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::error::{OpaqueHiddenTypeMismatch, TypeMismatchReason};
19 use crate::metadata::ModChild;
20 use crate::middle::privacy::AccessLevels;
21 use crate::mir::{Body, GeneratorLayout};
22 use crate::traits::{self, Reveal};
24 use crate::ty::fast_reject::SimplifiedType;
25 use crate::ty::util::Discr;
30 use rustc_ast::node_id::NodeMap;
31 use rustc_attr as attr;
32 use rustc_data_structures::fingerprint::Fingerprint;
33 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
34 use rustc_data_structures::intern::{Interned, WithStableHash};
35 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
36 use rustc_data_structures::tagged_ptr::CopyTaggedPtr;
38 use rustc_hir::def::{CtorKind, CtorOf, DefKind, LifetimeRes, Res};
39 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LocalDefIdMap};
41 use rustc_index::vec::IndexVec;
42 use rustc_macros::HashStable;
43 use rustc_query_system::ich::StableHashingContext;
44 use rustc_span::hygiene::MacroKind;
45 use rustc_span::symbol::{kw, sym, Ident, Symbol};
46 use rustc_span::{ExpnId, Span};
47 use rustc_target::abi::{Align, VariantIdx};
52 use std::hash::{Hash, Hasher};
53 use std::ops::ControlFlow;
56 pub use crate::ty::diagnostics::*;
57 pub use rustc_type_ir::InferTy::*;
58 pub use rustc_type_ir::RegionKind::*;
59 pub use rustc_type_ir::TyKind::*;
60 pub use rustc_type_ir::*;
62 pub use self::binding::BindingMode;
63 pub use self::binding::BindingMode::*;
64 pub use self::closure::{
65 is_ancestor_or_same_capture, place_to_string_for_capture, BorrowKind, CaptureInfo,
66 CapturedPlace, ClosureKind, MinCaptureInformationMap, MinCaptureList,
67 RootVariableMinCaptureList, UpvarCapture, UpvarCaptureMap, UpvarId, UpvarListMap, UpvarPath,
70 pub use self::consts::{
71 Const, ConstInt, ConstKind, ConstS, InferConst, ScalarInt, Unevaluated, ValTree,
73 pub use self::context::{
74 tls, CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations,
75 CtxtInterners, DelaySpanBugEmitted, FreeRegionInfo, GeneratorDiagnosticData,
76 GeneratorInteriorTypeCause, GlobalCtxt, Lift, OnDiskCache, TyCtxt, TypeckResults, UserType,
77 UserTypeAnnotationIndex,
79 pub use self::instance::{Instance, InstanceDef};
80 pub use self::list::List;
81 pub use self::parameterized::ParameterizedOverTcx;
82 pub use self::rvalue_scopes::RvalueScopes;
83 pub use self::sty::BoundRegionKind::*;
85 Article, Binder, BoundRegion, BoundRegionKind, BoundTy, BoundTyKind, BoundVar,
86 BoundVariableKind, CanonicalPolyFnSig, ClosureSubsts, ClosureSubstsParts, ConstVid,
87 EarlyBinder, EarlyBoundRegion, ExistentialPredicate, ExistentialProjection,
88 ExistentialTraitRef, FnSig, FreeRegion, GenSig, GeneratorSubsts, GeneratorSubstsParts,
89 InlineConstSubsts, InlineConstSubstsParts, ParamConst, ParamTy, PolyExistentialProjection,
90 PolyExistentialTraitRef, PolyFnSig, PolyGenSig, PolyTraitRef, ProjectionTy, Region, RegionKind,
91 RegionVid, TraitRef, TyKind, TypeAndMut, UpvarSubsts, VarianceDiagInfo,
93 pub use self::trait_def::TraitDef;
96 pub mod abstract_const;
105 pub mod inhabitedness;
107 pub mod normalize_erasing_regions;
128 mod layout_sanity_check;
132 mod structural_impls;
137 pub type RegisteredTools = FxHashSet<Ident>;
140 pub struct ResolverOutputs {
141 pub visibilities: FxHashMap<LocalDefId, Visibility>,
142 /// This field is used to decide whether we should make `PRIVATE_IN_PUBLIC` a hard error.
143 pub has_pub_restricted: bool,
144 /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
145 pub expn_that_defined: FxHashMap<LocalDefId, ExpnId>,
146 /// Reference span for definitions.
147 pub source_span: IndexVec<LocalDefId, Span>,
148 pub access_levels: AccessLevels,
149 pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
150 pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
151 pub maybe_unused_extern_crates: Vec<(LocalDefId, Span)>,
152 pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>,
153 pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
154 /// Extern prelude entries. The value is `true` if the entry was introduced
155 /// via `extern crate` item and not `--extern` option or compiler built-in.
156 pub extern_prelude: FxHashMap<Symbol, bool>,
157 pub main_def: Option<MainDefinition>,
158 pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,
159 /// A list of proc macro LocalDefIds, written out in the order in which
160 /// they are declared in the static array generated by proc_macro_harness.
161 pub proc_macros: Vec<LocalDefId>,
162 /// Mapping from ident span to path span for paths that don't exist as written, but that
163 /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`.
164 pub confused_type_with_std_module: FxHashMap<Span, Span>,
165 pub registered_tools: RegisteredTools,
168 /// Resolutions that should only be used for lowering.
169 /// This struct is meant to be consumed by lowering.
171 pub struct ResolverAstLowering {
172 pub legacy_const_generic_args: FxHashMap<DefId, Option<Vec<usize>>>,
174 /// Resolutions for nodes that have a single resolution.
175 pub partial_res_map: NodeMap<hir::def::PartialRes>,
176 /// Resolutions for import nodes, which have multiple resolutions in different namespaces.
177 pub import_res_map: NodeMap<hir::def::PerNS<Option<Res<ast::NodeId>>>>,
178 /// Resolutions for labels (node IDs of their corresponding blocks or loops).
179 pub label_res_map: NodeMap<ast::NodeId>,
180 /// Resolutions for lifetimes.
181 pub lifetimes_res_map: NodeMap<LifetimeRes>,
182 /// Lifetime parameters that lowering will have to introduce.
183 pub extra_lifetime_params_map: NodeMap<Vec<(Ident, ast::NodeId, LifetimeRes)>>,
185 pub next_node_id: ast::NodeId,
187 pub node_id_to_def_id: FxHashMap<ast::NodeId, LocalDefId>,
188 pub def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
190 pub trait_map: NodeMap<Vec<hir::TraitCandidate>>,
191 /// A small map keeping true kinds of built-in macros that appear to be fn-like on
192 /// the surface (`macro` items in libcore), but are actually attributes or derives.
193 pub builtin_macro_kinds: FxHashMap<LocalDefId, MacroKind>,
196 #[derive(Clone, Copy, Debug)]
197 pub struct MainDefinition {
198 pub res: Res<ast::NodeId>,
203 impl MainDefinition {
204 pub fn opt_fn_def_id(self) -> Option<DefId> {
205 if let Res::Def(DefKind::Fn, def_id) = self.res { Some(def_id) } else { None }
209 /// The "header" of an impl is everything outside the body: a Self type, a trait
210 /// ref (in the case of a trait impl), and a set of predicates (from the
211 /// bounds / where-clauses).
212 #[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
213 pub struct ImplHeader<'tcx> {
214 pub impl_def_id: DefId,
215 pub self_ty: Ty<'tcx>,
216 pub trait_ref: Option<TraitRef<'tcx>>,
217 pub predicates: Vec<Predicate<'tcx>>,
220 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
221 pub enum ImplSubject<'tcx> {
222 Trait(TraitRef<'tcx>),
226 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable, Debug)]
227 #[derive(TypeFoldable, TypeVisitable)]
228 pub enum ImplPolarity {
229 /// `impl Trait for Type`
231 /// `impl !Trait for Type`
233 /// `#[rustc_reservation_impl] impl Trait for Type`
235 /// This is a "stability hack", not a real Rust feature.
236 /// See #64631 for details.
241 /// Flips polarity by turning `Positive` into `Negative` and `Negative` into `Positive`.
242 pub fn flip(&self) -> Option<ImplPolarity> {
244 ImplPolarity::Positive => Some(ImplPolarity::Negative),
245 ImplPolarity::Negative => Some(ImplPolarity::Positive),
246 ImplPolarity::Reservation => None,
251 impl fmt::Display for ImplPolarity {
252 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
254 Self::Positive => f.write_str("positive"),
255 Self::Negative => f.write_str("negative"),
256 Self::Reservation => f.write_str("reservation"),
261 #[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, Encodable, Decodable, HashStable)]
262 pub enum Visibility {
263 /// Visible everywhere (including in other crates).
265 /// Visible only in the given crate-local module.
269 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
270 pub enum BoundConstness {
273 /// `T: ~const Trait`
275 /// Requires resolving to const only when we are in a const context.
279 impl BoundConstness {
280 /// Reduce `self` and `constness` to two possible combined states instead of four.
281 pub fn and(&mut self, constness: hir::Constness) -> hir::Constness {
282 match (constness, self) {
283 (hir::Constness::Const, BoundConstness::ConstIfConst) => hir::Constness::Const,
285 *this = BoundConstness::NotConst;
286 hir::Constness::NotConst
292 impl fmt::Display for BoundConstness {
293 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
295 Self::NotConst => f.write_str("normal"),
296 Self::ConstIfConst => f.write_str("`~const`"),
301 #[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, TyEncodable, TyDecodable, HashStable)]
302 #[derive(TypeFoldable, TypeVisitable)]
303 pub struct ClosureSizeProfileData<'tcx> {
304 /// Tuple containing the types of closure captures before the feature `capture_disjoint_fields`
305 pub before_feature_tys: Ty<'tcx>,
306 /// Tuple containing the types of closure captures after the feature `capture_disjoint_fields`
307 pub after_feature_tys: Ty<'tcx>,
310 pub trait DefIdTree: Copy {
311 fn opt_parent(self, id: DefId) -> Option<DefId>;
315 fn parent(self, id: DefId) -> DefId {
316 match self.opt_parent(id) {
318 // not `unwrap_or_else` to avoid breaking caller tracking
319 None => bug!("{id:?} doesn't have a parent"),
325 fn opt_local_parent(self, id: LocalDefId) -> Option<LocalDefId> {
326 self.opt_parent(id.to_def_id()).map(DefId::expect_local)
331 fn local_parent(self, id: LocalDefId) -> LocalDefId {
332 self.parent(id.to_def_id()).expect_local()
335 fn is_descendant_of(self, mut descendant: DefId, ancestor: DefId) -> bool {
336 if descendant.krate != ancestor.krate {
340 while descendant != ancestor {
341 match self.opt_parent(descendant) {
342 Some(parent) => descendant = parent,
343 None => return false,
350 impl<'tcx> DefIdTree for TyCtxt<'tcx> {
352 fn opt_parent(self, id: DefId) -> Option<DefId> {
353 self.def_key(id).parent.map(|index| DefId { index, ..id })
358 /// Returns `true` if an item with this visibility is accessible from the given block.
