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;
127 mod layout_sanity_check;
131 mod structural_impls;
136 pub type RegisteredTools = FxHashSet<Ident>;
139 pub struct ResolverOutputs {
140 pub visibilities: FxHashMap<LocalDefId, Visibility>,
141 /// This field is used to decide whether we should make `PRIVATE_IN_PUBLIC` a hard error.
142 pub has_pub_restricted: bool,
143 /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
144 pub expn_that_defined: FxHashMap<LocalDefId, ExpnId>,
145 /// Reference span for definitions.
146 pub source_span: IndexVec<LocalDefId, Span>,
147 pub access_levels: AccessLevels,
148 pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
149 pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
150 pub maybe_unused_extern_crates: Vec<(LocalDefId, Span)>,
151 pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>,
152 pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
153 /// Extern prelude entries. The value is `true` if the entry was introduced
154 /// via `extern crate` item and not `--extern` option or compiler built-in.
155 pub extern_prelude: FxHashMap<Symbol, bool>,
156 pub main_def: Option<MainDefinition>,
157 pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,
158 /// A list of proc macro LocalDefIds, written out in the order in which
159 /// they are declared in the static array generated by proc_macro_harness.
160 pub proc_macros: Vec<LocalDefId>,
161 /// Mapping from ident span to path span for paths that don't exist as written, but that
162 /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`.
163 pub confused_type_with_std_module: FxHashMap<Span, Span>,
164 pub registered_tools: RegisteredTools,
167 /// Resolutions that should only be used for lowering.
168 /// This struct is meant to be consumed by lowering.
170 pub struct ResolverAstLowering {
171 pub legacy_const_generic_args: FxHashMap<DefId, Option<Vec<usize>>>,
173 /// Resolutions for nodes that have a single resolution.
174 pub partial_res_map: NodeMap<hir::def::PartialRes>,
175 /// Resolutions for import nodes, which have multiple resolutions in different namespaces.
176 pub import_res_map: NodeMap<hir::def::PerNS<Option<Res<ast::NodeId>>>>,
177 /// Resolutions for labels (node IDs of their corresponding blocks or loops).
178 pub label_res_map: NodeMap<ast::NodeId>,
179 /// Resolutions for lifetimes.
180 pub lifetimes_res_map: NodeMap<LifetimeRes>,
181 /// Mapping from generics `def_id`s to TAIT generics `def_id`s.
182 /// For each captured lifetime (e.g., 'a), we create a new lifetime parameter that is a generic
183 /// defined on the TAIT, so we have type Foo<'a1> = ... and we establish a mapping in this
184 /// field from the original parameter 'a to the new parameter 'a1.
185 pub generics_def_id_map: Vec<FxHashMap<LocalDefId, LocalDefId>>,
186 /// Lifetime parameters that lowering will have to introduce.
187 pub extra_lifetime_params_map: NodeMap<Vec<(Ident, ast::NodeId, LifetimeRes)>>,
189 pub next_node_id: ast::NodeId,
191 pub node_id_to_def_id: FxHashMap<ast::NodeId, LocalDefId>,
192 pub def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
194 pub trait_map: NodeMap<Vec<hir::TraitCandidate>>,
195 /// A small map keeping true kinds of built-in macros that appear to be fn-like on
196 /// the surface (`macro` items in libcore), but are actually attributes or derives.
197 pub builtin_macro_kinds: FxHashMap<LocalDefId, MacroKind>,
200 #[derive(Clone, Copy, Debug)]
201 pub struct MainDefinition {
202 pub res: Res<ast::NodeId>,
207 impl MainDefinition {
208 pub fn opt_fn_def_id(self) -> Option<DefId> {
209 if let Res::Def(DefKind::Fn, def_id) = self.res { Some(def_id) } else { None }
213 /// The "header" of an impl is everything outside the body: a Self type, a trait
214 /// ref (in the case of a trait impl), and a set of predicates (from the
215 /// bounds / where-clauses).
216 #[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
217 pub struct ImplHeader<'tcx> {
218 pub impl_def_id: DefId,
219 pub self_ty: Ty<'tcx>,
220 pub trait_ref: Option<TraitRef<'tcx>>,
221 pub predicates: Vec<Predicate<'tcx>>,
224 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
225 pub enum ImplSubject<'tcx> {
226 Trait(TraitRef<'tcx>),
230 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable, Debug)]
231 #[derive(TypeFoldable, TypeVisitable)]
232 pub enum ImplPolarity {
233 /// `impl Trait for Type`
235 /// `impl !Trait for Type`
237 /// `#[rustc_reservation_impl] impl Trait for Type`
239 /// This is a "stability hack", not a real Rust feature.
240 /// See #64631 for details.
245 /// Flips polarity by turning `Positive` into `Negative` and `Negative` into `Positive`.
246 pub fn flip(&self) -> Option<ImplPolarity> {
248 ImplPolarity::Positive => Some(ImplPolarity::Negative),
249 ImplPolarity::Negative => Some(ImplPolarity::Positive),
250 ImplPolarity::Reservation => None,
255 impl fmt::Display for ImplPolarity {
256 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
258 Self::Positive => f.write_str("positive"),
259 Self::Negative => f.write_str("negative"),
260 Self::Reservation => f.write_str("reservation"),
265 #[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, Encodable, Decodable, HashStable)]
266 pub enum Visibility {
267 /// Visible everywhere (including in other crates).
269 /// Visible only in the given crate-local module.
273 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)]
274 pub enum BoundConstness {
277 /// `T: ~const Trait`
279 /// Requires resolving to const only when we are in a const context.
283 impl BoundConstness {
284 /// Reduce `self` and `constness` to two possible combined states instead of four.
285 pub fn and(&mut self, constness: hir::Constness) -> hir::Constness {
286 match (constness, self) {
287 (hir::Constness::Const, BoundConstness::ConstIfConst) => hir::Constness::Const,
289 *this = BoundConstness::NotConst;
290 hir::Constness::NotConst
296 impl fmt::Display for BoundConstness {
297 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
299 Self::NotConst => f.write_str("normal"),
300 Self::ConstIfConst => f.write_str("`~const`"),
305 #[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, TyEncodable, TyDecodable, HashStable)]
306 #[derive(TypeFoldable, TypeVisitable)]
307 pub struct ClosureSizeProfileData<'tcx> {
308 /// Tuple containing the types of closure captures before the feature `capture_disjoint_fields`
309 pub before_feature_tys: Ty<'tcx>,
310 /// Tuple containing the types of closure captures after the feature `capture_disjoint_fields`
311 pub after_feature_tys: Ty<'tcx>,
314 pub trait DefIdTree: Copy {
315 fn opt_parent(self, id: DefId) -> Option<DefId>;
319 fn parent(self, id: DefId) -> DefId {
320 match self.opt_parent(id) {
322 // not `unwrap_or_else` to avoid breaking caller tracking
323 None => bug!("{id:?} doesn't have a parent"),
329 fn opt_local_parent(self, id: LocalDefId) -> Option<LocalDefId> {
330 self.opt_parent(id.to_def_id()).map(DefId::expect_local)
335 fn local_parent(self, id: LocalDefId) -> LocalDefId {
336 self.parent(id.to_def_id()).expect_local()
339 fn is_descendant_of(self, mut descendant: DefId, ancestor: DefId) -> bool {
340 if descendant.krate != ancestor.krate {
344 while descendant != ancestor {
345 match self.opt_parent(descendant) {
346 Some(parent) => descendant = parent,
347 None => return false,
354 impl<'tcx> DefIdTree for TyCtxt<'tcx> {
356 fn opt_parent(self, id: DefId) -> Option<DefId> {
357 self.def_key(id).parent.map(|index| DefId { index, ..id })
362 /// Returns `true` if an item with this visibility is accessible from the given block.
363 pub fn is_accessible_from<T: DefIdTree>(self, module: DefId, tree: T) -> bool {
364 let restriction = match self {
365 // Public items are visible everywhere.
366 Visibility::Public => return true,
367 // Restricted items are visible in an arbitrary local module.
368 Visibility::Restricted(other) if other.krate != module.krate => return false,
369 Visibility::Restricted(module) => module,
372 tree.is_descendant_of(module, restriction)
375 /// Returns `true` if this visibility is at least as accessible as the given visibility
376 pub fn is_at_least<T: DefIdTree>(self, vis: Visibility, tree: T) -> bool {
377 let vis_restriction = match vis {
378 Visibility::Public => return self == Visibility::Public,
379 Visibility::Restricted(module) => module,
382 self.is_accessible_from(vis_restriction, tree)
385 // Returns `true` if this item is visible anywhere in the local crate.
386 pub fn is_visible_locally(self) -> bool {
388 Visibility::Public => true,
389 Visibility::Restricted(def_id) => def_id.is_local(),
393 pub fn is_public(self) -> bool {
394 matches!(self, Visibility::Public)
398 /// The crate variances map is computed during typeck and contains the
399 /// variance of every item in the local crate. You should not use it
400 /// directly, because to do so will make your pass dependent on the
401 /// HIR of every item in the local crate. Instead, use
402 /// `tcx.variances_of()` to get the variance for a *particular*
404 #[derive(HashStable, Debug)]
405 pub struct CrateVariancesMap<'tcx> {
406 /// For each item with generics, maps to a vector of the variance
407 /// of its generics. If an item has no generics, it will have no
409 pub variances: FxHashMap<DefId, &'tcx [ty::Variance]>,
412 // Contains information needed to resolve types and (in the future) look up
413 // the types of AST nodes.
