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, TypeSuperFoldable};
13 pub use self::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
14 pub use self::AssocItemContainer::*;
15 pub use self::BorrowKind::*;
16 pub use self::IntVarValue::*;
17 pub use self::Variance::*;
18 use crate::metadata::ModChild;
19 use crate::middle::privacy::AccessLevels;
20 use crate::mir::{Body, GeneratorLayout};
21 use crate::traits::{self, Reveal};
23 use crate::ty::fast_reject::SimplifiedType;
24 use crate::ty::util::Discr;
29 use rustc_ast::node_id::NodeMap;
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, LifetimeRes, Res};
38 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LocalDefIdMap};
40 use rustc_index::vec::IndexVec;
41 use rustc_macros::HashStable;
42 use rustc_query_system::ich::StableHashingContext;
43 use rustc_span::hygiene::MacroKind;
44 use rustc_span::symbol::{kw, sym, Ident, Symbol};
45 use rustc_span::{ExpnId, Span};
46 use rustc_target::abi::{Align, VariantIdx};
51 use std::hash::{Hash, Hasher};
52 use std::ops::ControlFlow;
55 pub use crate::ty::diagnostics::*;
56 pub use rustc_type_ir::InferTy::*;
57 pub use rustc_type_ir::RegionKind::*;
58 pub use rustc_type_ir::TyKind::*;
59 pub use rustc_type_ir::*;
61 pub use self::binding::BindingMode;
62 pub use self::binding::BindingMode::*;
63 pub use self::closure::{
64 is_ancestor_or_same_capture, place_to_string_for_capture, BorrowKind, CaptureInfo,
65 CapturedPlace, ClosureKind, MinCaptureInformationMap, MinCaptureList,
66 RootVariableMinCaptureList, UpvarCapture, UpvarCaptureMap, UpvarId, UpvarListMap, UpvarPath,
69 pub use self::consts::{
70 Const, ConstInt, ConstKind, ConstS, InferConst, ScalarInt, Unevaluated, ValTree,
72 pub use self::context::{
73 tls, CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations,
74 CtxtInterners, DelaySpanBugEmitted, FreeRegionInfo, GeneratorDiagnosticData,
75 GeneratorInteriorTypeCause, GlobalCtxt, Lift, OnDiskCache, TyCtxt, TypeckResults, UserType,
76 UserTypeAnnotationIndex,
78 pub use self::instance::{Instance, InstanceDef};
79 pub use self::list::List;
80 pub use self::parameterized::ParameterizedOverTcx;
81 pub use self::rvalue_scopes::RvalueScopes;
82 pub use self::sty::BoundRegionKind::*;
84 Article, Binder, BoundRegion, BoundRegionKind, BoundTy, BoundTyKind, BoundVar,
85 BoundVariableKind, CanonicalPolyFnSig, ClosureSubsts, ClosureSubstsParts, ConstVid,
86 EarlyBinder, EarlyBoundRegion, ExistentialPredicate, ExistentialProjection,
87 ExistentialTraitRef, FnSig, FreeRegion, GenSig, GeneratorSubsts, GeneratorSubstsParts,
88 InlineConstSubsts, InlineConstSubstsParts, ParamConst, ParamTy, PolyExistentialProjection,
89 PolyExistentialTraitRef, PolyFnSig, PolyGenSig, PolyTraitRef, ProjectionTy, Region, RegionKind,
90 RegionVid, TraitRef, TyKind, TypeAndMut, UpvarSubsts, VarianceDiagInfo,
92 pub use self::trait_def::TraitDef;
95 pub mod abstract_const;
104 pub mod inhabitedness;
106 pub mod normalize_erasing_regions;
130 mod structural_impls;
135 pub type RegisteredTools = FxHashSet<Ident>;
138 pub struct ResolverOutputs {
139 pub visibilities: FxHashMap<LocalDefId, Visibility>,
140 /// This field is used to decide whether we should make `PRIVATE_IN_PUBLIC` a hard error.
141 pub has_pub_restricted: bool,
142 /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
143 pub expn_that_defined: FxHashMap<LocalDefId, ExpnId>,
144 /// Reference span for definitions.
145 pub source_span: IndexVec<LocalDefId, Span>,
146 pub access_levels: AccessLevels,
147 pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
148 pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
149 pub maybe_unused_extern_crates: Vec<(LocalDefId, Span)>,
150 pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>,
151 pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
152 /// Extern prelude entries. The value is `true` if the entry was introduced
153 /// via `extern crate` item and not `--extern` option or compiler built-in.
154 pub extern_prelude: FxHashMap<Symbol, bool>,
155 pub main_def: Option<MainDefinition>,
156 pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,
157 /// A list of proc macro LocalDefIds, written out in the order in which
158 /// they are declared in the static array generated by proc_macro_harness.
159 pub proc_macros: Vec<LocalDefId>,
160 /// Mapping from ident span to path span for paths that don't exist as written, but that
161 /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`.
162 pub confused_type_with_std_module: FxHashMap<Span, Span>,
163 pub registered_tools: RegisteredTools,
166 /// Resolutions that should only be used for lowering.
167 /// This struct is meant to be consumed by lowering.
169 pub struct ResolverAstLowering {
170 pub legacy_const_generic_args: FxHashMap<DefId, Option<Vec<usize>>>,
172 /// Resolutions for nodes that have a single resolution.
173 pub partial_res_map: NodeMap<hir::def::PartialRes>,
174 /// Resolutions for import nodes, which have multiple resolutions in different namespaces.
175 pub import_res_map: NodeMap<hir::def::PerNS<Option<Res<ast::NodeId>>>>,
176 /// Resolutions for labels (node IDs of their corresponding blocks or loops).
177 pub label_res_map: NodeMap<ast::NodeId>,
178 /// Resolutions for lifetimes.
179 pub lifetimes_res_map: NodeMap<LifetimeRes>,
180 /// Mapping from generics `def_id`s to TAIT generics `def_id`s.
181 /// For each captured lifetime (e.g., 'a), we create a new lifetime parameter that is a generic
182 /// defined on the TAIT, so we have type Foo<'a1> = ... and we establish a mapping in this
183 /// field from the original parameter 'a to the new parameter 'a1.
184 pub generics_def_id_map: Vec<FxHashMap<LocalDefId, LocalDefId>>,
185 /// Lifetime parameters that lowering will have to introduce.
186 pub extra_lifetime_params_map: NodeMap<Vec<(Ident, ast::NodeId, LifetimeRes)>>,
188 pub next_node_id: ast::NodeId,
190 pub node_id_to_def_id: FxHashMap<ast::NodeId, LocalDefId>,
191 pub def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
193 pub trait_map: NodeMap<Vec<hir::TraitCandidate>>,
194 /// A small map keeping true kinds of built-in macros that appear to be fn-like on
195 /// the surface (`macro` items in libcore), but are actually attributes or derives.
196 pub builtin_macro_kinds: FxHashMap<LocalDefId, MacroKind>,
199 #[derive(Clone, Copy, Debug)]
200 pub struct MainDefinition {
201 pub res: Res<ast::NodeId>,
206 impl MainDefinition {
207 pub fn opt_fn_def_id(self) -> Option<DefId> {
208 if let Res::Def(DefKind::Fn, def_id) = self.res { Some(def_id) } else { None }
212 /// The "header" of an impl is everything outside the body: a Self type, a trait
213 /// ref (in the case of a trait impl), and a set of predicates (from the
214 /// bounds / where-clauses).
215 #[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
216 pub struct ImplHeader<'tcx> {
217 pub impl_def_id: DefId,
218 pub self_ty: Ty<'tcx>,
219 pub trait_ref: Option<TraitRef<'tcx>>,
220 pub predicates: Vec<Predicate<'tcx>>,
223 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
224 pub enum ImplSubject<'tcx> {
225 Trait(TraitRef<'tcx>),
229 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable, Debug)]
230 #[derive(TypeFoldable, TypeVisitable)]
231 pub enum ImplPolarity {
232 /// `impl Trait for Type`
234 /// `impl !Trait for Type`
236 /// `#[rustc_reservation_impl] impl Trait for Type`
238 /// This is a "stability hack", not a real Rust feature.
239 /// See #64631 for details.
244 /// Flips polarity by turning `Positive` into `Negative` and `Negative` into `Positive`.
245 pub fn flip(&self) -> Option<ImplPolarity> {
247 ImplPolarity::Positive => Some(ImplPolarity::Negative),
248 ImplPolarity::Negative => Some(ImplPolarity::Positive),
249 ImplPolarity::Reservation => None,
254 impl fmt::Display for ImplPolarity {
255 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
257 Self::Positive => f.write_str("positive"),
258 Self::Negative => f.write_str("negative"),
259 Self::Reservation => f.write_str("reservation"),
264 #[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, Encodable, Decodable, HashStable)]
265 pub enum Visibility {
266 /// Visible everywhere (including in other crates).
268 /// Visible only in the given crate-local module.
270 /// Not visible anywhere in the local crate. This is the visibility of private external items.
274 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
275 pub enum BoundConstness {
278 /// `T: ~const Trait`
280 /// Requires resolving to const only when we are in a const context.
284 impl BoundConstness {
285 /// Reduce `self` and `constness` to two possible combined states instead of four.
286 pub fn and(&mut self, constness: hir::Constness) -> hir::Constness {
287 match (constness, self) {
288 (hir::Constness::Const, BoundConstness::ConstIfConst) => hir::Constness::Const,
290 *this = BoundConstness::NotConst;
291 hir::Constness::NotConst
297 impl fmt::Display for BoundConstness {
298 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
300 Self::NotConst => f.write_str("normal"),
301 Self::ConstIfConst => f.write_str("`~const`"),
306 #[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, TyEncodable, TyDecodable, HashStable)]
307 #[derive(TypeFoldable, TypeVisitable)]
308 pub struct ClosureSizeProfileData<'tcx> {
309 /// Tuple containing the types of closure captures before the feature `capture_disjoint_fields`
310 pub before_feature_tys: Ty<'tcx>,
311 /// Tuple containing the types of closure captures after the feature `capture_disjoint_fields`
312 pub after_feature_tys: Ty<'tcx>,
315 pub trait DefIdTree: Copy {
316 fn opt_parent(self, id: DefId) -> Option<DefId>;
320 fn parent(self, id: DefId) -> DefId {
321 match self.opt_parent(id) {
323 // not `unwrap_or_else` to avoid breaking caller tracking
324 None => bug!("{id:?} doesn't have a parent"),
330 fn opt_local_parent(self, id: LocalDefId) -> Option<LocalDefId> {
331 self.opt_parent(id.to_def_id()).map(DefId::expect_local)
336 fn local_parent(self, id: LocalDefId) -> LocalDefId {
337 self.parent(id.to_def_id()).expect_local()
340 fn is_descendant_of(self, mut descendant: DefId, ancestor: DefId) -> bool {
341 if descendant.krate != ancestor.krate {
345 while descendant != ancestor {
346 match self.opt_parent(descendant) {
347 Some(parent) => descendant = parent,
348 None => return false,
355 impl<'tcx> DefIdTree for TyCtxt<'tcx> {
357 fn opt_parent(self, id: DefId) -> Option<DefId> {
358 self.def_key(id).parent.map(|index| DefId { index, ..id })
363 /// Returns `true` if an item with this visibility is accessible from the given block.