359 pub fn is_accessible_from<T: DefIdTree>(self, module: DefId, tree: T) -> bool {
360 let restriction = match self {
361 // Public items are visible everywhere.
362 Visibility::Public => return true,
363 // Restricted items are visible in an arbitrary local module.
364 Visibility::Restricted(other) if other.krate != module.krate => return false,
365 Visibility::Restricted(module) => module,
368 tree.is_descendant_of(module, restriction)
371 /// Returns `true` if this visibility is at least as accessible as the given visibility
372 pub fn is_at_least<T: DefIdTree>(self, vis: Visibility, tree: T) -> bool {
373 let vis_restriction = match vis {
374 Visibility::Public => return self == Visibility::Public,
375 Visibility::Restricted(module) => module,
378 self.is_accessible_from(vis_restriction, tree)
381 // Returns `true` if this item is visible anywhere in the local crate.
382 pub fn is_visible_locally(self) -> bool {
384 Visibility::Public => true,
385 Visibility::Restricted(def_id) => def_id.is_local(),
389 pub fn is_public(self) -> bool {
390 matches!(self, Visibility::Public)
394 /// The crate variances map is computed during typeck and contains the
395 /// variance of every item in the local crate. You should not use it
396 /// directly, because to do so will make your pass dependent on the
397 /// HIR of every item in the local crate. Instead, use
398 /// `tcx.variances_of()` to get the variance for a *particular*
400 #[derive(HashStable, Debug)]
401 pub struct CrateVariancesMap<'tcx> {
402 /// For each item with generics, maps to a vector of the variance
403 /// of its generics. If an item has no generics, it will have no
405 pub variances: FxHashMap<DefId, &'tcx [ty::Variance]>,
408 // Contains information needed to resolve types and (in the future) look up
409 // the types of AST nodes.
410 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
411 pub struct CReaderCacheKey {
412 pub cnum: Option<CrateNum>,
416 /// Represents a type.
419 /// - This is a very "dumb" struct (with no derives and no `impls`).
420 /// - Values of this type are always interned and thus unique, and are stored
421 /// as an `Interned<TyS>`.
422 /// - `Ty` (which contains a reference to a `Interned<TyS>`) or `Interned<TyS>`
423 /// should be used everywhere instead of `TyS`. In particular, `Ty` has most
424 /// of the relevant methods.
425 #[derive(PartialEq, Eq, PartialOrd, Ord)]
426 #[allow(rustc::usage_of_ty_tykind)]
427 pub(crate) struct TyS<'tcx> {
428 /// This field shouldn't be used directly and may be removed in the future.
429 /// Use `Ty::kind()` instead.
432 /// This field provides fast access to information that is also contained
435 /// This field shouldn't be used directly and may be removed in the future.
436 /// Use `Ty::flags()` instead.
439 /// This field provides fast access to information that is also contained
442 /// This is a kind of confusing thing: it stores the smallest
445 /// (a) the binder itself captures nothing but
446 /// (b) all the late-bound things within the type are captured
447 /// by some sub-binder.
449 /// So, for a type without any late-bound things, like `u32`, this
450 /// will be *innermost*, because that is the innermost binder that
451 /// captures nothing. But for a type `&'D u32`, where `'D` is a
452 /// late-bound region with De Bruijn index `D`, this would be `D + 1`
453 /// -- the binder itself does not capture `D`, but `D` is captured
454 /// by an inner binder.
456 /// We call this concept an "exclusive" binder `D` because all
457 /// De Bruijn indices within the type are contained within `0..D`
459 outer_exclusive_binder: ty::DebruijnIndex,
462 // `TyS` is used a lot. Make sure it doesn't unintentionally get bigger.
463 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
464 static_assert_size!(TyS<'_>, 40);
466 // We are actually storing a stable hash cache next to the type, so let's
467 // also check the full size
468 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
469 static_assert_size!(WithStableHash<TyS<'_>>, 56);
471 /// Use this rather than `TyS`, whenever possible.
472 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
473 #[rustc_diagnostic_item = "Ty"]
474 #[rustc_pass_by_value]
475 pub struct Ty<'tcx>(Interned<'tcx, WithStableHash<TyS<'tcx>>>);
477 impl<'tcx> TyCtxt<'tcx> {
478 /// A "bool" type used in rustc_mir_transform unit tests when we
479 /// have not spun up a TyCtxt.
480 pub const BOOL_TY_FOR_UNIT_TESTING: Ty<'tcx> = Ty(Interned::new_unchecked(&WithStableHash {
483 flags: TypeFlags::empty(),
484 outer_exclusive_binder: DebruijnIndex::from_usize(0),
486 stable_hash: Fingerprint::ZERO,
490 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for TyS<'tcx> {
492 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
496 // The other fields just provide fast access to information that is
497 // also contained in `kind`, so no need to hash them.
500 outer_exclusive_binder: _,
503 kind.hash_stable(hcx, hasher)
507 impl ty::EarlyBoundRegion {
508 /// Does this early bound region have a name? Early bound regions normally
509 /// always have names except when using anonymous lifetimes (`'_`).
510 pub fn has_name(&self) -> bool {
511 self.name != kw::UnderscoreLifetime
515 /// Represents a predicate.
517 /// See comments on `TyS`, which apply here too (albeit for
518 /// `PredicateS`/`Predicate` rather than `TyS`/`Ty`).
520 pub(crate) struct PredicateS<'tcx> {
521 kind: Binder<'tcx, PredicateKind<'tcx>>,
523 /// See the comment for the corresponding field of [TyS].
524 outer_exclusive_binder: ty::DebruijnIndex,
527 // This type is used a lot. Make sure it doesn't unintentionally get bigger.
528 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
529 static_assert_size!(PredicateS<'_>, 56);
531 /// Use this rather than `PredicateS`, whenever possible.
532 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
533 #[rustc_pass_by_value]
534 pub struct Predicate<'tcx>(Interned<'tcx, PredicateS<'tcx>>);
536 impl<'tcx> Predicate<'tcx> {
537 /// Gets the inner `Binder<'tcx, PredicateKind<'tcx>>`.
539 pub fn kind(self) -> Binder<'tcx, PredicateKind<'tcx>> {
544 pub fn flags(self) -> TypeFlags {
549 pub fn outer_exclusive_binder(self) -> DebruijnIndex {
550 self.0.outer_exclusive_binder
553 /// Flips the polarity of a Predicate.
555 /// Given `T: Trait` predicate it returns `T: !Trait` and given `T: !Trait` returns `T: Trait`.
556 pub fn flip_polarity(self, tcx: TyCtxt<'tcx>) -> Option<Predicate<'tcx>> {
559 .map_bound(|kind| match kind {
560 PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) => {
561 Some(PredicateKind::Trait(TraitPredicate {
564 polarity: polarity.flip()?,
572 Some(tcx.mk_predicate(kind))
575 pub fn without_const(mut self, tcx: TyCtxt<'tcx>) -> Self {
576 if let PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) = self.kind().skip_binder()
577 && constness != BoundConstness::NotConst
579 self = tcx.mk_predicate(self.kind().rebind(PredicateKind::Trait(TraitPredicate {
581 constness: BoundConstness::NotConst,
588 /// Whether this projection can be soundly normalized.
590 /// Wf predicates must not be normalized, as normalization
591 /// can remove required bounds which would cause us to
592 /// unsoundly accept some programs. See #91068.
594 pub fn allow_normalization(self) -> bool {
595 match self.kind().skip_binder() {
596 PredicateKind::WellFormed(_) => false,
597 PredicateKind::Trait(_)
598 | PredicateKind::RegionOutlives(_)
599 | PredicateKind::TypeOutlives(_)
600 | PredicateKind::Projection(_)
601 | PredicateKind::ObjectSafe(_)
602 | PredicateKind::ClosureKind(_, _, _)
603 | PredicateKind::Subtype(_)
604 | PredicateKind::Coerce(_)
605 | PredicateKind::ConstEvaluatable(_)
606 | PredicateKind::ConstEquate(_, _)
607 | PredicateKind::TypeWellFormedFromEnv(_) => true,
612 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> {
613 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
617 // The other fields just provide fast access to information that is
618 // also contained in `kind`, so no need to hash them.
620 outer_exclusive_binder: _,
623 kind.hash_stable(hcx, hasher);
627 impl rustc_errors::IntoDiagnosticArg for Predicate<'_> {
628 fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
629 rustc_errors::DiagnosticArgValue::Str(std::borrow::Cow::Owned(self.to_string()))
633 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
634 #[derive(HashStable, TypeFoldable, TypeVisitable)]
635 pub enum PredicateKind<'tcx> {
636 /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
637 /// the `Self` type of the trait reference and `A`, `B`, and `C`
638 /// would be the type parameters.
639 Trait(TraitPredicate<'tcx>),
642 RegionOutlives(RegionOutlivesPredicate<'tcx>),
645 TypeOutlives(TypeOutlivesPredicate<'tcx>),
647 /// `where <T as TraitRef>::Name == X`, approximately.
648 /// See the `ProjectionPredicate` struct for details.
649 Projection(ProjectionPredicate<'tcx>),
651 /// No syntax: `T` well-formed.
652 WellFormed(GenericArg<'tcx>),
654 /// Trait must be object-safe.
657 /// No direct syntax. May be thought of as `where T: FnFoo<...>`
658 /// for some substitutions `...` and `T` being a closure type.
659 /// Satisfied (or refuted) once we know the closure's kind.
660 ClosureKind(DefId, SubstsRef<'tcx>, ClosureKind),
664 /// This obligation is created most often when we have two
665 /// unresolved type variables and hence don't have enough
666 /// information to process the subtyping obligation yet.