414 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
415 pub struct CReaderCacheKey {
416 pub cnum: Option<CrateNum>,
420 /// Represents a type.
423 /// - This is a very "dumb" struct (with no derives and no `impls`).
424 /// - Values of this type are always interned and thus unique, and are stored
425 /// as an `Interned<TyS>`.
426 /// - `Ty` (which contains a reference to a `Interned<TyS>`) or `Interned<TyS>`
427 /// should be used everywhere instead of `TyS`. In particular, `Ty` has most
428 /// of the relevant methods.
429 #[derive(PartialEq, Eq, PartialOrd, Ord)]
430 #[allow(rustc::usage_of_ty_tykind)]
431 pub(crate) struct TyS<'tcx> {
432 /// This field shouldn't be used directly and may be removed in the future.
433 /// Use `Ty::kind()` instead.
436 /// This field provides fast access to information that is also contained
439 /// This field shouldn't be used directly and may be removed in the future.
440 /// Use `Ty::flags()` instead.
443 /// This field provides fast access to information that is also contained
446 /// This is a kind of confusing thing: it stores the smallest
449 /// (a) the binder itself captures nothing but
450 /// (b) all the late-bound things within the type are captured
451 /// by some sub-binder.
453 /// So, for a type without any late-bound things, like `u32`, this
454 /// will be *innermost*, because that is the innermost binder that
455 /// captures nothing. But for a type `&'D u32`, where `'D` is a
456 /// late-bound region with De Bruijn index `D`, this would be `D + 1`
457 /// -- the binder itself does not capture `D`, but `D` is captured
458 /// by an inner binder.
460 /// We call this concept an "exclusive" binder `D` because all
461 /// De Bruijn indices within the type are contained within `0..D`
463 outer_exclusive_binder: ty::DebruijnIndex,
466 // `TyS` is used a lot. Make sure it doesn't unintentionally get bigger.
467 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
468 static_assert_size!(TyS<'_>, 40);
470 // We are actually storing a stable hash cache next to the type, so let's
471 // also check the full size
472 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
473 static_assert_size!(WithStableHash<TyS<'_>>, 56);
475 /// Use this rather than `TyS`, whenever possible.
476 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)]
477 #[rustc_diagnostic_item = "Ty"]
478 #[rustc_pass_by_value]
479 pub struct Ty<'tcx>(Interned<'tcx, WithStableHash<TyS<'tcx>>>);
481 impl<'tcx> TyCtxt<'tcx> {
482 /// A "bool" type used in rustc_mir_transform unit tests when we
483 /// have not spun up a TyCtxt.
484 pub const BOOL_TY_FOR_UNIT_TESTING: Ty<'tcx> = Ty(Interned::new_unchecked(&WithStableHash {
487 flags: TypeFlags::empty(),
488 outer_exclusive_binder: DebruijnIndex::from_usize(0),
490 stable_hash: Fingerprint::ZERO,
494 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for TyS<'tcx> {
496 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
500 // The other fields just provide fast access to information that is
501 // also contained in `kind`, so no need to hash them.
504 outer_exclusive_binder: _,
507 kind.hash_stable(hcx, hasher)
511 impl ty::EarlyBoundRegion {
512 /// Does this early bound region have a name? Early bound regions normally
513 /// always have names except when using anonymous lifetimes (`'_`).
514 pub fn has_name(&self) -> bool {
515 self.name != kw::UnderscoreLifetime
519 /// Represents a predicate.
521 /// See comments on `TyS`, which apply here too (albeit for
522 /// `PredicateS`/`Predicate` rather than `TyS`/`Ty`).
524 pub(crate) struct PredicateS<'tcx> {
525 kind: Binder<'tcx, PredicateKind<'tcx>>,
527 /// See the comment for the corresponding field of [TyS].
528 outer_exclusive_binder: ty::DebruijnIndex,
531 // This type is used a lot. Make sure it doesn't unintentionally get bigger.
532 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
533 static_assert_size!(PredicateS<'_>, 56);
535 /// Use this rather than `PredicateS`, whenever possible.
536 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
537 #[rustc_pass_by_value]
538 pub struct Predicate<'tcx>(Interned<'tcx, PredicateS<'tcx>>);
540 impl<'tcx> Predicate<'tcx> {
541 /// Gets the inner `Binder<'tcx, PredicateKind<'tcx>>`.
543 pub fn kind(self) -> Binder<'tcx, PredicateKind<'tcx>> {
548 pub fn flags(self) -> TypeFlags {
553 pub fn outer_exclusive_binder(self) -> DebruijnIndex {
554 self.0.outer_exclusive_binder
557 /// Flips the polarity of a Predicate.
559 /// Given `T: Trait` predicate it returns `T: !Trait` and given `T: !Trait` returns `T: Trait`.
560 pub fn flip_polarity(self, tcx: TyCtxt<'tcx>) -> Option<Predicate<'tcx>> {
563 .map_bound(|kind| match kind {
564 PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) => {
565 Some(PredicateKind::Trait(TraitPredicate {
568 polarity: polarity.flip()?,
576 Some(tcx.mk_predicate(kind))
579 pub fn without_const(mut self, tcx: TyCtxt<'tcx>) -> Self {
580 if let PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) = self.kind().skip_binder()
581 && constness != BoundConstness::NotConst
583 self = tcx.mk_predicate(self.kind().rebind(PredicateKind::Trait(TraitPredicate {
585 constness: BoundConstness::NotConst,
592 /// Whether this projection can be soundly normalized.
594 /// Wf predicates must not be normalized, as normalization
595 /// can remove required bounds which would cause us to
596 /// unsoundly accept some programs. See #91068.
598 pub fn allow_normalization(self) -> bool {
599 match self.kind().skip_binder() {
600 PredicateKind::WellFormed(_) => false,
601 PredicateKind::Trait(_)
602 | PredicateKind::RegionOutlives(_)
603 | PredicateKind::TypeOutlives(_)
604 | PredicateKind::Projection(_)
605 | PredicateKind::ObjectSafe(_)
606 | PredicateKind::ClosureKind(_, _, _)
607 | PredicateKind::Subtype(_)
608 | PredicateKind::Coerce(_)
609 | PredicateKind::ConstEvaluatable(_)
610 | PredicateKind::ConstEquate(_, _)
611 | PredicateKind::TypeWellFormedFromEnv(_) => true,
616 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> {
617 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
621 // The other fields just provide fast access to information that is
622 // also contained in `kind`, so no need to hash them.
624 outer_exclusive_binder: _,
627 kind.hash_stable(hcx, hasher);
631 impl rustc_errors::IntoDiagnosticArg for Predicate<'_> {
632 fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
633 rustc_errors::DiagnosticArgValue::Str(std::borrow::Cow::Owned(self.to_string()))
637 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
638 #[derive(HashStable, TypeFoldable, TypeVisitable)]
639 pub enum PredicateKind<'tcx> {
640 /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
641 /// the `Self` type of the trait reference and `A`, `B`, and `C`
642 /// would be the type parameters.
643 Trait(TraitPredicate<'tcx>),
646 RegionOutlives(RegionOutlivesPredicate<'tcx>),
649 TypeOutlives(TypeOutlivesPredicate<'tcx>),
651 /// `where <T as TraitRef>::Name == X`, approximately.
652 /// See the `ProjectionPredicate` struct for details.
653 Projection(ProjectionPredicate<'tcx>),
655 /// No syntax: `T` well-formed.
656 WellFormed(GenericArg<'tcx>),
658 /// Trait must be object-safe.
661 /// No direct syntax. May be thought of as `where T: FnFoo<...>`
662 /// for some substitutions `...` and `T` being a closure type.
663 /// Satisfied (or refuted) once we know the closure's kind.
664 ClosureKind(DefId, SubstsRef<'tcx>, ClosureKind),
668 /// This obligation is created most often when we have two
669 /// unresolved type variables and hence don't have enough
670 /// information to process the subtyping obligation yet.
671 Subtype(SubtypePredicate<'tcx>),
673 /// `T1` coerced to `T2`
675 /// Like a subtyping obligation, this is created most often
676 /// when we have two unresolved type variables and hence
677 /// don't have enough information to process the coercion
678 /// obligation yet. At the moment, we actually process coercions
679 /// very much like subtyping and don't handle the full coercion
681 Coerce(CoercePredicate<'tcx>),
683 /// Constant initializer must evaluate successfully.
684 ConstEvaluatable(ty::Unevaluated<'tcx, ()>),
686 /// Constants must be equal. The first component is the const that is expected.
687 ConstEquate(Const<'tcx>, Const<'tcx>),
689 /// Represents a type found in the environment that we can use for implied bounds.
691 /// Only used for Chalk.
692 TypeWellFormedFromEnv(Ty<'tcx>),
695 /// The crate outlives map is computed during typeck and contains the
696 /// outlives of every item in the local crate. You should not use it
697 /// directly, because to do so will make your pass dependent on the
698 /// HIR of every item in the local crate. Instead, use
699 /// `tcx.inferred_outlives_of()` to get the outlives for a *particular*
701 #[derive(HashStable, Debug)]
702 pub struct CratePredicatesMap<'tcx> {
703 /// For each struct with outlive bounds, maps to a vector of the
704 /// predicate of its outlive bounds. If an item has no outlives
705 /// bounds, it will have no entry.