364 pub fn is_accessible_from<T: DefIdTree>(self, module: DefId, tree: T) -> bool {
365 let restriction = match self {
366 // Public items are visible everywhere.
367 Visibility::Public => return true,
368 // Private items from other crates are visible nowhere.
369 Visibility::Invisible => return false,
370 // Restricted items are visible in an arbitrary local module.
371 Visibility::Restricted(other) if other.krate != module.krate => return false,
372 Visibility::Restricted(module) => module,
375 tree.is_descendant_of(module, restriction)
378 /// Returns `true` if this visibility is at least as accessible as the given visibility
379 pub fn is_at_least<T: DefIdTree>(self, vis: Visibility, tree: T) -> bool {
380 let vis_restriction = match vis {
381 Visibility::Public => return self == Visibility::Public,
382 Visibility::Invisible => return true,
383 Visibility::Restricted(module) => module,
386 self.is_accessible_from(vis_restriction, tree)
389 // Returns `true` if this item is visible anywhere in the local crate.
390 pub fn is_visible_locally(self) -> bool {
392 Visibility::Public => true,
393 Visibility::Restricted(def_id) => def_id.is_local(),
394 Visibility::Invisible => false,
398 pub fn is_public(self) -> bool {
399 matches!(self, Visibility::Public)
403 /// The crate variances map is computed during typeck and contains the
404 /// variance of every item in the local crate. You should not use it
405 /// directly, because to do so will make your pass dependent on the
406 /// HIR of every item in the local crate. Instead, use
407 /// `tcx.variances_of()` to get the variance for a *particular*
409 #[derive(HashStable, Debug)]
410 pub struct CrateVariancesMap<'tcx> {
411 /// For each item with generics, maps to a vector of the variance
412 /// of its generics. If an item has no generics, it will have no
414 pub variances: FxHashMap<DefId, &'tcx [ty::Variance]>,
417 // Contains information needed to resolve types and (in the future) look up
418 // the types of AST nodes.
419 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
420 pub struct CReaderCacheKey {
421 pub cnum: Option<CrateNum>,
425 /// Represents a type.
428 /// - This is a very "dumb" struct (with no derives and no `impls`).
429 /// - Values of this type are always interned and thus unique, and are stored
430 /// as an `Interned<TyS>`.
431 /// - `Ty` (which contains a reference to a `Interned<TyS>`) or `Interned<TyS>`
432 /// should be used everywhere instead of `TyS`. In particular, `Ty` has most
433 /// of the relevant methods.
434 #[derive(PartialEq, Eq, PartialOrd, Ord)]
435 #[allow(rustc::usage_of_ty_tykind)]
436 pub(crate) struct TyS<'tcx> {
437 /// This field shouldn't be used directly and may be removed in the future.
438 /// Use `Ty::kind()` instead.
441 /// This field provides fast access to information that is also contained
444 /// This field shouldn't be used directly and may be removed in the future.
445 /// Use `Ty::flags()` instead.
448 /// This field provides fast access to information that is also contained
451 /// This is a kind of confusing thing: it stores the smallest
454 /// (a) the binder itself captures nothing but
455 /// (b) all the late-bound things within the type are captured
456 /// by some sub-binder.
458 /// So, for a type without any late-bound things, like `u32`, this
459 /// will be *innermost*, because that is the innermost binder that
460 /// captures nothing. But for a type `&'D u32`, where `'D` is a
461 /// late-bound region with De Bruijn index `D`, this would be `D + 1`
462 /// -- the binder itself does not capture `D`, but `D` is captured
463 /// by an inner binder.
465 /// We call this concept an "exclusive" binder `D` because all
466 /// De Bruijn indices within the type are contained within `0..D`
468 outer_exclusive_binder: ty::DebruijnIndex,
471 // `TyS` is used a lot. Make sure it doesn't unintentionally get bigger.
472 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
473 static_assert_size!(TyS<'_>, 40);
475 // We are actually storing a stable hash cache next to the type, so let's
476 // also check the full size
477 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
478 static_assert_size!(WithStableHash<TyS<'_>>, 56);
480 /// Use this rather than `TyS`, whenever possible.
481 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
482 #[rustc_diagnostic_item = "Ty"]
483 #[rustc_pass_by_value]
484 pub struct Ty<'tcx>(Interned<'tcx, WithStableHash<TyS<'tcx>>>);
486 impl<'tcx> TyCtxt<'tcx> {
487 /// A "bool" type used in rustc_mir_transform unit tests when we
488 /// have not spun up a TyCtxt.
489 pub const BOOL_TY_FOR_UNIT_TESTING: Ty<'tcx> = Ty(Interned::new_unchecked(&WithStableHash {
492 flags: TypeFlags::empty(),
493 outer_exclusive_binder: DebruijnIndex::from_usize(0),
495 stable_hash: Fingerprint::ZERO,
499 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for TyS<'tcx> {
501 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
505 // The other fields just provide fast access to information that is
506 // also contained in `kind`, so no need to hash them.
509 outer_exclusive_binder: _,
512 kind.hash_stable(hcx, hasher)
516 impl ty::EarlyBoundRegion {
517 /// Does this early bound region have a name? Early bound regions normally
518 /// always have names except when using anonymous lifetimes (`'_`).
519 pub fn has_name(&self) -> bool {
520 self.name != kw::UnderscoreLifetime
524 /// Represents a predicate.
526 /// See comments on `TyS`, which apply here too (albeit for
527 /// `PredicateS`/`Predicate` rather than `TyS`/`Ty`).
529 pub(crate) struct PredicateS<'tcx> {
530 kind: Binder<'tcx, PredicateKind<'tcx>>,
532 /// See the comment for the corresponding field of [TyS].
533 outer_exclusive_binder: ty::DebruijnIndex,
536 // This type is used a lot. Make sure it doesn't unintentionally get bigger.
537 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
538 static_assert_size!(PredicateS<'_>, 56);
540 /// Use this rather than `PredicateS`, whenever possible.
541 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
542 #[rustc_pass_by_value]
543 pub struct Predicate<'tcx>(Interned<'tcx, PredicateS<'tcx>>);
545 impl<'tcx> Predicate<'tcx> {
546 /// Gets the inner `Binder<'tcx, PredicateKind<'tcx>>`.
548 pub fn kind(self) -> Binder<'tcx, PredicateKind<'tcx>> {
553 pub fn flags(self) -> TypeFlags {
558 pub fn outer_exclusive_binder(self) -> DebruijnIndex {
559 self.0.outer_exclusive_binder
562 /// Flips the polarity of a Predicate.
564 /// Given `T: Trait` predicate it returns `T: !Trait` and given `T: !Trait` returns `T: Trait`.
565 pub fn flip_polarity(self, tcx: TyCtxt<'tcx>) -> Option<Predicate<'tcx>> {
568 .map_bound(|kind| match kind {
569 PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) => {
570 Some(PredicateKind::Trait(TraitPredicate {
573 polarity: polarity.flip()?,
581 Some(tcx.mk_predicate(kind))
584 pub fn without_const(mut self, tcx: TyCtxt<'tcx>) -> Self {
585 if let PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) = self.kind().skip_binder()
586 && constness != BoundConstness::NotConst
588 self = tcx.mk_predicate(self.kind().rebind(PredicateKind::Trait(TraitPredicate {
590 constness: BoundConstness::NotConst,
598 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> {
599 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
603 // The other fields just provide fast access to information that is
604 // also contained in `kind`, so no need to hash them.
606 outer_exclusive_binder: _,
609 kind.hash_stable(hcx, hasher);
613 impl rustc_errors::IntoDiagnosticArg for Predicate<'_> {
614 fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
615 rustc_errors::DiagnosticArgValue::Str(std::borrow::Cow::Owned(self.to_string()))
619 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
620 #[derive(HashStable, TypeFoldable, TypeVisitable)]
621 pub enum PredicateKind<'tcx> {
622 /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
623 /// the `Self` type of the trait reference and `A`, `B`, and `C`
624 /// would be the type parameters.
625 Trait(TraitPredicate<'tcx>),
628 RegionOutlives(RegionOutlivesPredicate<'tcx>),
631 TypeOutlives(TypeOutlivesPredicate<'tcx>),
633 /// `where <T as TraitRef>::Name == X`, approximately.
634 /// See the `ProjectionPredicate` struct for details.
635 Projection(ProjectionPredicate<'tcx>),
637 /// No syntax: `T` well-formed.
638 WellFormed(GenericArg<'tcx>),
640 /// Trait must be object-safe.
643 /// No direct syntax. May be thought of as `where T: FnFoo<...>`
644 /// for some substitutions `...` and `T` being a closure type.
645 /// Satisfied (or refuted) once we know the closure's kind.
646 ClosureKind(DefId, SubstsRef<'tcx>, ClosureKind),
650 /// This obligation is created most often when we have two
651 /// unresolved type variables and hence don't have enough
652 /// information to process the subtyping obligation yet.
653 Subtype(SubtypePredicate<'tcx>),
655 /// `T1` coerced to `T2`
657 /// Like a subtyping obligation, this is created most often
658 /// when we have two unresolved type variables and hence
659 /// don't have enough information to process the coercion
660 /// obligation yet. At the moment, we actually process coercions
661 /// very much like subtyping and don't handle the full coercion
663 Coerce(CoercePredicate<'tcx>),
665 /// Constant initializer must evaluate successfully.
