self` is a strict subset of
1166 /// those in `other` (`self < other`).
1167 pub fn cannot_name(self, other: UniverseIndex) -> bool {
1168 self.private < other.private
1172 /// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are
1173 /// identified by both a universe, as well as a name residing within that universe. Distinct bound
1174 /// regions/types/consts within the same universe simply have an unknown relationship to one
1176 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, PartialOrd, Ord)]
1177 pub struct Placeholder<T> {
1178 pub universe: UniverseIndex,
1182 impl<'a, T> HashStable<StableHashingContext<'a>> for Placeholder<T>
1184 T: HashStable<StableHashingContext<'a>>,
1186 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1187 self.universe.hash_stable(hcx, hasher);
1188 self.name.hash_stable(hcx, hasher);
1192 pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
1194 pub type PlaceholderType = Placeholder<BoundVar>;
1196 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
1197 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
1198 pub struct BoundConst<'tcx> {
1203 pub type PlaceholderConst<'tcx> = Placeholder<BoundConst<'tcx>>;
1205 /// A `DefId` which, in case it is a const argument, is potentially bundled with
1206 /// the `DefId` of the generic parameter it instantiates.
1208 /// This is used to avoid calls to `type_of` for const arguments during typeck
1209 /// which cause cycle errors.
1214 /// fn foo<const N: usize>(&self) -> [u8; N] { [0; N] }
1215 /// // ^ const parameter
1219 /// fn foo<const M: u8>(&self) -> usize { 42 }
1220 /// // ^ const parameter
1225 /// let _b = a.foo::<{ 3 + 7 }>();
1226 /// // ^^^^^^^^^ const argument
1230 /// Let's look at the call `a.foo::<{ 3 + 7 }>()` here. We do not know
1231 /// which `foo` is used until we know the type of `a`.
1233 /// We only know the type of `a` once we are inside of `typeck(main)`.
1234 /// We also end up normalizing the type of `_b` during `typeck(main)` which
1235 /// requires us to evaluate the const argument.
1237 /// To evaluate that const argument we need to know its type,
1238 /// which we would get using `type_of(const_arg)`. This requires us to
1239 /// resolve `foo` as it can be either `usize` or `u8` in this example.
1240 /// However, resolving `foo` once again requires `typeck(main)` to get the type of `a`,
1241 /// which results in a cycle.
1243 /// In short we must not call `type_of(const_arg)` during `typeck(main)`.
1245 /// When first creating the `ty::Const` of the const argument inside of `typeck` we have
1246 /// already resolved `foo` so we know which const parameter this argument instantiates.
1247 /// This means that we also know the expected result of `type_of(const_arg)` even if we
1248 /// aren't allowed to call that query: it is equal to `type_of(const_param)` which is
1249 /// trivial to compute.
1251 /// If we now want to use that constant in a place which potentially needs its type
1252 /// we also pass the type of its `const_param`. This is the point of `WithOptConstParam`,
1253 /// except that instead of a `Ty` we bundle the `DefId` of the const parameter.
1254 /// Meaning that we need to use `type_of(const_param_did)` if `const_param_did` is `Some`
1255 /// to get the type of `did`.
1256 #[derive(Copy, Clone, Debug, TypeFoldable, Lift, TyEncodable, TyDecodable)]
1257 #[derive(PartialEq, Eq, PartialOrd, Ord)]
1258 #[derive(Hash, HashStable)]
1259 pub struct WithOptConstParam<T> {
1261 /// The `DefId` of the corresponding generic parameter in case `did` is
1262 /// a const argument.
1264 /// Note that even if `did` is a const argument, this may still be `None`.
1265 /// All queries taking `WithOptConstParam` start by calling `tcx.opt_const_param_of(def.did)`
1266 /// to potentially update `param_did` in the case it is `None`.
1267 pub const_param_did: Option<DefId>,
1270 impl<T> WithOptConstParam<T> {
1271 /// Creates a new `WithOptConstParam` setting `const_param_did` to `None`.
1273 pub fn unknown(did: T) -> WithOptConstParam<T> {
1274 WithOptConstParam { did, const_param_did: None }
1278 impl WithOptConstParam<LocalDefId> {
1279 /// Returns `Some((did, param_did))` if `def_id` is a const argument,
1280 /// `None` otherwise.
1282 pub fn try_lookup(did: LocalDefId, tcx: TyCtxt<'_>) -> Option<(LocalDefId, DefId)> {
1283 tcx.opt_const_param_of(did).map(|param_did| (did, param_did))
1286 /// In case `self` is unknown but `self.did` is a const argument, this returns
1287 /// a `WithOptConstParam` with the correct `const_param_did`.
