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
13 FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitor,
15 pub use self::AssocItemContainer::*;
16 pub use self::BorrowKind::*;
17 pub use self::IntVarValue::*;
18 pub use self::Variance::*;
19 use crate::metadata::ModChild;
20 use crate::middle::privacy::AccessLevels;
21 use crate::mir::{Body, GeneratorLayout};
22 use crate::traits::{self, Reveal};
24 use crate::ty::fast_reject::SimplifiedType;
25 use crate::ty::util::Discr;
30 use rustc_attr as attr;
31 use rustc_data_structures::fingerprint::Fingerprint;
32 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
33 use rustc_data_structures::intern::{Interned, WithStableHash};
34 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
35 use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
37 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
38 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LocalDefIdMap};
40 use rustc_macros::HashStable;
41 use rustc_query_system::ich::StableHashingContext;
42 use rustc_session::cstore::CrateStoreDyn;
43 use rustc_span::symbol::{kw, sym, Ident, Symbol};
45 use rustc_target::abi::Align;
51 use std::ops::ControlFlow;
54 pub use crate::ty::diagnostics::*;
55 pub use rustc_type_ir::InferTy::*;
56 pub use rustc_type_ir::TyKind::*;
57 pub use rustc_type_ir::*;
59 pub use self::binding::BindingMode;
60 pub use self::binding::BindingMode::*;
61 pub use self::closure::{
62 is_ancestor_or_same_capture, place_to_string_for_capture, BorrowKind, CaptureInfo,
63 CapturedPlace, ClosureKind, MinCaptureInformationMap, MinCaptureList,
64 RootVariableMinCaptureList, UpvarCapture, UpvarCaptureMap, UpvarId, UpvarListMap, UpvarPath,
67 pub use self::consts::{
68 Const, ConstInt, ConstKind, ConstS, InferConst, ScalarInt, Unevaluated, ValTree,
70 pub use self::context::{
71 tls, CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations,
72 CtxtInterners, DelaySpanBugEmitted, FreeRegionInfo, GeneratorDiagnosticData,
73 GeneratorInteriorTypeCause, GlobalCtxt, Lift, OnDiskCache, TyCtxt, TypeckResults, UserType,
74 UserTypeAnnotationIndex,
76 pub use self::instance::{Instance, InstanceDef};
77 pub use self::list::List;
78 pub use self::parameterized::ParameterizedOverTcx;
79 pub use self::rvalue_scopes::RvalueScopes;
80 pub use self::sty::BoundRegionKind::*;
81 pub use self::sty::RegionKind::*;
83 Article, Binder, BoundRegion, BoundRegionKind, BoundTy, BoundTyKind, BoundVar,
84 BoundVariableKind, CanonicalPolyFnSig, ClosureSubsts, ClosureSubstsParts, ConstVid,
85 EarlyBinder, EarlyBoundRegion, ExistentialPredicate, ExistentialProjection,
86 ExistentialTraitRef, FnSig, FreeRegion, GenSig, GeneratorSubsts, GeneratorSubstsParts,
87 InlineConstSubsts, InlineConstSubstsParts, ParamConst, ParamTy, PolyExistentialProjection,
88 PolyExistentialTraitRef, PolyFnSig, PolyGenSig, PolyTraitRef, ProjectionTy, Region, RegionKind,
89 RegionVid, TraitRef, TyKind, TypeAndMut, UpvarSubsts, VarianceDiagInfo,
91 pub use self::trait_def::TraitDef;
102 pub mod inhabitedness;
104 pub mod normalize_erasing_regions;
127 mod structural_impls;
132 pub type RegisteredTools = FxHashSet<Ident>;
135 pub struct ResolverOutputs {
136 pub definitions: rustc_hir::definitions::Definitions,
137 pub cstore: Box<CrateStoreDyn>,
138 pub visibilities: FxHashMap<LocalDefId, Visibility>,
139 /// This field is used to decide whether we should make `PRIVATE_IN_PUBLIC` a hard error.
140 pub has_pub_restricted: bool,
141 pub access_levels: AccessLevels,
142 pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
143 pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
144 pub maybe_unused_extern_crates: Vec<(LocalDefId, Span)>,
145 pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>,
146 pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
147 /// Extern prelude entries. The value is `true` if the entry was introduced
148 /// via `extern crate` item and not `--extern` option or compiler built-in.
149 pub extern_prelude: FxHashMap<Symbol, bool>,
150 pub main_def: Option<MainDefinition>,
151 pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,
152 /// A list of proc macro LocalDefIds, written out in the order in which
153 /// they are declared in the static array generated by proc_macro_harness.
154 pub proc_macros: Vec<LocalDefId>,
155 /// Mapping from ident span to path span for paths that don't exist as written, but that
156 /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`.
157 pub confused_type_with_std_module: FxHashMap<Span, Span>,
158 pub registered_tools: RegisteredTools,
161 #[derive(Clone, Copy, Debug)]
162 pub struct MainDefinition {
163 pub res: Res<ast::NodeId>,
168 impl MainDefinition {
169 pub fn opt_fn_def_id(self) -> Option<DefId> {
170 if let Res::Def(DefKind::Fn, def_id) = self.res { Some(def_id) } else { None }
174 /// The "header" of an impl is everything outside the body: a Self type, a trait
175 /// ref (in the case of a trait impl), and a set of predicates (from the
176 /// bounds / where-clauses).
177 #[derive(Clone, Debug, TypeFoldable)]
178 pub struct ImplHeader<'tcx> {
179 pub impl_def_id: DefId,
180 pub self_ty: Ty<'tcx>,
181 pub trait_ref: Option<TraitRef<'tcx>>,
182 pub predicates: Vec<Predicate<'tcx>>,
185 #[derive(Copy, Clone, Debug, TypeFoldable)]
186 pub enum ImplSubject<'tcx> {
187 Trait(TraitRef<'tcx>),
203 pub enum ImplPolarity {
204 /// `impl Trait for Type`
206 /// `impl !Trait for Type`
208 /// `#[rustc_reservation_impl] impl Trait for Type`
210 /// This is a "stability hack", not a real Rust feature.
211 /// See #64631 for details.
216 /// Flips polarity by turning `Positive` into `Negative` and `Negative` into `Positive`.
217 pub fn flip(&self) -> Option<ImplPolarity> {
219 ImplPolarity::Positive => Some(ImplPolarity::Negative),
220 ImplPolarity::Negative => Some(ImplPolarity::Positive),
221 ImplPolarity::Reservation => None,
226 impl fmt::Display for ImplPolarity {
227 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
229 Self::Positive => f.write_str("positive"),
230 Self::Negative => f.write_str("negative"),
231 Self::Reservation => f.write_str("reservation"),
236 #[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, Encodable, Decodable, HashStable)]
237 pub enum Visibility {
238 /// Visible everywhere (including in other crates).
240 /// Visible only in the given crate-local module.
242 /// Not visible anywhere in the local crate. This is the visibility of private external items.
246 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
247 pub enum BoundConstness {
250 /// `T: ~const Trait`
252 /// Requires resolving to const only when we are in a const context.
256 impl BoundConstness {
257 /// Reduce `self` and `constness` to two possible combined states instead of four.
258 pub fn and(&mut self, constness: hir::Constness) -> hir::Constness {
259 match (constness, self) {
260 (hir::Constness::Const, BoundConstness::ConstIfConst) => hir::Constness::Const,
262 *this = BoundConstness::NotConst;
263 hir::Constness::NotConst
269 impl fmt::Display for BoundConstness {
270 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
272 Self::NotConst => f.write_str("normal"),
273 Self::ConstIfConst => f.write_str("`~const`"),
290 pub struct ClosureSizeProfileData<'tcx> {
291 /// Tuple containing the types of closure captures before the feature `capture_disjoint_fields`
292 pub before_feature_tys: Ty<'tcx>,
293 /// Tuple containing the types of closure captures after the feature `capture_disjoint_fields`
294 pub after_feature_tys: Ty<'tcx>,
297 pub trait DefIdTree: Copy {
298 fn opt_parent(self, id: DefId) -> Option<DefId>;
302 fn parent(self, id: DefId) -> DefId {
303 match self.opt_parent(id) {
305 // not `unwrap_or_else` to avoid breaking caller tracking
306 None => bug!("{id:?} doesn't have a parent"),
312 fn opt_local_parent(self, id: LocalDefId) -> Option<LocalDefId> {
313 self.opt_parent(id.to_def_id()).map(DefId::expect_local)
318 fn local_parent(self, id: LocalDefId) -> LocalDefId {
319 self.parent(id.to_def_id()).expect_local()
322 fn is_descendant_of(self, mut descendant: DefId, ancestor: DefId) -> bool {
323 if descendant.krate != ancestor.krate {
327 while descendant != ancestor {
328 match self.opt_parent(descendant) {
329 Some(parent) => descendant = parent,
330 None => return false,
337 impl<'tcx> DefIdTree for TyCtxt<'tcx> {
339 fn opt_parent(self, id: DefId) -> Option<DefId> {
340 self.def_key(id).parent.map(|index| DefId { index, ..id })
345 /// Returns `true` if an item with this visibility is accessible from the given block.
346 pub fn is_accessible_from<T: DefIdTree>(self, module: DefId, tree: T) -> bool {
347 let restriction = match self {
348 // Public items are visible everywhere.
349 Visibility::Public => return true,
350 // Private items from other crates are visible nowhere.
351 Visibility::Invisible => return false,
352 // Restricted items are visible in an arbitrary local module.
353 Visibility::Restricted(other) if other.krate != module.krate => return false,
354 Visibility::Restricted(module) => module,
357 tree.is_descendant_of(module, restriction)
360 /// Returns `true` if this visibility is at least as accessible as the given visibility
361 pub fn is_at_least<T: DefIdTree>(self, vis: Visibility, tree: T) -> bool {
362 let vis_restriction = match vis {
363 Visibility::Public => return self == Visibility::Public,
364 Visibility::Invisible => return true,
365 Visibility::Restricted(module) => module,
368 self.is_accessible_from(vis_restriction, tree)
371 // Returns `true` if this item is visible anywhere in the local crate.