666 ConstEvaluatable(ty::Unevaluated<'tcx, ()>),
668 /// Constants must be equal. The first component is the const that is expected.
669 ConstEquate(Const<'tcx>, Const<'tcx>),
671 /// Represents a type found in the environment that we can use for implied bounds.
673 /// Only used for Chalk.
674 TypeWellFormedFromEnv(Ty<'tcx>),
677 /// The crate outlives map is computed during typeck and contains the
678 /// outlives of every item in the local crate. You should not use it
679 /// directly, because to do so will make your pass dependent on the
680 /// HIR of every item in the local crate. Instead, use
681 /// `tcx.inferred_outlives_of()` to get the outlives for a *particular*
683 #[derive(HashStable, Debug)]
684 pub struct CratePredicatesMap<'tcx> {
685 /// For each struct with outlive bounds, maps to a vector of the
686 /// predicate of its outlive bounds. If an item has no outlives
687 /// bounds, it will have no entry.
688 pub predicates: FxHashMap<DefId, &'tcx [(Predicate<'tcx>, Span)]>,
691 impl<'tcx> Predicate<'tcx> {
692 /// Performs a substitution suitable for going from a
693 /// poly-trait-ref to supertraits that must hold if that
694 /// poly-trait-ref holds. This is slightly different from a normal
695 /// substitution in terms of what happens with bound regions. See
696 /// lengthy comment below for details.
697 pub fn subst_supertrait(
700 trait_ref: &ty::PolyTraitRef<'tcx>,
701 ) -> Predicate<'tcx> {
702 // The interaction between HRTB and supertraits is not entirely
703 // obvious. Let me walk you (and myself) through an example.
705 // Let's start with an easy case. Consider two traits:
707 // trait Foo<'a>: Bar<'a,'a> { }
708 // trait Bar<'b,'c> { }
710 // Now, if we have a trait reference `for<'x> T: Foo<'x>`, then
711 // we can deduce that `for<'x> T: Bar<'x,'x>`. Basically, if we
712 // knew that `Foo<'x>` (for any 'x) then we also know that
713 // `Bar<'x,'x>` (for any 'x). This more-or-less falls out from
714 // normal substitution.
716 // In terms of why this is sound, the idea is that whenever there
717 // is an impl of `T:Foo<'a>`, it must show that `T:Bar<'a,'a>`
718 // holds. So if there is an impl of `T:Foo<'a>` that applies to
719 // all `'a`, then we must know that `T:Bar<'a,'a>` holds for all
722 // Another example to be careful of is this:
724 // trait Foo1<'a>: for<'b> Bar1<'a,'b> { }
725 // trait Bar1<'b,'c> { }
727 // Here, if we have `for<'x> T: Foo1<'x>`, then what do we know?
728 // The answer is that we know `for<'x,'b> T: Bar1<'x,'b>`. The
729 // reason is similar to the previous example: any impl of
730 // `T:Foo1<'x>` must show that `for<'b> T: Bar1<'x, 'b>`. So
731 // basically we would want to collapse the bound lifetimes from
732 // the input (`trait_ref`) and the supertraits.
734 // To achieve this in practice is fairly straightforward. Let's
735 // consider the more complicated scenario:
737 // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x`
738 // has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`,
739 // where both `'x` and `'b` would have a DB index of 1.
740 // The substitution from the input trait-ref is therefore going to be
741 // `'a => 'x` (where `'x` has a DB index of 1).
742 // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an
743 // early-bound parameter and `'b' is a late-bound parameter with a
745 // - If we replace `'a` with `'x` from the input, it too will have
746 // a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>`
747 // just as we wanted.
749 // There is only one catch. If we just apply the substitution `'a
750 // => 'x` to `for<'b> Bar1<'a,'b>`, the substitution code will
751 // adjust the DB index because we substituting into a binder (it
752 // tries to be so smart...) resulting in `for<'x> for<'b>
753 // Bar1<'x,'b>` (we have no syntax for this, so use your
754 // imagination). Basically the 'x will have DB index of 2 and 'b
755 // will have DB index of 1. Not quite what we want. So we apply
756 // the substitution to the *contents* of the trait reference,
757 // rather than the trait reference itself (put another way, the
758 // substitution code expects equal binding levels in the values
759 // from the substitution and the value being substituted into, and
760 // this trick achieves that).
762 // Working through the second example:
763 // trait_ref: for<'x> T: Foo1<'^0.0>; substs: [T, '^0.0]
764 // predicate: for<'b> Self: Bar1<'a, '^0.0>; substs: [Self, 'a, '^0.0]
765 // We want to end up with:
766 // for<'x, 'b> T: Bar1<'^0.0, '^0.1>
768 // 1) We must shift all bound vars in predicate by the length
769 // of trait ref's bound vars. So, we would end up with predicate like
770 // Self: Bar1<'a, '^0.1>
771 // 2) We can then apply the trait substs to this, ending up with
772 // T: Bar1<'^0.0, '^0.1>
773 // 3) Finally, to create the final bound vars, we concatenate the bound
774 // vars of the trait ref with those of the predicate:
776 let bound_pred = self.kind();
777 let pred_bound_vars = bound_pred.bound_vars();
778 let trait_bound_vars = trait_ref.bound_vars();
779 // 1) Self: Bar1<'a, '^0.0> -> Self: Bar1<'a, '^0.1>
781 tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
782 // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
783 let new = EarlyBinder(shifted_pred).subst(tcx, trait_ref.skip_binder().substs);
784 // 3) ['x] + ['b] -> ['x, 'b]
786 tcx.mk_bound_variable_kinds(trait_bound_vars.iter().chain(pred_bound_vars));
787 tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars))
791 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
792 #[derive(HashStable, TypeFoldable, TypeVisitable)]
793 pub struct TraitPredicate<'tcx> {
794 pub trait_ref: TraitRef<'tcx>,
796 pub constness: BoundConstness,
798 /// If polarity is Positive: we are proving that the trait is implemented.
800 /// If polarity is Negative: we are proving that a negative impl of this trait
801 /// exists. (Note that coherence also checks whether negative impls of supertraits
802 /// exist via a series of predicates.)
804 /// If polarity is Reserved: that's a bug.
805 pub polarity: ImplPolarity,
808 pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
810 impl<'tcx> TraitPredicate<'tcx> {
811 pub fn remap_constness(&mut self, param_env: &mut ParamEnv<'tcx>) {
812 *param_env = param_env.with_constness(self.constness.and(param_env.constness()))
815 /// Remap the constness of this predicate before emitting it for diagnostics.
816 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
817 // this is different to `remap_constness` that callees want to print this predicate
818 // in case of selection errors. `T: ~const Drop` bounds cannot end up here when the
819 // param_env is not const because it is always satisfied in non-const contexts.
820 if let hir::Constness::NotConst = param_env.constness() {
821 self.constness = ty::BoundConstness::NotConst;
825 pub fn def_id(self) -> DefId {
826 self.trait_ref.def_id
829 pub fn self_ty(self) -> Ty<'tcx> {
830 self.trait_ref.self_ty()
834 pub fn is_const_if_const(self) -> bool {
835 self.constness == BoundConstness::ConstIfConst
838 pub fn is_constness_satisfied_by(self, constness: hir::Constness) -> bool {
839 match (self.constness, constness) {
840 (BoundConstness::NotConst, _)
841 | (BoundConstness::ConstIfConst, hir::Constness::Const) => true,
842 (BoundConstness::ConstIfConst, hir::Constness::NotConst) => false,
847 impl<'tcx> PolyTraitPredicate<'tcx> {
848 pub fn def_id(self) -> DefId {
849 // Ok to skip binder since trait `DefId` does not care about regions.
850 self.skip_binder().def_id()
853 pub fn self_ty(self) -> ty::Binder<'tcx, Ty<'tcx>> {
854 self.map_bound(|trait_ref| trait_ref.self_ty())
857 /// Remap the constness of this predicate before emitting it for diagnostics.
858 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
859 *self = self.map_bound(|mut p| {
860 p.remap_constness_diag(param_env);
866 pub fn is_const_if_const(self) -> bool {
867 self.skip_binder().is_const_if_const()
871 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
872 #[derive(HashStable, TypeFoldable, TypeVisitable)]
873 pub struct OutlivesPredicate<A, B>(pub A, pub B); // `A: B`
874 pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>;
875 pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>;
876 pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>;
877 pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>;
879 /// Encodes that `a` must be a subtype of `b`. The `a_is_expected` flag indicates
880 /// whether the `a` type is the type that we should label as "expected" when
881 /// presenting user diagnostics.
882 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
883 #[derive(HashStable, TypeFoldable, TypeVisitable)]
884 pub struct SubtypePredicate<'tcx> {
885 pub a_is_expected: bool,
889 pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>;
891 /// Encodes that we have to coerce *from* the `a` type to the `b` type.
892 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
893 #[derive(HashStable, TypeFoldable, TypeVisitable)]
894 pub struct CoercePredicate<'tcx> {
898 pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
900 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, TyEncodable, TyDecodable)]
901 #[derive(HashStable, TypeFoldable, TypeVisitable)]
902 pub enum Term<'tcx> {
907 impl<'tcx> From<Ty<'tcx>> for Term<'tcx> {
908 fn from(ty: Ty<'tcx>) -> Self {
913 impl<'tcx> From<Const<'tcx>> for Term<'tcx> {
914 fn from(c: Const<'tcx>) -> Self {
919 impl<'tcx> Term<'tcx> {
920 pub fn ty(&self) -> Option<Ty<'tcx>> {
921 if let Term::Ty(ty) = self { Some(*ty) } else { None }
924 pub fn ct(&self) -> Option<Const<'tcx>> {
925 if let Term::Const(c) = self { Some(*c) } else { None }
928 pub fn into_arg(self) -> GenericArg<'tcx> {
930 Term::Ty(ty) => ty.into(),
931 Term::Const(c) => c.into(),
936 /// This kind of predicate has no *direct* correspondent in the
937 /// syntax, but it roughly corresponds to the syntactic forms:
939 /// 1. `T: TraitRef<..., Item = Type>`
940 /// 2. `<T as TraitRef<...>>::Item == Type` (NYI)
942 /// In particular, form #1 is "desugared" to the combination of a
943 /// normal trait predicate (`T: TraitRef<...>`) and one of these
944 /// predicates. Form #2 is a broader form in that it also permits
945 /// equality between arbitrary types. Processing an instance of
946 /// Form #2 eventually yields one of these `ProjectionPredicate`
947 /// instances to normalize the LHS.