1289 pub fn try_upgrade(self, tcx: TyCtxt<'_>) -> Option<WithOptConstParam<LocalDefId>> {
1290 if self.const_param_did.is_none() {
1291 if let const_param_did @ Some(_) = tcx.opt_const_param_of(self.did) {
1292 return Some(WithOptConstParam { did: self.did, const_param_did });
1299 pub fn to_global(self) -> WithOptConstParam<DefId> {
1300 WithOptConstParam { did: self.did.to_def_id(), const_param_did: self.const_param_did }
1303 pub fn def_id_for_type_of(self) -> DefId {
1304 if let Some(did) = self.const_param_did { did } else { self.did.to_def_id() }
1308 impl WithOptConstParam<DefId> {
1309 pub fn as_local(self) -> Option<WithOptConstParam<LocalDefId>> {
1312 .map(|did| WithOptConstParam { did, const_param_did: self.const_param_did })
1315 pub fn as_const_arg(self) -> Option<(LocalDefId, DefId)> {
1316 if let Some(param_did) = self.const_param_did {
1317 if let Some(did) = self.did.as_local() {
1318 return Some((did, param_did));
1325 pub fn is_local(self) -> bool {
1329 pub fn def_id_for_type_of(self) -> DefId {
1330 self.const_param_did.unwrap_or(self.did)
1334 /// When type checking, we use the `ParamEnv` to track
1335 /// details about the set of where-clauses that are in scope at this
1336 /// particular point.
1337 #[derive(Copy, Clone, Hash, PartialEq, Eq)]
1338 pub struct ParamEnv<'tcx> {
1339 /// This packs both caller bounds and the reveal enum into one pointer.
1341 /// Caller bounds are `Obligation`s that the caller must satisfy. This is
1342 /// basically the set of bounds on the in-scope type parameters, translated
1343 /// into `Obligation`s, and elaborated and normalized.
1345 /// Use the `caller_bounds()` method to access.
1347 /// Typically, this is `Reveal::UserFacing`, but during codegen we
1348 /// want `Reveal::All`.
1350 /// Note: This is packed, use the reveal() method to access it.
1351 packed: CopyTaggedPtr<&'tcx List<Predicate<'tcx>>, ParamTag, true>,
1354 #[derive(Copy, Clone)]
1356 reveal: traits::Reveal,
1357 constness: hir::Constness,
1360 unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag {
1361 const BITS: usize = 2;
1363 fn into_usize(self) -> usize {
1365 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0,
1366 Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1,
1367 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2,
1368 Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3,
1372 unsafe fn from_usize(ptr: usize) -> Self {
1374 0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
1375 1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
1376 2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
1377 3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const },
1378 _ => std::hint::unreachable_unchecked(),
1383 impl<'tcx> fmt::Debug for ParamEnv<'tcx> {
1384 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1385 f.debug_struct("ParamEnv")
1386 .field("caller_bounds", &self.caller_bounds())
1387 .field("reveal", &self.reveal())
1388 .field("constness", &self.constness())
1393 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
1394 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1395 self.caller_bounds().hash_stable(hcx, hasher);
1396 self.reveal().hash_stable(hcx, hasher);
1397 self.constness().hash_stable(hcx, hasher);
1401 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
1402 fn try_super_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>(
1405 ) -> Result<Self, F::Error> {
1407 self.caller_bounds().try_fold_with(folder)?,
1408 self.reveal().try_fold_with(folder)?,
1409 self.constness().try_fold_with(folder)?,
1413 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1414 self.caller_bounds().visit_with(visitor)?;
1415 self.reveal().visit_with(visitor)?;
1416 self.constness().visit_with(visitor)
1420 impl<'tcx> ParamEnv<'tcx> {
1421 /// Construct a trait environment suitable for contexts where
1422 /// there are no where-clauses in scope. Hidden types (like `impl
1423 /// Trait`) are left hidden, so this is suitable for ordinary
1426 pub fn empty() -> Self {
1427 Self::new(List::empty(), Reveal::UserFacing, hir::Constness::NotConst)
1431 pub fn caller_bounds(self) -> &'tcx List<Predicate<'tcx>> {
1432 self.packed.pointer()
1436 pub fn reveal(self) -> traits::Reveal {
1437 self.packed.tag().reveal
1441 pub fn constness(self) -> hir::Constness {
1442 self.packed.tag().constness
1446 pub fn is_const(self) -> bool {
1447 self.packed.tag().constness == hir::Constness::Const
1450 /// Construct a trait environment with no where-clauses in scope
1451 /// where the values of all `impl Trait` and other hidden types
1452 /// are revealed. This is suitable for monomorphized, post-typeck
1453 /// environments like codegen or doing optimizations.
1455 /// N.B., if you want to have predicates in scope, use `ParamEnv::new`,
1456 /// or invoke `param_env.with_reveal_all()`.
1458 pub fn reveal_all() -> Self {
1459 Self::new(List::empty(), Reveal::All, hir::Constness::NotConst)
1462 /// Construct a trait environment with the given set of predicates.