706 pub predicates: FxHashMap<DefId, &'tcx [(Predicate<'tcx>, Span)]>,
709 impl<'tcx> Predicate<'tcx> {
710 /// Performs a substitution suitable for going from a
711 /// poly-trait-ref to supertraits that must hold if that
712 /// poly-trait-ref holds. This is slightly different from a normal
713 /// substitution in terms of what happens with bound regions. See
714 /// lengthy comment below for details.
715 pub fn subst_supertrait(
718 trait_ref: &ty::PolyTraitRef<'tcx>,
719 ) -> Predicate<'tcx> {
720 // The interaction between HRTB and supertraits is not entirely
721 // obvious. Let me walk you (and myself) through an example.
723 // Let's start with an easy case. Consider two traits:
725 // trait Foo<'a>: Bar<'a,'a> { }
726 // trait Bar<'b,'c> { }
728 // Now, if we have a trait reference `for<'x> T: Foo<'x>`, then
729 // we can deduce that `for<'x> T: Bar<'x,'x>`. Basically, if we
730 // knew that `Foo<'x>` (for any 'x) then we also know that
731 // `Bar<'x,'x>` (for any 'x). This more-or-less falls out from
732 // normal substitution.
734 // In terms of why this is sound, the idea is that whenever there
735 // is an impl of `T:Foo<'a>`, it must show that `T:Bar<'a,'a>`
736 // holds. So if there is an impl of `T:Foo<'a>` that applies to
737 // all `'a`, then we must know that `T:Bar<'a,'a>` holds for all
740 // Another example to be careful of is this:
742 // trait Foo1<'a>: for<'b> Bar1<'a,'b> { }
743 // trait Bar1<'b,'c> { }
745 // Here, if we have `for<'x> T: Foo1<'x>`, then what do we know?
746 // The answer is that we know `for<'x,'b> T: Bar1<'x,'b>`. The
747 // reason is similar to the previous example: any impl of
748 // `T:Foo1<'x>` must show that `for<'b> T: Bar1<'x, 'b>`. So
749 // basically we would want to collapse the bound lifetimes from
750 // the input (`trait_ref`) and the supertraits.
752 // To achieve this in practice is fairly straightforward. Let's
753 // consider the more complicated scenario:
755 // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x`
756 // has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`,
757 // where both `'x` and `'b` would have a DB index of 1.
758 // The substitution from the input trait-ref is therefore going to be
759 // `'a => 'x` (where `'x` has a DB index of 1).
760 // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an
761 // early-bound parameter and `'b' is a late-bound parameter with a
763 // - If we replace `'a` with `'x` from the input, it too will have
764 // a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>`
765 // just as we wanted.
767 // There is only one catch. If we just apply the substitution `'a
768 // => 'x` to `for<'b> Bar1<'a,'b>`, the substitution code will
769 // adjust the DB index because we substituting into a binder (it
770 // tries to be so smart...) resulting in `for<'x> for<'b>
771 // Bar1<'x,'b>` (we have no syntax for this, so use your
772 // imagination). Basically the 'x will have DB index of 2 and 'b
773 // will have DB index of 1. Not quite what we want. So we apply
774 // the substitution to the *contents* of the trait reference,
775 // rather than the trait reference itself (put another way, the
776 // substitution code expects equal binding levels in the values
777 // from the substitution and the value being substituted into, and
778 // this trick achieves that).
780 // Working through the second example:
781 // trait_ref: for<'x> T: Foo1<'^0.0>; substs: [T, '^0.0]
782 // predicate: for<'b> Self: Bar1<'a, '^0.0>; substs: [Self, 'a, '^0.0]
783 // We want to end up with:
784 // for<'x, 'b> T: Bar1<'^0.0, '^0.1>
786 // 1) We must shift all bound vars in predicate by the length
787 // of trait ref's bound vars. So, we would end up with predicate like
788 // Self: Bar1<'a, '^0.1>
789 // 2) We can then apply the trait substs to this, ending up with
790 // T: Bar1<'^0.0, '^0.1>
791 // 3) Finally, to create the final bound vars, we concatenate the bound
792 // vars of the trait ref with those of the predicate:
794 let bound_pred = self.kind();
795 let pred_bound_vars = bound_pred.bound_vars();
796 let trait_bound_vars = trait_ref.bound_vars();
797 // 1) Self: Bar1<'a, '^0.0> -> Self: Bar1<'a, '^0.1>
799 tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
800 // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
801 let new = EarlyBinder(shifted_pred).subst(tcx, trait_ref.skip_binder().substs);
802 // 3) ['x] + ['b] -> ['x, 'b]
804 tcx.mk_bound_variable_kinds(trait_bound_vars.iter().chain(pred_bound_vars));
805 tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars))
809 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
810 #[derive(HashStable, TypeFoldable, TypeVisitable)]
811 pub struct TraitPredicate<'tcx> {
812 pub trait_ref: TraitRef<'tcx>,
814 pub constness: BoundConstness,
816 /// If polarity is Positive: we are proving that the trait is implemented.
818 /// If polarity is Negative: we are proving that a negative impl of this trait
819 /// exists. (Note that coherence also checks whether negative impls of supertraits
820 /// exist via a series of predicates.)
822 /// If polarity is Reserved: that's a bug.
823 pub polarity: ImplPolarity,
826 pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
828 impl<'tcx> TraitPredicate<'tcx> {
829 pub fn remap_constness(&mut self, param_env: &mut ParamEnv<'tcx>) {
830 *param_env = param_env.with_constness(self.constness.and(param_env.constness()))
833 /// Remap the constness of this predicate before emitting it for diagnostics.
834 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
835 // this is different to `remap_constness` that callees want to print this predicate
836 // in case of selection errors. `T: ~const Drop` bounds cannot end up here when the
837 // param_env is not const because it is always satisfied in non-const contexts.
838 if let hir::Constness::NotConst = param_env.constness() {
839 self.constness = ty::BoundConstness::NotConst;
843 pub fn def_id(self) -> DefId {
844 self.trait_ref.def_id
847 pub fn self_ty(self) -> Ty<'tcx> {
848 self.trait_ref.self_ty()
852 pub fn is_const_if_const(self) -> bool {
853 self.constness == BoundConstness::ConstIfConst
856 pub fn is_constness_satisfied_by(self, constness: hir::Constness) -> bool {
857 match (self.constness, constness) {
858 (BoundConstness::NotConst, _)
859 | (BoundConstness::ConstIfConst, hir::Constness::Const) => true,
860 (BoundConstness::ConstIfConst, hir::Constness::NotConst) => false,
865 impl<'tcx> PolyTraitPredicate<'tcx> {
866 pub fn def_id(self) -> DefId {
867 // Ok to skip binder since trait `DefId` does not care about regions.
868 self.skip_binder().def_id()
871 pub fn self_ty(self) -> ty::Binder<'tcx, Ty<'tcx>> {
872 self.map_bound(|trait_ref| trait_ref.self_ty())
875 /// Remap the constness of this predicate before emitting it for diagnostics.
876 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
877 *self = self.map_bound(|mut p| {
878 p.remap_constness_diag(param_env);
884 pub fn is_const_if_const(self) -> bool {
885 self.skip_binder().is_const_if_const()
889 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
890 #[derive(HashStable, TypeFoldable, TypeVisitable)]
891 pub struct OutlivesPredicate<A, B>(pub A, pub B); // `A: B`
892 pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>;
893 pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>;
894 pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>;
895 pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>;
897 /// Encodes that `a` must be a subtype of `b`. The `a_is_expected` flag indicates
898 /// whether the `a` type is the type that we should label as "expected" when
899 /// presenting user diagnostics.
900 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
901 #[derive(HashStable, TypeFoldable, TypeVisitable)]
902 pub struct SubtypePredicate<'tcx> {
903 pub a_is_expected: bool,
907 pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>;
909 /// Encodes that we have to coerce *from* the `a` type to the `b` type.
910 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
911 #[derive(HashStable, TypeFoldable, TypeVisitable)]
912 pub struct CoercePredicate<'tcx> {
916 pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
918 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, TyEncodable, TyDecodable)]
919 #[derive(HashStable, TypeFoldable, TypeVisitable)]
920 pub enum Term<'tcx> {
925 impl<'tcx> From<Ty<'tcx>> for Term<'tcx> {
926 fn from(ty: Ty<'tcx>) -> Self {
931 impl<'tcx> From<Const<'tcx>> for Term<'tcx> {
932 fn from(c: Const<'tcx>) -> Self {
937 impl<'tcx> Term<'tcx> {
938 pub fn ty(&self) -> Option<Ty<'tcx>> {
939 if let Term::Ty(ty) = self { Some(*ty) } else { None }
942 pub fn ct(&self) -> Option<Const<'tcx>> {
943 if let Term::Const(c) = self { Some(*c) } else { None }
946 pub fn into_arg(self) -> GenericArg<'tcx> {
948 Term::Ty(ty) => ty.into(),
949 Term::Const(c) => c.into(),
954 /// This kind of predicate has no *direct* correspondent in the
955 /// syntax, but it roughly corresponds to the syntactic forms:
957 /// 1. `T: TraitRef<..., Item = Type>`
958 /// 2. `<T as TraitRef<...>>::Item == Type` (NYI)
960 /// In particular, form #1 is "desugared" to the combination of a
961 /// normal trait predicate (`T: TraitRef<...>`) and one of these
962 /// predicates. Form #2 is a broader form in that it also permits
963 /// equality between arbitrary types. Processing an instance of
964 /// Form #2 eventually yields one of these `ProjectionPredicate`
965 /// instances to normalize the LHS.