667 Subtype(SubtypePredicate<'tcx>),
669 /// `T1` coerced to `T2`
671 /// Like a subtyping obligation, this is created most often
672 /// when we have two unresolved type variables and hence
673 /// don't have enough information to process the coercion
674 /// obligation yet. At the moment, we actually process coercions
675 /// very much like subtyping and don't handle the full coercion
677 Coerce(CoercePredicate<'tcx>),
679 /// Constant initializer must evaluate successfully.
680 ConstEvaluatable(ty::Unevaluated<'tcx, ()>),
682 /// Constants must be equal. The first component is the const that is expected.
683 ConstEquate(Const<'tcx>, Const<'tcx>),
685 /// Represents a type found in the environment that we can use for implied bounds.
687 /// Only used for Chalk.
688 TypeWellFormedFromEnv(Ty<'tcx>),
691 /// The crate outlives map is computed during typeck and contains the
692 /// outlives of every item in the local crate. You should not use it
693 /// directly, because to do so will make your pass dependent on the
694 /// HIR of every item in the local crate. Instead, use
695 /// `tcx.inferred_outlives_of()` to get the outlives for a *particular*
697 #[derive(HashStable, Debug)]
698 pub struct CratePredicatesMap<'tcx> {
699 /// For each struct with outlive bounds, maps to a vector of the
700 /// predicate of its outlive bounds. If an item has no outlives
701 /// bounds, it will have no entry.
702 pub predicates: FxHashMap<DefId, &'tcx [(Predicate<'tcx>, Span)]>,
705 impl<'tcx> Predicate<'tcx> {
706 /// Performs a substitution suitable for going from a
707 /// poly-trait-ref to supertraits that must hold if that
708 /// poly-trait-ref holds. This is slightly different from a normal
709 /// substitution in terms of what happens with bound regions. See
710 /// lengthy comment below for details.
711 pub fn subst_supertrait(
714 trait_ref: &ty::PolyTraitRef<'tcx>,
715 ) -> Predicate<'tcx> {
716 // The interaction between HRTB and supertraits is not entirely
717 // obvious. Let me walk you (and myself) through an example.
719 // Let's start with an easy case. Consider two traits:
721 // trait Foo<'a>: Bar<'a,'a> { }
722 // trait Bar<'b,'c> { }
724 // Now, if we have a trait reference `for<'x> T: Foo<'x>`, then
725 // we can deduce that `for<'x> T: Bar<'x,'x>`. Basically, if we
726 // knew that `Foo<'x>` (for any 'x) then we also know that
727 // `Bar<'x,'x>` (for any 'x). This more-or-less falls out from
728 // normal substitution.
730 // In terms of why this is sound, the idea is that whenever there
731 // is an impl of `T:Foo<'a>`, it must show that `T:Bar<'a,'a>`
732 // holds. So if there is an impl of `T:Foo<'a>` that applies to
733 // all `'a`, then we must know that `T:Bar<'a,'a>` holds for all
736 // Another example to be careful of is this:
738 // trait Foo1<'a>: for<'b> Bar1<'a,'b> { }
739 // trait Bar1<'b,'c> { }
741 // Here, if we have `for<'x> T: Foo1<'x>`, then what do we know?
742 // The answer is that we know `for<'x,'b> T: Bar1<'x,'b>`. The
743 // reason is similar to the previous example: any impl of
744 // `T:Foo1<'x>` must show that `for<'b> T: Bar1<'x, 'b>`. So
745 // basically we would want to collapse the bound lifetimes from
746 // the input (`trait_ref`) and the supertraits.
748 // To achieve this in practice is fairly straightforward. Let's
749 // consider the more complicated scenario:
751 // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x`
752 // has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`,
753 // where both `'x` and `'b` would have a DB index of 1.
754 // The substitution from the input trait-ref is therefore going to be
755 // `'a => 'x` (where `'x` has a DB index of 1).
756 // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an
757 // early-bound parameter and `'b' is a late-bound parameter with a
759 // - If we replace `'a` with `'x` from the input, it too will have
760 // a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>`
761 // just as we wanted.
763 // There is only one catch. If we just apply the substitution `'a
764 // => 'x` to `for<'b> Bar1<'a,'b>`, the substitution code will
765 // adjust the DB index because we substituting into a binder (it
766 // tries to be so smart...) resulting in `for<'x> for<'b>
767 // Bar1<'x,'b>` (we have no syntax for this, so use your
768 // imagination). Basically the 'x will have DB index of 2 and 'b
769 // will have DB index of 1. Not quite what we want. So we apply
770 // the substitution to the *contents* of the trait reference,
771 // rather than the trait reference itself (put another way, the
772 // substitution code expects equal binding levels in the values
773 // from the substitution and the value being substituted into, and
774 // this trick achieves that).
776 // Working through the second example:
777 // trait_ref: for<'x> T: Foo1<'^0.0>; substs: [T, '^0.0]
778 // predicate: for<'b> Self: Bar1<'a, '^0.0>; substs: [Self, 'a, '^0.0]
779 // We want to end up with:
780 // for<'x, 'b> T: Bar1<'^0.0, '^0.1>
782 // 1) We must shift all bound vars in predicate by the length
783 // of trait ref's bound vars. So, we would end up with predicate like
784 // Self: Bar1<'a, '^0.1>
785 // 2) We can then apply the trait substs to this, ending up with
786 // T: Bar1<'^0.0, '^0.1>
787 // 3) Finally, to create the final bound vars, we concatenate the bound
788 // vars of the trait ref with those of the predicate:
790 let bound_pred = self.kind();
791 let pred_bound_vars = bound_pred.bound_vars();
792 let trait_bound_vars = trait_ref.bound_vars();
793 // 1) Self: Bar1<'a, '^0.0> -> Self: Bar1<'a, '^0.1>
795 tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
796 // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
797 let new = EarlyBinder(shifted_pred).subst(tcx, trait_ref.skip_binder().substs);
798 // 3) ['x] + ['b] -> ['x, 'b]
800 tcx.mk_bound_variable_kinds(trait_bound_vars.iter().chain(pred_bound_vars));
801 tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars))
805 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
806 #[derive(HashStable, TypeFoldable, TypeVisitable)]
807 pub struct TraitPredicate<'tcx> {
808 pub trait_ref: TraitRef<'tcx>,
810 pub constness: BoundConstness,
812 /// If polarity is Positive: we are proving that the trait is implemented.
814 /// If polarity is Negative: we are proving that a negative impl of this trait
815 /// exists. (Note that coherence also checks whether negative impls of supertraits
816 /// exist via a series of predicates.)
818 /// If polarity is Reserved: that's a bug.
819 pub polarity: ImplPolarity,
822 pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
824 impl<'tcx> TraitPredicate<'tcx> {
825 pub fn remap_constness(&mut self, param_env: &mut ParamEnv<'tcx>) {
826 *param_env = param_env.with_constness(self.constness.and(param_env.constness()))
829 /// Remap the constness of this predicate before emitting it for diagnostics.
830 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
831 // this is different to `remap_constness` that callees want to print this predicate
832 // in case of selection errors. `T: ~const Drop` bounds cannot end up here when the
833 // param_env is not const because it is always satisfied in non-const contexts.
834 if let hir::Constness::NotConst = param_env.constness() {
835 self.constness = ty::BoundConstness::NotConst;
839 pub fn def_id(self) -> DefId {
840 self.trait_ref.def_id
843 pub fn self_ty(self) -> Ty<'tcx> {
844 self.trait_ref.self_ty()
848 pub fn is_const_if_const(self) -> bool {
849 self.constness == BoundConstness::ConstIfConst
852 pub fn is_constness_satisfied_by(self, constness: hir::Constness) -> bool {
853 match (self.constness, constness) {
854 (BoundConstness::NotConst, _)
855 | (BoundConstness::ConstIfConst, hir::Constness::Const) => true,
856 (BoundConstness::ConstIfConst, hir::Constness::NotConst) => false,
861 impl<'tcx> PolyTraitPredicate<'tcx> {
862 pub fn def_id(self) -> DefId {
863 // Ok to skip binder since trait `DefId` does not care about regions.
864 self.skip_binder().def_id()
867 pub fn self_ty(self) -> ty::Binder<'tcx, Ty<'tcx>> {
868 self.map_bound(|trait_ref| trait_ref.self_ty())
871 /// Remap the constness of this predicate before emitting it for diagnostics.
872 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
873 *self = self.map_bound(|mut p| {
874 p.remap_constness_diag(param_env);
880 pub fn is_const_if_const(self) -> bool {
881 self.skip_binder().is_const_if_const()
885 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
886 #[derive(HashStable, TypeFoldable, TypeVisitable)]
887 pub struct OutlivesPredicate<A, B>(pub A, pub B); // `A: B`
888 pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>;
889 pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>;
890 pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>;
891 pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>;
893 /// Encodes that `a` must be a subtype of `b`. The `a_is_expected` flag indicates
894 /// whether the `a` type is the type that we should label as "expected" when
895 /// presenting user diagnostics.
896 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
897 #[derive(HashStable, TypeFoldable, TypeVisitable)]
898 pub struct SubtypePredicate<'tcx> {
899 pub a_is_expected: bool,
903 pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>;
905 /// Encodes that we have to coerce *from* the `a` type to the `b` type.
906 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
907 #[derive(HashStable, TypeFoldable, TypeVisitable)]
908 pub struct CoercePredicate<'tcx> {
912 pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
914 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, TyEncodable, TyDecodable)]
915 #[derive(HashStable, TypeFoldable, TypeVisitable)]
916 pub enum Term<'tcx> {
921 impl<'tcx> From<Ty<'tcx>> for Term<'tcx> {
922 fn from(ty: Ty<'tcx>) -> Self {
927 impl<'tcx> From<Const<'tcx>> for Term<'tcx> {
928 fn from(c: Const<'tcx>) -> Self {
933 impl<'tcx> Term<'tcx> {
934 pub fn ty(&self) -> Option<Ty<'tcx>> {
935 if let Term::Ty(ty) = self { Some(*ty) } else { None }
938 pub fn ct(&self) -> Option<Const<'tcx>> {
939 if let Term::Const(c) = self { Some(*c) } else { None }
942 pub fn into_arg(self) -> GenericArg<'tcx> {
944 Term::Ty(ty) => ty.into(),
945 Term::Const(c) => c.into(),
950 /// This kind of predicate has no *direct* correspondent in the
951 /// syntax, but it roughly corresponds to the syntactic forms:
953 /// 1. `T: TraitRef<..., Item = Type>`
954 /// 2. `<T as TraitRef<...>>::Item == Type` (NYI)
956 /// In particular, form #1 is "desugared" to the combination of a
957 /// normal trait predicate (`T: TraitRef<...>`) and one of these
958 /// predicates. Form #2 is a broader form in that it also permits
959 /// equality between arbitrary types. Processing an instance of
960 /// Form #2 eventually yields one of these `ProjectionPredicate`
961 /// instances to normalize the LHS.