1465 caller_bounds: &'tcx List<Predicate<'tcx>>,
1467 constness: hir::Constness,
1469 ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal, constness }) }
1472 pub fn with_user_facing(mut self) -> Self {
1473 self.packed.set_tag(ParamTag { reveal: Reveal::UserFacing, ..self.packed.tag() });
1478 pub fn with_constness(mut self, constness: hir::Constness) -> Self {
1479 self.packed.set_tag(ParamTag { constness, ..self.packed.tag() });
1484 pub fn with_const(mut self) -> Self {
1485 self.packed.set_tag(ParamTag { constness: hir::Constness::Const, ..self.packed.tag() });
1490 pub fn without_const(mut self) -> Self {
1491 self.packed.set_tag(ParamTag { constness: hir::Constness::NotConst, ..self.packed.tag() });
1496 pub fn remap_constness_with(&mut self, mut constness: ty::BoundConstness) {
1497 *self = self.with_constness(constness.and(self.constness()))
1500 /// Returns a new parameter environment with the same clauses, but
1501 /// which "reveals" the true results of projections in all cases
1502 /// (even for associated types that are specializable). This is
1503 /// the desired behavior during codegen and certain other special
1504 /// contexts; normally though we want to use `Reveal::UserFacing`,
1505 /// which is the default.
1506 /// All opaque types in the caller_bounds of the `ParamEnv`
1507 /// will be normalized to their underlying types.
1508 /// See PR #65989 and issue #65918 for more details
1509 pub fn with_reveal_all_normalized(self, tcx: TyCtxt<'tcx>) -> Self {
1510 if self.packed.tag().reveal == traits::Reveal::All {
1515 tcx.normalize_opaque_types(self.caller_bounds()),
1521 /// Returns this same environment but with no caller bounds.
1523 pub fn without_caller_bounds(self) -> Self {
1524 Self::new(List::empty(), self.reveal(), self.constness())
1527 /// Creates a suitable environment in which to perform trait
1528 /// queries on the given value. When type-checking, this is simply
1529 /// the pair of the environment plus value. But when reveal is set to
1530 /// All, then if `value` does not reference any type parameters, we will
1531 /// pair it with the empty environment. This improves caching and is generally
1534 /// N.B., we preserve the environment when type-checking because it
1535 /// is possible for the user to have wacky where-clauses like
1536 /// `where Box<u32>: Copy`, which are clearly never
1537 /// satisfiable. We generally want to behave as if they were true,
1538 /// although the surrounding function is never reachable.
1539 pub fn and<T: TypeFoldable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
1540 match self.reveal() {
1541 Reveal::UserFacing => ParamEnvAnd { param_env: self, value },
1544 if value.is_global() {
1545 ParamEnvAnd { param_env: self.without_caller_bounds(), value }
1547 ParamEnvAnd { param_env: self, value }
1554 // FIXME(ecstaticmorse): Audit all occurrences of `without_const().to_predicate(tcx)` to ensure that
1555 // the constness of trait bounds is being propagated correctly.
1556 impl<'tcx> PolyTraitRef<'tcx> {
1558 pub fn with_constness(self, constness: BoundConstness) -> PolyTraitPredicate<'tcx> {
1559 self.map_bound(|trait_ref| ty::TraitPredicate {
1562 polarity: ty::ImplPolarity::Positive,
1567 pub fn without_const(self) -> PolyTraitPredicate<'tcx> {
1568 self.with_constness(BoundConstness::NotConst)
1572 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable)]
1573 pub struct ParamEnvAnd<'tcx, T> {
1574 pub param_env: ParamEnv<'tcx>,
1578 impl<'tcx, T> ParamEnvAnd<'tcx, T> {
1579 pub fn into_parts(self) -> (ParamEnv<'tcx>, T) {
1580 (self.param_env, self.value)
1584 pub fn without_const(mut self) -> Self {
1585 self.param_env = self.param_env.without_const();
1590 impl<'a, 'tcx, T> HashStable<StableHashingContext<'a>> for ParamEnvAnd<'tcx, T>
1592 T: HashStable<StableHashingContext<'a>>,
1594 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1595 let ParamEnvAnd { ref param_env, ref value } = *self;
1597 param_env.hash_stable(hcx, hasher);
1598 value.hash_stable(hcx, hasher);
1602 #[derive(Copy, Clone, Debug, HashStable)]
1603 pub struct Destructor {
1604 /// The `DefId` of the destructor method
1606 /// The constness of the destructor method
1607 pub constness: hir::Constness,
1611 #[derive(HashStable, TyEncodable, TyDecodable)]
1612 pub struct VariantFlags: u32 {
1613 const NO_VARIANT_FLAGS = 0;
1614 /// Indicates whether the field list of this variant is `#[non_exhaustive]`.
1615 const IS_FIELD_LIST_NON_EXHAUSTIVE = 1 << 0;
1616 /// Indicates whether this variant was obtained as part of recovering from
1617 /// a syntactic error. May be incomplete or bogus.
1618 const IS_RECOVERED = 1 << 1;
1622 /// Definition of a variant -- a struct's fields or an enum variant.
1623 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1624 pub struct VariantDef {
1625 /// `DefId` that identifies the variant itself.
1626 /// If this variant belongs to a struct or union, then this is a copy of its `DefId`.
1628 /// `DefId` that identifies the variant's constructor.
1629 /// If this variant is a struct variant, then this is `None`.
1630 pub ctor_def_id: Option<DefId>,
1631 /// Variant or struct name.
1633 /// Discriminant of this variant.