948 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
949 #[derive(HashStable, TypeFoldable, TypeVisitable)]
950 pub struct ProjectionPredicate<'tcx> {
951 pub projection_ty: ProjectionTy<'tcx>,
952 pub term: Term<'tcx>,
955 pub type PolyProjectionPredicate<'tcx> = Binder<'tcx, ProjectionPredicate<'tcx>>;
957 impl<'tcx> PolyProjectionPredicate<'tcx> {
958 /// Returns the `DefId` of the trait of the associated item being projected.
960 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
961 self.skip_binder().projection_ty.trait_def_id(tcx)
964 /// Get the [PolyTraitRef] required for this projection to be well formed.
965 /// Note that for generic associated types the predicates of the associated
966 /// type also need to be checked.
968 pub fn required_poly_trait_ref(&self, tcx: TyCtxt<'tcx>) -> PolyTraitRef<'tcx> {
969 // Note: unlike with `TraitRef::to_poly_trait_ref()`,
970 // `self.0.trait_ref` is permitted to have escaping regions.
971 // This is because here `self` has a `Binder` and so does our
972 // return value, so we are preserving the number of binding
974 self.map_bound(|predicate| predicate.projection_ty.trait_ref(tcx))
977 pub fn term(&self) -> Binder<'tcx, Term<'tcx>> {
978 self.map_bound(|predicate| predicate.term)
981 /// The `DefId` of the `TraitItem` for the associated type.
983 /// Note that this is not the `DefId` of the `TraitRef` containing this
984 /// associated type, which is in `tcx.associated_item(projection_def_id()).container`.
985 pub fn projection_def_id(&self) -> DefId {
986 // Ok to skip binder since trait `DefId` does not care about regions.
987 self.skip_binder().projection_ty.item_def_id
991 pub trait ToPolyTraitRef<'tcx> {
992 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx>;
995 impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
996 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> {
997 self.map_bound_ref(|trait_pred| trait_pred.trait_ref)
1001 pub trait ToPredicate<'tcx> {
1002 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx>;
1005 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
1007 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1008 tcx.mk_predicate(self)
1012 impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
1013 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1014 self.map_bound(PredicateKind::Trait).to_predicate(tcx)
1018 impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
1019 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1020 self.map_bound(PredicateKind::RegionOutlives).to_predicate(tcx)
1024 impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> {
1025 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1026 self.map_bound(PredicateKind::TypeOutlives).to_predicate(tcx)
1030 impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
1031 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1032 self.map_bound(PredicateKind::Projection).to_predicate(tcx)
1036 impl<'tcx> Predicate<'tcx> {
1037 pub fn to_opt_poly_trait_pred(self) -> Option<PolyTraitPredicate<'tcx>> {
1038 let predicate = self.kind();
1039 match predicate.skip_binder() {
1040 PredicateKind::Trait(t) => Some(predicate.rebind(t)),
1041 PredicateKind::Projection(..)
1042 | PredicateKind::Subtype(..)
1043 | PredicateKind::Coerce(..)
1044 | PredicateKind::RegionOutlives(..)
1045 | PredicateKind::WellFormed(..)
1046 | PredicateKind::ObjectSafe(..)
1047 | PredicateKind::ClosureKind(..)
1048 | PredicateKind::TypeOutlives(..)
1049 | PredicateKind::ConstEvaluatable(..)
1050 | PredicateKind::ConstEquate(..)
1051 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1055 pub fn to_opt_poly_projection_pred(self) -> Option<PolyProjectionPredicate<'tcx>> {
1056 let predicate = self.kind();
1057 match predicate.skip_binder() {
1058 PredicateKind::Projection(t) => Some(predicate.rebind(t)),
1059 PredicateKind::Trait(..)
1060 | PredicateKind::Subtype(..)
1061 | PredicateKind::Coerce(..)
1062 | PredicateKind::RegionOutlives(..)
1063 | PredicateKind::WellFormed(..)
1064 | PredicateKind::ObjectSafe(..)
1065 | PredicateKind::ClosureKind(..)
1066 | PredicateKind::TypeOutlives(..)
1067 | PredicateKind::ConstEvaluatable(..)
1068 | PredicateKind::ConstEquate(..)
1069 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1073 pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> {
1074 let predicate = self.kind();
1075 match predicate.skip_binder() {
1076 PredicateKind::TypeOutlives(data) => Some(predicate.rebind(data)),
1077 PredicateKind::Trait(..)
1078 | PredicateKind::Projection(..)
1079 | PredicateKind::Subtype(..)
1080 | PredicateKind::Coerce(..)
1081 | PredicateKind::RegionOutlives(..)
1082 | PredicateKind::WellFormed(..)
1083 | PredicateKind::ObjectSafe(..)
1084 | PredicateKind::ClosureKind(..)
1085 | PredicateKind::ConstEvaluatable(..)
1086 | PredicateKind::ConstEquate(..)
1087 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1092 /// Represents the bounds declared on a particular set of type
1093 /// parameters. Should eventually be generalized into a flag list of
1094 /// where-clauses. You can obtain an `InstantiatedPredicates` list from a
1095 /// `GenericPredicates` by using the `instantiate` method. Note that this method
1096 /// reflects an important semantic invariant of `InstantiatedPredicates`: while
1097 /// the `GenericPredicates` are expressed in terms of the bound type
1098 /// parameters of the impl/trait/whatever, an `InstantiatedPredicates` instance
1099 /// represented a set of bounds for some particular instantiation,
1100 /// meaning that the generic parameters have been substituted with
1104 /// ```ignore (illustrative)
1105 /// struct Foo<T, U: Bar<T>> { ... }
1107 /// Here, the `GenericPredicates` for `Foo` would contain a list of bounds like
1108 /// `[[], [U:Bar<T>]]`. Now if there were some particular reference
1109 /// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[],
1110 /// [usize:Bar<isize>]]`.
1111 #[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
1112 pub struct InstantiatedPredicates<'tcx> {
1113 pub predicates: Vec<Predicate<'tcx>>,
1114 pub spans: Vec<Span>,
1117 impl<'tcx> InstantiatedPredicates<'tcx> {
1118 pub fn empty() -> InstantiatedPredicates<'tcx> {
1119 InstantiatedPredicates { predicates: vec![], spans: vec![] }
1122 pub fn is_empty(&self) -> bool {
1123 self.predicates.is_empty()
1127 #[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable, Lift)]
1128 #[derive(TypeFoldable, TypeVisitable)]
1129 pub struct OpaqueTypeKey<'tcx> {
1130 pub def_id: LocalDefId,
1131 pub substs: SubstsRef<'tcx>,
1134 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
1135 pub struct OpaqueHiddenType<'tcx> {
1136 /// The span of this particular definition of the opaque type. So
1139 /// ```ignore (incomplete snippet)
1140 /// type Foo = impl Baz;
1141 /// fn bar() -> Foo {
1142 /// // ^^^ This is the span we are looking for!
1146 /// In cases where the fn returns `(impl Trait, impl Trait)` or
1147 /// other such combinations, the result is currently
1148 /// over-approximated, but better than nothing.
1151 /// The type variable that represents the value of the opaque type
1152 /// that we require. In other words, after we compile this function,
1153 /// we will be created a constraint like:
1154 /// ```ignore (pseudo-rust)
1157 /// where `?C` is the value of this type variable. =) It may
1158 /// naturally refer to the type and lifetime parameters in scope
1159 /// in this function, though ultimately it should only reference
1160 /// those that are arguments to `Foo` in the constraint above. (In
1161 /// other words, `?C` should not include `'b`, even though it's a
1162 /// lifetime parameter on `foo`.)
1166 impl<'tcx> OpaqueHiddenType<'tcx> {
1167 pub fn report_mismatch(&self, other: &Self, tcx: TyCtxt<'tcx>) {
1168 // Found different concrete types for the opaque type.
1169 let mut err = tcx.sess.struct_span_err(
1171 "concrete type differs from previous defining opaque type use",
1173 err.span_label(other.span, format!("expected `{}`, got `{}`", self.ty, other.ty));
1174 if self.span == other.span {
1177 "this expression supplies two conflicting concrete types for the same opaque type",
1180 err.span_note(self.span, "previous use here");
1186 /// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are
1187 /// identified by both a universe, as well as a name residing within that universe. Distinct bound
1188 /// regions/types/consts within the same universe simply have an unknown relationship to one
1190 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
1191 #[derive(HashStable, TyEncodable, TyDecodable)]
1192 pub struct Placeholder<T> {
1193 pub universe: UniverseIndex,
1197 pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
1199 pub type PlaceholderType = Placeholder<BoundVar>;
1201 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
1202 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
1203 pub struct BoundConst<'tcx> {
1208 pub type PlaceholderConst<'tcx> = Placeholder<BoundVar>;
1210 /// A `DefId` which, in case it is a const argument, is potentially bundled with
1211 /// the `DefId` of the generic parameter it instantiates.
1213 /// This is used to avoid calls to `type_of` for const arguments during typeck
1214 /// which cause cycle errors.
1219 /// fn foo<const N: usize>(&self) -> [u8; N] { [0; N] }
1220 /// // ^ const parameter
1224 /// fn foo<const M: u8>(&self) -> usize { 42 }
1225 /// // ^ const parameter
1230 /// let _b = a.foo::<{ 3 + 7 }>();
1231 /// // ^^^^^^^^^ const argument
1235 /// Let's look at the call `a.foo::<{ 3 + 7 }>()` here. We do not know
1236 /// which `foo` is used until we know the type of `a`.
1238 /// We only know the type of `a` once we are inside of `typeck(main)`.
1239 /// We also end up normalizing the type of `_b` during `typeck(main)` which
1240 /// requires us to evaluate the const argument.
1242 /// To evaluate that const argument we need to know its type,
1243 /// which we would get using `type_of(const_arg)`. This requires us to
1244 /// resolve `foo` as it can be either `usize` or `u8` in this example.
1245 /// However, resolving `foo` once again requires `typeck(main)` to get the type of `a`,
1246 /// which results in a cycle.
1248 /// In short we must not call `type_of(const_arg)` during `typeck(main)`.
