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;
35 use rustc_data_structures::stable_hasher::{HashStable, NodeIdHashingMode, 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>;
293 fn local_parent(self, id: LocalDefId) -> Option<LocalDefId> {
294 Some(self.parent(id.to_def_id())?.expect_local())
297 fn is_descendant_of(self, mut descendant: DefId, ancestor: DefId) -> bool {
298 if descendant.krate != ancestor.krate {
302 while descendant != ancestor {
303 match self.parent(descendant) {
304 Some(parent) => descendant = parent,
305 None => return false,
312 impl<'tcx> DefIdTree for TyCtxt<'tcx> {
313 fn parent(self, id: DefId) -> Option<DefId> {
314 self.def_key(id).parent.map(|index| DefId { index, ..id })
319 pub fn from_hir(visibility: &hir::Visibility<'_>, id: hir::HirId, tcx: TyCtxt<'_>) -> Self {
320 match visibility.node {
321 hir::VisibilityKind::Public => Visibility::Public,
322 hir::VisibilityKind::Crate(_) => Visibility::Restricted(DefId::local(CRATE_DEF_INDEX)),
323 hir::VisibilityKind::Restricted { ref path, .. } => match path.res {
324 // If there is no resolution, `resolve` will have already reported an error, so
325 // assume that the visibility is public to avoid reporting more privacy errors.
326 Res::Err => Visibility::Public,
327 def => Visibility::Restricted(def.def_id()),
329 hir::VisibilityKind::Inherited => {
330 Visibility::Restricted(tcx.parent_module(id).to_def_id())
335 /// Returns `true` if an item with this visibility is accessible from the given block.
336 pub fn is_accessible_from<T: DefIdTree>(self, module: DefId, tree: T) -> bool {
337 let restriction = match self {
338 // Public items are visible everywhere.
339 Visibility::Public => return true,
340 // Private items from other crates are visible nowhere.
341 Visibility::Invisible => return false,
342 // Restricted items are visible in an arbitrary local module.
343 Visibility::Restricted(other) if other.krate != module.krate => return false,
344 Visibility::Restricted(module) => module,
347 tree.is_descendant_of(module, restriction)
350 /// Returns `true` if this visibility is at least as accessible as the given visibility
351 pub fn is_at_least<T: DefIdTree>(self, vis: Visibility, tree: T) -> bool {
352 let vis_restriction = match vis {
353 Visibility::Public => return self == Visibility::Public,
354 Visibility::Invisible => return true,
355 Visibility::Restricted(module) => module,
358 self.is_accessible_from(vis_restriction, tree)
361 // Returns `true` if this item is visible anywhere in the local crate.
362 pub fn is_visible_locally(self) -> bool {
364 Visibility::Public => true,
365 Visibility::Restricted(def_id) => def_id.is_local(),
366 Visibility::Invisible => false,
370 pub fn is_public(self) -> bool {
371 matches!(self, Visibility::Public)
375 /// The crate variances map is computed during typeck and contains the
376 /// variance of every item in the local crate. You should not use it
377 /// directly, because to do so will make your pass dependent on the
378 /// HIR of every item in the local crate. Instead, use
379 /// `tcx.variances_of()` to get the variance for a *particular*
381 #[derive(HashStable, Debug)]
382 pub struct CrateVariancesMap<'tcx> {
383 /// For each item with generics, maps to a vector of the variance
384 /// of its generics. If an item has no generics, it will have no
386 pub variances: FxHashMap<DefId, &'tcx [ty::Variance]>,
389 // Contains information needed to resolve types and (in the future) look up
390 // the types of AST nodes.
391 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
392 pub struct CReaderCacheKey {
393 pub cnum: Option<CrateNum>,
397 /// Represents a type.
400 /// - This is a very "dumb" struct (with no derives and no `impls`).
401 /// - Values of this type are always interned and thus unique, and are stored
402 /// as an `Interned<TyS>`.
403 /// - `Ty` (which contains a reference to a `Interned<TyS>`) or `Interned<TyS>`
404 /// should be used everywhere instead of `TyS`. In particular, `Ty` has most
405 /// of the relevant methods.
406 #[derive(PartialEq, Eq, PartialOrd, Ord)]
407 #[allow(rustc::usage_of_ty_tykind)]
408 crate struct TyS<'tcx> {
409 /// This field shouldn't be used directly and may be removed in the future.
410 /// Use `Ty::kind()` instead.
413 /// This field provides fast access to information that is also contained
416 /// This field shouldn't be used directly and may be removed in the future.
417 /// Use `Ty::flags()` instead.
420 /// This field provides fast access to information that is also contained
423 /// This is a kind of confusing thing: it stores the smallest
426 /// (a) the binder itself captures nothing but
427 /// (b) all the late-bound things within the type are captured
428 /// by some sub-binder.
430 /// So, for a type without any late-bound things, like `u32`, this
431 /// will be *innermost*, because that is the innermost binder that
432 /// captures nothing. But for a type `&'D u32`, where `'D` is a
433 /// late-bound region with De Bruijn index `D`, this would be `D + 1`
434 /// -- the binder itself does not capture `D`, but `D` is captured
435 /// by an inner binder.
437 /// We call this concept an "exclusive" binder `D` because all
438 /// De Bruijn indices within the type are contained within `0..D`
440 outer_exclusive_binder: ty::DebruijnIndex,
442 /// The stable hash of the type. This way hashing of types will not have to work
443 /// on the address of the type anymore, but can instead just read this field
444 stable_hash: Fingerprint,
447 // `TyS` is used a lot. Make sure it doesn't unintentionally get bigger.
448 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
449 static_assert_size!(TyS<'_>, 56);
451 /// Use this rather than `TyS`, whenever possible.
452 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
453 #[rustc_diagnostic_item = "Ty"]
454 #[rustc_pass_by_value]
455 pub struct Ty<'tcx>(Interned<'tcx, TyS<'tcx>>);
457 // Statics only used for internal testing.
458 pub static BOOL_TY: Ty<'static> = Ty(Interned::new_unchecked(&BOOL_TYS));
459 static BOOL_TYS: TyS<'static> = TyS {
461 flags: TypeFlags::empty(),
462 outer_exclusive_binder: DebruijnIndex::from_usize(0),
463 stable_hash: Fingerprint::ZERO,
466 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Ty<'tcx> {
467 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
471 // The other fields just provide fast access to information that is
472 // also contained in `kind`, so no need to hash them.
475 outer_exclusive_binder: _,
480 if *stable_hash == Fingerprint::ZERO {
481 // No cached hash available. This can only mean that incremental is disabled.
482 // We don't cache stable hashes in non-incremental mode, because they are used
483 // so rarely that the performance actually suffers.
485 let stable_hash: Fingerprint = {
486 let mut hasher = StableHasher::new();
487 hcx.while_hashing_spans(false, |hcx| {
488 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
489 kind.hash_stable(hcx, &mut hasher)
494 stable_hash.hash_stable(hcx, hasher);
496 stable_hash.hash_stable(hcx, hasher);
501 impl ty::EarlyBoundRegion {
502 /// Does this early bound region have a name? Early bound regions normally
503 /// always have names except when using anonymous lifetimes (`'_`).
504 pub fn has_name(&self) -> bool {
505 self.name != kw::UnderscoreLifetime
509 /// Represents a predicate.
511 /// See comments on `TyS`, which apply here too (albeit for
512 /// `PredicateS`/`Predicate` rather than `TyS`/`Ty`).
514 crate struct PredicateS<'tcx> {
515 kind: Binder<'tcx, PredicateKind<'tcx>>,
517 /// See the comment for the corresponding field of [TyS].
518 outer_exclusive_binder: ty::DebruijnIndex,
521 // This type is used a lot. Make sure it doesn't unintentionally get bigger.
522 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
523 static_assert_size!(PredicateS<'_>, 56);
525 /// Use this rather than `PredicateS`, whenever possible.
526 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
527 #[rustc_pass_by_value]
528 pub struct Predicate<'tcx>(Interned<'tcx, PredicateS<'tcx>>);
530 impl<'tcx> Predicate<'tcx> {
531 /// Gets the inner `Binder<'tcx, PredicateKind<'tcx>>`.
533 pub fn kind(self) -> Binder<'tcx, PredicateKind<'tcx>> {
538 pub fn flags(self) -> TypeFlags {
543 pub fn outer_exclusive_binder(self) -> DebruijnIndex {
544 self.0.outer_exclusive_binder
547 /// Flips the polarity of a Predicate.
549 /// Given `T: Trait` predicate it returns `T: !Trait` and given `T: !Trait` returns `T: Trait`.
550 pub fn flip_polarity(self, tcx: TyCtxt<'tcx>) -> Option<Predicate<'tcx>> {
553 .map_bound(|kind| match kind {
554 PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) => {
555 Some(PredicateKind::Trait(TraitPredicate {
558 polarity: polarity.flip()?,
566 Some(tcx.mk_predicate(kind))
570 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> {
571 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
575 // The other fields just provide fast access to information that is
576 // also contained in `kind`, so no need to hash them.