962 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
963 #[derive(HashStable, TypeFoldable, TypeVisitable)]
964 pub struct ProjectionPredicate<'tcx> {
965 pub projection_ty: ProjectionTy<'tcx>,
966 pub term: Term<'tcx>,
969 pub type PolyProjectionPredicate<'tcx> = Binder<'tcx, ProjectionPredicate<'tcx>>;
971 impl<'tcx> PolyProjectionPredicate<'tcx> {
972 /// Returns the `DefId` of the trait of the associated item being projected.
974 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
975 self.skip_binder().projection_ty.trait_def_id(tcx)
978 /// Get the [PolyTraitRef] required for this projection to be well formed.
979 /// Note that for generic associated types the predicates of the associated
980 /// type also need to be checked.
982 pub fn required_poly_trait_ref(&self, tcx: TyCtxt<'tcx>) -> PolyTraitRef<'tcx> {
983 // Note: unlike with `TraitRef::to_poly_trait_ref()`,
984 // `self.0.trait_ref` is permitted to have escaping regions.
985 // This is because here `self` has a `Binder` and so does our
986 // return value, so we are preserving the number of binding
988 self.map_bound(|predicate| predicate.projection_ty.trait_ref(tcx))
991 pub fn term(&self) -> Binder<'tcx, Term<'tcx>> {
992 self.map_bound(|predicate| predicate.term)
995 /// The `DefId` of the `TraitItem` for the associated type.
997 /// Note that this is not the `DefId` of the `TraitRef` containing this
998 /// associated type, which is in `tcx.associated_item(projection_def_id()).container`.
999 pub fn projection_def_id(&self) -> DefId {
1000 // Ok to skip binder since trait `DefId` does not care about regions.
1001 self.skip_binder().projection_ty.item_def_id
1005 pub trait ToPolyTraitRef<'tcx> {
1006 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx>;
1009 impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
1010 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> {
1011 self.map_bound_ref(|trait_pred| trait_pred.trait_ref)
1015 pub trait ToPredicate<'tcx> {
1016 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx>;
1019 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
1021 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1022 tcx.mk_predicate(self)
1026 impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
1027 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1028 self.map_bound(PredicateKind::Trait).to_predicate(tcx)
1032 impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
1033 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1034 self.map_bound(PredicateKind::RegionOutlives).to_predicate(tcx)
1038 impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> {
1039 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1040 self.map_bound(PredicateKind::TypeOutlives).to_predicate(tcx)
1044 impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
1045 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1046 self.map_bound(PredicateKind::Projection).to_predicate(tcx)
1050 impl<'tcx> Predicate<'tcx> {
1051 pub fn to_opt_poly_trait_pred(self) -> Option<PolyTraitPredicate<'tcx>> {
1052 let predicate = self.kind();
1053 match predicate.skip_binder() {
1054 PredicateKind::Trait(t) => Some(predicate.rebind(t)),
1055 PredicateKind::Projection(..)
1056 | PredicateKind::Subtype(..)
1057 | PredicateKind::Coerce(..)
1058 | PredicateKind::RegionOutlives(..)
1059 | PredicateKind::WellFormed(..)
1060 | PredicateKind::ObjectSafe(..)
1061 | PredicateKind::ClosureKind(..)
1062 | PredicateKind::TypeOutlives(..)
1063 | PredicateKind::ConstEvaluatable(..)
1064 | PredicateKind::ConstEquate(..)
1065 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1069 pub fn to_opt_poly_projection_pred(self) -> Option<PolyProjectionPredicate<'tcx>> {
1070 let predicate = self.kind();
1071 match predicate.skip_binder() {
1072 PredicateKind::Projection(t) => Some(predicate.rebind(t)),
1073 PredicateKind::Trait(..)
1074 | PredicateKind::Subtype(..)
1075 | PredicateKind::Coerce(..)
1076 | PredicateKind::RegionOutlives(..)
1077 | PredicateKind::WellFormed(..)
1078 | PredicateKind::ObjectSafe(..)
1079 | PredicateKind::ClosureKind(..)
1080 | PredicateKind::TypeOutlives(..)
1081 | PredicateKind::ConstEvaluatable(..)
1082 | PredicateKind::ConstEquate(..)
1083 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1087 pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> {
1088 let predicate = self.kind();
1089 match predicate.skip_binder() {
1090 PredicateKind::TypeOutlives(data) => Some(predicate.rebind(data)),
1091 PredicateKind::Trait(..)
1092 | PredicateKind::Projection(..)
1093 | PredicateKind::Subtype(..)
1094 | PredicateKind::Coerce(..)
1095 | PredicateKind::RegionOutlives(..)
1096 | PredicateKind::WellFormed(..)
1097 | PredicateKind::ObjectSafe(..)
1098 | PredicateKind::ClosureKind(..)
1099 | PredicateKind::ConstEvaluatable(..)
1100 | PredicateKind::ConstEquate(..)
1101 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1106 /// Represents the bounds declared on a particular set of type
1107 /// parameters. Should eventually be generalized into a flag list of
1108 /// where-clauses. You can obtain an `InstantiatedPredicates` list from a
1109 /// `GenericPredicates` by using the `instantiate` method. Note that this method
1110 /// reflects an important semantic invariant of `InstantiatedPredicates`: while
1111 /// the `GenericPredicates` are expressed in terms of the bound type
1112 /// parameters of the impl/trait/whatever, an `InstantiatedPredicates` instance
1113 /// represented a set of bounds for some particular instantiation,
1114 /// meaning that the generic parameters have been substituted with
1118 /// ```ignore (illustrative)
1119 /// struct Foo<T, U: Bar<T>> { ... }
1121 /// Here, the `GenericPredicates` for `Foo` would contain a list of bounds like
1122 /// `[[], [U:Bar<T>]]`. Now if there were some particular reference
1123 /// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[],
1124 /// [usize:Bar<isize>]]`.
1125 #[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
1126 pub struct InstantiatedPredicates<'tcx> {
1127 pub predicates: Vec<Predicate<'tcx>>,
1128 pub spans: Vec<Span>,
1131 impl<'tcx> InstantiatedPredicates<'tcx> {
1132 pub fn empty() -> InstantiatedPredicates<'tcx> {
1133 InstantiatedPredicates { predicates: vec![], spans: vec![] }
1136 pub fn is_empty(&self) -> bool {
1137 self.predicates.is_empty()
1141 #[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable, Lift)]
1142 #[derive(TypeFoldable, TypeVisitable)]
1143 pub struct OpaqueTypeKey<'tcx> {
1144 pub def_id: LocalDefId,
1145 pub substs: SubstsRef<'tcx>,
1148 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
1149 pub struct OpaqueHiddenType<'tcx> {
1150 /// The span of this particular definition of the opaque type. So
1153 /// ```ignore (incomplete snippet)
1154 /// type Foo = impl Baz;
1155 /// fn bar() -> Foo {
1156 /// // ^^^ This is the span we are looking for!
1160 /// In cases where the fn returns `(impl Trait, impl Trait)` or
1161 /// other such combinations, the result is currently
1162 /// over-approximated, but better than nothing.
1165 /// The type variable that represents the value of the opaque type
1166 /// that we require. In other words, after we compile this function,
1167 /// we will be created a constraint like:
1168 /// ```ignore (pseudo-rust)
1171 /// where `?C` is the value of this type variable. =) It may
1172 /// naturally refer to the type and lifetime parameters in scope
1173 /// in this function, though ultimately it should only reference
1174 /// those that are arguments to `Foo` in the constraint above. (In
1175 /// other words, `?C` should not include `'b`, even though it's a
1176 /// lifetime parameter on `foo`.)
1180 impl<'tcx> OpaqueHiddenType<'tcx> {
1181 pub fn report_mismatch(&self, other: &Self, tcx: TyCtxt<'tcx>) {
1182 // Found different concrete types for the opaque type.
1183 let sub_diag = if self.span == other.span {
1184 TypeMismatchReason::ConflictType { span: self.span }
1186 TypeMismatchReason::PreviousUse { span: self.span }
1188 tcx.sess.emit_err(OpaqueHiddenTypeMismatch {
1191 other_span: other.span,
1197 /// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are
1198 /// identified by both a universe, as well as a name residing within that universe. Distinct bound
1199 /// regions/types/consts within the same universe simply have an unknown relationship to one
1201 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
1202 #[derive(HashStable, TyEncodable, TyDecodable)]
1203 pub struct Placeholder<T> {
1204 pub universe: UniverseIndex,
1208 pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
1210 pub type PlaceholderType = Placeholder<BoundVar>;
1212 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
1213 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
1214 pub struct BoundConst<'tcx> {
1219 pub type PlaceholderConst<'tcx> = Placeholder<BoundVar>;
1221 /// A `DefId` which, in case it is a const argument, is potentially bundled with
1222 /// the `DefId` of the generic parameter it instantiates.
1224 /// This is used to avoid calls to `type_of` for const arguments during typeck
1225 /// which cause cycle errors.
1230 /// fn foo<const N: usize>(&self) -> [u8; N] { [0; N] }
1231 /// // ^ const parameter
1235 /// fn foo<const M: u8>(&self) -> usize { 42 }
1236 /// // ^ const parameter
1241 /// let _b = a.foo::<{ 3 + 7 }>();
1242 /// // ^^^^^^^^^ const argument
1246 /// Let's look at the call `a.foo::<{ 3 + 7 }>()` here. We do not know
1247 /// which `foo` is used until we know the type of `a`.
1249 /// We only know the type of `a` once we are inside of `typeck(main)`.
1250 /// We also end up normalizing the type of `_b` during `typeck(main)` which
1251 /// requires us to evaluate the const argument.
1253 /// To evaluate that const argument we need to know its type,
1254 /// which we would get using `type_of(const_arg)`. This requires us to
1255 /// resolve `foo` as it can be either `usize` or `u8` in this example.
1256 /// However, resolving `foo` once again requires `typeck(main)` to get the type of `a`,
1257 /// which results in a cycle.