966 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
967 #[derive(HashStable, TypeFoldable, TypeVisitable)]
968 pub struct ProjectionPredicate<'tcx> {
969 pub projection_ty: ProjectionTy<'tcx>,
970 pub term: Term<'tcx>,
973 pub type PolyProjectionPredicate<'tcx> = Binder<'tcx, ProjectionPredicate<'tcx>>;
975 impl<'tcx> PolyProjectionPredicate<'tcx> {
976 /// Returns the `DefId` of the trait of the associated item being projected.
978 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
979 self.skip_binder().projection_ty.trait_def_id(tcx)
982 /// Get the [PolyTraitRef] required for this projection to be well formed.
983 /// Note that for generic associated types the predicates of the associated
984 /// type also need to be checked.
986 pub fn required_poly_trait_ref(&self, tcx: TyCtxt<'tcx>) -> PolyTraitRef<'tcx> {
987 // Note: unlike with `TraitRef::to_poly_trait_ref()`,
988 // `self.0.trait_ref` is permitted to have escaping regions.
989 // This is because here `self` has a `Binder` and so does our
990 // return value, so we are preserving the number of binding
992 self.map_bound(|predicate| predicate.projection_ty.trait_ref(tcx))
995 pub fn term(&self) -> Binder<'tcx, Term<'tcx>> {
996 self.map_bound(|predicate| predicate.term)
999 /// The `DefId` of the `TraitItem` for the associated type.
1001 /// Note that this is not the `DefId` of the `TraitRef` containing this
1002 /// associated type, which is in `tcx.associated_item(projection_def_id()).container`.
1003 pub fn projection_def_id(&self) -> DefId {
1004 // Ok to skip binder since trait `DefId` does not care about regions.
1005 self.skip_binder().projection_ty.item_def_id
1009 pub trait ToPolyTraitRef<'tcx> {
1010 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx>;
1013 impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
1014 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> {
1015 self.map_bound_ref(|trait_pred| trait_pred.trait_ref)
1019 pub trait ToPredicate<'tcx> {
1020 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx>;
1023 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
1025 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1026 tcx.mk_predicate(self)
1030 impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
1031 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1032 self.map_bound(PredicateKind::Trait).to_predicate(tcx)
1036 impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
1037 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1038 self.map_bound(PredicateKind::RegionOutlives).to_predicate(tcx)
1042 impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> {
1043 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1044 self.map_bound(PredicateKind::TypeOutlives).to_predicate(tcx)
1048 impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
1049 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1050 self.map_bound(PredicateKind::Projection).to_predicate(tcx)
1054 impl<'tcx> Predicate<'tcx> {
1055 pub fn to_opt_poly_trait_pred(self) -> Option<PolyTraitPredicate<'tcx>> {
1056 let predicate = self.kind();
1057 match predicate.skip_binder() {
1058 PredicateKind::Trait(t) => Some(predicate.rebind(t)),
1059 PredicateKind::Projection(..)
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_poly_projection_pred(self) -> Option<PolyProjectionPredicate<'tcx>> {
1074 let predicate = self.kind();
1075 match predicate.skip_binder() {
1076 PredicateKind::Projection(t) => Some(predicate.rebind(t)),
1077 PredicateKind::Trait(..)
1078 | PredicateKind::Subtype(..)
1079 | PredicateKind::Coerce(..)
1080 | PredicateKind::RegionOutlives(..)
1081 | PredicateKind::WellFormed(..)
1082 | PredicateKind::ObjectSafe(..)
1083 | PredicateKind::ClosureKind(..)
1084 | PredicateKind::TypeOutlives(..)
1085 | PredicateKind::ConstEvaluatable(..)
1086 | PredicateKind::ConstEquate(..)
1087 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1091 pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> {
1092 let predicate = self.kind();
1093 match predicate.skip_binder() {
1094 PredicateKind::TypeOutlives(data) => Some(predicate.rebind(data)),
1095 PredicateKind::Trait(..)
1096 | PredicateKind::Projection(..)
1097 | PredicateKind::Subtype(..)
1098 | PredicateKind::Coerce(..)
1099 | PredicateKind::RegionOutlives(..)
1100 | PredicateKind::WellFormed(..)
1101 | PredicateKind::ObjectSafe(..)
1102 | PredicateKind::ClosureKind(..)
1103 | PredicateKind::ConstEvaluatable(..)
1104 | PredicateKind::ConstEquate(..)
1105 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1110 /// Represents the bounds declared on a particular set of type
1111 /// parameters. Should eventually be generalized into a flag list of
1112 /// where-clauses. You can obtain an `InstantiatedPredicates` list from a
1113 /// `GenericPredicates` by using the `instantiate` method. Note that this method
1114 /// reflects an important semantic invariant of `InstantiatedPredicates`: while
1115 /// the `GenericPredicates` are expressed in terms of the bound type
1116 /// parameters of the impl/trait/whatever, an `InstantiatedPredicates` instance
1117 /// represented a set of bounds for some particular instantiation,
1118 /// meaning that the generic parameters have been substituted with
1122 /// ```ignore (illustrative)
1123 /// struct Foo<T, U: Bar<T>> { ... }
1125 /// Here, the `GenericPredicates` for `Foo` would contain a list of bounds like
1126 /// `[[], [U:Bar<T>]]`. Now if there were some particular reference
1127 /// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[],
1128 /// [usize:Bar<isize>]]`.
1129 #[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
1130 pub struct InstantiatedPredicates<'tcx> {
1131 pub predicates: Vec<Predicate<'tcx>>,
1132 pub spans: Vec<Span>,
1135 impl<'tcx> InstantiatedPredicates<'tcx> {
1136 pub fn empty() -> InstantiatedPredicates<'tcx> {
1137 InstantiatedPredicates { predicates: vec![], spans: vec![] }
1140 pub fn is_empty(&self) -> bool {
1141 self.predicates.is_empty()
1145 #[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable, Lift)]
1146 #[derive(TypeFoldable, TypeVisitable)]
1147 pub struct OpaqueTypeKey<'tcx> {
1148 pub def_id: LocalDefId,
1149 pub substs: SubstsRef<'tcx>,
1152 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
1153 pub struct OpaqueHiddenType<'tcx> {
1154 /// The span of this particular definition of the opaque type. So
1157 /// ```ignore (incomplete snippet)
1158 /// type Foo = impl Baz;
1159 /// fn bar() -> Foo {
1160 /// // ^^^ This is the span we are looking for!
1164 /// In cases where the fn returns `(impl Trait, impl Trait)` or
1165 /// other such combinations, the result is currently
1166 /// over-approximated, but better than nothing.
1169 /// The type variable that represents the value of the opaque type
1170 /// that we require. In other words, after we compile this function,
1171 /// we will be created a constraint like:
1172 /// ```ignore (pseudo-rust)
1175 /// where `?C` is the value of this type variable. =) It may
1176 /// naturally refer to the type and lifetime parameters in scope
1177 /// in this function, though ultimately it should only reference
1178 /// those that are arguments to `Foo` in the constraint above. (In
1179 /// other words, `?C` should not include `'b`, even though it's a
1180 /// lifetime parameter on `foo`.)
1184 impl<'tcx> OpaqueHiddenType<'tcx> {
1185 pub fn report_mismatch(&self, other: &Self, tcx: TyCtxt<'tcx>) {
1186 // Found different concrete types for the opaque type.
1187 let mut err = tcx.sess.struct_span_err(
1189 "concrete type differs from previous defining opaque type use",
1191 err.span_label(other.span, format!("expected `{}`, got `{}`", self.ty, other.ty));
1192 if self.span == other.span {
1195 "this expression supplies two conflicting concrete types for the same opaque type",
1198 err.span_note(self.span, "previous use here");
1204 /// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are
1205 /// identified by both a universe, as well as a name residing within that universe. Distinct bound
1206 /// regions/types/consts within the same universe simply have an unknown relationship to one
1208 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
1209 #[derive(HashStable, TyEncodable, TyDecodable)]
1210 pub struct Placeholder<T> {
1211 pub universe: UniverseIndex,
1215 pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
1217 pub type PlaceholderType = Placeholder<BoundVar>;
1219 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
1220 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
1221 pub struct BoundConst<'tcx> {
1226 pub type PlaceholderConst<'tcx> = Placeholder<BoundVar>;
1228 /// A `DefId` which, in case it is a const argument, is potentially bundled with
1229 /// the `DefId` of the generic parameter it instantiates.
1231 /// This is used to avoid calls to `type_of` for const arguments during typeck
1232 /// which cause cycle errors.
1237 /// fn foo<const N: usize>(&self) -> [u8; N] { [0; N] }
1238 /// // ^ const parameter
1242 /// fn foo<const M: u8>(&self) -> usize { 42 }
1243 /// // ^ const parameter
1248 /// let _b = a.foo::<{ 3 + 7 }>();
1249 /// // ^^^^^^^^^ const argument
1253 /// Let's look at the call `a.foo::<{ 3 + 7 }>()` here. We do not know
1254 /// which `foo` is used until we know the type of `a`.
1256 /// We only know the type of `a` once we are inside of `typeck(main)`.
1257 /// We also end up normalizing the type of `_b` during `typeck(main)` which
1258 /// requires us to evaluate the const argument.