578 outer_exclusive_binder: _,
581 kind.hash_stable(hcx, hasher);
585 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
586 #[derive(HashStable, TypeFoldable)]
587 pub enum PredicateKind<'tcx> {
588 /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
589 /// the `Self` type of the trait reference and `A`, `B`, and `C`
590 /// would be the type parameters.
591 Trait(TraitPredicate<'tcx>),
594 RegionOutlives(RegionOutlivesPredicate<'tcx>),
597 TypeOutlives(TypeOutlivesPredicate<'tcx>),
599 /// `where <T as TraitRef>::Name == X`, approximately.
600 /// See the `ProjectionPredicate` struct for details.
601 Projection(ProjectionPredicate<'tcx>),
603 /// No syntax: `T` well-formed.
604 WellFormed(GenericArg<'tcx>),
606 /// Trait must be object-safe.
609 /// No direct syntax. May be thought of as `where T: FnFoo<...>`
610 /// for some substitutions `...` and `T` being a closure type.
611 /// Satisfied (or refuted) once we know the closure's kind.
612 ClosureKind(DefId, SubstsRef<'tcx>, ClosureKind),
616 /// This obligation is created most often when we have two
617 /// unresolved type variables and hence don't have enough
618 /// information to process the subtyping obligation yet.
619 Subtype(SubtypePredicate<'tcx>),
621 /// `T1` coerced to `T2`
623 /// Like a subtyping obligation, this is created most often
624 /// when we have two unresolved type variables and hence
625 /// don't have enough information to process the coercion
626 /// obligation yet. At the moment, we actually process coercions
627 /// very much like subtyping and don't handle the full coercion
629 Coerce(CoercePredicate<'tcx>),
631 /// Constant initializer must evaluate successfully.
632 ConstEvaluatable(ty::Unevaluated<'tcx, ()>),
634 /// Constants must be equal. The first component is the const that is expected.
635 ConstEquate(Const<'tcx>, Const<'tcx>),
637 /// Represents a type found in the environment that we can use for implied bounds.
639 /// Only used for Chalk.
640 TypeWellFormedFromEnv(Ty<'tcx>),
643 /// The crate outlives map is computed during typeck and contains the
644 /// outlives of every item in the local crate. You should not use it
645 /// directly, because to do so will make your pass dependent on the
646 /// HIR of every item in the local crate. Instead, use
647 /// `tcx.inferred_outlives_of()` to get the outlives for a *particular*
649 #[derive(HashStable, Debug)]
650 pub struct CratePredicatesMap<'tcx> {
651 /// For each struct with outlive bounds, maps to a vector of the
652 /// predicate of its outlive bounds. If an item has no outlives
653 /// bounds, it will have no entry.
654 pub predicates: FxHashMap<DefId, &'tcx [(Predicate<'tcx>, Span)]>,
657 impl<'tcx> Predicate<'tcx> {
658 /// Performs a substitution suitable for going from a
659 /// poly-trait-ref to supertraits that must hold if that
660 /// poly-trait-ref holds. This is slightly different from a normal
661 /// substitution in terms of what happens with bound regions. See
662 /// lengthy comment below for details.
663 pub fn subst_supertrait(
666 trait_ref: &ty::PolyTraitRef<'tcx>,
667 ) -> Predicate<'tcx> {
668 // The interaction between HRTB and supertraits is not entirely
669 // obvious. Let me walk you (and myself) through an example.
671 // Let's start with an easy case. Consider two traits:
673 // trait Foo<'a>: Bar<'a,'a> { }
674 // trait Bar<'b,'c> { }
676 // Now, if we have a trait reference `for<'x> T: Foo<'x>`, then
677 // we can deduce that `for<'x> T: Bar<'x,'x>`. Basically, if we
678 // knew that `Foo<'x>` (for any 'x) then we also know that
679 // `Bar<'x,'x>` (for any 'x). This more-or-less falls out from
680 // normal substitution.
682 // In terms of why this is sound, the idea is that whenever there
683 // is an impl of `T:Foo<'a>`, it must show that `T:Bar<'a,'a>`
684 // holds. So if there is an impl of `T:Foo<'a>` that applies to
685 // all `'a`, then we must know that `T:Bar<'a,'a>` holds for all
688 // Another example to be careful of is this:
690 // trait Foo1<'a>: for<'b> Bar1<'a,'b> { }
691 // trait Bar1<'b,'c> { }
693 // Here, if we have `for<'x> T: Foo1<'x>`, then what do we know?
694 // The answer is that we know `for<'x,'b> T: Bar1<'x,'b>`. The
695 // reason is similar to the previous example: any impl of
696 // `T:Foo1<'x>` must show that `for<'b> T: Bar1<'x, 'b>`. So
697 // basically we would want to collapse the bound lifetimes from
698 // the input (`trait_ref`) and the supertraits.
700 // To achieve this in practice is fairly straightforward. Let's
701 // consider the more complicated scenario:
703 // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x`
704 // has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`,
705 // where both `'x` and `'b` would have a DB index of 1.
706 // The substitution from the input trait-ref is therefore going to be
707 // `'a => 'x` (where `'x` has a DB index of 1).
708 // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an
709 // early-bound parameter and `'b' is a late-bound parameter with a
711 // - If we replace `'a` with `'x` from the input, it too will have
712 // a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>`
713 // just as we wanted.
715 // There is only one catch. If we just apply the substitution `'a
716 // => 'x` to `for<'b> Bar1<'a,'b>`, the substitution code will
717 // adjust the DB index because we substituting into a binder (it
718 // tries to be so smart...) resulting in `for<'x> for<'b>
719 // Bar1<'x,'b>` (we have no syntax for this, so use your
720 // imagination). Basically the 'x will have DB index of 2 and 'b
721 // will have DB index of 1. Not quite what we want. So we apply
722 // the substitution to the *contents* of the trait reference,
723 // rather than the trait reference itself (put another way, the
724 // substitution code expects equal binding levels in the values
725 // from the substitution and the value being substituted into, and
726 // this trick achieves that).
728 // Working through the second example:
729 // trait_ref: for<'x> T: Foo1<'^0.0>; substs: [T, '^0.0]
730 // predicate: for<'b> Self: Bar1<'a, '^0.0>; substs: [Self, 'a, '^0.0]
731 // We want to end up with:
732 // for<'x, 'b> T: Bar1<'^0.0, '^0.1>
734 // 1) We must shift all bound vars in predicate by the length
735 // of trait ref's bound vars. So, we would end up with predicate like
736 // Self: Bar1<'a, '^0.1>
737 // 2) We can then apply the trait substs to this, ending up with
738 // T: Bar1<'^0.0, '^0.1>
739 // 3) Finally, to create the final bound vars, we concatenate the bound
740 // vars of the trait ref with those of the predicate:
742 let bound_pred = self.kind();
743 let pred_bound_vars = bound_pred.bound_vars();
744 let trait_bound_vars = trait_ref.bound_vars();
745 // 1) Self: Bar1<'a, '^0.0> -> Self: Bar1<'a, '^0.1>
747 tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
748 // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
749 let new = shifted_pred.subst(tcx, trait_ref.skip_binder().substs);
750 // 3) ['x] + ['b] -> ['x, 'b]
752 tcx.mk_bound_variable_kinds(trait_bound_vars.iter().chain(pred_bound_vars));
753 tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars))
757 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
758 #[derive(HashStable, TypeFoldable)]
759 pub struct TraitPredicate<'tcx> {
760 pub trait_ref: TraitRef<'tcx>,
762 pub constness: BoundConstness,
764 /// If polarity is Positive: we are proving that the trait is implemented.
766 /// If polarity is Negative: we are proving that a negative impl of this trait
767 /// exists. (Note that coherence also checks whether negative impls of supertraits
768 /// exist via a series of predicates.)
770 /// If polarity is Reserved: that's a bug.
771 pub polarity: ImplPolarity,
774 pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
776 impl<'tcx> TraitPredicate<'tcx> {
777 pub fn remap_constness(&mut self, tcx: TyCtxt<'tcx>, param_env: &mut ParamEnv<'tcx>) {
778 if unlikely!(Some(self.trait_ref.def_id) == tcx.lang_items().drop_trait()) {
779 // remap without changing constness of this predicate.
780 // this is because `T: ~const Drop` has a different meaning to `T: Drop`
781 // FIXME(fee1-dead): remove this logic after beta bump
782 param_env.remap_constness_with(self.constness)
784 *param_env = param_env.with_constness(self.constness.and(param_env.constness()))
788 /// Remap the constness of this predicate before emitting it for diagnostics.
789 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
790 // this is different to `remap_constness` that callees want to print this predicate
791 // in case of selection errors. `T: ~const Drop` bounds cannot end up here when the
792 // param_env is not const because we it is always satisfied in non-const contexts.