1259 /// In short we must not call `type_of(const_arg)` during `typeck(main)`.
1261 /// When first creating the `ty::Const` of the const argument inside of `typeck` we have
1262 /// already resolved `foo` so we know which const parameter this argument instantiates.
1263 /// This means that we also know the expected result of `type_of(const_arg)` even if we
1264 /// aren't allowed to call that query: it is equal to `type_of(const_param)` which is
1265 /// trivial to compute.
1267 /// If we now want to use that constant in a place which potentially needs its type
1268 /// we also pass the type of its `const_param`. This is the point of `WithOptConstParam`,
1269 /// except that instead of a `Ty` we bundle the `DefId` of the const parameter.
1270 /// Meaning that we need to use `type_of(const_param_did)` if `const_param_did` is `Some`
1271 /// to get the type of `did`.
1272 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, Lift, TyEncodable, TyDecodable)]
1273 #[derive(PartialEq, Eq, PartialOrd, Ord)]
1274 #[derive(Hash, HashStable)]
1275 pub struct WithOptConstParam<T> {
1277 /// The `DefId` of the corresponding generic parameter in case `did` is
1278 /// a const argument.
1280 /// Note that even if `did` is a const argument, this may still be `None`.
1281 /// All queries taking `WithOptConstParam` start by calling `tcx.opt_const_param_of(def.did)`
1282 /// to potentially update `param_did` in the case it is `None`.
1283 pub const_param_did: Option<DefId>,
1286 impl<T> WithOptConstParam<T> {
1287 /// Creates a new `WithOptConstParam` setting `const_param_did` to `None`.
1289 pub fn unknown(did: T) -> WithOptConstParam<T> {
1290 WithOptConstParam { did, const_param_did: None }
1294 impl WithOptConstParam<LocalDefId> {
1295 /// Returns `Some((did, param_did))` if `def_id` is a const argument,
1296 /// `None` otherwise.
1298 pub fn try_lookup(did: LocalDefId, tcx: TyCtxt<'_>) -> Option<(LocalDefId, DefId)> {
1299 tcx.opt_const_param_of(did).map(|param_did| (did, param_did))
1302 /// In case `self` is unknown but `self.did` is a const argument, this returns
1303 /// a `WithOptConstParam` with the correct `const_param_did`.
1305 pub fn try_upgrade(self, tcx: TyCtxt<'_>) -> Option<WithOptConstParam<LocalDefId>> {
1306 if self.const_param_did.is_none() {
1307 if let const_param_did @ Some(_) = tcx.opt_const_param_of(self.did) {
1308 return Some(WithOptConstParam { did: self.did, const_param_did });
1315 pub fn to_global(self) -> WithOptConstParam<DefId> {
1316 WithOptConstParam { did: self.did.to_def_id(), const_param_did: self.const_param_did }
1319 pub fn def_id_for_type_of(self) -> DefId {
1320 if let Some(did) = self.const_param_did { did } else { self.did.to_def_id() }
1324 impl WithOptConstParam<DefId> {
1325 pub fn as_local(self) -> Option<WithOptConstParam<LocalDefId>> {
1328 .map(|did| WithOptConstParam { did, const_param_did: self.const_param_did })
1331 pub fn as_const_arg(self) -> Option<(LocalDefId, DefId)> {
1332 if let Some(param_did) = self.const_param_did {
1333 if let Some(did) = self.did.as_local() {
1334 return Some((did, param_did));
1341 pub fn is_local(self) -> bool {
1345 pub fn def_id_for_type_of(self) -> DefId {
1346 self.const_param_did.unwrap_or(self.did)
1350 /// When type checking, we use the `ParamEnv` to track
1351 /// details about the set of where-clauses that are in scope at this
1352 /// particular point.
1353 #[derive(Copy, Clone, Hash, PartialEq, Eq)]
1354 pub struct ParamEnv<'tcx> {
1355 /// This packs both caller bounds and the reveal enum into one pointer.
1357 /// Caller bounds are `Obligation`s that the caller must satisfy. This is
1358 /// basically the set of bounds on the in-scope type parameters, translated
1359 /// into `Obligation`s, and elaborated and normalized.
1361 /// Use the `caller_bounds()` method to access.
1363 /// Typically, this is `Reveal::UserFacing`, but during codegen we
1364 /// want `Reveal::All`.
1366 /// Note: This is packed, use the reveal() method to access it.
1367 packed: CopyTaggedPtr<&'tcx List<Predicate<'tcx>>, ParamTag, true>,
1370 #[derive(Copy, Clone)]
1372 reveal: traits::Reveal,
1373 constness: hir::Constness,
1376 unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag {
1377 const BITS: usize = 2;
1379 fn into_usize(self) -> usize {
1381 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0,
1382 Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1,
1383 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2,
1384 Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3,
1388 unsafe fn from_usize(ptr: usize) -> Self {
1390 0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
1391 1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
1392 2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
1393 3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const },
1394 _ => std::hint::unreachable_unchecked(),
1399 impl<'tcx> fmt::Debug for ParamEnv<'tcx> {
1400 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1401 f.debug_struct("ParamEnv")
1402 .field("caller_bounds", &self.caller_bounds())
1403 .field("reveal", &self.reveal())
1404 .field("constness", &self.constness())
1409 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
1410 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1411 self.caller_bounds().hash_stable(hcx, hasher);
1412 self.reveal().hash_stable(hcx, hasher);
1413 self.constness().hash_stable(hcx, hasher);
1417 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
1418 fn try_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>(
1421 ) -> Result<Self, F::Error> {
1423 self.caller_bounds().try_fold_with(folder)?,
1424 self.reveal().try_fold_with(folder)?,
1425 self.constness().try_fold_with(folder)?,
1430 impl<'tcx> TypeVisitable<'tcx> for ParamEnv<'tcx> {
1431 fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1432 self.caller_bounds().visit_with(visitor)?;
1433 self.reveal().visit_with(visitor)?;
1434 self.constness().visit_with(visitor)
1438 impl<'tcx> ParamEnv<'tcx> {
1439 /// Construct a trait environment suitable for contexts where
1440 /// there are no where-clauses in scope. Hidden types (like `impl
1441 /// Trait`) are left hidden, so this is suitable for ordinary
1444 pub fn empty() -> Self {
1445 Self::new(List::empty(), Reveal::UserFacing, hir::Constness::NotConst)
1449 pub fn caller_bounds(self) -> &'tcx List<Predicate<'tcx>> {
1450 self.packed.pointer()
1454 pub fn reveal(self) -> traits::Reveal {
1455 self.packed.tag().reveal
1459 pub fn constness(self) -> hir::Constness {
1460 self.packed.tag().constness
1464 pub fn is_const(self) -> bool {
1465 self.packed.tag().constness == hir::Constness::Const
1468 /// Construct a trait environment with no where-clauses in scope
1469 /// where the values of all `impl Trait` and other hidden types
1470 /// are revealed. This is suitable for monomorphized, post-typeck
1471 /// environments like codegen or doing optimizations.
1473 /// N.B., if you want to have predicates in scope, use `ParamEnv::new`,
1474 /// or invoke `param_env.with_reveal_all()`.
1476 pub fn reveal_all() -> Self {
1477 Self::new(List::empty(), Reveal::All, hir::Constness::NotConst)
1480 /// Construct a trait environment with the given set of predicates.
1483 caller_bounds: &'tcx List<Predicate<'tcx>>,
1485 constness: hir::Constness,
1487 ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal, constness }) }
1490 pub fn with_user_facing(mut self) -> Self {
1491 self.packed.set_tag(ParamTag { reveal: Reveal::UserFacing, ..self.packed.tag() });
1496 pub fn with_constness(mut self, constness: hir::Constness) -> Self {
1497 self.packed.set_tag(ParamTag { constness, ..self.packed.tag() });
1502 pub fn with_const(mut self) -> Self {
1503 self.packed.set_tag(ParamTag { constness: hir::Constness::Const, ..self.packed.tag() });
1508 pub fn without_const(mut self) -> Self {
1509 self.packed.set_tag(ParamTag { constness: hir::Constness::NotConst, ..self.packed.tag() });
1514 pub fn remap_constness_with(&mut self, mut constness: ty::BoundConstness) {
1515 *self = self.with_constness(constness.and(self.constness()))
1518 /// Returns a new parameter environment with the same clauses, but
1519 /// which "reveals" the true results of projections in all cases
1520 /// (even for associated types that are specializable). This is
1521 /// the desired behavior during codegen and certain other special
1522 /// contexts; normally though we want to use `Reveal::UserFacing`,
1523 /// which is the default.
1524 /// All opaque types in the caller_bounds of the `ParamEnv`
1525 /// will be normalized to their underlying types.
1526 /// See PR #65989 and issue #65918 for more details
1527 pub fn with_reveal_all_normalized(self, tcx: TyCtxt<'tcx>) -> Self {
1528 if self.packed.tag().reveal == traits::Reveal::All {
1533 tcx.normalize_opaque_types(self.caller_bounds()),
1539 /// Returns this same environment but with no caller bounds.
1541 pub fn without_caller_bounds(self) -> Self {
1542 Self::new(List::empty(), self.reveal(), self.constness())
1545 /// Creates a suitable environment in which to perform trait
1546 /// queries on the given value. When type-checking, this is simply
1547 /// the pair of the environment plus value. But when reveal is set to
1548 /// All, then if `value` does not reference any type parameters, we will
1549 /// pair it with the empty environment. This improves caching and is generally
1552 /// N.B., we preserve the environment when type-checking because it
1553 /// is possible for the user to have wacky where-clauses like
1554 /// `where Box<u32>: Copy`, which are clearly never
1555 /// satisfiable. We generally want to behave as if they were true,
1556 /// although the surrounding function is never reachable.
1557 pub fn and<T: TypeVisitable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
1558 match self.reveal() {
1559 Reveal::UserFacing => ParamEnvAnd { param_env: self, value },
1562 if value.is_global() {
1563 ParamEnvAnd { param_env: self.without_caller_bounds(), value }
1565 ParamEnvAnd { param_env: self, value }
1572 // FIXME(ecstaticmorse): Audit all occurrences of `without_const().to_predicate(tcx)` to ensure that
1573 // the constness of trait bounds is being propagated correctly.