1260 /// To evaluate that const argument we need to know its type,
1261 /// which we would get using `type_of(const_arg)`. This requires us to
1262 /// resolve `foo` as it can be either `usize` or `u8` in this example.
1263 /// However, resolving `foo` once again requires `typeck(main)` to get the type of `a`,
1264 /// which results in a cycle.
1266 /// In short we must not call `type_of(const_arg)` during `typeck(main)`.
1268 /// When first creating the `ty::Const` of the const argument inside of `typeck` we have
1269 /// already resolved `foo` so we know which const parameter this argument instantiates.
1270 /// This means that we also know the expected result of `type_of(const_arg)` even if we
1271 /// aren't allowed to call that query: it is equal to `type_of(const_param)` which is
1272 /// trivial to compute.
1274 /// If we now want to use that constant in a place which potentially needs its type
1275 /// we also pass the type of its `const_param`. This is the point of `WithOptConstParam`,
1276 /// except that instead of a `Ty` we bundle the `DefId` of the const parameter.
1277 /// Meaning that we need to use `type_of(const_param_did)` if `const_param_did` is `Some`
1278 /// to get the type of `did`.
1279 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, Lift, TyEncodable, TyDecodable)]
1280 #[derive(PartialEq, Eq, PartialOrd, Ord)]
1281 #[derive(Hash, HashStable)]
1282 pub struct WithOptConstParam<T> {
1284 /// The `DefId` of the corresponding generic parameter in case `did` is
1285 /// a const argument.
1287 /// Note that even if `did` is a const argument, this may still be `None`.
1288 /// All queries taking `WithOptConstParam` start by calling `tcx.opt_const_param_of(def.did)`
1289 /// to potentially update `param_did` in the case it is `None`.
1290 pub const_param_did: Option<DefId>,
1293 impl<T> WithOptConstParam<T> {
1294 /// Creates a new `WithOptConstParam` setting `const_param_did` to `None`.
1296 pub fn unknown(did: T) -> WithOptConstParam<T> {
1297 WithOptConstParam { did, const_param_did: None }
1301 impl WithOptConstParam<LocalDefId> {
1302 /// Returns `Some((did, param_did))` if `def_id` is a const argument,
1303 /// `None` otherwise.
1305 pub fn try_lookup(did: LocalDefId, tcx: TyCtxt<'_>) -> Option<(LocalDefId, DefId)> {
1306 tcx.opt_const_param_of(did).map(|param_did| (did, param_did))
1309 /// In case `self` is unknown but `self.did` is a const argument, this returns
1310 /// a `WithOptConstParam` with the correct `const_param_did`.
1312 pub fn try_upgrade(self, tcx: TyCtxt<'_>) -> Option<WithOptConstParam<LocalDefId>> {
1313 if self.const_param_did.is_none() {
1314 if let const_param_did @ Some(_) = tcx.opt_const_param_of(self.did) {
1315 return Some(WithOptConstParam { did: self.did, const_param_did });
1322 pub fn to_global(self) -> WithOptConstParam<DefId> {
1323 WithOptConstParam { did: self.did.to_def_id(), const_param_did: self.const_param_did }
1326 pub fn def_id_for_type_of(self) -> DefId {
1327 if let Some(did) = self.const_param_did { did } else { self.did.to_def_id() }
1331 impl WithOptConstParam<DefId> {
1332 pub fn as_local(self) -> Option<WithOptConstParam<LocalDefId>> {
1335 .map(|did| WithOptConstParam { did, const_param_did: self.const_param_did })
1338 pub fn as_const_arg(self) -> Option<(LocalDefId, DefId)> {
1339 if let Some(param_did) = self.const_param_did {
1340 if let Some(did) = self.did.as_local() {
1341 return Some((did, param_did));
1348 pub fn is_local(self) -> bool {
1352 pub fn def_id_for_type_of(self) -> DefId {
1353 self.const_param_did.unwrap_or(self.did)
1357 /// When type checking, we use the `ParamEnv` to track
1358 /// details about the set of where-clauses that are in scope at this
1359 /// particular point.
1360 #[derive(Copy, Clone, Hash, PartialEq, Eq)]
1361 pub struct ParamEnv<'tcx> {
1362 /// This packs both caller bounds and the reveal enum into one pointer.
1364 /// Caller bounds are `Obligation`s that the caller must satisfy. This is
1365 /// basically the set of bounds on the in-scope type parameters, translated
1366 /// into `Obligation`s, and elaborated and normalized.
1368 /// Use the `caller_bounds()` method to access.
1370 /// Typically, this is `Reveal::UserFacing`, but during codegen we
1371 /// want `Reveal::All`.
1373 /// Note: This is packed, use the reveal() method to access it.
1374 packed: CopyTaggedPtr<&'tcx List<Predicate<'tcx>>, ParamTag, true>,
1377 #[derive(Copy, Clone)]
1379 reveal: traits::Reveal,
1380 constness: hir::Constness,
1383 unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag {
1384 const BITS: usize = 2;
1386 fn into_usize(self) -> usize {
1388 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0,
1389 Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1,
1390 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2,
1391 Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3,
1395 unsafe fn from_usize(ptr: usize) -> Self {
1397 0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
1398 1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
1399 2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
1400 3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const },
1401 _ => std::hint::unreachable_unchecked(),
1406 impl<'tcx> fmt::Debug for ParamEnv<'tcx> {
1407 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1408 f.debug_struct("ParamEnv")
1409 .field("caller_bounds", &self.caller_bounds())
1410 .field("reveal", &self.reveal())
1411 .field("constness", &self.constness())
1416 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
1417 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1418 self.caller_bounds().hash_stable(hcx, hasher);
1419 self.reveal().hash_stable(hcx, hasher);
1420 self.constness().hash_stable(hcx, hasher);
1424 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
1425 fn try_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>(
1428 ) -> Result<Self, F::Error> {
1430 self.caller_bounds().try_fold_with(folder)?,
1431 self.reveal().try_fold_with(folder)?,
1432 self.constness().try_fold_with(folder)?,
1437 impl<'tcx> TypeVisitable<'tcx> for ParamEnv<'tcx> {
1438 fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1439 self.caller_bounds().visit_with(visitor)?;
1440 self.reveal().visit_with(visitor)?;
1441 self.constness().visit_with(visitor)
1445 impl<'tcx> ParamEnv<'tcx> {
1446 /// Construct a trait environment suitable for contexts where
1447 /// there are no where-clauses in scope. Hidden types (like `impl
1448 /// Trait`) are left hidden, so this is suitable for ordinary
1451 pub fn empty() -> Self {
1452 Self::new(List::empty(), Reveal::UserFacing, hir::Constness::NotConst)
1456 pub fn caller_bounds(self) -> &'tcx List<Predicate<'tcx>> {
1457 self.packed.pointer()
1461 pub fn reveal(self) -> traits::Reveal {
1462 self.packed.tag().reveal
1466 pub fn constness(self) -> hir::Constness {
1467 self.packed.tag().constness
1471 pub fn is_const(self) -> bool {
1472 self.packed.tag().constness == hir::Constness::Const
1475 /// Construct a trait environment with no where-clauses in scope
1476 /// where the values of all `impl Trait` and other hidden types
1477 /// are revealed. This is suitable for monomorphized, post-typeck
1478 /// environments like codegen or doing optimizations.
1480 /// N.B., if you want to have predicates in scope, use `ParamEnv::new`,
1481 /// or invoke `param_env.with_reveal_all()`.
1483 pub fn reveal_all() -> Self {
1484 Self::new(List::empty(), Reveal::All, hir::Constness::NotConst)
1487 /// Construct a trait environment with the given set of predicates.
1490 caller_bounds: &'tcx List<Predicate<'tcx>>,
1492 constness: hir::Constness,
1494 ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal, constness }) }
1497 pub fn with_user_facing(mut self) -> Self {
1498 self.packed.set_tag(ParamTag { reveal: Reveal::UserFacing, ..self.packed.tag() });
1503 pub fn with_constness(mut self, constness: hir::Constness) -> Self {
1504 self.packed.set_tag(ParamTag { constness, ..self.packed.tag() });
1509 pub fn with_const(mut self) -> Self {
1510 self.packed.set_tag(ParamTag { constness: hir::Constness::Const, ..self.packed.tag() });
1515 pub fn without_const(mut self) -> Self {
1516 self.packed.set_tag(ParamTag { constness: hir::Constness::NotConst, ..self.packed.tag() });
1521 pub fn remap_constness_with(&mut self, mut constness: ty::BoundConstness) {
1522 *self = self.with_constness(constness.and(self.constness()))
1525 /// Returns a new parameter environment with the same clauses, but
1526 /// which "reveals" the true results of projections in all cases
1527 /// (even for associated types that are specializable). This is
1528 /// the desired behavior during codegen and certain other special
1529 /// contexts; normally though we want to use `Reveal::UserFacing`,
1530 /// which is the default.
1531 /// All opaque types in the caller_bounds of the `ParamEnv`
1532 /// will be normalized to their underlying types.
1533 /// See PR #65989 and issue #65918 for more details
1534 pub fn with_reveal_all_normalized(self, tcx: TyCtxt<'tcx>) -> Self {
1535 if self.packed.tag().reveal == traits::Reveal::All {
1540 tcx.normalize_opaque_types(self.caller_bounds()),
1546 /// Returns this same environment but with no caller bounds.