372 pub fn is_visible_locally(self) -> bool {
374 Visibility::Public => true,
375 Visibility::Restricted(def_id) => def_id.is_local(),
376 Visibility::Invisible => false,
380 pub fn is_public(self) -> bool {
381 matches!(self, Visibility::Public)
385 /// The crate variances map is computed during typeck and contains the
386 /// variance of every item in the local crate. You should not use it
387 /// directly, because to do so will make your pass dependent on the
388 /// HIR of every item in the local crate. Instead, use
389 /// `tcx.variances_of()` to get the variance for a *particular*
391 #[derive(HashStable, Debug)]
392 pub struct CrateVariancesMap<'tcx> {
393 /// For each item with generics, maps to a vector of the variance
394 /// of its generics. If an item has no generics, it will have no
396 pub variances: FxHashMap<DefId, &'tcx [ty::Variance]>,
399 // Contains information needed to resolve types and (in the future) look up
400 // the types of AST nodes.
401 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
402 pub struct CReaderCacheKey {
403 pub cnum: Option<CrateNum>,
407 /// Represents a type.
410 /// - This is a very "dumb" struct (with no derives and no `impls`).
411 /// - Values of this type are always interned and thus unique, and are stored
412 /// as an `Interned<TyS>`.
413 /// - `Ty` (which contains a reference to a `Interned<TyS>`) or `Interned<TyS>`
414 /// should be used everywhere instead of `TyS`. In particular, `Ty` has most
415 /// of the relevant methods.
416 #[derive(PartialEq, Eq, PartialOrd, Ord)]
417 #[allow(rustc::usage_of_ty_tykind)]
418 pub(crate) struct TyS<'tcx> {
419 /// This field shouldn't be used directly and may be removed in the future.
420 /// Use `Ty::kind()` instead.
423 /// This field provides fast access to information that is also contained
426 /// This field shouldn't be used directly and may be removed in the future.
427 /// Use `Ty::flags()` instead.
430 /// This field provides fast access to information that is also contained
433 /// This is a kind of confusing thing: it stores the smallest
436 /// (a) the binder itself captures nothing but
437 /// (b) all the late-bound things within the type are captured
438 /// by some sub-binder.
440 /// So, for a type without any late-bound things, like `u32`, this
441 /// will be *innermost*, because that is the innermost binder that
442 /// captures nothing. But for a type `&'D u32`, where `'D` is a
443 /// late-bound region with De Bruijn index `D`, this would be `D + 1`
444 /// -- the binder itself does not capture `D`, but `D` is captured
445 /// by an inner binder.
447 /// We call this concept an "exclusive" binder `D` because all
448 /// De Bruijn indices within the type are contained within `0..D`
450 outer_exclusive_binder: ty::DebruijnIndex,
453 // `TyS` is used a lot. Make sure it doesn't unintentionally get bigger.
454 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
455 static_assert_size!(TyS<'_>, 40);
457 // We are actually storing a stable hash cache next to the type, so let's
458 // also check the full size
459 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
460 static_assert_size!(WithStableHash<TyS<'_>>, 56);
462 /// Use this rather than `TyS`, whenever possible.
463 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
464 #[rustc_diagnostic_item = "Ty"]
465 #[rustc_pass_by_value]
466 pub struct Ty<'tcx>(Interned<'tcx, WithStableHash<TyS<'tcx>>>);
468 impl<'tcx> TyCtxt<'tcx> {
469 /// A "bool" type used in rustc_mir_transform unit tests when we
470 /// have not spun up a TyCtxt.
471 pub const BOOL_TY_FOR_UNIT_TESTING: Ty<'tcx> = Ty(Interned::new_unchecked(&WithStableHash {
474 flags: TypeFlags::empty(),
475 outer_exclusive_binder: DebruijnIndex::from_usize(0),
477 stable_hash: Fingerprint::ZERO,
481 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for TyS<'tcx> {
483 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
487 // The other fields just provide fast access to information that is
488 // also contained in `kind`, so no need to hash them.
491 outer_exclusive_binder: _,
494 kind.hash_stable(hcx, hasher)
498 impl ty::EarlyBoundRegion {
499 /// Does this early bound region have a name? Early bound regions normally
500 /// always have names except when using anonymous lifetimes (`'_`).
501 pub fn has_name(&self) -> bool {
502 self.name != kw::UnderscoreLifetime
506 /// Represents a predicate.
508 /// See comments on `TyS`, which apply here too (albeit for
509 /// `PredicateS`/`Predicate` rather than `TyS`/`Ty`).
511 pub(crate) struct PredicateS<'tcx> {
512 kind: Binder<'tcx, PredicateKind<'tcx>>,
514 /// See the comment for the corresponding field of [TyS].
515 outer_exclusive_binder: ty::DebruijnIndex,
518 // This type is used a lot. Make sure it doesn't unintentionally get bigger.
519 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
520 static_assert_size!(PredicateS<'_>, 56);
522 /// Use this rather than `PredicateS`, whenever possible.
523 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
524 #[rustc_pass_by_value]
525 pub struct Predicate<'tcx>(Interned<'tcx, PredicateS<'tcx>>);
527 impl<'tcx> Predicate<'tcx> {
528 /// Gets the inner `Binder<'tcx, PredicateKind<'tcx>>`.
530 pub fn kind(self) -> Binder<'tcx, PredicateKind<'tcx>> {
535 pub fn flags(self) -> TypeFlags {
540 pub fn outer_exclusive_binder(self) -> DebruijnIndex {
541 self.0.outer_exclusive_binder
544 /// Flips the polarity of a Predicate.
546 /// Given `T: Trait` predicate it returns `T: !Trait` and given `T: !Trait` returns `T: Trait`.
547 pub fn flip_polarity(self, tcx: TyCtxt<'tcx>) -> Option<Predicate<'tcx>> {
550 .map_bound(|kind| match kind {
551 PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) => {
552 Some(PredicateKind::Trait(TraitPredicate {
555 polarity: polarity.flip()?,
563 Some(tcx.mk_predicate(kind))
567 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> {
568 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
572 // The other fields just provide fast access to information that is
573 // also contained in `kind`, so no need to hash them.
575 outer_exclusive_binder: _,
578 kind.hash_stable(hcx, hasher);
582 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
583 #[derive(HashStable, TypeFoldable)]
584 pub enum PredicateKind<'tcx> {
585 /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
586 /// the `Self` type of the trait reference and `A`, `B`, and `C`
587 /// would be the type parameters.
588 Trait(TraitPredicate<'tcx>),
591 RegionOutlives(RegionOutlivesPredicate<'tcx>),
594 TypeOutlives(TypeOutlivesPredicate<'tcx>),
596 /// `where <T as TraitRef>::Name == X`, approximately.
597 /// See the `ProjectionPredicate` struct for details.
598 Projection(ProjectionPredicate<'tcx>),
600 /// No syntax: `T` well-formed.
601 WellFormed(GenericArg<'tcx>),
603 /// Trait must be object-safe.
606 /// No direct syntax. May be thought of as `where T: FnFoo<...>`
607 /// for some substitutions `...` and `T` being a closure type.
608 /// Satisfied (or refuted) once we know the closure's kind.
609 ClosureKind(DefId, SubstsRef<'tcx>, ClosureKind),
613 /// This obligation is created most often when we have two
614 /// unresolved type variables and hence don't have enough
615 /// information to process the subtyping obligation yet.
616 Subtype(SubtypePredicate<'tcx>),
618 /// `T1` coerced to `T2`
620 /// Like a subtyping obligation, this is created most often
621 /// when we have two unresolved type variables and hence
622 /// don't have enough information to process the coercion
623 /// obligation yet. At the moment, we actually process coercions
624 /// very much like subtyping and don't handle the full coercion
626 Coerce(CoercePredicate<'tcx>),
628 /// Constant initializer must evaluate successfully.
629 ConstEvaluatable(ty::Unevaluated<'tcx, ()>),
631 /// Constants must be equal. The first component is the const that is expected.
632 ConstEquate(Const<'tcx>, Const<'tcx>),
634 /// Represents a type found in the environment that we can use for implied bounds.
636 /// Only used for Chalk.
637 TypeWellFormedFromEnv(Ty<'tcx>),
640 /// The crate outlives map is computed during typeck and contains the
641 /// outlives of every item in the local crate. You should not use it
642 /// directly, because to do so will make your pass dependent on the
643 /// HIR of every item in the local crate. Instead, use
644 /// `tcx.inferred_outlives_of()` to get the outlives for a *particular*
646 #[derive(HashStable, Debug)]
647 pub struct CratePredicatesMap<'tcx> {
648 /// For each struct with outlive bounds, maps to a vector of the
649 /// predicate of its outlive bounds. If an item has no outlives
650 /// bounds, it will have no entry.
651 pub predicates: FxHashMap<DefId, &'tcx [(Predicate<'tcx>, Span)]>,
654 impl<'tcx> Predicate<'tcx> {
655 /// Performs a substitution suitable for going from a
656 /// poly-trait-ref to supertraits that must hold if that
657 /// poly-trait-ref holds. This is slightly different from a normal
658 /// substitution in terms of what happens with bound regions. See
659 /// lengthy comment below for details.
660 pub fn subst_supertrait(
663 trait_ref: &ty::PolyTraitRef<'tcx>,
664 ) -> Predicate<'tcx> {
665 // The interaction between HRTB and supertraits is not entirely
666 // obvious. Let me walk you (and myself) through an example.
668 // Let's start with an easy case. Consider two traits:
670 // trait Foo<'a>: Bar<'a,'a> { }
671 // trait Bar<'b,'c> { }
673 // Now, if we have a trait reference `for<'x> T: Foo<'x>`, then
674 // we can deduce that `for<'x> T: Bar<'x,'x>`. Basically, if we
675 // knew that `Foo<'x>` (for any 'x) then we also know that
676 // `Bar<'x,'x>` (for any 'x). This more-or-less falls out from
677 // normal substitution.