1574 impl<'tcx> PolyTraitRef<'tcx> {
1576 pub fn with_constness(self, constness: BoundConstness) -> PolyTraitPredicate<'tcx> {
1577 self.map_bound(|trait_ref| ty::TraitPredicate {
1580 polarity: ty::ImplPolarity::Positive,
1585 pub fn without_const(self) -> PolyTraitPredicate<'tcx> {
1586 self.with_constness(BoundConstness::NotConst)
1590 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
1591 #[derive(HashStable)]
1592 pub struct ParamEnvAnd<'tcx, T> {
1593 pub param_env: ParamEnv<'tcx>,
1597 impl<'tcx, T> ParamEnvAnd<'tcx, T> {
1598 pub fn into_parts(self) -> (ParamEnv<'tcx>, T) {
1599 (self.param_env, self.value)
1603 pub fn without_const(mut self) -> Self {
1604 self.param_env = self.param_env.without_const();
1609 #[derive(Copy, Clone, Debug, HashStable, Encodable, Decodable)]
1610 pub struct Destructor {
1611 /// The `DefId` of the destructor method
1613 /// The constness of the destructor method
1614 pub constness: hir::Constness,
1618 #[derive(HashStable, TyEncodable, TyDecodable)]
1619 pub struct VariantFlags: u32 {
1620 const NO_VARIANT_FLAGS = 0;
1621 /// Indicates whether the field list of this variant is `#[non_exhaustive]`.
1622 const IS_FIELD_LIST_NON_EXHAUSTIVE = 1 << 0;
1623 /// Indicates whether this variant was obtained as part of recovering from
1624 /// a syntactic error. May be incomplete or bogus.
1625 const IS_RECOVERED = 1 << 1;
1629 /// Definition of a variant -- a struct's fields or an enum variant.
1630 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1631 pub struct VariantDef {
1632 /// `DefId` that identifies the variant itself.
1633 /// If this variant belongs to a struct or union, then this is a copy of its `DefId`.
1635 /// `DefId` that identifies the variant's constructor.
1636 /// If this variant is a struct variant, then this is `None`.
1637 pub ctor_def_id: Option<DefId>,
1638 /// Variant or struct name.
1640 /// Discriminant of this variant.
1641 pub discr: VariantDiscr,
1642 /// Fields of this variant.
1643 pub fields: Vec<FieldDef>,
1644 /// Type of constructor of variant.
1645 pub ctor_kind: CtorKind,
1646 /// Flags of the variant (e.g. is field list non-exhaustive)?
1647 flags: VariantFlags,
1651 /// Creates a new `VariantDef`.
1653 /// `variant_did` is the `DefId` that identifies the enum variant (if this `VariantDef`
1654 /// represents an enum variant).
1656 /// `ctor_did` is the `DefId` that identifies the constructor of unit or
1657 /// tuple-variants/structs. If this is a `struct`-variant then this should be `None`.
1659 /// `parent_did` is the `DefId` of the `AdtDef` representing the enum or struct that
1660 /// owns this variant. It is used for checking if a struct has `#[non_exhaustive]` w/out having
1661 /// to go through the redirect of checking the ctor's attributes - but compiling a small crate
1662 /// requires loading the `AdtDef`s for all the structs in the universe (e.g., coherence for any
1663 /// built-in trait), and we do not want to load attributes twice.
1665 /// If someone speeds up attribute loading to not be a performance concern, they can
1666 /// remove this hack and use the constructor `DefId` everywhere.
1669 variant_did: Option<DefId>,
1670 ctor_def_id: Option<DefId>,
1671 discr: VariantDiscr,
1672 fields: Vec<FieldDef>,
1673 ctor_kind: CtorKind,
1677 is_field_list_non_exhaustive: bool,
1680 "VariantDef::new(name = {:?}, variant_did = {:?}, ctor_def_id = {:?}, discr = {:?},
1681 fields = {:?}, ctor_kind = {:?}, adt_kind = {:?}, parent_did = {:?})",
1682 name, variant_did, ctor_def_id, discr, fields, ctor_kind, adt_kind, parent_did,
1685 let mut flags = VariantFlags::NO_VARIANT_FLAGS;
1686 if is_field_list_non_exhaustive {
1687 flags |= VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE;
1691 flags |= VariantFlags::IS_RECOVERED;
1695 def_id: variant_did.unwrap_or(parent_did),
1705 /// Is this field list non-exhaustive?
1707 pub fn is_field_list_non_exhaustive(&self) -> bool {
1708 self.flags.intersects(VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE)
1711 /// Was this variant obtained as part of recovering from a syntactic error?
1713 pub fn is_recovered(&self) -> bool {
1714 self.flags.intersects(VariantFlags::IS_RECOVERED)
1717 /// Computes the `Ident` of this variant by looking up the `Span`
1718 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1719 Ident::new(self.name, tcx.def_ident_span(self.def_id).unwrap())
1723 impl PartialEq for VariantDef {
1725 fn eq(&self, other: &Self) -> bool {
1726 // There should be only one `VariantDef` for each `def_id`, therefore
1727 // it is fine to implement `PartialEq` only based on `def_id`.
1729 // Below, we exhaustively destructure `self` and `other` so that if the
1730 // definition of `VariantDef` changes, a compile-error will be produced,
1731 // reminding us to revisit this assumption.
1753 lhs_def_id == rhs_def_id
1757 impl Eq for VariantDef {}
1759 impl Hash for VariantDef {
1761 fn hash<H: Hasher>(&self, s: &mut H) {
1762 // There should be only one `VariantDef` for each `def_id`, therefore
1763 // it is fine to implement `Hash` only based on `def_id`.
1765 // Below, we exhaustively destructure `self` so that if the definition
1766 // of `VariantDef` changes, a compile-error will be produced, reminding
1767 // us to revisit this assumption.
1769 let Self { def_id, ctor_def_id: _, name: _, discr: _, fields: _, ctor_kind: _, flags: _ } =
1776 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
1777 pub enum VariantDiscr {
1778 /// Explicit value for this variant, i.e., `X = 123`.
1779 /// The `DefId` corresponds to the embedded constant.
1782 /// The previous variant's discriminant plus one.
1783 /// For efficiency reasons, the distance from the
1784 /// last `Explicit` discriminant is being stored,
1785 /// or `0` for the first variant, if it has none.
1789 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1790 pub struct FieldDef {
1793 pub vis: Visibility,
1796 impl PartialEq for FieldDef {
1798 fn eq(&self, other: &Self) -> bool {
1799 // There should be only one `FieldDef` for each `did`, therefore it is
1800 // fine to implement `PartialEq` only based on `did`.
1802 // Below, we exhaustively destructure `self` so that if the definition
1803 // of `FieldDef` changes, a compile-error will be produced, reminding
1804 // us to revisit this assumption.
1806 let Self { did: lhs_did, name: _, vis: _ } = &self;
1808 let Self { did: rhs_did, name: _, vis: _ } = other;
1814 impl Eq for FieldDef {}
1816 impl Hash for FieldDef {
1818 fn hash<H: Hasher>(&self, s: &mut H) {
1819 // There should be only one `FieldDef` for each `did`, therefore it is
1820 // fine to implement `Hash` only based on `did`.
1822 // Below, we exhaustively destructure `self` so that if the definition
1823 // of `FieldDef` changes, a compile-error will be produced, reminding
1824 // us to revisit this assumption.
1826 let Self { did, name: _, vis: _ } = &self;
1833 #[derive(TyEncodable, TyDecodable, Default, HashStable)]
1834 pub struct ReprFlags: u8 {
1835 const IS_C = 1 << 0;
1836 const IS_SIMD = 1 << 1;
1837 const IS_TRANSPARENT = 1 << 2;
1838 // Internal only for now. If true, don't reorder fields.
1839 const IS_LINEAR = 1 << 3;
1840 // If true, the type's layout can be randomized using
1841 // the seed stored in `ReprOptions.layout_seed`
1842 const RANDOMIZE_LAYOUT = 1 << 4;
1843 // Any of these flags being set prevent field reordering optimisation.
1844 const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
1845 | ReprFlags::IS_SIMD.bits
1846 | ReprFlags::IS_LINEAR.bits;
1850 /// Represents the repr options provided by the user,
1851 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Default, HashStable)]
1852 pub struct ReprOptions {
1853 pub int: Option<attr::IntType>,
1854 pub align: Option<Align>,
1855 pub pack: Option<Align>,
1856 pub flags: ReprFlags,
1857 /// The seed to be used for randomizing a type's layout
1859 /// Note: This could technically be a `[u8; 16]` (a `u128`) which would
1860 /// be the "most accurate" hash as it'd encompass the item and crate
1861 /// hash without loss, but it does pay the price of being larger.
1862 /// Everything's a tradeoff, a `u64` seed should be sufficient for our
1863 /// purposes (primarily `-Z randomize-layout`)
1864 pub field_shuffle_seed: u64,
1868 pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions {
1869 let mut flags = ReprFlags::empty();
1870 let mut size = None;
1871 let mut max_align: Option<Align> = None;
1872 let mut min_pack: Option<Align> = None;
1874 // Generate a deterministically-derived seed from the item's path hash
1875 // to allow for cross-crate compilation to actually work
1876 let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash();
1878 // If the user defined a custom seed for layout randomization, xor the item's
1879 // path hash with the user defined seed, this will allowing determinism while
1880 // still allowing users to further randomize layout generation for e.g. fuzzing
1881 if let Some(user_seed) = tcx.sess.opts.unstable_opts.layout_seed {
1882 field_shuffle_seed ^= user_seed;
1885 for attr in tcx.get_attrs(did, sym::repr) {
1886 for r in attr::parse_repr_attr(&tcx.sess, attr) {
1887 flags.insert(match r {
1888 attr::ReprC => ReprFlags::IS_C,
1889 attr::ReprPacked(pack) => {
1890 let pack = Align::from_bytes(pack as u64).unwrap();
1891 min_pack = Some(if let Some(min_pack) = min_pack {
1898 attr::ReprTransparent => ReprFlags::IS_TRANSPARENT,
1899 attr::ReprSimd => ReprFlags::IS_SIMD,
1900 attr::ReprInt(i) => {
1904 attr::ReprAlign(align) => {
1905 max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap()));
1912 // If `-Z randomize-layout` was enabled for the type definition then we can
1913 // consider performing layout randomization
1914 if tcx.sess.opts.unstable_opts.randomize_layout {
1915 flags.insert(ReprFlags::RANDOMIZE_LAYOUT);
1918 // This is here instead of layout because the choice must make it into metadata.