1250 /// When first creating the `ty::Const` of the const argument inside of `typeck` we have
1251 /// already resolved `foo` so we know which const parameter this argument instantiates.
1252 /// This means that we also know the expected result of `type_of(const_arg)` even if we
1253 /// aren't allowed to call that query: it is equal to `type_of(const_param)` which is
1254 /// trivial to compute.
1256 /// If we now want to use that constant in a place which potentially needs its type
1257 /// we also pass the type of its `const_param`. This is the point of `WithOptConstParam`,
1258 /// except that instead of a `Ty` we bundle the `DefId` of the const parameter.
1259 /// Meaning that we need to use `type_of(const_param_did)` if `const_param_did` is `Some`
1260 /// to get the type of `did`.
1261 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, Lift, TyEncodable, TyDecodable)]
1262 #[derive(PartialEq, Eq, PartialOrd, Ord)]
1263 #[derive(Hash, HashStable)]
1264 pub struct WithOptConstParam<T> {
1266 /// The `DefId` of the corresponding generic parameter in case `did` is
1267 /// a const argument.
1269 /// Note that even if `did` is a const argument, this may still be `None`.
1270 /// All queries taking `WithOptConstParam` start by calling `tcx.opt_const_param_of(def.did)`
1271 /// to potentially update `param_did` in the case it is `None`.
1272 pub const_param_did: Option<DefId>,
1275 impl<T> WithOptConstParam<T> {
1276 /// Creates a new `WithOptConstParam` setting `const_param_did` to `None`.
1278 pub fn unknown(did: T) -> WithOptConstParam<T> {
1279 WithOptConstParam { did, const_param_did: None }
1283 impl WithOptConstParam<LocalDefId> {
1284 /// Returns `Some((did, param_did))` if `def_id` is a const argument,
1285 /// `None` otherwise.
1287 pub fn try_lookup(did: LocalDefId, tcx: TyCtxt<'_>) -> Option<(LocalDefId, DefId)> {
1288 tcx.opt_const_param_of(did).map(|param_did| (did, param_did))
1291 /// In case `self` is unknown but `self.did` is a const argument, this returns
1292 /// a `WithOptConstParam` with the correct `const_param_did`.
1294 pub fn try_upgrade(self, tcx: TyCtxt<'_>) -> Option<WithOptConstParam<LocalDefId>> {
1295 if self.const_param_did.is_none() {
1296 if let const_param_did @ Some(_) = tcx.opt_const_param_of(self.did) {
1297 return Some(WithOptConstParam { did: self.did, const_param_did });
1304 pub fn to_global(self) -> WithOptConstParam<DefId> {
1305 WithOptConstParam { did: self.did.to_def_id(), const_param_did: self.const_param_did }
1308 pub fn def_id_for_type_of(self) -> DefId {
1309 if let Some(did) = self.const_param_did { did } else { self.did.to_def_id() }
1313 impl WithOptConstParam<DefId> {
1314 pub fn as_local(self) -> Option<WithOptConstParam<LocalDefId>> {
1317 .map(|did| WithOptConstParam { did, const_param_did: self.const_param_did })
1320 pub fn as_const_arg(self) -> Option<(LocalDefId, DefId)> {
1321 if let Some(param_did) = self.const_param_did {
1322 if let Some(did) = self.did.as_local() {
1323 return Some((did, param_did));
1330 pub fn is_local(self) -> bool {
1334 pub fn def_id_for_type_of(self) -> DefId {
1335 self.const_param_did.unwrap_or(self.did)
1339 /// When type checking, we use the `ParamEnv` to track
1340 /// details about the set of where-clauses that are in scope at this
1341 /// particular point.
1342 #[derive(Copy, Clone, Hash, PartialEq, Eq)]
1343 pub struct ParamEnv<'tcx> {
1344 /// This packs both caller bounds and the reveal enum into one pointer.
1346 /// Caller bounds are `Obligation`s that the caller must satisfy. This is
1347 /// basically the set of bounds on the in-scope type parameters, translated
1348 /// into `Obligation`s, and elaborated and normalized.
1350 /// Use the `caller_bounds()` method to access.
1352 /// Typically, this is `Reveal::UserFacing`, but during codegen we
1353 /// want `Reveal::All`.
1355 /// Note: This is packed, use the reveal() method to access it.
1356 packed: CopyTaggedPtr<&'tcx List<Predicate<'tcx>>, ParamTag, true>,
1359 #[derive(Copy, Clone)]
1361 reveal: traits::Reveal,
1362 constness: hir::Constness,
1365 unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag {
1366 const BITS: usize = 2;
1368 fn into_usize(self) -> usize {
1370 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0,
1371 Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1,
1372 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2,
1373 Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3,
1377 unsafe fn from_usize(ptr: usize) -> Self {
1379 0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
1380 1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
1381 2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
1382 3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const },
1383 _ => std::hint::unreachable_unchecked(),
1388 impl<'tcx> fmt::Debug for ParamEnv<'tcx> {
1389 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1390 f.debug_struct("ParamEnv")
1391 .field("caller_bounds", &self.caller_bounds())
1392 .field("reveal", &self.reveal())
1393 .field("constness", &self.constness())
1398 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
1399 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1400 self.caller_bounds().hash_stable(hcx, hasher);
1401 self.reveal().hash_stable(hcx, hasher);
1402 self.constness().hash_stable(hcx, hasher);
1406 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
1407 fn try_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>(
1410 ) -> Result<Self, F::Error> {
1412 self.caller_bounds().try_fold_with(folder)?,
1413 self.reveal().try_fold_with(folder)?,
1414 self.constness().try_fold_with(folder)?,
1419 impl<'tcx> TypeVisitable<'tcx> for ParamEnv<'tcx> {
1420 fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1421 self.caller_bounds().visit_with(visitor)?;
1422 self.reveal().visit_with(visitor)?;
1423 self.constness().visit_with(visitor)
1427 impl<'tcx> ParamEnv<'tcx> {
1428 /// Construct a trait environment suitable for contexts where
1429 /// there are no where-clauses in scope. Hidden types (like `impl
1430 /// Trait`) are left hidden, so this is suitable for ordinary
1433 pub fn empty() -> Self {
1434 Self::new(List::empty(), Reveal::UserFacing, hir::Constness::NotConst)
1438 pub fn caller_bounds(self) -> &'tcx List<Predicate<'tcx>> {
1439 self.packed.pointer()
1443 pub fn reveal(self) -> traits::Reveal {
1444 self.packed.tag().reveal
1448 pub fn constness(self) -> hir::Constness {
1449 self.packed.tag().constness
1453 pub fn is_const(self) -> bool {
1454 self.packed.tag().constness == hir::Constness::Const
1457 /// Construct a trait environment with no where-clauses in scope
1458 /// where the values of all `impl Trait` and other hidden types
1459 /// are revealed. This is suitable for monomorphized, post-typeck
1460 /// environments like codegen or doing optimizations.
1462 /// N.B., if you want to have predicates in scope, use `ParamEnv::new`,
1463 /// or invoke `param_env.with_reveal_all()`.
1465 pub fn reveal_all() -> Self {
1466 Self::new(List::empty(), Reveal::All, hir::Constness::NotConst)
1469 /// Construct a trait environment with the given set of predicates.
1472 caller_bounds: &'tcx List<Predicate<'tcx>>,
1474 constness: hir::Constness,
1476 ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal, constness }) }
1479 pub fn with_user_facing(mut self) -> Self {
1480 self.packed.set_tag(ParamTag { reveal: Reveal::UserFacing, ..self.packed.tag() });
1485 pub fn with_constness(mut self, constness: hir::Constness) -> Self {
1486 self.packed.set_tag(ParamTag { constness, ..self.packed.tag() });
1491 pub fn with_const(mut self) -> Self {
1492 self.packed.set_tag(ParamTag { constness: hir::Constness::Const, ..self.packed.tag() });
1497 pub fn without_const(mut self) -> Self {
1498 self.packed.set_tag(ParamTag { constness: hir::Constness::NotConst, ..self.packed.tag() });
1503 pub fn remap_constness_with(&mut self, mut constness: ty::BoundConstness) {
1504 *self = self.with_constness(constness.and(self.constness()))
1507 /// Returns a new parameter environment with the same clauses, but
1508 /// which "reveals" the true results of projections in all cases
1509 /// (even for associated types that are specializable). This is
1510 /// the desired behavior during codegen and certain other special
1511 /// contexts; normally though we want to use `Reveal::UserFacing`,
1512 /// which is the default.
1513 /// All opaque types in the caller_bounds of the `ParamEnv`
1514 /// will be normalized to their underlying types.
1515 /// See PR #65989 and issue #65918 for more details
1516 pub fn with_reveal_all_normalized(self, tcx: TyCtxt<'tcx>) -> Self {
1517 if self.packed.tag().reveal == traits::Reveal::All {
1522 tcx.normalize_opaque_types(self.caller_bounds()),
1528 /// Returns this same environment but with no caller bounds.
1530 pub fn without_caller_bounds(self) -> Self {
1531 Self::new(List::empty(), self.reveal(), self.constness())
1534 /// Creates a suitable environment in which to perform trait
1535 /// queries on the given value. When type-checking, this is simply
1536 /// the pair of the environment plus value. But when reveal is set to
1537 /// All, then if `value` does not reference any type parameters, we will
1538 /// pair it with the empty environment. This improves caching and is generally
1541 /// N.B., we preserve the environment when type-checking because it
1542 /// is possible for the user to have wacky where-clauses like
1543 /// `where Box<u32>: Copy`, which are clearly never
1544 /// satisfiable. We generally want to behave as if they were true,
1545 /// although the surrounding function is never reachable.
1546 pub fn and<T: TypeVisitable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
1547 match self.reveal() {
1548 Reveal::UserFacing => ParamEnvAnd { param_env: self, value },
1551 if value.is_global() {
1552 ParamEnvAnd { param_env: self.without_caller_bounds(), value }
1554 ParamEnvAnd { param_env: self, value }
1561 // FIXME(ecstaticmorse): Audit all occurrences of `without_const().to_predicate(tcx)` to ensure that
1562 // the constness of trait bounds is being propagated correctly.