793 if let hir::Constness::NotConst = param_env.constness() {
794 self.constness = ty::BoundConstness::NotConst;
798 pub fn def_id(self) -> DefId {
799 self.trait_ref.def_id
802 pub fn self_ty(self) -> Ty<'tcx> {
803 self.trait_ref.self_ty()
807 pub fn is_const_if_const(self) -> bool {
808 self.constness == BoundConstness::ConstIfConst
812 impl<'tcx> PolyTraitPredicate<'tcx> {
813 pub fn def_id(self) -> DefId {
814 // Ok to skip binder since trait `DefId` does not care about regions.
815 self.skip_binder().def_id()
818 pub fn self_ty(self) -> ty::Binder<'tcx, Ty<'tcx>> {
819 self.map_bound(|trait_ref| trait_ref.self_ty())
822 /// Remap the constness of this predicate before emitting it for diagnostics.
823 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
824 *self = self.map_bound(|mut p| {
825 p.remap_constness_diag(param_env);
831 pub fn is_const_if_const(self) -> bool {
832 self.skip_binder().is_const_if_const()
836 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
837 #[derive(HashStable, TypeFoldable)]
838 pub struct OutlivesPredicate<A, B>(pub A, pub B); // `A: B`
839 pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>;
840 pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>;
841 pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>;
842 pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>;
844 /// Encodes that `a` must be a subtype of `b`. The `a_is_expected` flag indicates
845 /// whether the `a` type is the type that we should label as "expected" when
846 /// presenting user diagnostics.
847 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
848 #[derive(HashStable, TypeFoldable)]
849 pub struct SubtypePredicate<'tcx> {
850 pub a_is_expected: bool,
854 pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>;
856 /// Encodes that we have to coerce *from* the `a` type to the `b` type.
857 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
858 #[derive(HashStable, TypeFoldable)]
859 pub struct CoercePredicate<'tcx> {
863 pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
865 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, TyEncodable, TyDecodable)]
866 #[derive(HashStable, TypeFoldable)]
867 pub enum Term<'tcx> {
872 impl<'tcx> From<Ty<'tcx>> for Term<'tcx> {
873 fn from(ty: Ty<'tcx>) -> Self {
878 impl<'tcx> From<Const<'tcx>> for Term<'tcx> {
879 fn from(c: Const<'tcx>) -> Self {
884 impl<'tcx> Term<'tcx> {
885 pub fn ty(&self) -> Option<Ty<'tcx>> {
886 if let Term::Ty(ty) = self { Some(*ty) } else { None }
888 pub fn ct(&self) -> Option<Const<'tcx>> {
889 if let Term::Const(c) = self { Some(*c) } else { None }
893 /// This kind of predicate has no *direct* correspondent in the
894 /// syntax, but it roughly corresponds to the syntactic forms:
896 /// 1. `T: TraitRef<..., Item = Type>`
897 /// 2. `<T as TraitRef<...>>::Item == Type` (NYI)
899 /// In particular, form #1 is "desugared" to the combination of a
900 /// normal trait predicate (`T: TraitRef<...>`) and one of these
901 /// predicates. Form #2 is a broader form in that it also permits
902 /// equality between arbitrary types. Processing an instance of
903 /// Form #2 eventually yields one of these `ProjectionPredicate`
904 /// instances to normalize the LHS.
905 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
906 #[derive(HashStable, TypeFoldable)]
907 pub struct ProjectionPredicate<'tcx> {
908 pub projection_ty: ProjectionTy<'tcx>,
909 pub term: Term<'tcx>,
912 pub type PolyProjectionPredicate<'tcx> = Binder<'tcx, ProjectionPredicate<'tcx>>;
914 impl<'tcx> PolyProjectionPredicate<'tcx> {
915 /// Returns the `DefId` of the trait of the associated item being projected.
917 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
918 self.skip_binder().projection_ty.trait_def_id(tcx)
921 /// Get the [PolyTraitRef] required for this projection to be well formed.
922 /// Note that for generic associated types the predicates of the associated
923 /// type also need to be checked.
925 pub fn required_poly_trait_ref(&self, tcx: TyCtxt<'tcx>) -> PolyTraitRef<'tcx> {
926 // Note: unlike with `TraitRef::to_poly_trait_ref()`,
927 // `self.0.trait_ref` is permitted to have escaping regions.
928 // This is because here `self` has a `Binder` and so does our
929 // return value, so we are preserving the number of binding
931 self.map_bound(|predicate| predicate.projection_ty.trait_ref(tcx))
934 pub fn term(&self) -> Binder<'tcx, Term<'tcx>> {
935 self.map_bound(|predicate| predicate.term)
938 /// The `DefId` of the `TraitItem` for the associated type.
940 /// Note that this is not the `DefId` of the `TraitRef` containing this
941 /// associated type, which is in `tcx.associated_item(projection_def_id()).container`.
942 pub fn projection_def_id(&self) -> DefId {
943 // Ok to skip binder since trait `DefId` does not care about regions.
944 self.skip_binder().projection_ty.item_def_id
948 pub trait ToPolyTraitRef<'tcx> {
949 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx>;
952 impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
953 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> {
954 self.map_bound_ref(|trait_pred| trait_pred.trait_ref)
958 pub trait ToPredicate<'tcx> {
959 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx>;
962 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
964 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
965 tcx.mk_predicate(self)
969 impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
970 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
971 self.map_bound(PredicateKind::Trait).to_predicate(tcx)
975 impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
976 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
977 self.map_bound(PredicateKind::RegionOutlives).to_predicate(tcx)
981 impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> {
982 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
983 self.map_bound(PredicateKind::TypeOutlives).to_predicate(tcx)
987 impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
988 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
989 self.map_bound(PredicateKind::Projection).to_predicate(tcx)
993 impl<'tcx> Predicate<'tcx> {
994 pub fn to_opt_poly_trait_pred(self) -> Option<PolyTraitPredicate<'tcx>> {
995 let predicate = self.kind();
996 match predicate.skip_binder() {
997 PredicateKind::Trait(t) => Some(predicate.rebind(t)),
998 PredicateKind::Projection(..)
999 | PredicateKind::Subtype(..)
1000 | PredicateKind::Coerce(..)
1001 | PredicateKind::RegionOutlives(..)
1002 | PredicateKind::WellFormed(..)
1003 | PredicateKind::ObjectSafe(..)
1004 | PredicateKind::ClosureKind(..)
1005 | PredicateKind::TypeOutlives(..)
1006 | PredicateKind::ConstEvaluatable(..)
1007 | PredicateKind::ConstEquate(..)
1008 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1012 pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> {
1013 let predicate = self.kind();
1014 match predicate.skip_binder() {
1015 PredicateKind::TypeOutlives(data) => Some(predicate.rebind(data)),
1016 PredicateKind::Trait(..)
1017 | PredicateKind::Projection(..)
1018 | PredicateKind::Subtype(..)
1019 | PredicateKind::Coerce(..)
1020 | PredicateKind::RegionOutlives(..)
1021 | PredicateKind::WellFormed(..)
1022 | PredicateKind::ObjectSafe(..)
1023 | PredicateKind::ClosureKind(..)
1024 | PredicateKind::ConstEvaluatable(..)
1025 | PredicateKind::ConstEquate(..)
1026 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1031 /// Represents the bounds declared on a particular set of type
1032 /// parameters. Should eventually be generalized into a flag list of
1033 /// where-clauses. You can obtain an `InstantiatedPredicates` list from a
1034 /// `GenericPredicates` by using the `instantiate` method. Note that this method
1035 /// reflects an important semantic invariant of `InstantiatedPredicates`: while
1036 /// the `GenericPredicates` are expressed in terms of the bound type
1037 /// parameters of the impl/trait/whatever, an `InstantiatedPredicates` instance
1038 /// represented a set of bounds for some particular instantiation,
1039 /// meaning that the generic parameters have been substituted with
1044 /// struct Foo<T, U: Bar<T>> { ... }
1046 /// Here, the `GenericPredicates` for `Foo` would contain a list of bounds like
1047 /// `[[], [U:Bar<T>]]`. Now if there were some particular reference
1048 /// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[],
1049 /// [usize:Bar<isize>]]`.
1050 #[derive(Clone, Debug, TypeFoldable)]
1051 pub struct InstantiatedPredicates<'tcx> {
1052 pub predicates: Vec<Predicate<'tcx>>,
1053 pub spans: Vec<Span>,
1056 impl<'tcx> InstantiatedPredicates<'tcx> {
1057 pub fn empty() -> InstantiatedPredicates<'tcx> {
1058 InstantiatedPredicates { predicates: vec![], spans: vec![] }
1061 pub fn is_empty(&self) -> bool {
1062 self.predicates.is_empty()
1078 pub struct OpaqueTypeKey<'tcx> {
1080 pub substs: SubstsRef<'tcx>,
1083 #[derive(Copy, Clone, Debug, TypeFoldable, HashStable, TyEncodable, TyDecodable)]
1084 pub struct OpaqueHiddenType<'tcx> {
1085 /// The span of this particular definition of the opaque type. So
1088 /// ```ignore (incomplete snippet)
1089 /// type Foo = impl Baz;
1090 /// fn bar() -> Foo {
1091 /// // ^^^ This is the span we are looking for!