679 // In terms of why this is sound, the idea is that whenever there
680 // is an impl of `T:Foo<'a>`, it must show that `T:Bar<'a,'a>`
681 // holds. So if there is an impl of `T:Foo<'a>` that applies to
682 // all `'a`, then we must know that `T:Bar<'a,'a>` holds for all
685 // Another example to be careful of is this:
687 // trait Foo1<'a>: for<'b> Bar1<'a,'b> { }
688 // trait Bar1<'b,'c> { }
690 // Here, if we have `for<'x> T: Foo1<'x>`, then what do we know?
691 // The answer is that we know `for<'x,'b> T: Bar1<'x,'b>`. The
692 // reason is similar to the previous example: any impl of
693 // `T:Foo1<'x>` must show that `for<'b> T: Bar1<'x, 'b>`. So
694 // basically we would want to collapse the bound lifetimes from
695 // the input (`trait_ref`) and the supertraits.
697 // To achieve this in practice is fairly straightforward. Let's
698 // consider the more complicated scenario:
700 // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x`
701 // has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`,
702 // where both `'x` and `'b` would have a DB index of 1.
703 // The substitution from the input trait-ref is therefore going to be
704 // `'a => 'x` (where `'x` has a DB index of 1).
705 // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an
706 // early-bound parameter and `'b' is a late-bound parameter with a
708 // - If we replace `'a` with `'x` from the input, it too will have
709 // a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>`
710 // just as we wanted.
712 // There is only one catch. If we just apply the substitution `'a
713 // => 'x` to `for<'b> Bar1<'a,'b>`, the substitution code will
714 // adjust the DB index because we substituting into a binder (it
715 // tries to be so smart...) resulting in `for<'x> for<'b>
716 // Bar1<'x,'b>` (we have no syntax for this, so use your
717 // imagination). Basically the 'x will have DB index of 2 and 'b
718 // will have DB index of 1. Not quite what we want. So we apply
719 // the substitution to the *contents* of the trait reference,
720 // rather than the trait reference itself (put another way, the
721 // substitution code expects equal binding levels in the values
722 // from the substitution and the value being substituted into, and
723 // this trick achieves that).
725 // Working through the second example:
726 // trait_ref: for<'x> T: Foo1<'^0.0>; substs: [T, '^0.0]
727 // predicate: for<'b> Self: Bar1<'a, '^0.0>; substs: [Self, 'a, '^0.0]
728 // We want to end up with:
729 // for<'x, 'b> T: Bar1<'^0.0, '^0.1>
731 // 1) We must shift all bound vars in predicate by the length
732 // of trait ref's bound vars. So, we would end up with predicate like
733 // Self: Bar1<'a, '^0.1>
734 // 2) We can then apply the trait substs to this, ending up with
735 // T: Bar1<'^0.0, '^0.1>
736 // 3) Finally, to create the final bound vars, we concatenate the bound
737 // vars of the trait ref with those of the predicate:
739 let bound_pred = self.kind();
740 let pred_bound_vars = bound_pred.bound_vars();
741 let trait_bound_vars = trait_ref.bound_vars();
742 // 1) Self: Bar1<'a, '^0.0> -> Self: Bar1<'a, '^0.1>
744 tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
745 // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
746 let new = EarlyBinder(shifted_pred).subst(tcx, trait_ref.skip_binder().substs);
747 // 3) ['x] + ['b] -> ['x, 'b]
749 tcx.mk_bound_variable_kinds(trait_bound_vars.iter().chain(pred_bound_vars));
750 tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars))
754 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
755 #[derive(HashStable, TypeFoldable)]
756 pub struct TraitPredicate<'tcx> {
757 pub trait_ref: TraitRef<'tcx>,
759 pub constness: BoundConstness,
761 /// If polarity is Positive: we are proving that the trait is implemented.
763 /// If polarity is Negative: we are proving that a negative impl of this trait
764 /// exists. (Note that coherence also checks whether negative impls of supertraits
765 /// exist via a series of predicates.)
767 /// If polarity is Reserved: that's a bug.
768 pub polarity: ImplPolarity,
771 pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
773 impl<'tcx> TraitPredicate<'tcx> {
774 pub fn remap_constness(&mut self, tcx: TyCtxt<'tcx>, param_env: &mut ParamEnv<'tcx>) {
775 if unlikely!(Some(self.trait_ref.def_id) == tcx.lang_items().drop_trait()) {
776 // remap without changing constness of this predicate.
777 // this is because `T: ~const Drop` has a different meaning to `T: Drop`
778 // FIXME(fee1-dead): remove this logic after beta bump
779 param_env.remap_constness_with(self.constness)
781 *param_env = param_env.with_constness(self.constness.and(param_env.constness()))
785 /// Remap the constness of this predicate before emitting it for diagnostics.
786 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
787 // this is different to `remap_constness` that callees want to print this predicate
788 // in case of selection errors. `T: ~const Drop` bounds cannot end up here when the
789 // param_env is not const because we it is always satisfied in non-const contexts.
790 if let hir::Constness::NotConst = param_env.constness() {
791 self.constness = ty::BoundConstness::NotConst;
795 pub fn def_id(self) -> DefId {
796 self.trait_ref.def_id
799 pub fn self_ty(self) -> Ty<'tcx> {
800 self.trait_ref.self_ty()
804 pub fn is_const_if_const(self) -> bool {
805 self.constness == BoundConstness::ConstIfConst
809 impl<'tcx> PolyTraitPredicate<'tcx> {
810 pub fn def_id(self) -> DefId {
811 // Ok to skip binder since trait `DefId` does not care about regions.
812 self.skip_binder().def_id()
815 pub fn self_ty(self) -> ty::Binder<'tcx, Ty<'tcx>> {
816 self.map_bound(|trait_ref| trait_ref.self_ty())
819 /// Remap the constness of this predicate before emitting it for diagnostics.
820 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
821 *self = self.map_bound(|mut p| {
822 p.remap_constness_diag(param_env);
828 pub fn is_const_if_const(self) -> bool {
829 self.skip_binder().is_const_if_const()
833 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
834 #[derive(HashStable, TypeFoldable)]
835 pub struct OutlivesPredicate<A, B>(pub A, pub B); // `A: B`
836 pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>;
837 pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>;
838 pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>;
839 pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>;
841 /// Encodes that `a` must be a subtype of `b`. The `a_is_expected` flag indicates
842 /// whether the `a` type is the type that we should label as "expected" when
843 /// presenting user diagnostics.
844 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
845 #[derive(HashStable, TypeFoldable)]
846 pub struct SubtypePredicate<'tcx> {
847 pub a_is_expected: bool,
851 pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>;
853 /// Encodes that we have to coerce *from* the `a` type to the `b` type.
854 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
855 #[derive(HashStable, TypeFoldable)]
856 pub struct CoercePredicate<'tcx> {
860 pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
862 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, TyEncodable, TyDecodable)]
863 #[derive(HashStable, TypeFoldable)]
864 pub enum Term<'tcx> {
869 impl<'tcx> From<Ty<'tcx>> for Term<'tcx> {
870 fn from(ty: Ty<'tcx>) -> Self {
875 impl<'tcx> From<Const<'tcx>> for Term<'tcx> {
876 fn from(c: Const<'tcx>) -> Self {
881 impl<'tcx> Term<'tcx> {
882 pub fn ty(&self) -> Option<Ty<'tcx>> {
883 if let Term::Ty(ty) = self { Some(*ty) } else { None }
885 pub fn ct(&self) -> Option<Const<'tcx>> {
886 if let Term::Const(c) = self { Some(*c) } else { None }
890 /// This kind of predicate has no *direct* correspondent in the
891 /// syntax, but it roughly corresponds to the syntactic forms:
893 /// 1. `T: TraitRef<..., Item = Type>`
894 /// 2. `<T as TraitRef<...>>::Item == Type` (NYI)
896 /// In particular, form #1 is "desugared" to the combination of a
897 /// normal trait predicate (`T: TraitRef<...>`) and one of these
898 /// predicates. Form #2 is a broader form in that it also permits
899 /// equality between arbitrary types. Processing an instance of
900 /// Form #2 eventually yields one of these `ProjectionPredicate`
901 /// instances to normalize the LHS.
902 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
903 #[derive(HashStable, TypeFoldable)]
904 pub struct ProjectionPredicate<'tcx> {
905 pub projection_ty: ProjectionTy<'tcx>,
906 pub term: Term<'tcx>,
909 pub type PolyProjectionPredicate<'tcx> = Binder<'tcx, ProjectionPredicate<'tcx>>;
911 impl<'tcx> PolyProjectionPredicate<'tcx> {
912 /// Returns the `DefId` of the trait of the associated item being projected.
914 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
915 self.skip_binder().projection_ty.trait_def_id(tcx)
918 /// Get the [PolyTraitRef] required for this projection to be well formed.
919 /// Note that for generic associated types the predicates of the associated
920 /// type also need to be checked.
922 pub fn required_poly_trait_ref(&self, tcx: TyCtxt<'tcx>) -> PolyTraitRef<'tcx> {
923 // Note: unlike with `TraitRef::to_poly_trait_ref()`,
924 // `self.0.trait_ref` is permitted to have escaping regions.
925 // This is because here `self` has a `Binder` and so does our
926 // return value, so we are preserving the number of binding
928 self.map_bound(|predicate| predicate.projection_ty.trait_ref(tcx))
931 pub fn term(&self) -> Binder<'tcx, Term<'tcx>> {
932 self.map_bound(|predicate| predicate.term)
935 /// The `DefId` of the `TraitItem` for the associated type.
937 /// Note that this is not the `DefId` of the `TraitRef` containing this
938 /// associated type, which is in `tcx.associated_item(projection_def_id()).container`.
939 pub fn projection_def_id(&self) -> DefId {
940 // Ok to skip binder since trait `DefId` does not care about regions.