1919 if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) {
1920 flags.insert(ReprFlags::IS_LINEAR);
1923 Self { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed }
1927 pub fn simd(&self) -> bool {
1928 self.flags.contains(ReprFlags::IS_SIMD)
1932 pub fn c(&self) -> bool {
1933 self.flags.contains(ReprFlags::IS_C)
1937 pub fn packed(&self) -> bool {
1942 pub fn transparent(&self) -> bool {
1943 self.flags.contains(ReprFlags::IS_TRANSPARENT)
1947 pub fn linear(&self) -> bool {
1948 self.flags.contains(ReprFlags::IS_LINEAR)
1951 /// Returns the discriminant type, given these `repr` options.
1952 /// This must only be called on enums!
1953 pub fn discr_type(&self) -> attr::IntType {
1954 self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize))
1957 /// Returns `true` if this `#[repr()]` should inhabit "smart enum
1958 /// layout" optimizations, such as representing `Foo<&T>` as a
1960 pub fn inhibit_enum_layout_opt(&self) -> bool {
1961 self.c() || self.int.is_some()
1964 /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
1965 /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
1966 pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
1967 if let Some(pack) = self.pack {
1968 if pack.bytes() == 1 {
1973 self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
1976 /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
1977 /// was enabled for its declaration crate
1978 pub fn can_randomize_type_layout(&self) -> bool {
1979 !self.inhibit_struct_field_reordering_opt()
1980 && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
1983 /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
1984 pub fn inhibit_union_abi_opt(&self) -> bool {
1989 impl<'tcx> FieldDef {
1990 /// Returns the type of this field. The resulting type is not normalized. The `subst` is
1991 /// typically obtained via the second field of [`TyKind::Adt`].
1992 pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
1993 tcx.bound_type_of(self.did).subst(tcx, subst)
1996 /// Computes the `Ident` of this variant by looking up the `Span`
1997 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1998 Ident::new(self.name, tcx.def_ident_span(self.did).unwrap())
2002 pub type Attributes<'tcx> = impl Iterator<Item = &'tcx ast::Attribute>;
2003 #[derive(Debug, PartialEq, Eq)]
2004 pub enum ImplOverlapKind {
2005 /// These impls are always allowed to overlap.
2007 /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait
2010 /// These impls are allowed to overlap, but that raises
2011 /// an issue #33140 future-compatibility warning.
2013 /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's
2014 /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different.
2016 /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied
2017 /// that difference, making what reduces to the following set of impls:
2019 /// ```compile_fail,(E0119)
2021 /// impl Trait for dyn Send + Sync {}
2022 /// impl Trait for dyn Sync + Send {}
2025 /// Obviously, once we made these types be identical, that code causes a coherence
2026 /// error and a fairly big headache for us. However, luckily for us, the trait
2027 /// `Trait` used in this case is basically a marker trait, and therefore having
2028 /// overlapping impls for it is sound.
2030 /// To handle this, we basically regard the trait as a marker trait, with an additional
2031 /// future-compatibility warning. To avoid accidentally "stabilizing" this feature,
2032 /// it has the following restrictions:
2034 /// 1. The trait must indeed be a marker-like trait (i.e., no items), and must be
2036 /// 2. The trait-ref of both impls must be equal.
2037 /// 3. The trait-ref of both impls must be a trait object type consisting only of
2039 /// 4. Neither of the impls can have any where-clauses.
2041 /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed.
2045 impl<'tcx> TyCtxt<'tcx> {
2046 pub fn typeck_body(self, body: hir::BodyId) -> &'tcx TypeckResults<'tcx> {
2047 self.typeck(self.hir().body_owner_def_id(body))
2050 pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> {
2051 self.associated_items(id)
2052 .in_definition_order()
2053 .filter(move |item| item.kind == AssocKind::Fn && item.defaultness(self).has_value())
2056 /// Look up the name of a definition across crates. This does not look at HIR.
2057 pub fn opt_item_name(self, def_id: DefId) -> Option<Symbol> {
2058 if let Some(cnum) = def_id.as_crate_root() {
2059 Some(self.crate_name(cnum))
2061 let def_key = self.def_key(def_id);
2062 match def_key.disambiguated_data.data {
2063 // The name of a constructor is that of its parent.
2064 rustc_hir::definitions::DefPathData::Ctor => self
2065 .opt_item_name(DefId { krate: def_id.krate, index: def_key.parent.unwrap() }),
2066 // The name of opaque types only exists in HIR.
2067 rustc_hir::definitions::DefPathData::ImplTrait
2068 if let Some(def_id) = def_id.as_local() =>
2069 self.hir().opt_name(self.hir().local_def_id_to_hir_id(def_id)),
2070 _ => def_key.get_opt_name(),
2075 /// Look up the name of a definition across crates. This does not look at HIR.
2077 /// This method will ICE if the corresponding item does not have a name. In these cases, use
2078 /// [`opt_item_name`] instead.
2080 /// [`opt_item_name`]: Self::opt_item_name
2081 pub fn item_name(self, id: DefId) -> Symbol {
2082 self.opt_item_name(id).unwrap_or_else(|| {
2083 bug!("item_name: no name for {:?}", self.def_path(id));
2087 /// Look up the name and span of a definition.
2089 /// See [`item_name`][Self::item_name] for more information.
2090 pub fn opt_item_ident(self, def_id: DefId) -> Option<Ident> {
2091 let def = self.opt_item_name(def_id)?;
2094 .and_then(|id| self.def_ident_span(id))
2095 .unwrap_or(rustc_span::DUMMY_SP);
2096 Some(Ident::new(def, span))
2099 pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> {
2100 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2101 Some(self.associated_item(def_id))
2107 pub fn field_index(self, hir_id: hir::HirId, typeck_results: &TypeckResults<'_>) -> usize {
2108 typeck_results.field_indices().get(hir_id).cloned().expect("no index for a field")
2111 pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
2115 .position(|field| self.hygienic_eq(ident, field.ident(self), variant.def_id))
2118 /// Returns `true` if the impls are the same polarity and the trait either
2119 /// has no items or is annotated `#[marker]` and prevents item overrides.
2120 pub fn impls_are_allowed_to_overlap(
2124 ) -> Option<ImplOverlapKind> {
2125 // If either trait impl references an error, they're allowed to overlap,
2126 // as one of them essentially doesn't exist.
2127 if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.references_error())
2128 || self.impl_trait_ref(def_id2).map_or(false, |tr| tr.references_error())
2130 return Some(ImplOverlapKind::Permitted { marker: false });
2133 match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) {
2134 (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => {
2135 // `#[rustc_reservation_impl]` impls don't overlap with anything
2137 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (reservations)",
2140 return Some(ImplOverlapKind::Permitted { marker: false });
2142 (ImplPolarity::Positive, ImplPolarity::Negative)
2143 | (ImplPolarity::Negative, ImplPolarity::Positive) => {
2144 // `impl AutoTrait for Type` + `impl !AutoTrait for Type`
2146 "impls_are_allowed_to_overlap({:?}, {:?}) - None (differing polarities)",
2151 (ImplPolarity::Positive, ImplPolarity::Positive)
2152 | (ImplPolarity::Negative, ImplPolarity::Negative) => {}
2155 let is_marker_overlap = {
2156 let is_marker_impl = |def_id: DefId| -> bool {
2157 let trait_ref = self.impl_trait_ref(def_id);
2158 trait_ref.map_or(false, |tr| self.trait_def(tr.def_id).is_marker)
2160 is_marker_impl(def_id1) && is_marker_impl(def_id2)
2163 if is_marker_overlap {
2165 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (marker overlap)",
2168 Some(ImplOverlapKind::Permitted { marker: true })
2170 if let Some(self_ty1) = self.issue33140_self_ty(def_id1) {
2171 if let Some(self_ty2) = self.issue33140_self_ty(def_id2) {
2172 if self_ty1 == self_ty2 {
2174 "impls_are_allowed_to_overlap({:?}, {:?}) - issue #33140 HACK",
2177 return Some(ImplOverlapKind::Issue33140);
2180 "impls_are_allowed_to_overlap({:?}, {:?}) - found {:?} != {:?}",
2181 def_id1, def_id2, self_ty1, self_ty2
2187 debug!("impls_are_allowed_to_overlap({:?}, {:?}) = None", def_id1, def_id2);
2192 /// Returns `ty::VariantDef` if `res` refers to a struct,
2193 /// or variant or their constructors, panics otherwise.
2194 pub fn expect_variant_res(self, res: Res) -> &'tcx VariantDef {
2196 Res::Def(DefKind::Variant, did) => {
2197 let enum_did = self.parent(did);
2198 self.adt_def(enum_did).variant_with_id(did)
2200 Res::Def(DefKind::Struct | DefKind::Union, did) => self.adt_def(did).non_enum_variant(),
2201 Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => {
2202 let variant_did = self.parent(variant_ctor_did);
2203 let enum_did = self.parent(variant_did);
2204 self.adt_def(enum_did).variant_with_ctor_id(variant_ctor_did)
2206 Res::Def(DefKind::Ctor(CtorOf::Struct, ..), ctor_did) => {
2207 let struct_did = self.parent(ctor_did);
2208 self.adt_def(struct_did).non_enum_variant()
2210 _ => bug!("expect_variant_res used with unexpected res {:?}", res),
2214 /// Returns the possibly-auto-generated MIR of a `(DefId, Subst)` pair.
2215 #[instrument(skip(self), level = "debug")]
2216 pub fn instance_mir(self, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> {
2218 ty::InstanceDef::Item(def) => {
2219 debug!("calling def_kind on def: {:?}", def);
2220 let def_kind = self.def_kind(def.did);
2221 debug!("returned from def_kind: {:?}", def_kind);
2224 | DefKind::Static(..)
2225 | DefKind::AssocConst
2227 | DefKind::AnonConst
2228 | DefKind::InlineConst => self.mir_for_ctfe_opt_const_arg(def),
2229 // If the caller wants `mir_for_ctfe` of a function they should not be using
2230 // `instance_mir`, so we'll assume const fn also wants the optimized version.
2232 assert_eq!(def.const_param_did, None);
2233 self.optimized_mir(def.did)
2237 ty::InstanceDef::VTableShim(..)
2238 | ty::InstanceDef::ReifyShim(..)
2239 | ty::InstanceDef::Intrinsic(..)
2240 | ty::InstanceDef::FnPtrShim(..)
2241 | ty::InstanceDef::Virtual(..)