1095 /// In cases where the fn returns `(impl Trait, impl Trait)` or
1096 /// other such combinations, the result is currently
1097 /// over-approximated, but better than nothing.
1100 /// The type variable that represents the value of the opaque type
1101 /// that we require. In other words, after we compile this function,
1102 /// we will be created a constraint like:
1106 /// where `?C` is the value of this type variable. =) It may
1107 /// naturally refer to the type and lifetime parameters in scope
1108 /// in this function, though ultimately it should only reference
1109 /// those that are arguments to `Foo` in the constraint above. (In
1110 /// other words, `?C` should not include `'b`, even though it's a
1111 /// lifetime parameter on `foo`.)
1115 rustc_index::newtype_index! {
1116 /// "Universes" are used during type- and trait-checking in the
1117 /// presence of `for<..>` binders to control what sets of names are
1118 /// visible. Universes are arranged into a tree: the root universe
1119 /// contains names that are always visible. Each child then adds a new
1120 /// set of names that are visible, in addition to those of its parent.
1121 /// We say that the child universe "extends" the parent universe with
1124 /// To make this more concrete, consider this program:
1128 /// fn bar<T>(x: T) {
1129 /// let y: for<'a> fn(&'a u8, Foo) = ...;
1133 /// The struct name `Foo` is in the root universe U0. But the type
1134 /// parameter `T`, introduced on `bar`, is in an extended universe U1
1135 /// -- i.e., within `bar`, we can name both `T` and `Foo`, but outside
1136 /// of `bar`, we cannot name `T`. Then, within the type of `y`, the
1137 /// region `'a` is in a universe U2 that extends U1, because we can
1138 /// name it inside the fn type but not outside.
1140 /// Universes are used to do type- and trait-checking around these
1141 /// "forall" binders (also called **universal quantification**). The
1142 /// idea is that when, in the body of `bar`, we refer to `T` as a
1143 /// type, we aren't referring to any type in particular, but rather a
1144 /// kind of "fresh" type that is distinct from all other types we have
1145 /// actually declared. This is called a **placeholder** type, and we
1146 /// use universes to talk about this. In other words, a type name in
1147 /// universe 0 always corresponds to some "ground" type that the user
1148 /// declared, but a type name in a non-zero universe is a placeholder
1149 /// type -- an idealized representative of "types in general" that we
1150 /// use for checking generic functions.
1151 pub struct UniverseIndex {
1153 DEBUG_FORMAT = "U{}",
1157 impl UniverseIndex {
1158 pub const ROOT: UniverseIndex = UniverseIndex::from_u32(0);
1160 /// Returns the "next" universe index in order -- this new index
1161 /// is considered to extend all previous universes. This
1162 /// corresponds to entering a `forall` quantifier. So, for
1163 /// example, suppose we have this type in universe `U`:
1166 /// for<'a> fn(&'a u32)
1169 /// Once we "enter" into this `for<'a>` quantifier, we are in a
1170 /// new universe that extends `U` -- in this new universe, we can
1171 /// name the region `'a`, but that region was not nameable from
1172 /// `U` because it was not in scope there.
1173 pub fn next_universe(self) -> UniverseIndex {
1174 UniverseIndex::from_u32(self.private.checked_add(1).unwrap())
1177 /// Returns `true` if `self` can name a name from `other` -- in other words,
1178 /// if the set of names in `self` is a superset of those in
1179 /// `other` (`self >= other`).
1180 pub fn can_name(self, other: UniverseIndex) -> bool {
1181 self.private >= other.private
1184 /// Returns `true` if `self` cannot name some names from `other` -- in other
1185 /// words, if the set of names in `self` is a strict subset of
1186 /// those in `other` (`self < other`).
1187 pub fn cannot_name(self, other: UniverseIndex) -> bool {
1188 self.private < other.private
1192 /// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are
1193 /// identified by both a universe, as well as a name residing within that universe. Distinct bound
1194 /// regions/types/consts within the same universe simply have an unknown relationship to one
1196 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable, PartialOrd, Ord)]
1197 pub struct Placeholder<T> {
1198 pub universe: UniverseIndex,
1202 impl<'a, T> HashStable<StableHashingContext<'a>> for Placeholder<T>
1204 T: HashStable<StableHashingContext<'a>>,
1206 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1207 self.universe.hash_stable(hcx, hasher);
1208 self.name.hash_stable(hcx, hasher);
1212 pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
1214 pub type PlaceholderType = Placeholder<BoundVar>;
1216 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
1217 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
1218 pub struct BoundConst<'tcx> {
1223 pub type PlaceholderConst<'tcx> = Placeholder<BoundConst<'tcx>>;
1225 /// A `DefId` which, in case it is a const argument, is potentially bundled with
1226 /// the `DefId` of the generic parameter it instantiates.
1228 /// This is used to avoid calls to `type_of` for const arguments during typeck
1229 /// which cause cycle errors.
1234 /// fn foo<const N: usize>(&self) -> [u8; N] { [0; N] }
1235 /// // ^ const parameter
1239 /// fn foo<const M: u8>(&self) -> usize { 42 }
1240 /// // ^ const parameter
1245 /// let _b = a.foo::<{ 3 + 7 }>();
1246 /// // ^^^^^^^^^ const argument
1250 /// Let's look at the call `a.foo::<{ 3 + 7 }>()` here. We do not know
1251 /// which `foo` is used until we know the type of `a`.
1253 /// We only know the type of `a` once we are inside of `typeck(main)`.
1254 /// We also end up normalizing the type of `_b` during `typeck(main)` which
1255 /// requires us to evaluate the const argument.
1257 /// To evaluate that const argument we need to know its type,
1258 /// which we would get using `type_of(const_arg)`. This requires us to
1259 /// resolve `foo` as it can be either `usize` or `u8` in this example.
1260 /// However, resolving `foo` once again requires `typeck(main)` to get the type of `a`,
1261 /// which results in a cycle.
1263 /// In short we must not call `type_of(const_arg)` during `typeck(main)`.
1265 /// When first creating the `ty::Const` of the const argument inside of `typeck` we have
1266 /// already resolved `foo` so we know which const parameter this argument instantiates.
1267 /// This means that we also know the expected result of `type_of(const_arg)` even if we
1268 /// aren't allowed to call that query: it is equal to `type_of(const_param)` which is
1269 /// trivial to compute.
1271 /// If we now want to use that constant in a place which potentially needs its type
1272 /// we also pass the type of its `const_param`. This is the point of `WithOptConstParam`,
1273 /// except that instead of a `Ty` we bundle the `DefId` of the const parameter.
1274 /// Meaning that we need to use `type_of(const_param_did)` if `const_param_did` is `Some`
1275 /// to get the type of `did`.
1276 #[derive(Copy, Clone, Debug, TypeFoldable, Lift, TyEncodable, TyDecodable)]
1277 #[derive(PartialEq, Eq, PartialOrd, Ord)]
1278 #[derive(Hash, HashStable)]
1279 pub struct WithOptConstParam<T> {
1281 /// The `DefId` of the corresponding generic parameter in case `did` is
1282 /// a const argument.
1284 /// Note that even if `did` is a const argument, this may still be `None`.
1285 /// All queries taking `WithOptConstParam` start by calling `tcx.opt_const_param_of(def.did)`
1286 /// to potentially update `param_did` in the case it is `None`.
1287 pub const_param_did: Option<DefId>,
1290 impl<T> WithOptConstParam<T> {
1291 /// Creates a new `WithOptConstParam` setting `const_param_did` to `None`.
1293 pub fn unknown(did: T) -> WithOptConstParam<T> {
1294 WithOptConstParam { did, const_param_did: None }
1298 impl WithOptConstParam<LocalDefId> {
1299 /// Returns `Some((did, param_did))` if `def_id` is a const argument,
1300 /// `None` otherwise.
1302 pub fn try_lookup(did: LocalDefId, tcx: TyCtxt<'_>) -> Option<(LocalDefId, DefId)> {
1303 tcx.opt_const_param_of(did).map(|param_did| (did, param_did))
1306 /// In case `self` is unknown but `self.did` is a const argument, this returns
1307 /// a `WithOptConstParam` with the correct `const_param_did`.