941 self.skip_binder().projection_ty.item_def_id
945 pub trait ToPolyTraitRef<'tcx> {
946 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx>;
949 impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
950 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> {
951 self.map_bound_ref(|trait_pred| trait_pred.trait_ref)
955 pub trait ToPredicate<'tcx> {
956 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx>;
959 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
961 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
962 tcx.mk_predicate(self)
966 impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
967 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
968 self.map_bound(PredicateKind::Trait).to_predicate(tcx)
972 impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
973 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
974 self.map_bound(PredicateKind::RegionOutlives).to_predicate(tcx)
978 impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> {
979 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
980 self.map_bound(PredicateKind::TypeOutlives).to_predicate(tcx)
984 impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
985 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
986 self.map_bound(PredicateKind::Projection).to_predicate(tcx)
990 impl<'tcx> Predicate<'tcx> {
991 pub fn to_opt_poly_trait_pred(self) -> Option<PolyTraitPredicate<'tcx>> {
992 let predicate = self.kind();
993 match predicate.skip_binder() {
994 PredicateKind::Trait(t) => Some(predicate.rebind(t)),
995 PredicateKind::Projection(..)
996 | PredicateKind::Subtype(..)
997 | PredicateKind::Coerce(..)
998 | PredicateKind::RegionOutlives(..)
999 | PredicateKind::WellFormed(..)
1000 | PredicateKind::ObjectSafe(..)
1001 | PredicateKind::ClosureKind(..)
1002 | PredicateKind::TypeOutlives(..)
1003 | PredicateKind::ConstEvaluatable(..)
1004 | PredicateKind::ConstEquate(..)
1005 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1009 pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> {
1010 let predicate = self.kind();
1011 match predicate.skip_binder() {
1012 PredicateKind::TypeOutlives(data) => Some(predicate.rebind(data)),
1013 PredicateKind::Trait(..)
1014 | PredicateKind::Projection(..)
1015 | PredicateKind::Subtype(..)
1016 | PredicateKind::Coerce(..)
1017 | PredicateKind::RegionOutlives(..)
1018 | PredicateKind::WellFormed(..)
1019 | PredicateKind::ObjectSafe(..)
1020 | PredicateKind::ClosureKind(..)
1021 | PredicateKind::ConstEvaluatable(..)
1022 | PredicateKind::ConstEquate(..)
1023 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1028 /// Represents the bounds declared on a particular set of type
1029 /// parameters. Should eventually be generalized into a flag list of
1030 /// where-clauses. You can obtain an `InstantiatedPredicates` list from a
1031 /// `GenericPredicates` by using the `instantiate` method. Note that this method
1032 /// reflects an important semantic invariant of `InstantiatedPredicates`: while
1033 /// the `GenericPredicates` are expressed in terms of the bound type
1034 /// parameters of the impl/trait/whatever, an `InstantiatedPredicates` instance
1035 /// represented a set of bounds for some particular instantiation,
1036 /// meaning that the generic parameters have been substituted with
1040 /// ```ignore (illustrative)
1041 /// struct Foo<T, U: Bar<T>> { ... }
1043 /// Here, the `GenericPredicates` for `Foo` would contain a list of bounds like
1044 /// `[[], [U:Bar<T>]]`. Now if there were some particular reference
1045 /// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[],
1046 /// [usize:Bar<isize>]]`.
1047 #[derive(Clone, Debug, TypeFoldable)]
1048 pub struct InstantiatedPredicates<'tcx> {
1049 pub predicates: Vec<Predicate<'tcx>>,
1050 pub spans: Vec<Span>,
1053 impl<'tcx> InstantiatedPredicates<'tcx> {
1054 pub fn empty() -> InstantiatedPredicates<'tcx> {
1055 InstantiatedPredicates { predicates: vec![], spans: vec![] }
1058 pub fn is_empty(&self) -> bool {
1059 self.predicates.is_empty()
1075 pub struct OpaqueTypeKey<'tcx> {
1077 pub substs: SubstsRef<'tcx>,
1080 #[derive(Copy, Clone, Debug, TypeFoldable, HashStable, TyEncodable, TyDecodable)]
1081 pub struct OpaqueHiddenType<'tcx> {
1082 /// The span of this particular definition of the opaque type. So
1085 /// ```ignore (incomplete snippet)
1086 /// type Foo = impl Baz;
1087 /// fn bar() -> Foo {
1088 /// // ^^^ This is the span we are looking for!
1092 /// In cases where the fn returns `(impl Trait, impl Trait)` or
1093 /// other such combinations, the result is currently
1094 /// over-approximated, but better than nothing.
1097 /// The type variable that represents the value of the opaque type
1098 /// that we require. In other words, after we compile this function,
1099 /// we will be created a constraint like:
1100 /// ```ignore (pseudo-rust)
1103 /// where `?C` is the value of this type variable. =) It may
1104 /// naturally refer to the type and lifetime parameters in scope
1105 /// in this function, though ultimately it should only reference
1106 /// those that are arguments to `Foo` in the constraint above. (In
1107 /// other words, `?C` should not include `'b`, even though it's a
1108 /// lifetime parameter on `foo`.)
1112 impl<'tcx> OpaqueHiddenType<'tcx> {
1113 pub fn report_mismatch(&self, other: &Self, tcx: TyCtxt<'tcx>) {
1114 // Found different concrete types for the opaque type.
1115 let mut err = tcx.sess.struct_span_err(
1117 "concrete type differs from previous defining opaque type use",
1119 err.span_label(other.span, format!("expected `{}`, got `{}`", self.ty, other.ty));
1120 if self.span == other.span {
1123 "this expression supplies two conflicting concrete types for the same opaque type",
1126 err.span_note(self.span, "previous use here");
1132 rustc_index::newtype_index! {
1133 /// "Universes" are used during type- and trait-checking in the
1134 /// presence of `for<..>` binders to control what sets of names are
1135 /// visible. Universes are arranged into a tree: the root universe
1136 /// contains names that are always visible. Each child then adds a new
1137 /// set of names that are visible, in addition to those of its parent.
1138 /// We say that the child universe "extends" the parent universe with
1141 /// To make this more concrete, consider this program:
1143 /// ```ignore (illustrative)
1145 /// fn bar<T>(x: T) {
1146 /// let y: for<'a> fn(&'a u8, Foo) = ...;
1150 /// The struct name `Foo` is in the root universe U0. But the type
1151 /// parameter `T`, introduced on `bar`, is in an extended universe U1
1152 /// -- i.e., within `bar`, we can name both `T` and `Foo`, but outside
1153 /// of `bar`, we cannot name `T`. Then, within the type of `y`, the
1154 /// region `'a` is in a universe U2 that extends U1, because we can
1155 /// name it inside the fn type but not outside.
1157 /// Universes are used to do type- and trait-checking around these
1158 /// "forall" binders (also called **universal quantification**). The
1159 /// idea is that when, in the body of `bar`, we refer to `T` as a
1160 /// type, we aren't referring to any type in particular, but rather a
1161 /// kind of "fresh" type that is distinct from all other types we have
1162 /// actually declared. This is called a **placeholder** type, and we
1163 /// use universes to talk about this. In other words, a type name in
1164 /// universe 0 always corresponds to some "ground" type that the user
1165 /// declared, but a type name in a non-zero universe is a placeholder
1166 /// type -- an idealized representative of "types in general" that we
1167 /// use for checking generic functions.
1168 pub struct UniverseIndex {
1170 DEBUG_FORMAT = "U{}",
1174 impl UniverseIndex {
1175 pub const ROOT: UniverseIndex = UniverseIndex::from_u32(0);
1177 /// Returns the "next" universe index in order -- this new index
1178 /// is considered to extend all previous universes. This
1179 /// corresponds to entering a `forall` quantifier. So, for
1180 /// example, suppose we have this type in universe `U`:
1182 /// ```ignore (illustrative)
1183 /// for<'a> fn(&'a u32)
1186 /// Once we "enter" into this `for<'a>` quantifier, we are in a
1187 /// new universe that extends `U` -- in this new universe, we can
1188 /// name the region `'a`, but that region was not nameable from
1189 /// `U` because it was not in scope there.
1190 pub fn next_universe(self) -> UniverseIndex {
1191 UniverseIndex::from_u32(self.private.checked_add(1).unwrap())
1194 /// Returns `true` if `self` can name a name from `other` -- in other words,
1195 /// if the set of names in `self` is a superset of those in
1196 /// `other` (`self >= other`).
1197 pub fn can_name(self, other: UniverseIndex) -> bool {
1198 self.private >= other.private
1201 /// Returns `true` if `self` cannot name some names from `other` -- in other
1202 /// words, if the set of names in `self` is a strict subset of
1203 /// those in `other` (`self < other`).
1204 pub fn cannot_name(self, other: UniverseIndex) -> bool {
1205 self.private < other.private
1209 /// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are
1210 /// identified by both a universe, as well as a name residing within that universe. Distinct bound
1211 /// regions/types/consts within the same universe simply have an unknown relationship to one
1213 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, PartialOrd, Ord)]
1214 pub struct Placeholder<T> {
1215 pub universe: UniverseIndex,
1219 impl<'a, T> HashStable<StableHashingContext<'a>> for Placeholder<T>
1221 T: HashStable<StableHashingContext<'a>>,
1223 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1224 self.universe.hash_stable(hcx, hasher);
1225 self.name.hash_stable(hcx, hasher);
1229 pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
1231 pub type PlaceholderType = Placeholder<BoundVar>;
1233 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
1234 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
1235 pub struct BoundConst<'tcx> {
1240 pub type PlaceholderConst<'tcx> = Placeholder<BoundConst<'tcx>>;
1242 /// A `DefId` which, in case it is a const argument, is potentially bundled with
1243 /// the `DefId` of the generic parameter it instantiates.
1245 /// This is used to avoid calls to `type_of` for const arguments during typeck
1246 /// which cause cycle errors.