1563 impl<'tcx> PolyTraitRef<'tcx> {
1565 pub fn with_constness(self, constness: BoundConstness) -> PolyTraitPredicate<'tcx> {
1566 self.map_bound(|trait_ref| ty::TraitPredicate {
1569 polarity: ty::ImplPolarity::Positive,
1574 pub fn without_const(self) -> PolyTraitPredicate<'tcx> {
1575 self.with_constness(BoundConstness::NotConst)
1579 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
1580 #[derive(HashStable)]
1581 pub struct ParamEnvAnd<'tcx, T> {
1582 pub param_env: ParamEnv<'tcx>,
1586 impl<'tcx, T> ParamEnvAnd<'tcx, T> {
1587 pub fn into_parts(self) -> (ParamEnv<'tcx>, T) {
1588 (self.param_env, self.value)
1592 pub fn without_const(mut self) -> Self {
1593 self.param_env = self.param_env.without_const();
1598 #[derive(Copy, Clone, Debug, HashStable, Encodable, Decodable)]
1599 pub struct Destructor {
1600 /// The `DefId` of the destructor method
1602 /// The constness of the destructor method
1603 pub constness: hir::Constness,
1607 #[derive(HashStable, TyEncodable, TyDecodable)]
1608 pub struct VariantFlags: u32 {
1609 const NO_VARIANT_FLAGS = 0;
1610 /// Indicates whether the field list of this variant is `#[non_exhaustive]`.
1611 const IS_FIELD_LIST_NON_EXHAUSTIVE = 1 << 0;
1612 /// Indicates whether this variant was obtained as part of recovering from
1613 /// a syntactic error. May be incomplete or bogus.
1614 const IS_RECOVERED = 1 << 1;
1618 /// Definition of a variant -- a struct's fields or an enum variant.
1619 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1620 pub struct VariantDef {
1621 /// `DefId` that identifies the variant itself.
1622 /// If this variant belongs to a struct or union, then this is a copy of its `DefId`.
1624 /// `DefId` that identifies the variant's constructor.
1625 /// If this variant is a struct variant, then this is `None`.
1626 pub ctor_def_id: Option<DefId>,
1627 /// Variant or struct name.
1629 /// Discriminant of this variant.
1630 pub discr: VariantDiscr,
1631 /// Fields of this variant.
1632 pub fields: Vec<FieldDef>,
1633 /// Type of constructor of variant.
1634 pub ctor_kind: CtorKind,
1635 /// Flags of the variant (e.g. is field list non-exhaustive)?
1636 flags: VariantFlags,
1640 /// Creates a new `VariantDef`.
1642 /// `variant_did` is the `DefId` that identifies the enum variant (if this `VariantDef`
1643 /// represents an enum variant).
1645 /// `ctor_did` is the `DefId` that identifies the constructor of unit or
1646 /// tuple-variants/structs. If this is a `struct`-variant then this should be `None`.
1648 /// `parent_did` is the `DefId` of the `AdtDef` representing the enum or struct that
1649 /// owns this variant. It is used for checking if a struct has `#[non_exhaustive]` w/out having
1650 /// to go through the redirect of checking the ctor's attributes - but compiling a small crate
1651 /// requires loading the `AdtDef`s for all the structs in the universe (e.g., coherence for any
1652 /// built-in trait), and we do not want to load attributes twice.
1654 /// If someone speeds up attribute loading to not be a performance concern, they can
1655 /// remove this hack and use the constructor `DefId` everywhere.
1658 variant_did: Option<DefId>,
1659 ctor_def_id: Option<DefId>,
1660 discr: VariantDiscr,
1661 fields: Vec<FieldDef>,
1662 ctor_kind: CtorKind,
1666 is_field_list_non_exhaustive: bool,
1669 "VariantDef::new(name = {:?}, variant_did = {:?}, ctor_def_id = {:?}, discr = {:?},
1670 fields = {:?}, ctor_kind = {:?}, adt_kind = {:?}, parent_did = {:?})",
1671 name, variant_did, ctor_def_id, discr, fields, ctor_kind, adt_kind, parent_did,
1674 let mut flags = VariantFlags::NO_VARIANT_FLAGS;
1675 if is_field_list_non_exhaustive {
1676 flags |= VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE;
1680 flags |= VariantFlags::IS_RECOVERED;
1684 def_id: variant_did.unwrap_or(parent_did),
1694 /// Is this field list non-exhaustive?
1696 pub fn is_field_list_non_exhaustive(&self) -> bool {
1697 self.flags.intersects(VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE)
1700 /// Was this variant obtained as part of recovering from a syntactic error?
1702 pub fn is_recovered(&self) -> bool {
1703 self.flags.intersects(VariantFlags::IS_RECOVERED)
1706 /// Computes the `Ident` of this variant by looking up the `Span`
1707 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1708 Ident::new(self.name, tcx.def_ident_span(self.def_id).unwrap())
1712 impl PartialEq for VariantDef {
1714 fn eq(&self, other: &Self) -> bool {
1715 // There should be only one `VariantDef` for each `def_id`, therefore
1716 // it is fine to implement `PartialEq` only based on `def_id`.
1718 // Below, we exhaustively destructure `self` and `other` so that if the
1719 // definition of `VariantDef` changes, a compile-error will be produced,
1720 // reminding us to revisit this assumption.
1742 lhs_def_id == rhs_def_id
1746 impl Eq for VariantDef {}
1748 impl Hash for VariantDef {
1750 fn hash<H: Hasher>(&self, s: &mut H) {
1751 // There should be only one `VariantDef` for each `def_id`, therefore
1752 // it is fine to implement `Hash` only based on `def_id`.
1754 // Below, we exhaustively destructure `self` so that if the definition
1755 // of `VariantDef` changes, a compile-error will be produced, reminding
1756 // us to revisit this assumption.
1758 let Self { def_id, ctor_def_id: _, name: _, discr: _, fields: _, ctor_kind: _, flags: _ } =
1765 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
1766 pub enum VariantDiscr {
1767 /// Explicit value for this variant, i.e., `X = 123`.
1768 /// The `DefId` corresponds to the embedded constant.
1771 /// The previous variant's discriminant plus one.
1772 /// For efficiency reasons, the distance from the
1773 /// last `Explicit` discriminant is being stored,
1774 /// or `0` for the first variant, if it has none.
1778 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1779 pub struct FieldDef {
1782 pub vis: Visibility,
1785 impl PartialEq for FieldDef {
1787 fn eq(&self, other: &Self) -> bool {
1788 // There should be only one `FieldDef` for each `did`, therefore it is
1789 // fine to implement `PartialEq` only based on `did`.
1791 // Below, we exhaustively destructure `self` so that if the definition
1792 // of `FieldDef` changes, a compile-error will be produced, reminding
1793 // us to revisit this assumption.
1795 let Self { did: lhs_did, name: _, vis: _ } = &self;
1797 let Self { did: rhs_did, name: _, vis: _ } = other;
1803 impl Eq for FieldDef {}
1805 impl Hash for FieldDef {
1807 fn hash<H: Hasher>(&self, s: &mut H) {
1808 // There should be only one `FieldDef` for each `did`, therefore it is
1809 // fine to implement `Hash` only based on `did`.
1811 // Below, we exhaustively destructure `self` so that if the definition
1812 // of `FieldDef` changes, a compile-error will be produced, reminding
1813 // us to revisit this assumption.
1815 let Self { did, name: _, vis: _ } = &self;
1822 #[derive(TyEncodable, TyDecodable, Default, HashStable)]
1823 pub struct ReprFlags: u8 {
1824 const IS_C = 1 << 0;
1825 const IS_SIMD = 1 << 1;
1826 const IS_TRANSPARENT = 1 << 2;
1827 // Internal only for now. If true, don't reorder fields.
1828 const IS_LINEAR = 1 << 3;
1829 // If true, the type's layout can be randomized using
1830 // the seed stored in `ReprOptions.layout_seed`
1831 const RANDOMIZE_LAYOUT = 1 << 4;
1832 // Any of these flags being set prevent field reordering optimisation.
1833 const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
1834 | ReprFlags::IS_SIMD.bits
1835 | ReprFlags::IS_LINEAR.bits;
1839 /// Represents the repr options provided by the user,
1840 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Default, HashStable)]
1841 pub struct ReprOptions {
1842 pub int: Option<attr::IntType>,
1843 pub align: Option<Align>,
1844 pub pack: Option<Align>,
1845 pub flags: ReprFlags,
1846 /// The seed to be used for randomizing a type's layout
1848 /// Note: This could technically be a `[u8; 16]` (a `u128`) which would
1849 /// be the "most accurate" hash as it'd encompass the item and crate
1850 /// hash without loss, but it does pay the price of being larger.
1851 /// Everything's a tradeoff, a `u64` seed should be sufficient for our
1852 /// purposes (primarily `-Z randomize-layout`)
1853 pub field_shuffle_seed: u64,
1857 pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions {
1858 let mut flags = ReprFlags::empty();
1859 let mut size = None;
1860 let mut max_align: Option<Align> = None;
1861 let mut min_pack: Option<Align> = None;
1863 // Generate a deterministically-derived seed from the item's path hash
1864 // to allow for cross-crate compilation to actually work
1865 let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash();
1867 // If the user defined a custom seed for layout randomization, xor the item's
1868 // path hash with the user defined seed, this will allowing determinism while
1869 // still allowing users to further randomize layout generation for e.g. fuzzing
1870 if let Some(user_seed) = tcx.sess.opts.unstable_opts.layout_seed {
1871 field_shuffle_seed ^= user_seed;
1874 for attr in tcx.get_attrs(did, sym::repr) {
1875 for r in attr::parse_repr_attr(&tcx.sess, attr) {
1876 flags.insert(match r {
1877 attr::ReprC => ReprFlags::IS_C,
1878 attr::ReprPacked(pack) => {
1879 let pack = Align::from_bytes(pack as u64).unwrap();
1880 min_pack = Some(if let Some(min_pack) = min_pack {
1887 attr::ReprTransparent => ReprFlags::IS_TRANSPARENT,
1888 attr::ReprSimd => ReprFlags::IS_SIMD,
1889 attr::ReprInt(i) => {
1893 attr::ReprAlign(align) => {
1894 max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap()));
1901 // If `-Z randomize-layout` was enabled for the type definition then we can
1902 // consider performing layout randomization
1903 if tcx.sess.opts.unstable_opts.randomize_layout {
1904 flags.insert(ReprFlags::RANDOMIZE_LAYOUT);
1907 // This is here instead of layout because the choice must make it into metadata.