1309 pub fn try_upgrade(self, tcx: TyCtxt<'_>) -> Option<WithOptConstParam<LocalDefId>> {
1310 if self.const_param_did.is_none() {
1311 if let const_param_did @ Some(_) = tcx.opt_const_param_of(self.did) {
1312 return Some(WithOptConstParam { did: self.did, const_param_did });
1319 pub fn to_global(self) -> WithOptConstParam<DefId> {
1320 WithOptConstParam { did: self.did.to_def_id(), const_param_did: self.const_param_did }
1323 pub fn def_id_for_type_of(self) -> DefId {
1324 if let Some(did) = self.const_param_did { did } else { self.did.to_def_id() }
1328 impl WithOptConstParam<DefId> {
1329 pub fn as_local(self) -> Option<WithOptConstParam<LocalDefId>> {
1332 .map(|did| WithOptConstParam { did, const_param_did: self.const_param_did })
1335 pub fn as_const_arg(self) -> Option<(LocalDefId, DefId)> {
1336 if let Some(param_did) = self.const_param_did {
1337 if let Some(did) = self.did.as_local() {
1338 return Some((did, param_did));
1345 pub fn is_local(self) -> bool {
1349 pub fn def_id_for_type_of(self) -> DefId {
1350 self.const_param_did.unwrap_or(self.did)
1354 /// When type checking, we use the `ParamEnv` to track
1355 /// details about the set of where-clauses that are in scope at this
1356 /// particular point.
1357 #[derive(Copy, Clone, Hash, PartialEq, Eq)]
1358 pub struct ParamEnv<'tcx> {
1359 /// This packs both caller bounds and the reveal enum into one pointer.
1361 /// Caller bounds are `Obligation`s that the caller must satisfy. This is
1362 /// basically the set of bounds on the in-scope type parameters, translated
1363 /// into `Obligation`s, and elaborated and normalized.
1365 /// Use the `caller_bounds()` method to access.
1367 /// Typically, this is `Reveal::UserFacing`, but during codegen we
1368 /// want `Reveal::All`.
1370 /// Note: This is packed, use the reveal() method to access it.
1371 packed: CopyTaggedPtr<&'tcx List<Predicate<'tcx>>, ParamTag, true>,
1374 #[derive(Copy, Clone)]
1376 reveal: traits::Reveal,
1377 constness: hir::Constness,
1380 unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag {
1381 const BITS: usize = 2;
1383 fn into_usize(self) -> usize {
1385 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0,
1386 Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1,
1387 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2,
1388 Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3,
1392 unsafe fn from_usize(ptr: usize) -> Self {
1394 0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
1395 1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
1396 2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
1397 3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const },
1398 _ => std::hint::unreachable_unchecked(),
1403 impl<'tcx> fmt::Debug for ParamEnv<'tcx> {
1404 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1405 f.debug_struct("ParamEnv")
1406 .field("caller_bounds", &self.caller_bounds())
1407 .field("reveal", &self.reveal())
1408 .field("constness", &self.constness())
1413 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
1414 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1415 self.caller_bounds().hash_stable(hcx, hasher);
1416 self.reveal().hash_stable(hcx, hasher);
1417 self.constness().hash_stable(hcx, hasher);
1421 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
1422 fn try_super_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>(
1425 ) -> Result<Self, F::Error> {
1427 self.caller_bounds().try_fold_with(folder)?,
1428 self.reveal().try_fold_with(folder)?,
1429 self.constness().try_fold_with(folder)?,
1433 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1434 self.caller_bounds().visit_with(visitor)?;
1435 self.reveal().visit_with(visitor)?;
1436 self.constness().visit_with(visitor)
1440 impl<'tcx> ParamEnv<'tcx> {
1441 /// Construct a trait environment suitable for contexts where
1442 /// there are no where-clauses in scope. Hidden types (like `impl
1443 /// Trait`) are left hidden, so this is suitable for ordinary
1446 pub fn empty() -> Self {
1447 Self::new(List::empty(), Reveal::UserFacing, hir::Constness::NotConst)
1451 pub fn caller_bounds(self) -> &'tcx List<Predicate<'tcx>> {
1452 self.packed.pointer()
1456 pub fn reveal(self) -> traits::Reveal {
1457 self.packed.tag().reveal
1461 pub fn constness(self) -> hir::Constness {
1462 self.packed.tag().constness
1466 pub fn is_const(self) -> bool {
1467 self.packed.tag().constness == hir::Constness::Const
1470 /// Construct a trait environment with no where-clauses in scope
1471 /// where the values of all `impl Trait` and other hidden types
1472 /// are revealed. This is suitable for monomorphized, post-typeck
1473 /// environments like codegen or doing optimizations.
1475 /// N.B., if you want to have predicates in scope, use `ParamEnv::new`,
1476 /// or invoke `param_env.with_reveal_all()`.
1478 pub fn reveal_all() -> Self {
1479 Self::new(List::empty(), Reveal::All, hir::Constness::NotConst)
1482 /// Construct a trait environment with the given set of predicates.
1485 caller_bounds: &'tcx List<Predicate<'tcx>>,
1487 constness: hir::Constness,
1489 ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal, constness }) }
1492 pub fn with_user_facing(mut self) -> Self {
1493 self.packed.set_tag(ParamTag { reveal: Reveal::UserFacing, ..self.packed.tag() });
1498 pub fn with_constness(mut self, constness: hir::Constness) -> Self {
1499 self.packed.set_tag(ParamTag { constness, ..self.packed.tag() });
1504 pub fn with_const(mut self) -> Self {
1505 self.packed.set_tag(ParamTag { constness: hir::Constness::Const, ..self.packed.tag() });
1510 pub fn without_const(mut self) -> Self {
1511 self.packed.set_tag(ParamTag { constness: hir::Constness::NotConst, ..self.packed.tag() });
1516 pub fn remap_constness_with(&mut self, mut constness: ty::BoundConstness) {
1517 *self = self.with_constness(constness.and(self.constness()))
1520 /// Returns a new parameter environment with the same clauses, but
1521 /// which "reveals" the true results of projections in all cases
1522 /// (even for associated types that are specializable). This is
1523 /// the desired behavior during codegen and certain other special
1524 /// contexts; normally though we want to use `Reveal::UserFacing`,
1525 /// which is the default.
1526 /// All opaque types in the caller_bounds of the `ParamEnv`
1527 /// will be normalized to their underlying types.
1528 /// See PR #65989 and issue #65918 for more details
1529 pub fn with_reveal_all_normalized(self, tcx: TyCtxt<'tcx>) -> Self {
1530 if self.packed.tag().reveal == traits::Reveal::All {
1535 tcx.normalize_opaque_types(self.caller_bounds()),
1541 /// Returns this same environment but with no caller bounds.
1543 pub fn without_caller_bounds(self) -> Self {
1544 Self::new(List::empty(), self.reveal(), self.constness())
1547 /// Creates a suitable environment in which to perform trait
1548 /// queries on the given value. When type-checking, this is simply
1549 /// the pair of the environment plus value. But when reveal is set to
1550 /// All, then if `value` does not reference any type parameters, we will
1551 /// pair it with the empty environment. This improves caching and is generally
1554 /// N.B., we preserve the environment when type-checking because it
1555 /// is possible for the user to have wacky where-clauses like
1556 /// `where Box<u32>: Copy`, which are clearly never
1557 /// satisfiable. We generally want to behave as if they were true,
1558 /// although the surrounding function is never reachable.
1559 pub fn and<T: TypeFoldable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
1560 match self.reveal() {
1561 Reveal::UserFacing => ParamEnvAnd { param_env: self, value },
1564 if value.is_global() {
1565 ParamEnvAnd { param_env: self.without_caller_bounds(), value }
1567 ParamEnvAnd { param_env: self, value }
1574 // FIXME(ecstaticmorse): Audit all occurrences of `without_const().to_predicate(tcx)` to ensure that
1575 // the constness of trait bounds is being propagated correctly.
1576 impl<'tcx> PolyTraitRef<'tcx> {
1578 pub fn with_constness(self, constness: BoundConstness) -> PolyTraitPredicate<'tcx> {
1579 self.map_bound(|trait_ref| ty::TraitPredicate {
1582 polarity: ty::ImplPolarity::Positive,
1587 pub fn without_const(self) -> PolyTraitPredicate<'tcx> {
1588 self.with_constness(BoundConstness::NotConst)
1592 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable)]
1593 pub struct ParamEnvAnd<'tcx, T> {
1594 pub param_env: ParamEnv<'tcx>,
1598 impl<'tcx, T> ParamEnvAnd<'tcx, T> {
1599 pub fn into_parts(self) -> (ParamEnv<'tcx>, T) {
1600 (self.param_env, self.value)
1604 pub fn without_const(mut self) -> Self {
1605 self.param_env = self.param_env.without_const();
1610 impl<'a, 'tcx, T> HashStable<StableHashingContext<'a>> for ParamEnvAnd<'tcx, T>
1612 T: HashStable<StableHashingContext<'a>>,
1614 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1615 let ParamEnvAnd { ref param_env, ref value } = *self;
1617 param_env.hash_stable(hcx, hasher);
1618 value.hash_stable(hcx, hasher);
1622 #[derive(Copy, Clone, Debug, HashStable)]
1623 pub struct Destructor {
1624 /// The `DefId` of the destructor method
1626 /// The constness of the destructor method
1627 pub constness: hir::Constness,
1631 #[derive(HashStable, TyEncodable, TyDecodable)]
1632 pub struct VariantFlags: u32 {
1633 const NO_VARIANT_FLAGS = 0;
1634 /// Indicates whether the field list of this variant is `#[non_exhaustive]`.