1251 /// fn foo<const N: usize>(&self) -> [u8; N] { [0; N] }
1252 /// // ^ const parameter
1256 /// fn foo<const M: u8>(&self) -> usize { 42 }
1257 /// // ^ const parameter
1262 /// let _b = a.foo::<{ 3 + 7 }>();
1263 /// // ^^^^^^^^^ const argument
1267 /// Let's look at the call `a.foo::<{ 3 + 7 }>()` here. We do not know
1268 /// which `foo` is used until we know the type of `a`.
1270 /// We only know the type of `a` once we are inside of `typeck(main)`.
1271 /// We also end up normalizing the type of `_b` during `typeck(main)` which
1272 /// requires us to evaluate the const argument.
1274 /// To evaluate that const argument we need to know its type,
1275 /// which we would get using `type_of(const_arg)`. This requires us to
1276 /// resolve `foo` as it can be either `usize` or `u8` in this example.
1277 /// However, resolving `foo` once again requires `typeck(main)` to get the type of `a`,
1278 /// which results in a cycle.
1280 /// In short we must not call `type_of(const_arg)` during `typeck(main)`.
1282 /// When first creating the `ty::Const` of the const argument inside of `typeck` we have
1283 /// already resolved `foo` so we know which const parameter this argument instantiates.
1284 /// This means that we also know the expected result of `type_of(const_arg)` even if we
1285 /// aren't allowed to call that query: it is equal to `type_of(const_param)` which is
1286 /// trivial to compute.
1288 /// If we now want to use that constant in a place which potentially needs its type
1289 /// we also pass the type of its `const_param`. This is the point of `WithOptConstParam`,
1290 /// except that instead of a `Ty` we bundle the `DefId` of the const parameter.
1291 /// Meaning that we need to use `type_of(const_param_did)` if `const_param_did` is `Some`
1292 /// to get the type of `did`.
1293 #[derive(Copy, Clone, Debug, TypeFoldable, Lift, TyEncodable, TyDecodable)]
1294 #[derive(PartialEq, Eq, PartialOrd, Ord)]
1295 #[derive(Hash, HashStable)]
1296 pub struct WithOptConstParam<T> {
1298 /// The `DefId` of the corresponding generic parameter in case `did` is
1299 /// a const argument.
1301 /// Note that even if `did` is a const argument, this may still be `None`.
1302 /// All queries taking `WithOptConstParam` start by calling `tcx.opt_const_param_of(def.did)`
1303 /// to potentially update `param_did` in the case it is `None`.
1304 pub const_param_did: Option<DefId>,
1307 impl<T> WithOptConstParam<T> {
1308 /// Creates a new `WithOptConstParam` setting `const_param_did` to `None`.
1310 pub fn unknown(did: T) -> WithOptConstParam<T> {
1311 WithOptConstParam { did, const_param_did: None }
1315 impl WithOptConstParam<LocalDefId> {
1316 /// Returns `Some((did, param_did))` if `def_id` is a const argument,
1317 /// `None` otherwise.
1319 pub fn try_lookup(did: LocalDefId, tcx: TyCtxt<'_>) -> Option<(LocalDefId, DefId)> {
1320 tcx.opt_const_param_of(did).map(|param_did| (did, param_did))
1323 /// In case `self` is unknown but `self.did` is a const argument, this returns
1324 /// a `WithOptConstParam` with the correct `const_param_did`.
1326 pub fn try_upgrade(self, tcx: TyCtxt<'_>) -> Option<WithOptConstParam<LocalDefId>> {
1327 if self.const_param_did.is_none() {
1328 if let const_param_did @ Some(_) = tcx.opt_const_param_of(self.did) {
1329 return Some(WithOptConstParam { did: self.did, const_param_did });
1336 pub fn to_global(self) -> WithOptConstParam<DefId> {
1337 WithOptConstParam { did: self.did.to_def_id(), const_param_did: self.const_param_did }
1340 pub fn def_id_for_type_of(self) -> DefId {
1341 if let Some(did) = self.const_param_did { did } else { self.did.to_def_id() }
1345 impl WithOptConstParam<DefId> {
1346 pub fn as_local(self) -> Option<WithOptConstParam<LocalDefId>> {
1349 .map(|did| WithOptConstParam { did, const_param_did: self.const_param_did })
1352 pub fn as_const_arg(self) -> Option<(LocalDefId, DefId)> {
1353 if let Some(param_did) = self.const_param_did {
1354 if let Some(did) = self.did.as_local() {
1355 return Some((did, param_did));
1362 pub fn is_local(self) -> bool {
1366 pub fn def_id_for_type_of(self) -> DefId {
1367 self.const_param_did.unwrap_or(self.did)
1371 /// When type checking, we use the `ParamEnv` to track
1372 /// details about the set of where-clauses that are in scope at this
1373 /// particular point.
1374 #[derive(Copy, Clone, Hash, PartialEq, Eq)]
1375 pub struct ParamEnv<'tcx> {
1376 /// This packs both caller bounds and the reveal enum into one pointer.
1378 /// Caller bounds are `Obligation`s that the caller must satisfy. This is
1379 /// basically the set of bounds on the in-scope type parameters, translated
1380 /// into `Obligation`s, and elaborated and normalized.
1382 /// Use the `caller_bounds()` method to access.
1384 /// Typically, this is `Reveal::UserFacing`, but during codegen we
1385 /// want `Reveal::All`.
1387 /// Note: This is packed, use the reveal() method to access it.
1388 packed: CopyTaggedPtr<&'tcx List<Predicate<'tcx>>, ParamTag, true>,
1391 #[derive(Copy, Clone)]
1393 reveal: traits::Reveal,
1394 constness: hir::Constness,
1397 unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag {
1398 const BITS: usize = 2;
1400 fn into_usize(self) -> usize {
1402 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0,
1403 Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1,
1404 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2,
1405 Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3,
1409 unsafe fn from_usize(ptr: usize) -> Self {
1411 0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
1412 1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
1413 2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
1414 3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const },
1415 _ => std::hint::unreachable_unchecked(),
1420 impl<'tcx> fmt::Debug for ParamEnv<'tcx> {
1421 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1422 f.debug_struct("ParamEnv")
1423 .field("caller_bounds", &self.caller_bounds())
1424 .field("reveal", &self.reveal())
1425 .field("constness", &self.constness())
1430 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
1431 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1432 self.caller_bounds().hash_stable(hcx, hasher);
1433 self.reveal().hash_stable(hcx, hasher);
1434 self.constness().hash_stable(hcx, hasher);
1438 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
1439 fn try_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>(
1442 ) -> Result<Self, F::Error> {
1444 self.caller_bounds().try_fold_with(folder)?,
1445 self.reveal().try_fold_with(folder)?,
1446 self.constness().try_fold_with(folder)?,
1450 fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1451 self.caller_bounds().visit_with(visitor)?;
1452 self.reveal().visit_with(visitor)?;
1453 self.constness().visit_with(visitor)
1457 impl<'tcx> ParamEnv<'tcx> {
1458 /// Construct a trait environment suitable for contexts where
1459 /// there are no where-clauses in scope. Hidden types (like `impl
1460 /// Trait`) are left hidden, so this is suitable for ordinary
1463 pub fn empty() -> Self {
1464 Self::new(List::empty(), Reveal::UserFacing, hir::Constness::NotConst)
1468 pub fn caller_bounds(self) -> &'tcx List<Predicate<'tcx>> {
1469 self.packed.pointer()
1473 pub fn reveal(self) -> traits::Reveal {
1474 self.packed.tag().reveal
1478 pub fn constness(self) -> hir::Constness {
1479 self.packed.tag().constness
1483 pub fn is_const(self) -> bool {
1484 self.packed.tag().constness == hir::Constness::Const
1487 /// Construct a trait environment with no where-clauses in scope
1488 /// where the values of all `impl Trait` and other hidden types
1489 /// are revealed. This is suitable for monomorphized, post-typeck
1490 /// environments like codegen or doing optimizations.
1492 /// N.B., if you want to have predicates in scope, use `ParamEnv::new`,
1493 /// or invoke `param_env.with_reveal_all()`.
1495 pub fn reveal_all() -> Self {
1496 Self::new(List::empty(), Reveal::All, hir::Constness::NotConst)
1499 /// Construct a trait environment with the given set of predicates.
1502 caller_bounds: &'tcx List<Predicate<'tcx>>,
1504 constness: hir::Constness,
1506 ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal, constness }) }
1509 pub fn with_user_facing(mut self) -> Self {
1510 self.packed.set_tag(ParamTag { reveal: Reveal::UserFacing, ..self.packed.tag() });
1515 pub fn with_constness(mut self, constness: hir::Constness) -> Self {
1516 self.packed.set_tag(ParamTag { constness, ..self.packed.tag() });
1521 pub fn with_const(mut self) -> Self {
1522 self.packed.set_tag(ParamTag { constness: hir::Constness::Const, ..self.packed.tag() });
1527 pub fn without_const(mut self) -> Self {
1528 self.packed.set_tag(ParamTag { constness: hir::Constness::NotConst, ..self.packed.tag() });
1533 pub fn remap_constness_with(&mut self, mut constness: ty::BoundConstness) {
1534 *self = self.with_constness(constness.and(self.constness()))
1537 /// Returns a new parameter environment with the same clauses, but
1538 /// which "reveals" the true results of projections in all cases
1539 /// (even for associated types that are specializable). This is
1540 /// the desired behavior during codegen and certain other special
1541 /// contexts; normally though we want to use `Reveal::UserFacing`,
1542 /// which is the default.
1543 /// All opaque types in the caller_bounds of the `ParamEnv`
1544 /// will be normalized to their underlying types.
1545 /// See PR #65989 and issue #65918 for more details
1546 pub fn with_reveal_all_normalized(self, tcx: TyCtxt<'tcx>) -> Self {
1547 if self.packed.tag().reveal == traits::Reveal::All {
1552 tcx.normalize_opaque_types(self.caller_bounds()),
1558 /// Returns this same environment but with no caller bounds.