1634 pub discr: VariantDiscr,
1635 /// Fields of this variant.
1636 pub fields: Vec<FieldDef>,
1637 /// Type of constructor of variant.
1638 pub ctor_kind: CtorKind,
1639 /// Flags of the variant (e.g. is field list non-exhaustive)?
1640 flags: VariantFlags,
1644 /// Creates a new `VariantDef`.
1646 /// `variant_did` is the `DefId` that identifies the enum variant (if this `VariantDef`
1647 /// represents an enum variant).
1649 /// `ctor_did` is the `DefId` that identifies the constructor of unit or
1650 /// tuple-variants/structs. If this is a `struct`-variant then this should be `None`.
1652 /// `parent_did` is the `DefId` of the `AdtDef` representing the enum or struct that
1653 /// owns this variant. It is used for checking if a struct has `#[non_exhaustive]` w/out having
1654 /// to go through the redirect of checking the ctor's attributes - but compiling a small crate
1655 /// requires loading the `AdtDef`s for all the structs in the universe (e.g., coherence for any
1656 /// built-in trait), and we do not want to load attributes twice.
1658 /// If someone speeds up attribute loading to not be a performance concern, they can
1659 /// remove this hack and use the constructor `DefId` everywhere.
1662 variant_did: Option<DefId>,
1663 ctor_def_id: Option<DefId>,
1664 discr: VariantDiscr,
1665 fields: Vec<FieldDef>,
1666 ctor_kind: CtorKind,
1670 is_field_list_non_exhaustive: bool,
1673 "VariantDef::new(name = {:?}, variant_did = {:?}, ctor_def_id = {:?}, discr = {:?},
1674 fields = {:?}, ctor_kind = {:?}, adt_kind = {:?}, parent_did = {:?})",
1675 name, variant_did, ctor_def_id, discr, fields, ctor_kind, adt_kind, parent_did,
1678 let mut flags = VariantFlags::NO_VARIANT_FLAGS;
1679 if is_field_list_non_exhaustive {
1680 flags |= VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE;
1684 flags |= VariantFlags::IS_RECOVERED;
1688 def_id: variant_did.unwrap_or(parent_did),
1698 /// Is this field list non-exhaustive?
1700 pub fn is_field_list_non_exhaustive(&self) -> bool {
1701 self.flags.intersects(VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE)
1704 /// Was this variant obtained as part of recovering from a syntactic error?
1706 pub fn is_recovered(&self) -> bool {
1707 self.flags.intersects(VariantFlags::IS_RECOVERED)
1710 /// Computes the `Ident` of this variant by looking up the `Span`
1711 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1712 Ident::new(self.name, tcx.def_ident_span(self.def_id).unwrap())
1716 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
1717 pub enum VariantDiscr {
1718 /// Explicit value for this variant, i.e., `X = 123`.
1719 /// The `DefId` corresponds to the embedded constant.
1722 /// The previous variant's discriminant plus one.
1723 /// For efficiency reasons, the distance from the
1724 /// last `Explicit` discriminant is being stored,
1725 /// or `0` for the first variant, if it has none.
1729 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1730 pub struct FieldDef {
1733 pub vis: Visibility,
1737 #[derive(TyEncodable, TyDecodable, Default, HashStable)]
1738 pub struct ReprFlags: u8 {
1739 const IS_C = 1 << 0;
1740 const IS_SIMD = 1 << 1;
1741 const IS_TRANSPARENT = 1 << 2;
1742 // Internal only for now. If true, don't reorder fields.
1743 const IS_LINEAR = 1 << 3;
1744 // If true, don't expose any niche to type's context.
1745 const HIDE_NICHE = 1 << 4;
1746 // If true, the type's layout can be randomized using
1747 // the seed stored in `ReprOptions.layout_seed`
1748 const RANDOMIZE_LAYOUT = 1 << 5;
1749 // Any of these flags being set prevent field reordering optimisation.
1750 const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
1751 | ReprFlags::IS_SIMD.bits
1752 | ReprFlags::IS_LINEAR.bits;
1756 /// Represents the repr options provided by the user,
1757 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Default, HashStable)]
1758 pub struct ReprOptions {
1759 pub int: Option<attr::IntType>,
1760 pub align: Option<Align>,
1761 pub pack: Option<Align>,
1762 pub flags: ReprFlags,
1763 /// The seed to be used for randomizing a type's layout
1765 /// Note: This could technically be a `[u8; 16]` (a `u128`) which would
1766 /// be the "most accurate" hash as it'd encompass the item and crate
1767 /// hash without loss, but it does pay the price of being larger.