1635 const IS_FIELD_LIST_NON_EXHAUSTIVE = 1 << 0;
1636 /// Indicates whether this variant was obtained as part of recovering from
1637 /// a syntactic error. May be incomplete or bogus.
1638 const IS_RECOVERED = 1 << 1;
1642 /// Definition of a variant -- a struct's fields or an enum variant.
1643 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1644 pub struct VariantDef {
1645 /// `DefId` that identifies the variant itself.
1646 /// If this variant belongs to a struct or union, then this is a copy of its `DefId`.
1648 /// `DefId` that identifies the variant's constructor.
1649 /// If this variant is a struct variant, then this is `None`.
1650 pub ctor_def_id: Option<DefId>,
1651 /// Variant or struct name.
1653 /// Discriminant of this variant.
1654 pub discr: VariantDiscr,
1655 /// Fields of this variant.
1656 pub fields: Vec<FieldDef>,
1657 /// Type of constructor of variant.
1658 pub ctor_kind: CtorKind,
1659 /// Flags of the variant (e.g. is field list non-exhaustive)?
1660 flags: VariantFlags,
1664 /// Creates a new `VariantDef`.
1666 /// `variant_did` is the `DefId` that identifies the enum variant (if this `VariantDef`
1667 /// represents an enum variant).
1669 /// `ctor_did` is the `DefId` that identifies the constructor of unit or
1670 /// tuple-variants/structs. If this is a `struct`-variant then this should be `None`.
1672 /// `parent_did` is the `DefId` of the `AdtDef` representing the enum or struct that
1673 /// owns this variant. It is used for checking if a struct has `#[non_exhaustive]` w/out having
1674 /// to go through the redirect of checking the ctor's attributes - but compiling a small crate
1675 /// requires loading the `AdtDef`s for all the structs in the universe (e.g., coherence for any
1676 /// built-in trait), and we do not want to load attributes twice.
1678 /// If someone speeds up attribute loading to not be a performance concern, they can
1679 /// remove this hack and use the constructor `DefId` everywhere.
1682 variant_did: Option<DefId>,
1683 ctor_def_id: Option<DefId>,
1684 discr: VariantDiscr,
1685 fields: Vec<FieldDef>,
1686 ctor_kind: CtorKind,
1690 is_field_list_non_exhaustive: bool,
1693 "VariantDef::new(name = {:?}, variant_did = {:?}, ctor_def_id = {:?}, discr = {:?},
1694 fields = {:?}, ctor_kind = {:?}, adt_kind = {:?}, parent_did = {:?})",
1695 name, variant_did, ctor_def_id, discr, fields, ctor_kind, adt_kind, parent_did,
1698 let mut flags = VariantFlags::NO_VARIANT_FLAGS;
1699 if is_field_list_non_exhaustive {
1700 flags |= VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE;
1704 flags |= VariantFlags::IS_RECOVERED;
1708 def_id: variant_did.unwrap_or(parent_did),
1718 /// Is this field list non-exhaustive?
1720 pub fn is_field_list_non_exhaustive(&self) -> bool {
1721 self.flags.intersects(VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE)
1724 /// Was this variant obtained as part of recovering from a syntactic error?
1726 pub fn is_recovered(&self) -> bool {
1727 self.flags.intersects(VariantFlags::IS_RECOVERED)
1730 /// Computes the `Ident` of this variant by looking up the `Span`
1731 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1732 Ident::new(self.name, tcx.def_ident_span(self.def_id).unwrap())
1736 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
1737 pub enum VariantDiscr {
1738 /// Explicit value for this variant, i.e., `X = 123`.
1739 /// The `DefId` corresponds to the embedded constant.
1742 /// The previous variant's discriminant plus one.
1743 /// For efficiency reasons, the distance from the
1744 /// last `Explicit` discriminant is being stored,
1745 /// or `0` for the first variant, if it has none.
1749 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1750 pub struct FieldDef {
1753 pub vis: Visibility,
1757 #[derive(TyEncodable, TyDecodable, Default, HashStable)]
1758 pub struct ReprFlags: u8 {
1759 const IS_C = 1 << 0;
1760 const IS_SIMD = 1 << 1;
1761 const IS_TRANSPARENT = 1 << 2;
1762 // Internal only for now. If true, don't reorder fields.
1763 const IS_LINEAR = 1 << 3;
1764 // If true, don't expose any niche to type's context.
1765 const HIDE_NICHE = 1 << 4;
1766 // If true, the type's layout can be randomized using
1767 // the seed stored in `ReprOptions.layout_seed`
1768 const RANDOMIZE_LAYOUT = 1 << 5;
1769 // Any of these flags being set prevent field reordering optimisation.
1770 const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
1771 | ReprFlags::IS_SIMD.bits
1772 | ReprFlags::IS_LINEAR.bits;
1776 /// Represents the repr options provided by the user,
1777 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Default, HashStable)]
1778 pub struct ReprOptions {
1779 pub int: Option<attr::IntType>,
1780 pub align: Option<Align>,
1781 pub pack: Option<Align>,
1782 pub flags: ReprFlags,
1783 /// The seed to be used for randomizing a type's layout
1785 /// Note: This could technically be a `[u8; 16]` (a `u128`) which would
1786 /// be the "most accurate" hash as it'd encompass the item and crate
1787 /// hash without loss, but it does pay the price of being larger.
1788 /// Everything's a tradeoff, a `u64` seed should be sufficient for our
1789 /// purposes (primarily `-Z randomize-layout`)
1790 pub field_shuffle_seed: u64,
1794 pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions {
1795 let mut flags = ReprFlags::empty();
1796 let mut size = None;
1797 let mut max_align: Option<Align> = None;
1798 let mut min_pack: Option<Align> = None;
1800 // Generate a deterministically-derived seed from the item's path hash
1801 // to allow for cross-crate compilation to actually work
1802 let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash();
1804 // If the user defined a custom seed for layout randomization, xor the item's
1805 // path hash with the user defined seed, this will allowing determinism while
1806 // still allowing users to further randomize layout generation for e.g. fuzzing
1807 if let Some(user_seed) = tcx.sess.opts.debugging_opts.layout_seed {
1808 field_shuffle_seed ^= user_seed;
1811 for attr in tcx.get_attrs(did).iter() {
1812 for r in attr::find_repr_attrs(&tcx.sess, attr) {
1813 flags.insert(match r {
1814 attr::ReprC => ReprFlags::IS_C,
1815 attr::ReprPacked(pack) => {
1816 let pack = Align::from_bytes(pack as u64).unwrap();
1817 min_pack = Some(if let Some(min_pack) = min_pack {
1824 attr::ReprTransparent => ReprFlags::IS_TRANSPARENT,
1825 attr::ReprNoNiche => ReprFlags::HIDE_NICHE,
1826 attr::ReprSimd => ReprFlags::IS_SIMD,
1827 attr::ReprInt(i) => {
1831 attr::ReprAlign(align) => {
1832 max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap()));
1839 // If `-Z randomize-layout` was enabled for the type definition then we can
1840 // consider performing layout randomization
1841 if tcx.sess.opts.debugging_opts.randomize_layout {
1842 flags.insert(ReprFlags::RANDOMIZE_LAYOUT);
1845 // This is here instead of layout because the choice must make it into metadata.
1846 if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) {
1847 flags.insert(ReprFlags::IS_LINEAR);
1850 Self { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed }
1854 pub fn simd(&self) -> bool {
1855 self.flags.contains(ReprFlags::IS_SIMD)
1859 pub fn c(&self) -> bool {
1860 self.flags.contains(ReprFlags::IS_C)
1864 pub fn packed(&self) -> bool {
1869 pub fn transparent(&self) -> bool {
1870 self.flags.contains(ReprFlags::IS_TRANSPARENT)
1874 pub fn linear(&self) -> bool {
1875 self.flags.contains(ReprFlags::IS_LINEAR)
1879 pub fn hide_niche(&self) -> bool {
1880 self.flags.contains(ReprFlags::HIDE_NICHE)
1883 /// Returns the discriminant type, given these `repr` options.
1884 /// This must only be called on enums!