1560 pub fn without_caller_bounds(self) -> Self {
1561 Self::new(List::empty(), self.reveal(), self.constness())
1564 /// Creates a suitable environment in which to perform trait
1565 /// queries on the given value. When type-checking, this is simply
1566 /// the pair of the environment plus value. But when reveal is set to
1567 /// All, then if `value` does not reference any type parameters, we will
1568 /// pair it with the empty environment. This improves caching and is generally
1571 /// N.B., we preserve the environment when type-checking because it
1572 /// is possible for the user to have wacky where-clauses like
1573 /// `where Box<u32>: Copy`, which are clearly never
1574 /// satisfiable. We generally want to behave as if they were true,
1575 /// although the surrounding function is never reachable.
1576 pub fn and<T: TypeFoldable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
1577 match self.reveal() {
1578 Reveal::UserFacing => ParamEnvAnd { param_env: self, value },
1581 if value.is_global() {
1582 ParamEnvAnd { param_env: self.without_caller_bounds(), value }
1584 ParamEnvAnd { param_env: self, value }
1591 // FIXME(ecstaticmorse): Audit all occurrences of `without_const().to_predicate(tcx)` to ensure that
1592 // the constness of trait bounds is being propagated correctly.
1593 impl<'tcx> PolyTraitRef<'tcx> {
1595 pub fn with_constness(self, constness: BoundConstness) -> PolyTraitPredicate<'tcx> {
1596 self.map_bound(|trait_ref| ty::TraitPredicate {
1599 polarity: ty::ImplPolarity::Positive,
1604 pub fn without_const(self) -> PolyTraitPredicate<'tcx> {
1605 self.with_constness(BoundConstness::NotConst)
1609 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable)]
1610 pub struct ParamEnvAnd<'tcx, T> {
1611 pub param_env: ParamEnv<'tcx>,
1615 impl<'tcx, T> ParamEnvAnd<'tcx, T> {
1616 pub fn into_parts(self) -> (ParamEnv<'tcx>, T) {
1617 (self.param_env, self.value)
1621 pub fn without_const(mut self) -> Self {
1622 self.param_env = self.param_env.without_const();
1627 impl<'a, 'tcx, T> HashStable<StableHashingContext<'a>> for ParamEnvAnd<'tcx, T>
1629 T: HashStable<StableHashingContext<'a>>,
1631 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1632 let ParamEnvAnd { ref param_env, ref value } = *self;
1634 param_env.hash_stable(hcx, hasher);
1635 value.hash_stable(hcx, hasher);
1639 #[derive(Copy, Clone, Debug, HashStable, Encodable, Decodable)]
1640 pub struct Destructor {
1641 /// The `DefId` of the destructor method
1643 /// The constness of the destructor method
1644 pub constness: hir::Constness,
1648 #[derive(HashStable, TyEncodable, TyDecodable)]
1649 pub struct VariantFlags: u32 {
1650 const NO_VARIANT_FLAGS = 0;
1651 /// Indicates whether the field list of this variant is `#[non_exhaustive]`.
1652 const IS_FIELD_LIST_NON_EXHAUSTIVE = 1 << 0;
1653 /// Indicates whether this variant was obtained as part of recovering from
1654 /// a syntactic error. May be incomplete or bogus.
1655 const IS_RECOVERED = 1 << 1;
1659 /// Definition of a variant -- a struct's fields or an enum variant.
1660 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1661 pub struct VariantDef {
1662 /// `DefId` that identifies the variant itself.
1663 /// If this variant belongs to a struct or union, then this is a copy of its `DefId`.
1665 /// `DefId` that identifies the variant's constructor.
1666 /// If this variant is a struct variant, then this is `None`.
1667 pub ctor_def_id: Option<DefId>,
1668 /// Variant or struct name.
1670 /// Discriminant of this variant.
1671 pub discr: VariantDiscr,
1672 /// Fields of this variant.
1673 pub fields: Vec<FieldDef>,
1674 /// Type of constructor of variant.
1675 pub ctor_kind: CtorKind,
1676 /// Flags of the variant (e.g. is field list non-exhaustive)?
1677 flags: VariantFlags,
1681 /// Creates a new `VariantDef`.
1683 /// `variant_did` is the `DefId` that identifies the enum variant (if this `VariantDef`
1684 /// represents an enum variant).
1686 /// `ctor_did` is the `DefId` that identifies the constructor of unit or
1687 /// tuple-variants/structs. If this is a `struct`-variant then this should be `None`.
1689 /// `parent_did` is the `DefId` of the `AdtDef` representing the enum or struct that
1690 /// owns this variant. It is used for checking if a struct has `#[non_exhaustive]` w/out having
1691 /// to go through the redirect of checking the ctor's attributes - but compiling a small crate
1692 /// requires loading the `AdtDef`s for all the structs in the universe (e.g., coherence for any
1693 /// built-in trait), and we do not want to load attributes twice.
1695 /// If someone speeds up attribute loading to not be a performance concern, they can
1696 /// remove this hack and use the constructor `DefId` everywhere.
1699 variant_did: Option<DefId>,
1700 ctor_def_id: Option<DefId>,
1701 discr: VariantDiscr,
1702 fields: Vec<FieldDef>,
1703 ctor_kind: CtorKind,
1707 is_field_list_non_exhaustive: bool,
1710 "VariantDef::new(name = {:?}, variant_did = {:?}, ctor_def_id = {:?}, discr = {:?},
1711 fields = {:?}, ctor_kind = {:?}, adt_kind = {:?}, parent_did = {:?})",
1712 name, variant_did, ctor_def_id, discr, fields, ctor_kind, adt_kind, parent_did,
1715 let mut flags = VariantFlags::NO_VARIANT_FLAGS;
1716 if is_field_list_non_exhaustive {
1717 flags |= VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE;
1721 flags |= VariantFlags::IS_RECOVERED;
1725 def_id: variant_did.unwrap_or(parent_did),
1735 /// Is this field list non-exhaustive?
1737 pub fn is_field_list_non_exhaustive(&self) -> bool {
1738 self.flags.intersects(VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE)
1741 /// Was this variant obtained as part of recovering from a syntactic error?
1743 pub fn is_recovered(&self) -> bool {
1744 self.flags.intersects(VariantFlags::IS_RECOVERED)
1747 /// Computes the `Ident` of this variant by looking up the `Span`
1748 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1749 Ident::new(self.name, tcx.def_ident_span(self.def_id).unwrap())
1753 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
1754 pub enum VariantDiscr {
1755 /// Explicit value for this variant, i.e., `X = 123`.
1756 /// The `DefId` corresponds to the embedded constant.
1759 /// The previous variant's discriminant plus one.
1760 /// For efficiency reasons, the distance from the
1761 /// last `Explicit` discriminant is being stored,
1762 /// or `0` for the first variant, if it has none.
1766 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1767 pub struct FieldDef {
1770 pub vis: Visibility,
1774 #[derive(TyEncodable, TyDecodable, Default, HashStable)]
1775 pub struct ReprFlags: u8 {
1776 const IS_C = 1 << 0;
1777 const IS_SIMD = 1 << 1;
1778 const IS_TRANSPARENT = 1 << 2;
1779 // Internal only for now. If true, don't reorder fields.
1780 const IS_LINEAR = 1 << 3;
1781 // If true, don't expose any niche to type's context.
1782 const HIDE_NICHE = 1 << 4;
1783 // If true, the type's layout can be randomized using
1784 // the seed stored in `ReprOptions.layout_seed`
1785 const RANDOMIZE_LAYOUT = 1 << 5;
1786 // Any of these flags being set prevent field reordering optimisation.
1787 const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
1788 | ReprFlags::IS_SIMD.bits
1789 | ReprFlags::IS_LINEAR.bits;
1793 /// Represents the repr options provided by the user,
1794 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Default, HashStable)]
1795 pub struct ReprOptions {
1796 pub int: Option<attr::IntType>,
1797 pub align: Option<Align>,
1798 pub pack: Option<Align>,
1799 pub flags: ReprFlags,
1800 /// The seed to be used for randomizing a type's layout
1802 /// Note: This could technically be a `[u8; 16]` (a `u128`) which would
1803 /// be the "most accurate" hash as it'd encompass the item and crate
1804 /// hash without loss, but it does pay the price of being larger.
1805 /// Everything's a tradeoff, a `u64` seed should be sufficient for our
1806 /// purposes (primarily `-Z randomize-layout`)
1807 pub field_shuffle_seed: u64,
1811 pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions {
1812 let mut flags = ReprFlags::empty();
1813 let mut size = None;
1814 let mut max_align: Option<Align> = None;
1815 let mut min_pack: Option<Align> = None;
1817 // Generate a deterministically-derived seed from the item's path hash
1818 // to allow for cross-crate compilation to actually work
1819 let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash();
1821 // If the user defined a custom seed for layout randomization, xor the item's
1822 // path hash with the user defined seed, this will allowing determinism while
1823 // still allowing users to further randomize layout generation for e.g. fuzzing
1824 if let Some(user_seed) = tcx.sess.opts.debugging_opts.layout_seed {
1825 field_shuffle_seed ^= user_seed;
1828 for attr in tcx.get_attrs(did, sym::repr) {
1829 for r in attr::parse_repr_attr(&tcx.sess, attr) {
1830 flags.insert(match r {
1831 attr::ReprC => ReprFlags::IS_C,
1832 attr::ReprPacked(pack) => {
1833 let pack = Align::from_bytes(pack as u64).unwrap();
1834 min_pack = Some(if let Some(min_pack) = min_pack {
1841 attr::ReprTransparent => ReprFlags::IS_TRANSPARENT,
1842 attr::ReprNoNiche => ReprFlags::HIDE_NICHE,
1843 attr::ReprSimd => ReprFlags::IS_SIMD,
1844 attr::ReprInt(i) => {
1848 attr::ReprAlign(align) => {
1849 max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap()));
1856 // If `-Z randomize-layout` was enabled for the type definition then we can
1857 // consider performing layout randomization
1858 if tcx.sess.opts.debugging_opts.randomize_layout {
1859 flags.insert(ReprFlags::RANDOMIZE_LAYOUT);
1862 // This is here instead of layout because the choice must make it into metadata.