1768 /// Everything's a tradeoff, a `u64` seed should be sufficient for our
1769 /// purposes (primarily `-Z randomize-layout`)
1770 pub field_shuffle_seed: u64,
1774 pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions {
1775 let mut flags = ReprFlags::empty();
1776 let mut size = None;
1777 let mut max_align: Option<Align> = None;
1778 let mut min_pack: Option<Align> = None;
1780 // Generate a deterministically-derived seed from the item's path hash
1781 // to allow for cross-crate compilation to actually work
1782 let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash();
1784 // If the user defined a custom seed for layout randomization, xor the item's
1785 // path hash with the user defined seed, this will allowing determinism while
1786 // still allowing users to further randomize layout generation for e.g. fuzzing
1787 if let Some(user_seed) = tcx.sess.opts.debugging_opts.layout_seed {
1788 field_shuffle_seed ^= user_seed;
1791 for attr in tcx.get_attrs(did).iter() {
1792 for r in attr::find_repr_attrs(&tcx.sess, attr) {
1793 flags.insert(match r {
1794 attr::ReprC => ReprFlags::IS_C,
1795 attr::ReprPacked(pack) => {
1796 let pack = Align::from_bytes(pack as u64).unwrap();
1797 min_pack = Some(if let Some(min_pack) = min_pack {
1804 attr::ReprTransparent => ReprFlags::IS_TRANSPARENT,
1805 attr::ReprNoNiche => ReprFlags::HIDE_NICHE,
1806 attr::ReprSimd => ReprFlags::IS_SIMD,
1807 attr::ReprInt(i) => {
1811 attr::ReprAlign(align) => {
1812 max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap()));
1819 // If `-Z randomize-layout` was enabled for the type definition then we can
1820 // consider performing layout randomization
1821 if tcx.sess.opts.debugging_opts.randomize_layout {
1822 flags.insert(ReprFlags::RANDOMIZE_LAYOUT);
1825 // This is here instead of layout because the choice must make it into metadata.
1826 if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) {
1827 flags.insert(ReprFlags::IS_LINEAR);
1830 Self { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed }
1834 pub fn simd(&self) -> bool {
1835 self.flags.contains(ReprFlags::IS_SIMD)
1839 pub fn c(&self) -> bool {
1840 self.flags.contains(ReprFlags::IS_C)
1844 pub fn packed(&self) -> bool {
1849 pub fn transparent(&self) -> bool {
1850 self.flags.contains(ReprFlags::IS_TRANSPARENT)
1854 pub fn linear(&self) -> bool {
1855 self.flags.contains(ReprFlags::IS_LINEAR)
1859 pub fn hide_niche(&self) -> bool {
1860 self.flags.contains(ReprFlags::HIDE_NICHE)
1863 /// Returns the discriminant type, given these `repr` options.
1864 /// This must only be called on enums!
1865 pub fn discr_type(&self) -> attr::IntType {
1866 self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize))
1869 /// Returns `true` if this `#[repr()]` should inhabit "smart enum
1870 /// layout" optimizations, such as representing `Foo<&T>` as a
1872 pub fn inhibit_enum_layout_opt(&self) -> bool {
1873 self.c() || self.int.is_some()
1876 /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
1877 /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
1878 pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
1879 if let Some(pack) = self.pack {
1880 if pack.bytes() == 1 {
1885 self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
1888 /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
1889 /// was enabled for its declaration crate
1890 pub fn can_randomize_type_layout(&self) -> bool {
1891 !self.inhibit_struct_field_reordering_opt()
1892 && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
1895 /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
1896 pub fn inhibit_union_abi_opt(&self) -> bool {
1901 impl<'tcx> FieldDef {
1902 /// Returns the type of this field. The resulting type is not normalized. The `subst` is
1903 /// typically obtained via the second field of [`TyKind::Adt`].
1904 pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
1905 tcx.type_of(self.did).subst(tcx, subst)
1908 /// Computes the `Ident` of this variant by looking up the `Span`
1909 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1910 Ident::new(self.name, tcx.def_ident_span(self.did).unwrap())
1914 pub type Attributes<'tcx> = &'tcx [ast::Attribute];
1916 #[derive(Debug, PartialEq, Eq)]
1917 pub enum ImplOverlapKind {
1918 /// These impls are always allowed to overlap.
1920 /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait
1923 /// These impls are allowed to overlap, but that raises
1924 /// an issue #33140 future-compatibility warning.
1926 /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's
1927 /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different.
1929 /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied
1930 /// that difference, making what reduces to the following set of impls:
1934 /// impl Trait for dyn Send + Sync {}
1935 /// impl Trait for dyn Sync + Send {}
1938 /// Obviously, once we made these types be identical, that code causes a coherence
1939 /// error and a fairly big headache for us. However, luckily for us, the trait
1940 /// `Trait` used in this case is basically a marker trait, and therefore having
1941 /// overlapping impls for it is sound.
1943 /// To handle this, we basically regard the trait as a marker trait, with an additional
1944 /// future-compatibility warning. To avoid accidentally "stabilizing" this feature,
1945 /// it has the following restrictions:
1947 /// 1. The trait must indeed be a marker-like trait (i.e., no items), and must be
1949 /// 2. The trait-ref of both impls must be equal.
1950 /// 3. The trait-ref of both impls must be a trait object type consisting only of
1952 /// 4. Neither of the impls can have any where-clauses.
1954 /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed.