1885 pub fn discr_type(&self) -> attr::IntType {
1886 self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize))
1889 /// Returns `true` if this `#[repr()]` should inhabit "smart enum
1890 /// layout" optimizations, such as representing `Foo<&T>` as a
1892 pub fn inhibit_enum_layout_opt(&self) -> bool {
1893 self.c() || self.int.is_some()
1896 /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
1897 /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
1898 pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
1899 if let Some(pack) = self.pack {
1900 if pack.bytes() == 1 {
1905 self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
1908 /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
1909 /// was enabled for its declaration crate
1910 pub fn can_randomize_type_layout(&self) -> bool {
1911 !self.inhibit_struct_field_reordering_opt()
1912 && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
1915 /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
1916 pub fn inhibit_union_abi_opt(&self) -> bool {
1921 impl<'tcx> FieldDef {
1922 /// Returns the type of this field. The resulting type is not normalized. The `subst` is
1923 /// typically obtained via the second field of [`TyKind::Adt`].
1924 pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
1925 tcx.type_of(self.did).subst(tcx, subst)
1928 /// Computes the `Ident` of this variant by looking up the `Span`
1929 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1930 Ident::new(self.name, tcx.def_ident_span(self.did).unwrap())
1934 pub type Attributes<'tcx> = &'tcx [ast::Attribute];
1936 #[derive(Debug, PartialEq, Eq)]
1937 pub enum ImplOverlapKind {
1938 /// These impls are always allowed to overlap.
1940 /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait
1943 /// These impls are allowed to overlap, but that raises
1944 /// an issue #33140 future-compatibility warning.
1946 /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's
1947 /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different.
1949 /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied
1950 /// that difference, making what reduces to the following set of impls:
1954 /// impl Trait for dyn Send + Sync {}
1955 /// impl Trait for dyn Sync + Send {}
1958 /// Obviously, once we made these types be identical, that code causes a coherence
1959 /// error and a fairly big headache for us. However, luckily for us, the trait
1960 /// `Trait` used in this case is basically a marker trait, and therefore having
1961 /// overlapping impls for it is sound.
1963 /// To handle this, we basically regard the trait as a marker trait, with an additional
1964 /// future-compatibility warning. To avoid accidentally "stabilizing" this feature,
1965 /// it has the following restrictions:
1967 /// 1. The trait must indeed be a marker-like trait (i.e., no items), and must be
1969 /// 2. The trait-ref of both impls must be equal.
1970 /// 3. The trait-ref of both impls must be a trait object type consisting only of
1972 /// 4. Neither of the impls can have any where-clauses.
1974 /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed.
1978 impl<'tcx> TyCtxt<'tcx> {
1979 pub fn typeck_body(self, body: hir::BodyId) -> &'tcx TypeckResults<'tcx> {
1980 self.typeck(self.hir().body_owner_def_id(body))
1983 pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> {
1984 self.associated_items(id)
1985 .in_definition_order()
1986 .filter(|item| item.kind == AssocKind::Fn && item.defaultness.has_value())
1989 fn item_name_from_hir(self, def_id: DefId) -> Option<Ident> {
1990 self.hir().get_if_local(def_id).and_then(|node| node.ident())
1993 fn item_name_from_def_id(self, def_id: DefId) -> Option<Symbol> {
1994 if def_id.index == CRATE_DEF_INDEX {
1995 Some(self.crate_name(def_id.krate))
1997 let def_key = self.def_key(def_id);
1998 match def_key.disambiguated_data.data {
1999 // The name of a constructor is that of its parent.
2000 rustc_hir::definitions::DefPathData::Ctor => self.item_name_from_def_id(DefId {
2001 krate: def_id.krate,
2002 index: def_key.parent.unwrap(),
2004 _ => def_key.disambiguated_data.data.get_opt_name(),
2009 /// Look up the name of an item across crates. This does not look at HIR.
2011 /// When possible, this function should be used for cross-crate lookups over
2012 /// [`opt_item_name`] to avoid invalidating the incremental cache. If you
2013 /// need to handle items without a name, or HIR items that will not be
2014 /// serialized cross-crate, or if you need the span of the item, use
2015 /// [`opt_item_name`] instead.
2017 /// [`opt_item_name`]: Self::opt_item_name
2018 pub fn item_name(self, id: DefId) -> Symbol {
2019 // Look at cross-crate items first to avoid invalidating the incremental cache
2020 // unless we have to.
2021 self.item_name_from_def_id(id).unwrap_or_else(|| {
2022 bug!("item_name: no name for {:?}", self.def_path(id));
2026 /// Look up the name and span of an item or [`Node`].
2028 /// See [`item_name`][Self::item_name] for more information.
2029 pub fn opt_item_name(self, def_id: DefId) -> Option<Ident> {
2030 // Look at the HIR first so the span will be correct if this is a local item.
2031 self.item_name_from_hir(def_id)
2032 .or_else(|| self.item_name_from_def_id(def_id).map(Ident::with_dummy_span))
2035 pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> {
2036 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2037 Some(self.associated_item(def_id))
2043 pub fn field_index(self, hir_id: hir::HirId, typeck_results: &TypeckResults<'_>) -> usize {
2044 typeck_results.field_indices().get(hir_id).cloned().expect("no index for a field")
2047 pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
2051 .position(|field| self.hygienic_eq(ident, field.ident(self), variant.def_id))
2054 /// Returns `true` if the impls are the same polarity and the trait either
2055 /// has no items or is annotated `#[marker]` and prevents item overrides.
2056 pub fn impls_are_allowed_to_overlap(
2060 ) -> Option<ImplOverlapKind> {
2061 // If either trait impl references an error, they're allowed to overlap,
2062 // as one of them essentially doesn't exist.
2063 if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.references_error())
2064 || self.impl_trait_ref(def_id2).map_or(false, |tr| tr.references_error())
2066 return Some(ImplOverlapKind::Permitted { marker: false });
2069 match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) {
2070 (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => {
2071 // `#[rustc_reservation_impl]` impls don't overlap with anything
2073 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (reservations)",
2076 return Some(ImplOverlapKind::Permitted { marker: false });
2078 (ImplPolarity::Positive, ImplPolarity::Negative)
2079 | (ImplPolarity::Negative, ImplPolarity::Positive) => {
2080 // `impl AutoTrait for Type` + `impl !AutoTrait for Type`
2082 "impls_are_allowed_to_overlap({:?}, {:?}) - None (differing polarities)",
2087 (ImplPolarity::Positive, ImplPolarity::Positive)
2088 | (ImplPolarity::Negative, ImplPolarity::Negative) => {}
2091 let is_marker_overlap = {
2092 let is_marker_impl = |def_id: DefId| -> bool {
2093 let trait_ref = self.impl_trait_ref(def_id);
2094 trait_ref.map_or(false, |tr| self.trait_def(tr.def_id).is_marker)
2096 is_marker_impl(def_id1) && is_marker_impl(def_id2)
2099 if is_marker_overlap {
2101 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (marker overlap)",
2104 Some(ImplOverlapKind::Permitted { marker: true })
2106 if let Some(self_ty1) = self.issue33140_self_ty(def_id1) {
2107 if let Some(self_ty2) = self.issue33140_self_ty(def_id2) {
2108 if self_ty1 == self_ty2 {
2110 "impls_are_allowed_to_overlap({:?}, {:?}) - issue #33140 HACK",
2113 return Some(ImplOverlapKind::Issue33140);
2116 "impls_are_allowed_to_overlap({:?}, {:?}) - found {:?} != {:?}",
2117 def_id1, def_id2, self_ty1, self_ty2
2123 debug!("impls_are_allowed_to_overlap({:?}, {:?}) = None", def_id1, def_id2);
2128 /// Returns `ty::VariantDef` if `res` refers to a struct,
2129 /// or variant or their constructors, panics otherwise.
2130 pub fn expect_variant_res(self, res: Res) -> &'tcx VariantDef {
2132 Res::Def(DefKind::Variant, did) => {
2133 let enum_did = self.parent(did).unwrap();
2134 self.adt_def(enum_did).variant_with_id(did)
2136 Res::Def(DefKind::Struct | DefKind::Union, did) => self.adt_def(did).non_enum_variant(),
2137 Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => {
2138 let variant_did = self.parent(variant_ctor_did).unwrap();
2139 let enum_did = self.parent(variant_did).unwrap();
2140 self.adt_def(enum_did).variant_with_ctor_id(variant_ctor_did)
2142 Res::Def(DefKind::Ctor(CtorOf::Struct, ..), ctor_did) => {
2143 let struct_did = self.parent(ctor_did).expect("struct ctor has no parent");
2144 self.adt_def(struct_did).non_enum_variant()
2146 _ => bug!("expect_variant_res used with unexpected res {:?}", res),
2150 /// Returns the possibly-auto-generated MIR of a `(DefId, Subst)` pair.
2151 pub fn instance_mir(self, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> {
2153 ty::InstanceDef::Item(def) => match self.def_kind(def.did) {
2155 | DefKind::Static(..)