1548 pub fn without_caller_bounds(self) -> Self {
1549 Self::new(List::empty(), self.reveal(), self.constness())
1552 /// Creates a suitable environment in which to perform trait
1553 /// queries on the given value. When type-checking, this is simply
1554 /// the pair of the environment plus value. But when reveal is set to
1555 /// All, then if `value` does not reference any type parameters, we will
1556 /// pair it with the empty environment. This improves caching and is generally
1559 /// N.B., we preserve the environment when type-checking because it
1560 /// is possible for the user to have wacky where-clauses like
1561 /// `where Box<u32>: Copy`, which are clearly never
1562 /// satisfiable. We generally want to behave as if they were true,
1563 /// although the surrounding function is never reachable.
1564 pub fn and<T: TypeVisitable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
1565 match self.reveal() {
1566 Reveal::UserFacing => ParamEnvAnd { param_env: self, value },
1569 if value.is_global() {
1570 ParamEnvAnd { param_env: self.without_caller_bounds(), value }
1572 ParamEnvAnd { param_env: self, value }
1579 // FIXME(ecstaticmorse): Audit all occurrences of `without_const().to_predicate(tcx)` to ensure that
1580 // the constness of trait bounds is being propagated correctly.
1581 impl<'tcx> PolyTraitRef<'tcx> {
1583 pub fn with_constness(self, constness: BoundConstness) -> PolyTraitPredicate<'tcx> {
1584 self.map_bound(|trait_ref| ty::TraitPredicate {
1587 polarity: ty::ImplPolarity::Positive,
1592 pub fn without_const(self) -> PolyTraitPredicate<'tcx> {
1593 self.with_constness(BoundConstness::NotConst)
1597 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
1598 #[derive(HashStable)]
1599 pub struct ParamEnvAnd<'tcx, T> {
1600 pub param_env: ParamEnv<'tcx>,
1604 impl<'tcx, T> ParamEnvAnd<'tcx, T> {
1605 pub fn into_parts(self) -> (ParamEnv<'tcx>, T) {
1606 (self.param_env, self.value)
1610 pub fn without_const(mut self) -> Self {
1611 self.param_env = self.param_env.without_const();
1616 #[derive(Copy, Clone, Debug, HashStable, Encodable, Decodable)]
1617 pub struct Destructor {
1618 /// The `DefId` of the destructor method
1620 /// The constness of the destructor method
1621 pub constness: hir::Constness,
1625 #[derive(HashStable, TyEncodable, TyDecodable)]
1626 pub struct VariantFlags: u32 {
1627 const NO_VARIANT_FLAGS = 0;
1628 /// Indicates whether the field list of this variant is `#[non_exhaustive]`.
1629 const IS_FIELD_LIST_NON_EXHAUSTIVE = 1 << 0;
1630 /// Indicates whether this variant was obtained as part of recovering from
1631 /// a syntactic error. May be incomplete or bogus.
1632 const IS_RECOVERED = 1 << 1;
1636 /// Definition of a variant -- a struct's fields or an enum variant.
1637 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1638 pub struct VariantDef {
1639 /// `DefId` that identifies the variant itself.
1640 /// If this variant belongs to a struct or union, then this is a copy of its `DefId`.
1642 /// `DefId` that identifies the variant's constructor.
1643 /// If this variant is a struct variant, then this is `None`.
1644 pub ctor_def_id: Option<DefId>,
1645 /// Variant or struct name.
1647 /// Discriminant of this variant.
1648 pub discr: VariantDiscr,
1649 /// Fields of this variant.
1650 pub fields: Vec<FieldDef>,
1651 /// Type of constructor of variant.
1652 pub ctor_kind: CtorKind,
1653 /// Flags of the variant (e.g. is field list non-exhaustive)?
1654 flags: VariantFlags,
1658 /// Creates a new `VariantDef`.
1660 /// `variant_did` is the `DefId` that identifies the enum variant (if this `VariantDef`
1661 /// represents an enum variant).
1663 /// `ctor_did` is the `DefId` that identifies the constructor of unit or
1664 /// tuple-variants/structs. If this is a `struct`-variant then this should be `None`.
1666 /// `parent_did` is the `DefId` of the `AdtDef` representing the enum or struct that
1667 /// owns this variant. It is used for checking if a struct has `#[non_exhaustive]` w/out having
1668 /// to go through the redirect of checking the ctor's attributes - but compiling a small crate
1669 /// requires loading the `AdtDef`s for all the structs in the universe (e.g., coherence for any
1670 /// built-in trait), and we do not want to load attributes twice.
1672 /// If someone speeds up attribute loading to not be a performance concern, they can
1673 /// remove this hack and use the constructor `DefId` everywhere.
1676 variant_did: Option<DefId>,
1677 ctor_def_id: Option<DefId>,
1678 discr: VariantDiscr,
1679 fields: Vec<FieldDef>,
1680 ctor_kind: CtorKind,
1684 is_field_list_non_exhaustive: bool,
1687 "VariantDef::new(name = {:?}, variant_did = {:?}, ctor_def_id = {:?}, discr = {:?},
1688 fields = {:?}, ctor_kind = {:?}, adt_kind = {:?}, parent_did = {:?})",
1689 name, variant_did, ctor_def_id, discr, fields, ctor_kind, adt_kind, parent_did,
1692 let mut flags = VariantFlags::NO_VARIANT_FLAGS;
1693 if is_field_list_non_exhaustive {
1694 flags |= VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE;
1698 flags |= VariantFlags::IS_RECOVERED;
1702 def_id: variant_did.unwrap_or(parent_did),
1712 /// Is this field list non-exhaustive?
1714 pub fn is_field_list_non_exhaustive(&self) -> bool {
1715 self.flags.intersects(VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE)
1718 /// Was this variant obtained as part of recovering from a syntactic error?
1720 pub fn is_recovered(&self) -> bool {
1721 self.flags.intersects(VariantFlags::IS_RECOVERED)
1724 /// Computes the `Ident` of this variant by looking up the `Span`
1725 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1726 Ident::new(self.name, tcx.def_ident_span(self.def_id).unwrap())
1730 impl PartialEq for VariantDef {
1732 fn eq(&self, other: &Self) -> bool {
1733 // There should be only one `VariantDef` for each `def_id`, therefore
1734 // it is fine to implement `PartialEq` only based on `def_id`.
1736 // Below, we exhaustively destructure `self` and `other` so that if the
1737 // definition of `VariantDef` changes, a compile-error will be produced,
1738 // reminding us to revisit this assumption.
1760 lhs_def_id == rhs_def_id
1764 impl Eq for VariantDef {}
1766 impl Hash for VariantDef {
1768 fn hash<H: Hasher>(&self, s: &mut H) {
1769 // There should be only one `VariantDef` for each `def_id`, therefore
1770 // it is fine to implement `Hash` only based on `def_id`.
1772 // Below, we exhaustively destructure `self` so that if the definition
1773 // of `VariantDef` changes, a compile-error will be produced, reminding
1774 // us to revisit this assumption.
1776 let Self { def_id, ctor_def_id: _, name: _, discr: _, fields: _, ctor_kind: _, flags: _ } =
1783 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
1784 pub enum VariantDiscr {
1785 /// Explicit value for this variant, i.e., `X = 123`.
1786 /// The `DefId` corresponds to the embedded constant.
1789 /// The previous variant's discriminant plus one.
1790 /// For efficiency reasons, the distance from the
1791 /// last `Explicit` discriminant is being stored,
1792 /// or `0` for the first variant, if it has none.
1796 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1797 pub struct FieldDef {
1800 pub vis: Visibility,
1803 impl PartialEq for FieldDef {
1805 fn eq(&self, other: &Self) -> bool {
1806 // There should be only one `FieldDef` for each `did`, therefore it is
1807 // fine to implement `PartialEq` only based on `did`.
1809 // Below, we exhaustively destructure `self` so that if the definition
1810 // of `FieldDef` changes, a compile-error will be produced, reminding
1811 // us to revisit this assumption.
1813 let Self { did: lhs_did, name: _, vis: _ } = &self;
1815 let Self { did: rhs_did, name: _, vis: _ } = other;
1821 impl Eq for FieldDef {}
1823 impl Hash for FieldDef {
1825 fn hash<H: Hasher>(&self, s: &mut H) {
1826 // There should be only one `FieldDef` for each `did`, therefore it is
1827 // fine to implement `Hash` only based on `did`.
1829 // Below, we exhaustively destructure `self` so that if the definition
1830 // of `FieldDef` changes, a compile-error will be produced, reminding
1831 // us to revisit this assumption.
1833 let Self { did, name: _, vis: _ } = &self;
1840 #[derive(TyEncodable, TyDecodable, Default, HashStable)]
1841 pub struct ReprFlags: u8 {
1842 const IS_C = 1 << 0;
1843 const IS_SIMD = 1 << 1;
1844 const IS_TRANSPARENT = 1 << 2;
1845 // Internal only for now. If true, don't reorder fields.
1846 const IS_LINEAR = 1 << 3;
1847 // If true, the type's layout can be randomized using
1848 // the seed stored in `ReprOptions.layout_seed`
1849 const RANDOMIZE_LAYOUT = 1 << 4;
1850 // Any of these flags being set prevent field reordering optimisation.