1958 impl<'tcx> TyCtxt<'tcx> {
1959 pub fn typeck_body(self, body: hir::BodyId) -> &'tcx TypeckResults<'tcx> {
1960 self.typeck(self.hir().body_owner_def_id(body))
1963 pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> {
1964 self.associated_items(id)
1965 .in_definition_order()
1966 .filter(|item| item.kind == AssocKind::Fn && item.defaultness.has_value())
1969 fn item_name_from_hir(self, def_id: DefId) -> Option<Ident> {
1970 self.hir().get_if_local(def_id).and_then(|node| node.ident())
1973 fn item_name_from_def_id(self, def_id: DefId) -> Option<Symbol> {
1974 if def_id.index == CRATE_DEF_INDEX {
1975 Some(self.crate_name(def_id.krate))
1977 let def_key = self.def_key(def_id);
1978 match def_key.disambiguated_data.data {
1979 // The name of a constructor is that of its parent.
1980 rustc_hir::definitions::DefPathData::Ctor => self.item_name_from_def_id(DefId {
1981 krate: def_id.krate,
1982 index: def_key.parent.unwrap(),
1984 _ => def_key.disambiguated_data.data.get_opt_name(),
1989 /// Look up the name of an item across crates. This does not look at HIR.
1991 /// When possible, this function should be used for cross-crate lookups over
1992 /// [`opt_item_name`] to avoid invalidating the incremental cache. If you
1993 /// need to handle items without a name, or HIR items that will not be
1994 /// serialized cross-crate, or if you need the span of the item, use
1995 /// [`opt_item_name`] instead.
1997 /// [`opt_item_name`]: Self::opt_item_name
1998 pub fn item_name(self, id: DefId) -> Symbol {
1999 // Look at cross-crate items first to avoid invalidating the incremental cache
2000 // unless we have to.
2001 self.item_name_from_def_id(id).unwrap_or_else(|| {
2002 bug!("item_name: no name for {:?}", self.def_path(id));
2006 /// Look up the name and span of an item or [`Node`].
2008 /// See [`item_name`][Self::item_name] for more information.
2009 pub fn opt_item_name(self, def_id: DefId) -> Option<Ident> {
2010 // Look at the HIR first so the span will be correct if this is a local item.
2011 self.item_name_from_hir(def_id)
2012 .or_else(|| self.item_name_from_def_id(def_id).map(Ident::with_dummy_span))
2015 pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> {
2016 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2017 Some(self.associated_item(def_id))
2023 pub fn field_index(self, hir_id: hir::HirId, typeck_results: &TypeckResults<'_>) -> usize {
2024 typeck_results.field_indices().get(hir_id).cloned().expect("no index for a field")
2027 pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
2031 .position(|field| self.hygienic_eq(ident, field.ident(self), variant.def_id))
2034 /// Returns `true` if the impls are the same polarity and the trait either
2035 /// has no items or is annotated `#[marker]` and prevents item overrides.
2036 pub fn impls_are_allowed_to_overlap(
2040 ) -> Option<ImplOverlapKind> {
2041 // If either trait impl references an error, they're allowed to overlap,
2042 // as one of them essentially doesn't exist.
2043 if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.references_error())
2044 || self.impl_trait_ref(def_id2).map_or(false, |tr| tr.references_error())
2046 return Some(ImplOverlapKind::Permitted { marker: false });
2049 match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) {
2050 (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => {
2051 // `#[rustc_reservation_impl]` impls don't overlap with anything
2053 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (reservations)",
2056 return Some(ImplOverlapKind::Permitted { marker: false });
2058 (ImplPolarity::Positive, ImplPolarity::Negative)
2059 | (ImplPolarity::Negative, ImplPolarity::Positive) => {
2060 // `impl AutoTrait for Type` + `impl !AutoTrait for Type`
2062 "impls_are_allowed_to_overlap({:?}, {:?}) - None (differing polarities)",
2067 (ImplPolarity::Positive, ImplPolarity::Positive)
2068 | (ImplPolarity::Negative, ImplPolarity::Negative) => {}
2071 let is_marker_overlap = {
2072 let is_marker_impl = |def_id: DefId| -> bool {
2073 let trait_ref = self.impl_trait_ref(def_id);
2074 trait_ref.map_or(false, |tr| self.trait_def(tr.def_id).is_marker)
2076 is_marker_impl(def_id1) && is_marker_impl(def_id2)
2079 if is_marker_overlap {
2081 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (marker overlap)",
2084 Some(ImplOverlapKind::Permitted { marker: true })
2086 if let Some(self_ty1) = self.issue33140_self_ty(def_id1) {
2087 if let Some(self_ty2) = self.issue33140_self_ty(def_id2) {
2088 if self_ty1 == self_ty2 {
2090 "impls_are_allowed_to_overlap({:?}, {:?}) - issue #33140 HACK",
2093 return Some(ImplOverlapKind::Issue33140);
2096 "impls_are_allowed_to_overlap({:?}, {:?}) - found {:?} != {:?}",
2097 def_id1, def_id2, self_ty1, self_ty2
2103 debug!("impls_are_allowed_to_overlap({:?}, {:?}) = None", def_id1, def_id2);
2108 /// Returns `ty::VariantDef` if `res` refers to a struct,
2109 /// or variant or their constructors, panics otherwise.