2156 | DefKind::AssocConst
2158 | DefKind::AnonConst
2159 | DefKind::InlineConst => self.mir_for_ctfe_opt_const_arg(def),
2160 // If the caller wants `mir_for_ctfe` of a function they should not be using
2161 // `instance_mir`, so we'll assume const fn also wants the optimized version.
2163 assert_eq!(def.const_param_did, None);
2164 self.optimized_mir(def.did)
2167 ty::InstanceDef::VtableShim(..)
2168 | ty::InstanceDef::ReifyShim(..)
2169 | ty::InstanceDef::Intrinsic(..)
2170 | ty::InstanceDef::FnPtrShim(..)
2171 | ty::InstanceDef::Virtual(..)
2172 | ty::InstanceDef::ClosureOnceShim { .. }
2173 | ty::InstanceDef::DropGlue(..)
2174 | ty::InstanceDef::CloneShim(..) => self.mir_shims(instance),
2178 /// Gets the attributes of a definition.
2179 pub fn get_attrs(self, did: DefId) -> Attributes<'tcx> {
2180 if let Some(did) = did.as_local() {
2181 self.hir().attrs(self.hir().local_def_id_to_hir_id(did))
2183 self.item_attrs(did)
2187 /// Determines whether an item is annotated with an attribute.
2188 pub fn has_attr(self, did: DefId, attr: Symbol) -> bool {
2189 self.sess.contains_name(&self.get_attrs(did), attr)
2192 /// Returns `true` if this is an `auto trait`.
2193 pub fn trait_is_auto(self, trait_def_id: DefId) -> bool {
2194 self.trait_def(trait_def_id).has_auto_impl
2197 /// Returns layout of a generator. Layout might be unavailable if the
2198 /// generator is tainted by errors.
2199 pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> {
2200 self.optimized_mir(def_id).generator_layout()
2203 /// Given the `DefId` of an impl, returns the `DefId` of the trait it implements.
2204 /// If it implements no trait, returns `None`.
2205 pub fn trait_id_of_impl(self, def_id: DefId) -> Option<DefId> {
2206 self.impl_trait_ref(def_id).map(|tr| tr.def_id)
2209 /// If the given defid describes a method belonging to an impl, returns the
2210 /// `DefId` of the impl that the method belongs to; otherwise, returns `None`.
2211 pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
2212 self.opt_associated_item(def_id).and_then(|trait_item| match trait_item.container {
2213 TraitContainer(_) => None,
2214 ImplContainer(def_id) => Some(def_id),
2218 /// Looks up the span of `impl_did` if the impl is local; otherwise returns `Err`
2219 /// with the name of the crate containing the impl.
2220 pub fn span_of_impl(self, impl_did: DefId) -> Result<Span, Symbol> {
2221 if let Some(impl_did) = impl_did.as_local() {
2222 Ok(self.def_span(impl_did))
2224 Err(self.crate_name(impl_did.krate))
2228 /// Hygienically compares a use-site name (`use_name`) for a field or an associated item with
2229 /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
2230 /// definition's parent/scope to perform comparison.
2231 pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
2232 // We could use `Ident::eq` here, but we deliberately don't. The name
2233 // comparison fails frequently, and we want to avoid the expensive
2234 // `normalize_to_macros_2_0()` calls required for the span comparison whenever possible.
2235 use_name.name == def_name.name
2239 .hygienic_eq(def_name.span.ctxt(), self.expn_that_defined(def_parent_def_id))
2242 pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident {
2243 ident.span.normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope));
2247 pub fn adjust_ident_and_get_scope(
2252 ) -> (Ident, DefId) {
2255 .normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope))
2256 .and_then(|actual_expansion| actual_expansion.expn_data().parent_module)
2257 .unwrap_or_else(|| self.parent_module(block).to_def_id());
2261 pub fn is_object_safe(self, key: DefId) -> bool {
2262 self.object_safety_violations(key).is_empty()
2266 pub fn is_const_fn_raw(self, def_id: DefId) -> bool {
2267 matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..))
2268 && self.impl_constness(def_id) == hir::Constness::Const
2272 /// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition.
2273 pub fn is_impl_trait_defn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<LocalDefId> {
2274 let def_id = def_id.as_local()?;
2275 if let Node::Item(item) = tcx.hir().get_by_def_id(def_id) {
2276 if let hir::ItemKind::OpaqueTy(ref opaque_ty) = item.kind {
2277 return match opaque_ty.origin {
2278 hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) => {
2281 hir::OpaqueTyOrigin::TyAlias => None,
2288 pub fn int_ty(ity: ast::IntTy) -> IntTy {
2290 ast::IntTy::Isize => IntTy::Isize,
2291 ast::IntTy::I8 => IntTy::I8,
2292 ast::IntTy::I16 => IntTy::I16,
2293 ast::IntTy::I32 => IntTy::I32,
2294 ast::IntTy::I64 => IntTy::I64,
2295 ast::IntTy::I128 => IntTy::I128,
2299 pub fn uint_ty(uty: ast::UintTy) -> UintTy {
2301 ast::UintTy::Usize => UintTy::Usize,
2302 ast::UintTy::U8 => UintTy::U8,
2303 ast::UintTy::U16 => UintTy::U16,
2304 ast::UintTy::U32 => UintTy::U32,
2305 ast::UintTy::U64 => UintTy::U64,
2306 ast::UintTy::U128 => UintTy::U128,
2310 pub fn float_ty(fty: ast::FloatTy) -> FloatTy {
2312 ast::FloatTy::F32 => FloatTy::F32,
2313 ast::FloatTy::F64 => FloatTy::F64,
2317 pub fn ast_int_ty(ity: IntTy) -> ast::IntTy {
2319 IntTy::Isize => ast::IntTy::Isize,
2320 IntTy::I8 => ast::IntTy::I8,
2321 IntTy::I16 => ast::IntTy::I16,
2322 IntTy::I32 => ast::IntTy::I32,
2323 IntTy::I64 => ast::IntTy::I64,
2324 IntTy::I128 => ast::IntTy::I128,
2328 pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy {
2330 UintTy::Usize => ast::UintTy::Usize,
2331 UintTy::U8 => ast::UintTy::U8,
2332 UintTy::U16 => ast::UintTy::U16,
2333 UintTy::U32 => ast::UintTy::U32,
2334 UintTy::U64 => ast::UintTy::U64,
2335 UintTy::U128 => ast::UintTy::U128,
2339 pub fn provide(providers: &mut ty::query::Providers) {
2340 closure::provide(providers);
2341 context::provide(providers);
2342 erase_regions::provide(providers);
2343 layout::provide(providers);
2344 util::provide(providers);
2345 print::provide(providers);
2346 super::util::bug::provide(providers);
2347 super::middle::provide(providers);
2348 *providers = ty::query::Providers {
2349 trait_impls_of: trait_def::trait_impls_of_provider,
2350 incoherent_impls: trait_def::incoherent_impls_provider,
2351 type_uninhabited_from: inhabitedness::type_uninhabited_from,
2352 const_param_default: consts::const_param_default,
2353 vtable_allocation: vtable::vtable_allocation_provider,
2358 /// A map for the local crate mapping each type to a vector of its
2359 /// inherent impls. This is not meant to be used outside of coherence;
2360 /// rather, you should request the vector for a specific type via
2361 /// `tcx.inherent_impls(def_id)` so as to minimize your dependencies
2362 /// (constructing this map requires touching the entire crate).
2363 #[derive(Clone, Debug, Default, HashStable)]
2364 pub struct CrateInherentImpls {
2365 pub inherent_impls: LocalDefIdMap<Vec<DefId>>,
2366 pub incoherent_impls: FxHashMap<SimplifiedType, Vec<LocalDefId>>,
2369 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, HashStable)]
2370 pub struct SymbolName<'tcx> {
2371 /// `&str` gives a consistent ordering, which ensures reproducible builds.
2372 pub name: &'tcx str,
2375 impl<'tcx> SymbolName<'tcx> {
2376 pub fn new(tcx: TyCtxt<'tcx>, name: &str) -> SymbolName<'tcx> {
2378 name: unsafe { str::from_utf8_unchecked(tcx.arena.alloc_slice(name.as_bytes())) },
2383 impl<'tcx> fmt::Display for SymbolName<'tcx> {
2384 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2385 fmt::Display::fmt(&self.name, fmt)
2389 impl<'tcx> fmt::Debug for SymbolName<'tcx> {
2390 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2391 fmt::Display::fmt(&self.name, fmt)
2395 #[derive(Debug, Default, Copy, Clone)]
2396 pub struct FoundRelationships {
2397 /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
2398 /// obligation, where:
2400 /// * `Foo` is not `Sized`
2401 /// * `(): Foo` may be satisfied
2402 pub self_in_trait: bool,
2403 /// This is true if we identified that this Ty (`?T`) is found in a `<_ as
2404 /// _>::AssocType = ?T`