1908 if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) {
1909 flags.insert(ReprFlags::IS_LINEAR);
1912 Self { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed }
1916 pub fn simd(&self) -> bool {
1917 self.flags.contains(ReprFlags::IS_SIMD)
1921 pub fn c(&self) -> bool {
1922 self.flags.contains(ReprFlags::IS_C)
1926 pub fn packed(&self) -> bool {
1931 pub fn transparent(&self) -> bool {
1932 self.flags.contains(ReprFlags::IS_TRANSPARENT)
1936 pub fn linear(&self) -> bool {
1937 self.flags.contains(ReprFlags::IS_LINEAR)
1940 /// Returns the discriminant type, given these `repr` options.
1941 /// This must only be called on enums!
1942 pub fn discr_type(&self) -> attr::IntType {
1943 self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize))
1946 /// Returns `true` if this `#[repr()]` should inhabit "smart enum
1947 /// layout" optimizations, such as representing `Foo<&T>` as a
1949 pub fn inhibit_enum_layout_opt(&self) -> bool {
1950 self.c() || self.int.is_some()
1953 /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
1954 /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
1955 pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
1956 if let Some(pack) = self.pack {
1957 if pack.bytes() == 1 {
1962 self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
1965 /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
1966 /// was enabled for its declaration crate
1967 pub fn can_randomize_type_layout(&self) -> bool {
1968 !self.inhibit_struct_field_reordering_opt()
1969 && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
1972 /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
1973 pub fn inhibit_union_abi_opt(&self) -> bool {
1978 impl<'tcx> FieldDef {
1979 /// Returns the type of this field. The resulting type is not normalized. The `subst` is
1980 /// typically obtained via the second field of [`TyKind::Adt`].
1981 pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
1982 tcx.bound_type_of(self.did).subst(tcx, subst)
1985 /// Computes the `Ident` of this variant by looking up the `Span`
1986 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1987 Ident::new(self.name, tcx.def_ident_span(self.did).unwrap())
1991 pub type Attributes<'tcx> = impl Iterator<Item = &'tcx ast::Attribute>;
1992 #[derive(Debug, PartialEq, Eq)]
1993 pub enum ImplOverlapKind {
1994 /// These impls are always allowed to overlap.
1996 /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait
1999 /// These impls are allowed to overlap, but that raises
2000 /// an issue #33140 future-compatibility warning.
2002 /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's
2003 /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different.
2005 /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied
2006 /// that difference, making what reduces to the following set of impls:
2008 /// ```compile_fail,(E0119)
2010 /// impl Trait for dyn Send + Sync {}
2011 /// impl Trait for dyn Sync + Send {}
2014 /// Obviously, once we made these types be identical, that code causes a coherence
2015 /// error and a fairly big headache for us. However, luckily for us, the trait
2016 /// `Trait` used in this case is basically a marker trait, and therefore having
2017 /// overlapping impls for it is sound.
2019 /// To handle this, we basically regard the trait as a marker trait, with an additional
2020 /// future-compatibility warning. To avoid accidentally "stabilizing" this feature,
2021 /// it has the following restrictions:
2023 /// 1. The trait must indeed be a marker-like trait (i.e., no items), and must be
2025 /// 2. The trait-ref of both impls must be equal.
2026 /// 3. The trait-ref of both impls must be a trait object type consisting only of
2028 /// 4. Neither of the impls can have any where-clauses.
2030 /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed.
2034 impl<'tcx> TyCtxt<'tcx> {
2035 pub fn typeck_body(self, body: hir::BodyId) -> &'tcx TypeckResults<'tcx> {
2036 self.typeck(self.hir().body_owner_def_id(body))
2039 pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> {
2040 self.associated_items(id)
2041 .in_definition_order()
2042 .filter(move |item| item.kind == AssocKind::Fn && item.defaultness(self).has_value())
2045 /// Look up the name of a definition across crates. This does not look at HIR.
2046 pub fn opt_item_name(self, def_id: DefId) -> Option<Symbol> {
2047 if let Some(cnum) = def_id.as_crate_root() {
2048 Some(self.crate_name(cnum))
2050 let def_key = self.def_key(def_id);
2051 match def_key.disambiguated_data.data {
2052 // The name of a constructor is that of its parent.
2053 rustc_hir::definitions::DefPathData::Ctor => self
2054 .opt_item_name(DefId { krate: def_id.krate, index: def_key.parent.unwrap() }),
2055 // The name of opaque types only exists in HIR.
2056 rustc_hir::definitions::DefPathData::ImplTrait
2057 if let Some(def_id) = def_id.as_local() =>
2058 self.hir().opt_name(self.hir().local_def_id_to_hir_id(def_id)),
2059 _ => def_key.get_opt_name(),
2064 /// Look up the name of a definition across crates. This does not look at HIR.
2066 /// This method will ICE if the corresponding item does not have a name. In these cases, use
2067 /// [`opt_item_name`] instead.
2069 /// [`opt_item_name`]: Self::opt_item_name
2070 pub fn item_name(self, id: DefId) -> Symbol {
2071 self.opt_item_name(id).unwrap_or_else(|| {
2072 bug!("item_name: no name for {:?}", self.def_path(id));
2076 /// Look up the name and span of a definition.
2078 /// See [`item_name`][Self::item_name] for more information.
2079 pub fn opt_item_ident(self, def_id: DefId) -> Option<Ident> {
2080 let def = self.opt_item_name(def_id)?;
2083 .and_then(|id| self.def_ident_span(id))
2084 .unwrap_or(rustc_span::DUMMY_SP);
2085 Some(Ident::new(def, span))
2088 pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> {
2089 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2090 Some(self.associated_item(def_id))
2096 pub fn field_index(self, hir_id: hir::HirId, typeck_results: &TypeckResults<'_>) -> usize {
2097 typeck_results.field_indices().get(hir_id).cloned().expect("no index for a field")
2100 pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
2104 .position(|field| self.hygienic_eq(ident, field.ident(self), variant.def_id))
2107 /// Returns `true` if the impls are the same polarity and the trait either
2108 /// has no items or is annotated `#[marker]` and prevents item overrides.
2109 pub fn impls_are_allowed_to_overlap(
2113 ) -> Option<ImplOverlapKind> {
2114 // If either trait impl references an error, they're allowed to overlap,
2115 // as one of them essentially doesn't exist.
2116 if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.references_error())
2117 || self.impl_trait_ref(def_id2).map_or(false, |tr| tr.references_error())
2119 return Some(ImplOverlapKind::Permitted { marker: false });
2122 match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) {
2123 (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => {
2124 // `#[rustc_reservation_impl]` impls don't overlap with anything
2126 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (reservations)",
2129 return Some(ImplOverlapKind::Permitted { marker: false });
2131 (ImplPolarity::Positive, ImplPolarity::Negative)
2132 | (ImplPolarity::Negative, ImplPolarity::Positive) => {
2133 // `impl AutoTrait for Type` + `impl !AutoTrait for Type`
2135 "impls_are_allowed_to_overlap({:?}, {:?}) - None (differing polarities)",
2140 (ImplPolarity::Positive, ImplPolarity::Positive)
2141 | (ImplPolarity::Negative, ImplPolarity::Negative) => {}
2144 let is_marker_overlap = {
2145 let is_marker_impl = |def_id: DefId| -> bool {
2146 let trait_ref = self.impl_trait_ref(def_id);
2147 trait_ref.map_or(false, |tr| self.trait_def(tr.def_id).is_marker)
2149 is_marker_impl(def_id1) && is_marker_impl(def_id2)
2152 if is_marker_overlap {
2154 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (marker overlap)",
2157 Some(ImplOverlapKind::Permitted { marker: true })
2159 if let Some(self_ty1) = self.issue33140_self_ty(def_id1) {
2160 if let Some(self_ty2) = self.issue33140_self_ty(def_id2) {
2161 if self_ty1 == self_ty2 {
2163 "impls_are_allowed_to_overlap({:?}, {:?}) - issue #33140 HACK",
2166 return Some(ImplOverlapKind::Issue33140);
2169 "impls_are_allowed_to_overlap({:?}, {:?}) - found {:?} != {:?}",
2170 def_id1, def_id2, self_ty1, self_ty2
2176 debug!("impls_are_allowed_to_overlap({:?}, {:?}) = None", def_id1, def_id2);
2181 /// Returns `ty::VariantDef` if `res` refers to a struct,
2182 /// or variant or their constructors, panics otherwise.
2183 pub fn expect_variant_res(self, res: Res) -> &'tcx VariantDef {
2185 Res::Def(DefKind::Variant, did) => {
2186 let enum_did = self.parent(did);
2187 self.adt_def(enum_did).variant_with_id(did)
2189 Res::Def(DefKind::Struct | DefKind::Union, did) => self.adt_def(did).non_enum_variant(),
2190 Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => {
2191 let variant_did = self.parent(variant_ctor_did);
2192 let enum_did = self.parent(variant_did);
2193 self.adt_def(enum_did).variant_with_ctor_id(variant_ctor_did)
2195 Res::Def(DefKind::Ctor(CtorOf::Struct, ..), ctor_did) => {
2196 let struct_did = self.parent(ctor_did);
2197 self.adt_def(struct_did).non_enum_variant()
2199 _ => bug!("expect_variant_res used with unexpected res {:?}", res),
2203 /// Returns the possibly-auto-generated MIR of a `(DefId, Subst)` pair.
2204 #[instrument(skip(self), level = "debug")]
2205 pub fn instance_mir(self, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> {
2207 ty::InstanceDef::Item(def) => {
2208 debug!("calling def_kind on def: {:?}", def);
2209 let def_kind = self.def_kind(def.did);
2210 debug!("returned from def_kind: {:?}", def_kind);
2213 | DefKind::Static(..)
2214 | DefKind::AssocConst
2216 | DefKind::AnonConst
2217 | DefKind::InlineConst => self.mir_for_ctfe_opt_const_arg(def),
2218 // If the caller wants `mir_for_ctfe` of a function they should not be using
2219 // `instance_mir`, so we'll assume const fn also wants the optimized version.
2221 assert_eq!(def.const_param_did, None);
2222 self.optimized_mir(def.did)
2226 ty::InstanceDef::VTableShim(..)
2227 | ty::InstanceDef::ReifyShim(..)