1851 const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
1852 | ReprFlags::IS_SIMD.bits
1853 | ReprFlags::IS_LINEAR.bits;
1857 /// Represents the repr options provided by the user,
1858 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Default, HashStable)]
1859 pub struct ReprOptions {
1860 pub int: Option<attr::IntType>,
1861 pub align: Option<Align>,
1862 pub pack: Option<Align>,
1863 pub flags: ReprFlags,
1864 /// The seed to be used for randomizing a type's layout
1866 /// Note: This could technically be a `[u8; 16]` (a `u128`) which would
1867 /// be the "most accurate" hash as it'd encompass the item and crate
1868 /// hash without loss, but it does pay the price of being larger.
1869 /// Everything's a tradeoff, a `u64` seed should be sufficient for our
1870 /// purposes (primarily `-Z randomize-layout`)
1871 pub field_shuffle_seed: u64,
1875 pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions {
1876 let mut flags = ReprFlags::empty();
1877 let mut size = None;
1878 let mut max_align: Option<Align> = None;
1879 let mut min_pack: Option<Align> = None;
1881 // Generate a deterministically-derived seed from the item's path hash
1882 // to allow for cross-crate compilation to actually work
1883 let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash();
1885 // If the user defined a custom seed for layout randomization, xor the item's
1886 // path hash with the user defined seed, this will allowing determinism while
1887 // still allowing users to further randomize layout generation for e.g. fuzzing
1888 if let Some(user_seed) = tcx.sess.opts.unstable_opts.layout_seed {
1889 field_shuffle_seed ^= user_seed;
1892 for attr in tcx.get_attrs(did, sym::repr) {
1893 for r in attr::parse_repr_attr(&tcx.sess, attr) {
1894 flags.insert(match r {
1895 attr::ReprC => ReprFlags::IS_C,
1896 attr::ReprPacked(pack) => {
1897 let pack = Align::from_bytes(pack as u64).unwrap();
1898 min_pack = Some(if let Some(min_pack) = min_pack {
1905 attr::ReprTransparent => ReprFlags::IS_TRANSPARENT,
1906 attr::ReprSimd => ReprFlags::IS_SIMD,
1907 attr::ReprInt(i) => {
1911 attr::ReprAlign(align) => {
1912 max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap()));
1919 // If `-Z randomize-layout` was enabled for the type definition then we can
1920 // consider performing layout randomization
1921 if tcx.sess.opts.unstable_opts.randomize_layout {
1922 flags.insert(ReprFlags::RANDOMIZE_LAYOUT);
1925 // This is here instead of layout because the choice must make it into metadata.
1926 if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) {
1927 flags.insert(ReprFlags::IS_LINEAR);
1930 Self { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed }
1934 pub fn simd(&self) -> bool {
1935 self.flags.contains(ReprFlags::IS_SIMD)
1939 pub fn c(&self) -> bool {
1940 self.flags.contains(ReprFlags::IS_C)
1944 pub fn packed(&self) -> bool {
1949 pub fn transparent(&self) -> bool {
1950 self.flags.contains(ReprFlags::IS_TRANSPARENT)
1954 pub fn linear(&self) -> bool {
1955 self.flags.contains(ReprFlags::IS_LINEAR)
1958 /// Returns the discriminant type, given these `repr` options.
1959 /// This must only be called on enums!
1960 pub fn discr_type(&self) -> attr::IntType {
1961 self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize))
1964 /// Returns `true` if this `#[repr()]` should inhabit "smart enum
1965 /// layout" optimizations, such as representing `Foo<&T>` as a
1967 pub fn inhibit_enum_layout_opt(&self) -> bool {
1968 self.c() || self.int.is_some()
1971 /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
1972 /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
1973 pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
1974 if let Some(pack) = self.pack {
1975 if pack.bytes() == 1 {
1980 self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
1983 /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
1984 /// was enabled for its declaration crate
1985 pub fn can_randomize_type_layout(&self) -> bool {
1986 !self.inhibit_struct_field_reordering_opt()
1987 && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
1990 /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
1991 pub fn inhibit_union_abi_opt(&self) -> bool {
1996 impl<'tcx> FieldDef {
1997 /// Returns the type of this field. The resulting type is not normalized. The `subst` is
1998 /// typically obtained via the second field of [`TyKind::Adt`].
1999 pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
2000 tcx.bound_type_of(self.did).subst(tcx, subst)
2003 /// Computes the `Ident` of this variant by looking up the `Span`
2004 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
2005 Ident::new(self.name, tcx.def_ident_span(self.did).unwrap())
2009 pub type Attributes<'tcx> = impl Iterator<Item = &'tcx ast::Attribute>;
2010 #[derive(Debug, PartialEq, Eq)]
2011 pub enum ImplOverlapKind {
2012 /// These impls are always allowed to overlap.
2014 /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait
2017 /// These impls are allowed to overlap, but that raises
2018 /// an issue #33140 future-compatibility warning.
2020 /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's
2021 /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different.
2023 /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied
2024 /// that difference, making what reduces to the following set of impls:
2026 /// ```compile_fail,(E0119)
2028 /// impl Trait for dyn Send + Sync {}
2029 /// impl Trait for dyn Sync + Send {}
2032 /// Obviously, once we made these types be identical, that code causes a coherence
2033 /// error and a fairly big headache for us. However, luckily for us, the trait
2034 /// `Trait` used in this case is basically a marker trait, and therefore having
2035 /// overlapping impls for it is sound.
2037 /// To handle this, we basically regard the trait as a marker trait, with an additional
2038 /// future-compatibility warning. To avoid accidentally "stabilizing" this feature,
2039 /// it has the following restrictions:
2041 /// 1. The trait must indeed be a marker-like trait (i.e., no items), and must be
2043 /// 2. The trait-ref of both impls must be equal.
2044 /// 3. The trait-ref of both impls must be a trait object type consisting only of
2046 /// 4. Neither of the impls can have any where-clauses.
2048 /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed.
2052 impl<'tcx> TyCtxt<'tcx> {
2053 pub fn typeck_body(self, body: hir::BodyId) -> &'tcx TypeckResults<'tcx> {
2054 self.typeck(self.hir().body_owner_def_id(body))
2057 pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> {
2058 self.associated_items(id)
2059 .in_definition_order()
2060 .filter(move |item| item.kind == AssocKind::Fn && item.defaultness(self).has_value())
2063 /// Look up the name of a definition across crates. This does not look at HIR.
2064 pub fn opt_item_name(self, def_id: DefId) -> Option<Symbol> {
2065 if let Some(cnum) = def_id.as_crate_root() {
2066 Some(self.crate_name(cnum))
2068 let def_key = self.def_key(def_id);
2069 match def_key.disambiguated_data.data {
2070 // The name of a constructor is that of its parent.
2071 rustc_hir::definitions::DefPathData::Ctor => self
2072 .opt_item_name(DefId { krate: def_id.krate, index: def_key.parent.unwrap() }),
2073 // The name of opaque types only exists in HIR.
2074 rustc_hir::definitions::DefPathData::ImplTrait
2075 if let Some(def_id) = def_id.as_local() =>
2076 self.hir().opt_name(self.hir().local_def_id_to_hir_id(def_id)),
2077 _ => def_key.get_opt_name(),
2082 /// Look up the name of a definition across crates. This does not look at HIR.
2084 /// This method will ICE if the corresponding item does not have a name. In these cases, use
2085 /// [`opt_item_name`] instead.
2087 /// [`opt_item_name`]: Self::opt_item_name
2088 pub fn item_name(self, id: DefId) -> Symbol {
2089 self.opt_item_name(id).unwrap_or_else(|| {
2090 bug!("item_name: no name for {:?}", self.def_path(id));
2094 /// Look up the name and span of a definition.
2096 /// See [`item_name`][Self::item_name] for more information.
2097 pub fn opt_item_ident(self, def_id: DefId) -> Option<Ident> {
2098 let def = self.opt_item_name(def_id)?;
2101 .and_then(|id| self.def_ident_span(id))
2102 .unwrap_or(rustc_span::DUMMY_SP);
2103 Some(Ident::new(def, span))
2106 pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> {
2107 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2108 Some(self.associated_item(def_id))
2114 pub fn field_index(self, hir_id: hir::HirId, typeck_results: &TypeckResults<'_>) -> usize {
2115 typeck_results.field_indices().get(hir_id).cloned().expect("no index for a field")
2118 pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
2122 .position(|field| self.hygienic_eq(ident, field.ident(self), variant.def_id))
2125 /// Returns `true` if the impls are the same polarity and the trait either
2126 /// has no items or is annotated `#[marker]` and prevents item overrides.
2127 pub fn impls_are_allowed_to_overlap(
2131 ) -> Option<ImplOverlapKind> {
2132 // If either trait impl references an error, they're allowed to overlap,
2133 // as one of them essentially doesn't exist.