2110 pub fn expect_variant_res(self, res: Res) -> &'tcx VariantDef {
2112 Res::Def(DefKind::Variant, did) => {
2113 let enum_did = self.parent(did).unwrap();
2114 self.adt_def(enum_did).variant_with_id(did)
2116 Res::Def(DefKind::Struct | DefKind::Union, did) => self.adt_def(did).non_enum_variant(),
2117 Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => {
2118 let variant_did = self.parent(variant_ctor_did).unwrap();
2119 let enum_did = self.parent(variant_did).unwrap();
2120 self.adt_def(enum_did).variant_with_ctor_id(variant_ctor_did)
2122 Res::Def(DefKind::Ctor(CtorOf::Struct, ..), ctor_did) => {
2123 let struct_did = self.parent(ctor_did).expect("struct ctor has no parent");
2124 self.adt_def(struct_did).non_enum_variant()
2126 _ => bug!("expect_variant_res used with unexpected res {:?}", res),
2130 /// Returns the possibly-auto-generated MIR of a `(DefId, Subst)` pair.
2131 pub fn instance_mir(self, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> {
2133 ty::InstanceDef::Item(def) => match self.def_kind(def.did) {
2135 | DefKind::Static(..)
2136 | DefKind::AssocConst
2138 | DefKind::AnonConst
2139 | DefKind::InlineConst => self.mir_for_ctfe_opt_const_arg(def),
2140 // If the caller wants `mir_for_ctfe` of a function they should not be using
2141 // `instance_mir`, so we'll assume const fn also wants the optimized version.
2143 assert_eq!(def.const_param_did, None);
2144 self.optimized_mir(def.did)
2147 ty::InstanceDef::VtableShim(..)
2148 | ty::InstanceDef::ReifyShim(..)
2149 | ty::InstanceDef::Intrinsic(..)
2150 | ty::InstanceDef::FnPtrShim(..)
2151 | ty::InstanceDef::Virtual(..)
2152 | ty::InstanceDef::ClosureOnceShim { .. }
2153 | ty::InstanceDef::DropGlue(..)
2154 | ty::InstanceDef::CloneShim(..) => self.mir_shims(instance),
2158 /// Gets the attributes of a definition.
2159 pub fn get_attrs(self, did: DefId) -> Attributes<'tcx> {
2160 if let Some(did) = did.as_local() {
2161 self.hir().attrs(self.hir().local_def_id_to_hir_id(did))
2163 self.item_attrs(did)
2167 /// Determines whether an item is annotated with an attribute.
2168 pub fn has_attr(self, did: DefId, attr: Symbol) -> bool {
2169 self.sess.contains_name(&self.get_attrs(did), attr)
2172 /// Returns `true` if this is an `auto trait`.
2173 pub fn trait_is_auto(self, trait_def_id: DefId) -> bool {
2174 self.trait_def(trait_def_id).has_auto_impl
2177 /// Returns layout of a generator. Layout might be unavailable if the
2178 /// generator is tainted by errors.
2179 pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> {
2180 self.optimized_mir(def_id).generator_layout()
2183 /// Given the `DefId` of an impl, returns the `DefId` of the trait it implements.
2184 /// If it implements no trait, returns `None`.
2185 pub fn trait_id_of_impl(self, def_id: DefId) -> Option<DefId> {
2186 self.impl_trait_ref(def_id).map(|tr| tr.def_id)
2189 /// If the given defid describes a method belonging to an impl, returns the
2190 /// `DefId` of the impl that the method belongs to; otherwise, returns `None`.
2191 pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
2192 self.opt_associated_item(def_id).and_then(|trait_item| match trait_item.container {
2193 TraitContainer(_) => None,
2194 ImplContainer(def_id) => Some(def_id),
2198 /// Looks up the span of `impl_did` if the impl is local; otherwise returns `Err`
2199 /// with the name of the crate containing the impl.
2200 pub fn span_of_impl(self, impl_did: DefId) -> Result<Span, Symbol> {
2201 if let Some(impl_did) = impl_did.as_local() {
2202 Ok(self.def_span(impl_did))
2204 Err(self.crate_name(impl_did.krate))
2208 /// Hygienically compares a use-site name (`use_name`) for a field or an associated item with
2209 /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
2210 /// definition's parent/scope to perform comparison.
2211 pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
2212 // We could use `Ident::eq` here, but we deliberately don't. The name
2213 // comparison fails frequently, and we want to avoid the expensive
2214 // `normalize_to_macros_2_0()` calls required for the span comparison whenever possible.
2215 use_name.name == def_name.name
2219 .hygienic_eq(def_name.span.ctxt(), self.expn_that_defined(def_parent_def_id))
2222 pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident {
2223 ident.span.normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope));
2227 pub fn adjust_ident_and_get_scope(
2232 ) -> (Ident, DefId) {
2235 .normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope))
2236 .and_then(|actual_expansion| actual_expansion.expn_data().parent_module)
2237 .unwrap_or_else(|| self.parent_module(block).to_def_id());
2241 pub fn is_object_safe(self, key: DefId) -> bool {
2242 self.object_safety_violations(key).is_empty()
2246 /// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition.