2228 | ty::InstanceDef::Intrinsic(..)
2229 | ty::InstanceDef::FnPtrShim(..)
2230 | ty::InstanceDef::Virtual(..)
2231 | ty::InstanceDef::ClosureOnceShim { .. }
2232 | ty::InstanceDef::DropGlue(..)
2233 | ty::InstanceDef::CloneShim(..) => self.mir_shims(instance),
2237 // FIXME(@lcnr): Remove this function.
2238 pub fn get_attrs_unchecked(self, did: DefId) -> &'tcx [ast::Attribute] {
2239 if let Some(did) = did.as_local() {
2240 self.hir().attrs(self.hir().local_def_id_to_hir_id(did))
2242 self.item_attrs(did)
2246 /// Gets all attributes with the given name.
2247 pub fn get_attrs(self, did: DefId, attr: Symbol) -> ty::Attributes<'tcx> {
2248 let filter_fn = move |a: &&ast::Attribute| a.has_name(attr);
2249 if let Some(did) = did.as_local() {
2250 self.hir().attrs(self.hir().local_def_id_to_hir_id(did)).iter().filter(filter_fn)
2251 } else if cfg!(debug_assertions) && rustc_feature::is_builtin_only_local(attr) {
2252 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2254 self.item_attrs(did).iter().filter(filter_fn)
2258 pub fn get_attr(self, did: DefId, attr: Symbol) -> Option<&'tcx ast::Attribute> {
2259 self.get_attrs(did, attr).next()
2262 /// Determines whether an item is annotated with an attribute.
2263 pub fn has_attr(self, did: DefId, attr: Symbol) -> bool {
2264 if cfg!(debug_assertions) && !did.is_local() && rustc_feature::is_builtin_only_local(attr) {
2265 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2267 self.get_attrs(did, attr).next().is_some()
2271 /// Returns `true` if this is an `auto trait`.
2272 pub fn trait_is_auto(self, trait_def_id: DefId) -> bool {
2273 self.trait_def(trait_def_id).has_auto_impl
2276 /// Returns layout of a generator. Layout might be unavailable if the
2277 /// generator is tainted by errors.
2278 pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> {
2279 self.optimized_mir(def_id).generator_layout()
2282 /// Given the `DefId` of an impl, returns the `DefId` of the trait it implements.
2283 /// If it implements no trait, returns `None`.
2284 pub fn trait_id_of_impl(self, def_id: DefId) -> Option<DefId> {
2285 self.impl_trait_ref(def_id).map(|tr| tr.def_id)
2288 /// If the given `DefId` describes an item belonging to a trait,
2289 /// returns the `DefId` of the trait that the trait item belongs to;
2290 /// otherwise, returns `None`.
2291 pub fn trait_of_item(self, def_id: DefId) -> Option<DefId> {
2292 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2293 let parent = self.parent(def_id);
2294 if let DefKind::Trait | DefKind::TraitAlias = self.def_kind(parent) {
2295 return Some(parent);
2301 /// If the given `DefId` describes a method belonging to an impl, returns the
2302 /// `DefId` of the impl that the method belongs to; otherwise, returns `None`.
2303 pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
2304 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2305 let parent = self.parent(def_id);
2306 if let DefKind::Impl = self.def_kind(parent) {
2307 return Some(parent);
2313 /// If the given `DefId` belongs to a trait that was automatically derived, returns `true`.
2314 pub fn is_builtin_derive(self, def_id: DefId) -> bool {
2315 self.has_attr(def_id, sym::automatically_derived)
2318 /// Looks up the span of `impl_did` if the impl is local; otherwise returns `Err`
2319 /// with the name of the crate containing the impl.
2320 pub fn span_of_impl(self, impl_did: DefId) -> Result<Span, Symbol> {
2321 if let Some(impl_did) = impl_did.as_local() {
2322 Ok(self.def_span(impl_did))
2324 Err(self.crate_name(impl_did.krate))
2328 /// Hygienically compares a use-site name (`use_name`) for a field or an associated item with
2329 /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
2330 /// definition's parent/scope to perform comparison.
2331 pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
2332 // We could use `Ident::eq` here, but we deliberately don't. The name
2333 // comparison fails frequently, and we want to avoid the expensive
2334 // `normalize_to_macros_2_0()` calls required for the span comparison whenever possible.
2335 use_name.name == def_name.name
2339 .hygienic_eq(def_name.span.ctxt(), self.expn_that_defined(def_parent_def_id))
2342 pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident {
2343 ident.span.normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope));
2347 pub fn adjust_ident_and_get_scope(
2352 ) -> (Ident, DefId) {
2355 .normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope))
2356 .and_then(|actual_expansion| actual_expansion.expn_data().parent_module)
2357 .unwrap_or_else(|| self.parent_module(block).to_def_id());
2361 pub fn is_object_safe(self, key: DefId) -> bool {
2362 self.object_safety_violations(key).is_empty()
2366 pub fn is_const_fn_raw(self, def_id: DefId) -> bool {
2367 matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..))
2368 && self.constness(def_id) == hir::Constness::Const
2372 pub fn is_const_default_method(self, def_id: DefId) -> bool {
2373 matches!(self.trait_of_item(def_id), Some(trait_id) if self.has_attr(trait_id, sym::const_trait))
2377 /// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition.
2378 pub fn is_impl_trait_defn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<LocalDefId> {
2379 let def_id = def_id.as_local()?;
2380 if let Node::Item(item) = tcx.hir().get_by_def_id(def_id) {
2381 if let hir::ItemKind::OpaqueTy(ref opaque_ty) = item.kind {
2382 return match opaque_ty.origin {
2383 hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) => {
2386 hir::OpaqueTyOrigin::TyAlias => None,
2393 pub fn int_ty(ity: ast::IntTy) -> IntTy {
2395 ast::IntTy::Isize => IntTy::Isize,
2396 ast::IntTy::I8 => IntTy::I8,
2397 ast::IntTy::I16 => IntTy::I16,
2398 ast::IntTy::I32 => IntTy::I32,
2399 ast::IntTy::I64 => IntTy::I64,
2400 ast::IntTy::I128 => IntTy::I128,
2404 pub fn uint_ty(uty: ast::UintTy) -> UintTy {
2406 ast::UintTy::Usize => UintTy::Usize,
2407 ast::UintTy::U8 => UintTy::U8,
2408 ast::UintTy::U16 => UintTy::U16,
2409 ast::UintTy::U32 => UintTy::U32,
2410 ast::UintTy::U64 => UintTy::U64,
2411 ast::UintTy::U128 => UintTy::U128,
2415 pub fn float_ty(fty: ast::FloatTy) -> FloatTy {
2417 ast::FloatTy::F32 => FloatTy::F32,
2418 ast::FloatTy::F64 => FloatTy::F64,
2422 pub fn ast_int_ty(ity: IntTy) -> ast::IntTy {
2424 IntTy::Isize => ast::IntTy::Isize,
2425 IntTy::I8 => ast::IntTy::I8,
2426 IntTy::I16 => ast::IntTy::I16,
2427 IntTy::I32 => ast::IntTy::I32,
2428 IntTy::I64 => ast::IntTy::I64,
2429 IntTy::I128 => ast::IntTy::I128,
2433 pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy {
2435 UintTy::Usize => ast::UintTy::Usize,
2436 UintTy::U8 => ast::UintTy::U8,
2437 UintTy::U16 => ast::UintTy::U16,
2438 UintTy::U32 => ast::UintTy::U32,
2439 UintTy::U64 => ast::UintTy::U64,
2440 UintTy::U128 => ast::UintTy::U128,
2444 pub fn provide(providers: &mut ty::query::Providers) {
2445 closure::provide(providers);
2446 context::provide(providers);
2447 erase_regions::provide(providers);
2448 layout::provide(providers);
2449 util::provide(providers);
2450 print::provide(providers);
2451 super::util::bug::provide(providers);
2452 super::middle::provide(providers);
2453 *providers = ty::query::Providers {
2454 trait_impls_of: trait_def::trait_impls_of_provider,
2455 incoherent_impls: trait_def::incoherent_impls_provider,
2456 type_uninhabited_from: inhabitedness::type_uninhabited_from,
2457 const_param_default: consts::const_param_default,
2458 vtable_allocation: vtable::vtable_allocation_provider,
2463 /// A map for the local crate mapping each type to a vector of its
2464 /// inherent impls. This is not meant to be used outside of coherence;
2465 /// rather, you should request the vector for a specific type via
2466 /// `tcx.inherent_impls(def_id)` so as to minimize your dependencies
2467 /// (constructing this map requires touching the entire crate).
2468 #[derive(Clone, Debug, Default, HashStable)]
2469 pub struct CrateInherentImpls {
2470 pub inherent_impls: LocalDefIdMap<Vec<DefId>>,
2471 pub incoherent_impls: FxHashMap<SimplifiedType, Vec<LocalDefId>>,
2474 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, HashStable)]
2475 pub struct SymbolName<'tcx> {
2476 /// `&str` gives a consistent ordering, which ensures reproducible builds.
2477 pub name: &'tcx str,
2480 impl<'tcx> SymbolName<'tcx> {
2481 pub fn new(tcx: TyCtxt<'tcx>, name: &str) -> SymbolName<'tcx> {
2483 name: unsafe { str::from_utf8_unchecked(tcx.arena.alloc_slice(name.as_bytes())) },
2488 impl<'tcx> fmt::Display for SymbolName<'tcx> {
2489 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2490 fmt::Display::fmt(&self.name, fmt)
2494 impl<'tcx> fmt::Debug for SymbolName<'tcx> {
2495 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2496 fmt::Display::fmt(&self.name, fmt)
2500 #[derive(Debug, Default, Copy, Clone)]
2501 pub struct FoundRelationships {
2502 /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
2503 /// obligation, where:
2505 /// * `Foo` is not `Sized`
2506 /// * `(): Foo` may be satisfied
2507 pub self_in_trait: bool,
2508 /// This is true if we identified that this Ty (`?T`) is found in a `<_ as
2509 /// _>::AssocType = ?T`
2513 /// The constituent parts of a type level constant of kind ADT or array.
2514 #[derive(Copy, Clone, Debug, HashStable)]
2515 pub struct DestructuredConst<'tcx> {
2516 pub variant: Option<VariantIdx>,
2517 pub fields: &'tcx [ty::Const<'tcx>],