2242 | ty::InstanceDef::ClosureOnceShim { .. }
2243 | ty::InstanceDef::DropGlue(..)
2244 | ty::InstanceDef::CloneShim(..) => self.mir_shims(instance),
2248 // FIXME(@lcnr): Remove this function.
2249 pub fn get_attrs_unchecked(self, did: DefId) -> &'tcx [ast::Attribute] {
2250 if let Some(did) = did.as_local() {
2251 self.hir().attrs(self.hir().local_def_id_to_hir_id(did))
2253 self.item_attrs(did)
2257 /// Gets all attributes with the given name.
2258 pub fn get_attrs(self, did: DefId, attr: Symbol) -> ty::Attributes<'tcx> {
2259 let filter_fn = move |a: &&ast::Attribute| a.has_name(attr);
2260 if let Some(did) = did.as_local() {
2261 self.hir().attrs(self.hir().local_def_id_to_hir_id(did)).iter().filter(filter_fn)
2262 } else if cfg!(debug_assertions) && rustc_feature::is_builtin_only_local(attr) {
2263 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2265 self.item_attrs(did).iter().filter(filter_fn)
2269 pub fn get_attr(self, did: DefId, attr: Symbol) -> Option<&'tcx ast::Attribute> {
2270 if cfg!(debug_assertions) && !rustc_feature::is_valid_for_get_attr(attr) {
2271 bug!("get_attr: unexpected called with DefId `{:?}`, attr `{:?}`", did, attr);
2273 self.get_attrs(did, attr).next()
2277 /// Determines whether an item is annotated with an attribute.
2278 pub fn has_attr(self, did: DefId, attr: Symbol) -> bool {
2279 if cfg!(debug_assertions) && !did.is_local() && rustc_feature::is_builtin_only_local(attr) {
2280 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2282 self.get_attrs(did, attr).next().is_some()
2286 /// Returns `true` if this is an `auto trait`.
2287 pub fn trait_is_auto(self, trait_def_id: DefId) -> bool {
2288 self.trait_def(trait_def_id).has_auto_impl
2291 /// Returns layout of a generator. Layout might be unavailable if the
2292 /// generator is tainted by errors.
2293 pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> {
2294 self.optimized_mir(def_id).generator_layout()
2297 /// Given the `DefId` of an impl, returns the `DefId` of the trait it implements.
2298 /// If it implements no trait, returns `None`.
2299 pub fn trait_id_of_impl(self, def_id: DefId) -> Option<DefId> {
2300 self.impl_trait_ref(def_id).map(|tr| tr.def_id)
2303 /// If the given `DefId` describes an item belonging to a trait,
2304 /// returns the `DefId` of the trait that the trait item belongs to;
2305 /// otherwise, returns `None`.
2306 pub fn trait_of_item(self, def_id: DefId) -> Option<DefId> {
2307 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2308 let parent = self.parent(def_id);
2309 if let DefKind::Trait | DefKind::TraitAlias = self.def_kind(parent) {
2310 return Some(parent);
2316 /// If the given `DefId` describes a method belonging to an impl, returns the
2317 /// `DefId` of the impl that the method belongs to; otherwise, returns `None`.
2318 pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
2319 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2320 let parent = self.parent(def_id);
2321 if let DefKind::Impl = self.def_kind(parent) {
2322 return Some(parent);
2328 /// If the given `DefId` belongs to a trait that was automatically derived, returns `true`.
2329 pub fn is_builtin_derive(self, def_id: DefId) -> bool {
2330 self.has_attr(def_id, sym::automatically_derived)
2333 /// Looks up the span of `impl_did` if the impl is local; otherwise returns `Err`
2334 /// with the name of the crate containing the impl.
2335 pub fn span_of_impl(self, impl_did: DefId) -> Result<Span, Symbol> {
2336 if let Some(impl_did) = impl_did.as_local() {
2337 Ok(self.def_span(impl_did))
2339 Err(self.crate_name(impl_did.krate))
2343 /// Hygienically compares a use-site name (`use_name`) for a field or an associated item with
2344 /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
2345 /// definition's parent/scope to perform comparison.
2346 pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
2347 // We could use `Ident::eq` here, but we deliberately don't. The name
2348 // comparison fails frequently, and we want to avoid the expensive
2349 // `normalize_to_macros_2_0()` calls required for the span comparison whenever possible.
2350 use_name.name == def_name.name
2354 .hygienic_eq(def_name.span.ctxt(), self.expn_that_defined(def_parent_def_id))
2357 pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident {
2358 ident.span.normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope));
2362 pub fn adjust_ident_and_get_scope(
2367 ) -> (Ident, DefId) {
2370 .normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope))
2371 .and_then(|actual_expansion| actual_expansion.expn_data().parent_module)
2372 .unwrap_or_else(|| self.parent_module(block).to_def_id());
2376 pub fn is_object_safe(self, key: DefId) -> bool {
2377 self.object_safety_violations(key).is_empty()
2381 pub fn is_const_fn_raw(self, def_id: DefId) -> bool {
2382 matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..))
2383 && self.constness(def_id) == hir::Constness::Const
2387 pub fn is_const_default_method(self, def_id: DefId) -> bool {
2388 matches!(self.trait_of_item(def_id), Some(trait_id) if self.has_attr(trait_id, sym::const_trait))
2392 /// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition.
2393 pub fn is_impl_trait_defn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<LocalDefId> {
2394 let def_id = def_id.as_local()?;
2395 if let Node::Item(item) = tcx.hir().get_by_def_id(def_id) {
2396 if let hir::ItemKind::OpaqueTy(ref opaque_ty) = item.kind {
2397 return match opaque_ty.origin {
2398 hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) => {
2401 hir::OpaqueTyOrigin::TyAlias => None,
2408 pub fn int_ty(ity: ast::IntTy) -> IntTy {
2410 ast::IntTy::Isize => IntTy::Isize,
2411 ast::IntTy::I8 => IntTy::I8,
2412 ast::IntTy::I16 => IntTy::I16,
2413 ast::IntTy::I32 => IntTy::I32,
2414 ast::IntTy::I64 => IntTy::I64,
2415 ast::IntTy::I128 => IntTy::I128,
2419 pub fn uint_ty(uty: ast::UintTy) -> UintTy {
2421 ast::UintTy::Usize => UintTy::Usize,
2422 ast::UintTy::U8 => UintTy::U8,
2423 ast::UintTy::U16 => UintTy::U16,
2424 ast::UintTy::U32 => UintTy::U32,
2425 ast::UintTy::U64 => UintTy::U64,
2426 ast::UintTy::U128 => UintTy::U128,
2430 pub fn float_ty(fty: ast::FloatTy) -> FloatTy {
2432 ast::FloatTy::F32 => FloatTy::F32,
2433 ast::FloatTy::F64 => FloatTy::F64,
2437 pub fn ast_int_ty(ity: IntTy) -> ast::IntTy {
2439 IntTy::Isize => ast::IntTy::Isize,
2440 IntTy::I8 => ast::IntTy::I8,
2441 IntTy::I16 => ast::IntTy::I16,
2442 IntTy::I32 => ast::IntTy::I32,
2443 IntTy::I64 => ast::IntTy::I64,
2444 IntTy::I128 => ast::IntTy::I128,
2448 pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy {
2450 UintTy::Usize => ast::UintTy::Usize,
2451 UintTy::U8 => ast::UintTy::U8,
2452 UintTy::U16 => ast::UintTy::U16,
2453 UintTy::U32 => ast::UintTy::U32,
2454 UintTy::U64 => ast::UintTy::U64,
2455 UintTy::U128 => ast::UintTy::U128,
2459 pub fn provide(providers: &mut ty::query::Providers) {
2460 closure::provide(providers);
2461 context::provide(providers);
2462 erase_regions::provide(providers);
2463 layout::provide(providers);
2464 util::provide(providers);
2465 print::provide(providers);
2466 super::util::bug::provide(providers);
2467 super::middle::provide(providers);
2468 *providers = ty::query::Providers {
2469 trait_impls_of: trait_def::trait_impls_of_provider,
2470 incoherent_impls: trait_def::incoherent_impls_provider,
2471 type_uninhabited_from: inhabitedness::type_uninhabited_from,
2472 const_param_default: consts::const_param_default,
2473 vtable_allocation: vtable::vtable_allocation_provider,
2478 /// A map for the local crate mapping each type to a vector of its
2479 /// inherent impls. This is not meant to be used outside of coherence;
2480 /// rather, you should request the vector for a specific type via
2481 /// `tcx.inherent_impls(def_id)` so as to minimize your dependencies
2482 /// (constructing this map requires touching the entire crate).
2483 #[derive(Clone, Debug, Default, HashStable)]
2484 pub struct CrateInherentImpls {
2485 pub inherent_impls: LocalDefIdMap<Vec<DefId>>,
2486 pub incoherent_impls: FxHashMap<SimplifiedType, Vec<LocalDefId>>,
2489 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, HashStable)]
2490 pub struct SymbolName<'tcx> {
2491 /// `&str` gives a consistent ordering, which ensures reproducible builds.
2492 pub name: &'tcx str,
2495 impl<'tcx> SymbolName<'tcx> {
2496 pub fn new(tcx: TyCtxt<'tcx>, name: &str) -> SymbolName<'tcx> {
2498 name: unsafe { str::from_utf8_unchecked(tcx.arena.alloc_slice(name.as_bytes())) },
2503 impl<'tcx> fmt::Display for SymbolName<'tcx> {
2504 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2505 fmt::Display::fmt(&self.name, fmt)
2509 impl<'tcx> fmt::Debug for SymbolName<'tcx> {
2510 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2511 fmt::Display::fmt(&self.name, fmt)
2515 #[derive(Debug, Default, Copy, Clone)]
2516 pub struct FoundRelationships {
2517 /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
2518 /// obligation, where:
2520 /// * `Foo` is not `Sized`
2521 /// * `(): Foo` may be satisfied
2522 pub self_in_trait: bool,
2523 /// This is true if we identified that this Ty (`?T`) is found in a `<_ as
2524 /// _>::AssocType = ?T`
2528 /// The constituent parts of a type level constant of kind ADT or array.
2529 #[derive(Copy, Clone, Debug, HashStable)]
2530 pub struct DestructuredConst<'tcx> {
2531 pub variant: Option<VariantIdx>,
2532 pub fields: &'tcx [ty::Const<'tcx>],