1863 if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) {
1864 flags.insert(ReprFlags::IS_LINEAR);
1867 Self { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed }
1871 pub fn simd(&self) -> bool {
1872 self.flags.contains(ReprFlags::IS_SIMD)
1876 pub fn c(&self) -> bool {
1877 self.flags.contains(ReprFlags::IS_C)
1881 pub fn packed(&self) -> bool {
1886 pub fn transparent(&self) -> bool {
1887 self.flags.contains(ReprFlags::IS_TRANSPARENT)
1891 pub fn linear(&self) -> bool {
1892 self.flags.contains(ReprFlags::IS_LINEAR)
1896 pub fn hide_niche(&self) -> bool {
1897 self.flags.contains(ReprFlags::HIDE_NICHE)
1900 /// Returns the discriminant type, given these `repr` options.
1901 /// This must only be called on enums!
1902 pub fn discr_type(&self) -> attr::IntType {
1903 self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize))
1906 /// Returns `true` if this `#[repr()]` should inhabit "smart enum
1907 /// layout" optimizations, such as representing `Foo<&T>` as a
1909 pub fn inhibit_enum_layout_opt(&self) -> bool {
1910 self.c() || self.int.is_some()
1913 /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
1914 /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
1915 pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
1916 if let Some(pack) = self.pack {
1917 if pack.bytes() == 1 {
1922 self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
1925 /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
1926 /// was enabled for its declaration crate
1927 pub fn can_randomize_type_layout(&self) -> bool {
1928 !self.inhibit_struct_field_reordering_opt()
1929 && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
1932 /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
1933 pub fn inhibit_union_abi_opt(&self) -> bool {
1938 impl<'tcx> FieldDef {
1939 /// Returns the type of this field. The resulting type is not normalized. The `subst` is
1940 /// typically obtained via the second field of [`TyKind::Adt`].
1941 pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
1942 tcx.bound_type_of(self.did).subst(tcx, subst)
1945 /// Computes the `Ident` of this variant by looking up the `Span`
1946 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1947 Ident::new(self.name, tcx.def_ident_span(self.did).unwrap())
1951 pub type Attributes<'tcx> = impl Iterator<Item = &'tcx ast::Attribute>;
1952 #[derive(Debug, PartialEq, Eq)]
1953 pub enum ImplOverlapKind {
1954 /// These impls are always allowed to overlap.
1956 /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait
1959 /// These impls are allowed to overlap, but that raises
1960 /// an issue #33140 future-compatibility warning.
1962 /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's
1963 /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different.
1965 /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied
1966 /// that difference, making what reduces to the following set of impls:
1968 /// ```compile_fail,(E0119)
1970 /// impl Trait for dyn Send + Sync {}
1971 /// impl Trait for dyn Sync + Send {}
1974 /// Obviously, once we made these types be identical, that code causes a coherence
1975 /// error and a fairly big headache for us. However, luckily for us, the trait
1976 /// `Trait` used in this case is basically a marker trait, and therefore having
1977 /// overlapping impls for it is sound.
1979 /// To handle this, we basically regard the trait as a marker trait, with an additional
1980 /// future-compatibility warning. To avoid accidentally "stabilizing" this feature,
1981 /// it has the following restrictions:
1983 /// 1. The trait must indeed be a marker-like trait (i.e., no items), and must be
1985 /// 2. The trait-ref of both impls must be equal.
1986 /// 3. The trait-ref of both impls must be a trait object type consisting only of
1988 /// 4. Neither of the impls can have any where-clauses.
1990 /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed.
1994 impl<'tcx> TyCtxt<'tcx> {
1995 pub fn typeck_body(self, body: hir::BodyId) -> &'tcx TypeckResults<'tcx> {
1996 self.typeck(self.hir().body_owner_def_id(body))
1999 pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> {
2000 self.associated_items(id)
2001 .in_definition_order()
2002 .filter(|item| item.kind == AssocKind::Fn && item.defaultness.has_value())
2005 /// Look up the name of a definition across crates. This does not look at HIR.
2006 pub fn opt_item_name(self, def_id: DefId) -> Option<Symbol> {
2007 if let Some(cnum) = def_id.as_crate_root() {
2008 Some(self.crate_name(cnum))
2010 let def_key = self.def_key(def_id);
2011 match def_key.disambiguated_data.data {
2012 // The name of a constructor is that of its parent.
2013 rustc_hir::definitions::DefPathData::Ctor => self
2014 .opt_item_name(DefId { krate: def_id.krate, index: def_key.parent.unwrap() }),
2015 // The name of opaque types only exists in HIR.
2016 rustc_hir::definitions::DefPathData::ImplTrait
2017 if let Some(def_id) = def_id.as_local() =>
2018 self.hir().opt_name(self.hir().local_def_id_to_hir_id(def_id)),
2019 _ => def_key.get_opt_name(),
2024 /// Look up the name of a definition across crates. This does not look at HIR.
2026 /// This method will ICE if the corresponding item does not have a name. In these cases, use
2027 /// [`opt_item_name`] instead.
2029 /// [`opt_item_name`]: Self::opt_item_name
2030 pub fn item_name(self, id: DefId) -> Symbol {
2031 self.opt_item_name(id).unwrap_or_else(|| {
2032 bug!("item_name: no name for {:?}", self.def_path(id));
2036 /// Look up the name and span of a definition.
2038 /// See [`item_name`][Self::item_name] for more information.
2039 pub fn opt_item_ident(self, def_id: DefId) -> Option<Ident> {
2040 let def = self.opt_item_name(def_id)?;
2043 .and_then(|id| self.def_ident_span(id))
2044 .unwrap_or(rustc_span::DUMMY_SP);
2045 Some(Ident::new(def, span))
2048 pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> {
2049 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2050 Some(self.associated_item(def_id))
2056 pub fn field_index(self, hir_id: hir::HirId, typeck_results: &TypeckResults<'_>) -> usize {
2057 typeck_results.field_indices().get(hir_id).cloned().expect("no index for a field")
2060 pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
2064 .position(|field| self.hygienic_eq(ident, field.ident(self), variant.def_id))
2067 /// Returns `true` if the impls are the same polarity and the trait either
2068 /// has no items or is annotated `#[marker]` and prevents item overrides.
2069 pub fn impls_are_allowed_to_overlap(
2073 ) -> Option<ImplOverlapKind> {
2074 // If either trait impl references an error, they're allowed to overlap,
2075 // as one of them essentially doesn't exist.
2076 if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.references_error())
2077 || self.impl_trait_ref(def_id2).map_or(false, |tr| tr.references_error())
2079 return Some(ImplOverlapKind::Permitted { marker: false });
2082 match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) {
2083 (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => {
2084 // `#[rustc_reservation_impl]` impls don't overlap with anything
2086 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (reservations)",
2089 return Some(ImplOverlapKind::Permitted { marker: false });
2091 (ImplPolarity::Positive, ImplPolarity::Negative)
2092 | (ImplPolarity::Negative, ImplPolarity::Positive) => {
2093 // `impl AutoTrait for Type` + `impl !AutoTrait for Type`
2095 "impls_are_allowed_to_overlap({:?}, {:?}) - None (differing polarities)",
2100 (ImplPolarity::Positive, ImplPolarity::Positive)
2101 | (ImplPolarity::Negative, ImplPolarity::Negative) => {}
2104 let is_marker_overlap = {
2105 let is_marker_impl = |def_id: DefId| -> bool {
2106 let trait_ref = self.impl_trait_ref(def_id);
2107 trait_ref.map_or(false, |tr| self.trait_def(tr.def_id).is_marker)
2109 is_marker_impl(def_id1) && is_marker_impl(def_id2)
2112 if is_marker_overlap {
2114 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (marker overlap)",
2117 Some(ImplOverlapKind::Permitted { marker: true })
2119 if let Some(self_ty1) = self.issue33140_self_ty(def_id1) {
2120 if let Some(self_ty2) = self.issue33140_self_ty(def_id2) {
2121 if self_ty1 == self_ty2 {
2123 "impls_are_allowed_to_overlap({:?}, {:?}) - issue #33140 HACK",
2126 return Some(ImplOverlapKind::Issue33140);
2129 "impls_are_allowed_to_overlap({:?}, {:?}) - found {:?} != {:?}",
2130 def_id1, def_id2, self_ty1, self_ty2
2136 debug!("impls_are_allowed_to_overlap({:?}, {:?}) = None", def_id1, def_id2);
2141 /// Returns `ty::VariantDef` if `res` refers to a struct,
2142 /// or variant or their constructors, panics otherwise.
2143 pub fn expect_variant_res(self, res: Res) -> &'tcx VariantDef {
2145 Res::Def(DefKind::Variant, did) => {
2146 let enum_did = self.parent(did);
2147 self.adt_def(enum_did).variant_with_id(did)
2149 Res::Def(DefKind::Struct | DefKind::Union, did) => self.adt_def(did).non_enum_variant(),
2150 Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => {
2151 let variant_did = self.parent(variant_ctor_did);
2152 let enum_did = self.parent(variant_did);
2153 self.adt_def(enum_did).variant_with_ctor_id(variant_ctor_did)
2155 Res::Def(DefKind::Ctor(CtorOf::Struct, ..), ctor_did) => {
2156 let struct_did = self.parent(ctor_did);
2157 self.adt_def(struct_did).non_enum_variant()
2159 _ => bug!("expect_variant_res used with unexpected res {:?}", res),
2163 /// Returns the possibly-auto-generated MIR of a `(DefId, Subst)` pair.
2164 #[instrument(skip(self), level = "debug")]
2165 pub fn instance_mir(self, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> {
2167 ty::InstanceDef::Item(def) => {
2168 debug!("calling def_kind on def: {:?}", def);
2169 let def_kind = self.def_kind(def.did);
2170 debug!("returned from def_kind: {:?}", def_kind);
2173 | DefKind::Static(..)
2174 | DefKind::AssocConst
2176 | DefKind::AnonConst
2177 | DefKind::InlineConst => self.mir_for_ctfe_opt_const_arg(def),
2178 // If the caller wants `mir_for_ctfe` of a function they should not be using
2179 // `instance_mir`, so we'll assume const fn also wants the optimized version.