2247 pub fn is_impl_trait_defn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<LocalDefId> {
2248 let def_id = def_id.as_local()?;
2249 if let Node::Item(item) = tcx.hir().get_by_def_id(def_id) {
2250 if let hir::ItemKind::OpaqueTy(ref opaque_ty) = item.kind {
2251 return match opaque_ty.origin {
2252 hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) => {
2255 hir::OpaqueTyOrigin::TyAlias => None,
2262 pub fn int_ty(ity: ast::IntTy) -> IntTy {
2264 ast::IntTy::Isize => IntTy::Isize,
2265 ast::IntTy::I8 => IntTy::I8,
2266 ast::IntTy::I16 => IntTy::I16,
2267 ast::IntTy::I32 => IntTy::I32,
2268 ast::IntTy::I64 => IntTy::I64,
2269 ast::IntTy::I128 => IntTy::I128,
2273 pub fn uint_ty(uty: ast::UintTy) -> UintTy {
2275 ast::UintTy::Usize => UintTy::Usize,
2276 ast::UintTy::U8 => UintTy::U8,
2277 ast::UintTy::U16 => UintTy::U16,
2278 ast::UintTy::U32 => UintTy::U32,
2279 ast::UintTy::U64 => UintTy::U64,
2280 ast::UintTy::U128 => UintTy::U128,
2284 pub fn float_ty(fty: ast::FloatTy) -> FloatTy {
2286 ast::FloatTy::F32 => FloatTy::F32,
2287 ast::FloatTy::F64 => FloatTy::F64,
2291 pub fn ast_int_ty(ity: IntTy) -> ast::IntTy {
2293 IntTy::Isize => ast::IntTy::Isize,
2294 IntTy::I8 => ast::IntTy::I8,
2295 IntTy::I16 => ast::IntTy::I16,
2296 IntTy::I32 => ast::IntTy::I32,
2297 IntTy::I64 => ast::IntTy::I64,
2298 IntTy::I128 => ast::IntTy::I128,
2302 pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy {
2304 UintTy::Usize => ast::UintTy::Usize,
2305 UintTy::U8 => ast::UintTy::U8,
2306 UintTy::U16 => ast::UintTy::U16,
2307 UintTy::U32 => ast::UintTy::U32,
2308 UintTy::U64 => ast::UintTy::U64,
2309 UintTy::U128 => ast::UintTy::U128,
2313 pub fn provide(providers: &mut ty::query::Providers) {
2314 closure::provide(providers);
2315 context::provide(providers);
2316 erase_regions::provide(providers);
2317 layout::provide(providers);
2318 util::provide(providers);
2319 print::provide(providers);
2320 super::util::bug::provide(providers);
2321 super::middle::provide(providers);
2322 *providers = ty::query::Providers {
2323 trait_impls_of: trait_def::trait_impls_of_provider,
2324 incoherent_impls: trait_def::incoherent_impls_provider,
2325 type_uninhabited_from: inhabitedness::type_uninhabited_from,
2326 const_param_default: consts::const_param_default,
2327 vtable_allocation: vtable::vtable_allocation_provider,
2332 /// A map for the local crate mapping each type to a vector of its
2333 /// inherent impls. This is not meant to be used outside of coherence;
2334 /// rather, you should request the vector for a specific type via
2335 /// `tcx.inherent_impls(def_id)` so as to minimize your dependencies
2336 /// (constructing this map requires touching the entire crate).
2337 #[derive(Clone, Debug, Default, HashStable)]
2338 pub struct CrateInherentImpls {
2339 pub inherent_impls: LocalDefIdMap<Vec<DefId>>,
2340 pub incoherent_impls: FxHashMap<SimplifiedType, Vec<LocalDefId>>,
2343 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, HashStable)]
2344 pub struct SymbolName<'tcx> {
2345 /// `&str` gives a consistent ordering, which ensures reproducible builds.
2346 pub name: &'tcx str,
2349 impl<'tcx> SymbolName<'tcx> {
2350 pub fn new(tcx: TyCtxt<'tcx>, name: &str) -> SymbolName<'tcx> {
2352 name: unsafe { str::from_utf8_unchecked(tcx.arena.alloc_slice(name.as_bytes())) },
2357 impl<'tcx> fmt::Display for SymbolName<'tcx> {
2358 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2359 fmt::Display::fmt(&self.name, fmt)
2363 impl<'tcx> fmt::Debug for SymbolName<'tcx> {
2364 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2365 fmt::Display::fmt(&self.name, fmt)
2369 #[derive(Debug, Default, Copy, Clone)]
2370 pub struct FoundRelationships {
2371 /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
2372 /// obligation, where:
2374 /// * `Foo` is not `Sized`
2375 /// * `(): Foo` may be satisfied
2376 pub self_in_trait: bool,
2377 /// This is true if we identified that this Ty (`?T`) is found in a `<_ as
2378 /// _>::AssocType = ?T`