2181 assert_eq!(def.const_param_did, None);
2182 self.optimized_mir(def.did)
2186 ty::InstanceDef::VtableShim(..)
2187 | ty::InstanceDef::ReifyShim(..)
2188 | ty::InstanceDef::Intrinsic(..)
2189 | ty::InstanceDef::FnPtrShim(..)
2190 | ty::InstanceDef::Virtual(..)
2191 | ty::InstanceDef::ClosureOnceShim { .. }
2192 | ty::InstanceDef::DropGlue(..)
2193 | ty::InstanceDef::CloneShim(..) => self.mir_shims(instance),
2197 // FIXME(@lcnr): Remove this function.
2198 pub fn get_attrs_unchecked(self, did: DefId) -> &'tcx [ast::Attribute] {
2199 if let Some(did) = did.as_local() {
2200 self.hir().attrs(self.hir().local_def_id_to_hir_id(did))
2202 self.item_attrs(did)
2206 /// Gets all attributes with the given name.
2207 pub fn get_attrs(self, did: DefId, attr: Symbol) -> ty::Attributes<'tcx> {
2208 let filter_fn = move |a: &&ast::Attribute| a.has_name(attr);
2209 if let Some(did) = did.as_local() {
2210 self.hir().attrs(self.hir().local_def_id_to_hir_id(did)).iter().filter(filter_fn)
2211 } else if cfg!(debug_assertions) && rustc_feature::is_builtin_only_local(attr) {
2212 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2214 self.item_attrs(did).iter().filter(filter_fn)
2218 pub fn get_attr(self, did: DefId, attr: Symbol) -> Option<&'tcx ast::Attribute> {
2219 self.get_attrs(did, attr).next()
2222 /// Determines whether an item is annotated with an attribute.
2223 pub fn has_attr(self, did: DefId, attr: Symbol) -> bool {
2224 if cfg!(debug_assertions) && !did.is_local() && rustc_feature::is_builtin_only_local(attr) {
2225 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2227 self.get_attrs(did, attr).next().is_some()
2231 /// Returns `true` if this is an `auto trait`.
2232 pub fn trait_is_auto(self, trait_def_id: DefId) -> bool {
2233 self.trait_def(trait_def_id).has_auto_impl
2236 /// Returns layout of a generator. Layout might be unavailable if the
2237 /// generator is tainted by errors.
2238 pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> {
2239 self.optimized_mir(def_id).generator_layout()
2242 /// Given the `DefId` of an impl, returns the `DefId` of the trait it implements.
2243 /// If it implements no trait, returns `None`.
2244 pub fn trait_id_of_impl(self, def_id: DefId) -> Option<DefId> {
2245 self.impl_trait_ref(def_id).map(|tr| tr.def_id)
2248 /// If the given `DefId` describes a method belonging to an impl, returns the
2249 /// `DefId` of the impl that the method belongs to; otherwise, returns `None`.
2250 pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
2251 self.opt_associated_item(def_id).and_then(|trait_item| match trait_item.container {
2252 TraitContainer(_) => None,
2253 ImplContainer(def_id) => Some(def_id),
2257 /// If the given `DefId` belongs to a trait that was automatically derived, returns `true`.
2258 pub fn is_builtin_derive(self, def_id: DefId) -> bool {
2259 self.has_attr(def_id, sym::automatically_derived)
2262 /// Looks up the span of `impl_did` if the impl is local; otherwise returns `Err`
2263 /// with the name of the crate containing the impl.
2264 pub fn span_of_impl(self, impl_did: DefId) -> Result<Span, Symbol> {
2265 if let Some(impl_did) = impl_did.as_local() {
2266 Ok(self.def_span(impl_did))
2268 Err(self.crate_name(impl_did.krate))
2272 /// Hygienically compares a use-site name (`use_name`) for a field or an associated item with
2273 /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
2274 /// definition's parent/scope to perform comparison.
2275 pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
2276 // We could use `Ident::eq` here, but we deliberately don't. The name
2277 // comparison fails frequently, and we want to avoid the expensive
2278 // `normalize_to_macros_2_0()` calls required for the span comparison whenever possible.
2279 use_name.name == def_name.name
2283 .hygienic_eq(def_name.span.ctxt(), self.expn_that_defined(def_parent_def_id))
2286 pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident {
2287 ident.span.normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope));
2291 pub fn adjust_ident_and_get_scope(
2296 ) -> (Ident, DefId) {
2299 .normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope))
2300 .and_then(|actual_expansion| actual_expansion.expn_data().parent_module)
2301 .unwrap_or_else(|| self.parent_module(block).to_def_id());
2305 pub fn is_object_safe(self, key: DefId) -> bool {
2306 self.object_safety_violations(key).is_empty()
2310 pub fn is_const_fn_raw(self, def_id: DefId) -> bool {
2311 matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..))
2312 && self.impl_constness(def_id) == hir::Constness::Const
2316 pub fn is_const_default_method(self, def_id: DefId) -> bool {
2317 matches!(self.trait_of_item(def_id), Some(trait_id) if self.has_attr(trait_id, sym::const_trait))
2321 /// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition.
2322 pub fn is_impl_trait_defn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<LocalDefId> {
2323 let def_id = def_id.as_local()?;
2324 if let Node::Item(item) = tcx.hir().get_by_def_id(def_id) {
2325 if let hir::ItemKind::OpaqueTy(ref opaque_ty) = item.kind {
2326 return match opaque_ty.origin {
2327 hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) => {
2330 hir::OpaqueTyOrigin::TyAlias => None,
2337 pub fn int_ty(ity: ast::IntTy) -> IntTy {
2339 ast::IntTy::Isize => IntTy::Isize,
2340 ast::IntTy::I8 => IntTy::I8,
2341 ast::IntTy::I16 => IntTy::I16,
2342 ast::IntTy::I32 => IntTy::I32,
2343 ast::IntTy::I64 => IntTy::I64,
2344 ast::IntTy::I128 => IntTy::I128,
2348 pub fn uint_ty(uty: ast::UintTy) -> UintTy {
2350 ast::UintTy::Usize => UintTy::Usize,
2351 ast::UintTy::U8 => UintTy::U8,
2352 ast::UintTy::U16 => UintTy::U16,
2353 ast::UintTy::U32 => UintTy::U32,
2354 ast::UintTy::U64 => UintTy::U64,
2355 ast::UintTy::U128 => UintTy::U128,
2359 pub fn float_ty(fty: ast::FloatTy) -> FloatTy {
2361 ast::FloatTy::F32 => FloatTy::F32,
2362 ast::FloatTy::F64 => FloatTy::F64,
2366 pub fn ast_int_ty(ity: IntTy) -> ast::IntTy {
2368 IntTy::Isize => ast::IntTy::Isize,
2369 IntTy::I8 => ast::IntTy::I8,
2370 IntTy::I16 => ast::IntTy::I16,
2371 IntTy::I32 => ast::IntTy::I32,
2372 IntTy::I64 => ast::IntTy::I64,
2373 IntTy::I128 => ast::IntTy::I128,
2377 pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy {
2379 UintTy::Usize => ast::UintTy::Usize,
2380 UintTy::U8 => ast::UintTy::U8,
2381 UintTy::U16 => ast::UintTy::U16,
2382 UintTy::U32 => ast::UintTy::U32,
2383 UintTy::U64 => ast::UintTy::U64,
2384 UintTy::U128 => ast::UintTy::U128,
2388 pub fn provide(providers: &mut ty::query::Providers) {
2389 closure::provide(providers);
2390 context::provide(providers);
2391 erase_regions::provide(providers);
2392 layout::provide(providers);
2393 util::provide(providers);
2394 print::provide(providers);
2395 super::util::bug::provide(providers);
2396 super::middle::provide(providers);
2397 *providers = ty::query::Providers {
2398 trait_impls_of: trait_def::trait_impls_of_provider,
2399 incoherent_impls: trait_def::incoherent_impls_provider,
2400 type_uninhabited_from: inhabitedness::type_uninhabited_from,
2401 const_param_default: consts::const_param_default,
2402 vtable_allocation: vtable::vtable_allocation_provider,
2407 /// A map for the local crate mapping each type to a vector of its
2408 /// inherent impls. This is not meant to be used outside of coherence;
2409 /// rather, you should request the vector for a specific type via
2410 /// `tcx.inherent_impls(def_id)` so as to minimize your dependencies
2411 /// (constructing this map requires touching the entire crate).
2412 #[derive(Clone, Debug, Default, HashStable)]
2413 pub struct CrateInherentImpls {
2414 pub inherent_impls: LocalDefIdMap<Vec<DefId>>,
2415 pub incoherent_impls: FxHashMap<SimplifiedType, Vec<LocalDefId>>,
2418 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, HashStable)]
2419 pub struct SymbolName<'tcx> {
2420 /// `&str` gives a consistent ordering, which ensures reproducible builds.
2421 pub name: &'tcx str,
2424 impl<'tcx> SymbolName<'tcx> {
2425 pub fn new(tcx: TyCtxt<'tcx>, name: &str) -> SymbolName<'tcx> {
2427 name: unsafe { str::from_utf8_unchecked(tcx.arena.alloc_slice(name.as_bytes())) },
2432 impl<'tcx> fmt::Display for SymbolName<'tcx> {
2433 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2434 fmt::Display::fmt(&self.name, fmt)
2438 impl<'tcx> fmt::Debug for SymbolName<'tcx> {
2439 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2440 fmt::Display::fmt(&self.name, fmt)
2444 #[derive(Debug, Default, Copy, Clone)]
2445 pub struct FoundRelationships {
2446 /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
2447 /// obligation, where:
2449 /// * `Foo` is not `Sized`
2450 /// * `(): Foo` may be satisfied
2451 pub self_in_trait: bool,
2452 /// This is true if we identified that this Ty (`?T`) is found in a `<_ as
2453 /// _>::AssocType = ?T`