2134 if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.references_error())
2135 || self.impl_trait_ref(def_id2).map_or(false, |tr| tr.references_error())
2137 return Some(ImplOverlapKind::Permitted { marker: false });
2140 match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) {
2141 (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => {
2142 // `#[rustc_reservation_impl]` impls don't overlap with anything
2144 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (reservations)",
2147 return Some(ImplOverlapKind::Permitted { marker: false });
2149 (ImplPolarity::Positive, ImplPolarity::Negative)
2150 | (ImplPolarity::Negative, ImplPolarity::Positive) => {
2151 // `impl AutoTrait for Type` + `impl !AutoTrait for Type`
2153 "impls_are_allowed_to_overlap({:?}, {:?}) - None (differing polarities)",
2158 (ImplPolarity::Positive, ImplPolarity::Positive)
2159 | (ImplPolarity::Negative, ImplPolarity::Negative) => {}
2162 let is_marker_overlap = {
2163 let is_marker_impl = |def_id: DefId| -> bool {
2164 let trait_ref = self.impl_trait_ref(def_id);
2165 trait_ref.map_or(false, |tr| self.trait_def(tr.def_id).is_marker)
2167 is_marker_impl(def_id1) && is_marker_impl(def_id2)
2170 if is_marker_overlap {
2172 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (marker overlap)",
2175 Some(ImplOverlapKind::Permitted { marker: true })
2177 if let Some(self_ty1) = self.issue33140_self_ty(def_id1) {
2178 if let Some(self_ty2) = self.issue33140_self_ty(def_id2) {
2179 if self_ty1 == self_ty2 {
2181 "impls_are_allowed_to_overlap({:?}, {:?}) - issue #33140 HACK",
2184 return Some(ImplOverlapKind::Issue33140);
2187 "impls_are_allowed_to_overlap({:?}, {:?}) - found {:?} != {:?}",
2188 def_id1, def_id2, self_ty1, self_ty2
2194 debug!("impls_are_allowed_to_overlap({:?}, {:?}) = None", def_id1, def_id2);
2199 /// Returns `ty::VariantDef` if `res` refers to a struct,
2200 /// or variant or their constructors, panics otherwise.
2201 pub fn expect_variant_res(self, res: Res) -> &'tcx VariantDef {
2203 Res::Def(DefKind::Variant, did) => {
2204 let enum_did = self.parent(did);
2205 self.adt_def(enum_did).variant_with_id(did)
2207 Res::Def(DefKind::Struct | DefKind::Union, did) => self.adt_def(did).non_enum_variant(),
2208 Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => {
2209 let variant_did = self.parent(variant_ctor_did);
2210 let enum_did = self.parent(variant_did);
2211 self.adt_def(enum_did).variant_with_ctor_id(variant_ctor_did)
2213 Res::Def(DefKind::Ctor(CtorOf::Struct, ..), ctor_did) => {
2214 let struct_did = self.parent(ctor_did);
2215 self.adt_def(struct_did).non_enum_variant()
2217 _ => bug!("expect_variant_res used with unexpected res {:?}", res),
2221 /// Returns the possibly-auto-generated MIR of a `(DefId, Subst)` pair.
2222 #[instrument(skip(self), level = "debug")]
2223 pub fn instance_mir(self, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> {
2225 ty::InstanceDef::Item(def) => {
2226 debug!("calling def_kind on def: {:?}", def);
2227 let def_kind = self.def_kind(def.did);
2228 debug!("returned from def_kind: {:?}", def_kind);
2231 | DefKind::Static(..)
2232 | DefKind::AssocConst
2234 | DefKind::AnonConst
2235 | DefKind::InlineConst => self.mir_for_ctfe_opt_const_arg(def),
2236 // If the caller wants `mir_for_ctfe` of a function they should not be using
2237 // `instance_mir`, so we'll assume const fn also wants the optimized version.
2239 assert_eq!(def.const_param_did, None);
2240 self.optimized_mir(def.did)
2244 ty::InstanceDef::VTableShim(..)
2245 | ty::InstanceDef::ReifyShim(..)
2246 | ty::InstanceDef::Intrinsic(..)
2247 | ty::InstanceDef::FnPtrShim(..)
2248 | ty::InstanceDef::Virtual(..)
2249 | ty::InstanceDef::ClosureOnceShim { .. }
2250 | ty::InstanceDef::DropGlue(..)
2251 | ty::InstanceDef::CloneShim(..) => self.mir_shims(instance),
2255 // FIXME(@lcnr): Remove this function.
2256 pub fn get_attrs_unchecked(self, did: DefId) -> &'tcx [ast::Attribute] {
2257 if let Some(did) = did.as_local() {
2258 self.hir().attrs(self.hir().local_def_id_to_hir_id(did))
2260 self.item_attrs(did)
2264 /// Gets all attributes with the given name.
2265 pub fn get_attrs(self, did: DefId, attr: Symbol) -> ty::Attributes<'tcx> {
2266 let filter_fn = move |a: &&ast::Attribute| a.has_name(attr);
2267 if let Some(did) = did.as_local() {
2268 self.hir().attrs(self.hir().local_def_id_to_hir_id(did)).iter().filter(filter_fn)
2269 } else if cfg!(debug_assertions) && rustc_feature::is_builtin_only_local(attr) {
2270 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2272 self.item_attrs(did).iter().filter(filter_fn)
2276 pub fn get_attr(self, did: DefId, attr: Symbol) -> Option<&'tcx ast::Attribute> {
2277 self.get_attrs(did, attr).next()
2280 /// Determines whether an item is annotated with an attribute.
2281 pub fn has_attr(self, did: DefId, attr: Symbol) -> bool {
2282 if cfg!(debug_assertions) && !did.is_local() && rustc_feature::is_builtin_only_local(attr) {
2283 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2285 self.get_attrs(did, attr).next().is_some()
2289 /// Returns `true` if this is an `auto trait`.
2290 pub fn trait_is_auto(self, trait_def_id: DefId) -> bool {
2291 self.trait_def(trait_def_id).has_auto_impl
2294 /// Returns layout of a generator. Layout might be unavailable if the
2295 /// generator is tainted by errors.
2296 pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> {
2297 self.optimized_mir(def_id).generator_layout()
2300 /// Given the `DefId` of an impl, returns the `DefId` of the trait it implements.
2301 /// If it implements no trait, returns `None`.
2302 pub fn trait_id_of_impl(self, def_id: DefId) -> Option<DefId> {
2303 self.impl_trait_ref(def_id).map(|tr| tr.def_id)
2306 /// If the given `DefId` describes an item belonging to a trait,
2307 /// returns the `DefId` of the trait that the trait item belongs to;
2308 /// otherwise, returns `None`.
2309 pub fn trait_of_item(self, def_id: DefId) -> Option<DefId> {
2310 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2311 let parent = self.parent(def_id);
2312 if let DefKind::Trait | DefKind::TraitAlias = self.def_kind(parent) {
2313 return Some(parent);
2319 /// If the given `DefId` describes a method belonging to an impl, returns the
2320 /// `DefId` of the impl that the method belongs to; otherwise, returns `None`.
2321 pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
2322 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
2323 let parent = self.parent(def_id);
2324 if let DefKind::Impl = self.def_kind(parent) {
2325 return Some(parent);
2331 /// If the given `DefId` belongs to a trait that was automatically derived, returns `true`.
2332 pub fn is_builtin_derive(self, def_id: DefId) -> bool {
2333 self.has_attr(def_id, sym::automatically_derived)
2336 /// Looks up the span of `impl_did` if the impl is local; otherwise returns `Err`
2337 /// with the name of the crate containing the impl.
2338 pub fn span_of_impl(self, impl_did: DefId) -> Result<Span, Symbol> {
2339 if let Some(impl_did) = impl_did.as_local() {
2340 Ok(self.def_span(impl_did))
2342 Err(self.crate_name(impl_did.krate))
2346 /// Hygienically compares a use-site name (`use_name`) for a field or an associated item with
2347 /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
2348 /// definition's parent/scope to perform comparison.
2349 pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
2350 // We could use `Ident::eq` here, but we deliberately don't. The name
2351 // comparison fails frequently, and we want to avoid the expensive
2352 // `normalize_to_macros_2_0()` calls required for the span comparison whenever possible.
2353 use_name.name == def_name.name
2357 .hygienic_eq(def_name.span.ctxt(), self.expn_that_defined(def_parent_def_id))
2360 pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident {
2361 ident.span.normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope));
2365 pub fn adjust_ident_and_get_scope(
2370 ) -> (Ident, DefId) {
2373 .normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope))
2374 .and_then(|actual_expansion| actual_expansion.expn_data().parent_module)
2375 .unwrap_or_else(|| self.parent_module(block).to_def_id());
2379 pub fn is_object_safe(self, key: DefId) -> bool {
2380 self.object_safety_violations(key).is_empty()
2384 pub fn is_const_fn_raw(self, def_id: DefId) -> bool {
2385 matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..))
2386 && self.constness(def_id) == hir::Constness::Const
2390 pub fn is_const_default_method(self, def_id: DefId) -> bool {
2391 matches!(self.trait_of_item(def_id), Some(trait_id) if self.has_attr(trait_id, sym::const_trait))
2395 /// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition.
2396 pub fn is_impl_trait_defn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<LocalDefId> {
2397 let def_id = def_id.as_local()?;
2398 if let Node::Item(item) = tcx.hir().get_by_def_id(def_id) {
2399 if let hir::ItemKind::OpaqueTy(ref opaque_ty) = item.kind {
2400 return match opaque_ty.origin {
2401 hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) => {
2404 hir::OpaqueTyOrigin::TyAlias => None,
2411 pub fn int_ty(ity: ast::IntTy) -> IntTy {
2413 ast::IntTy::Isize => IntTy::Isize,
2414 ast::IntTy::I8 => IntTy::I8,
2415 ast::IntTy::I16 => IntTy::I16,
2416 ast::IntTy::I32 => IntTy::I32,
2417 ast::IntTy::I64 => IntTy::I64,
2418 ast::IntTy::I128 => IntTy::I128,
2422 pub fn uint_ty(uty: ast::UintTy) -> UintTy {
2424 ast::UintTy::Usize => UintTy::Usize,
2425 ast::UintTy::U8 => UintTy::U8,
2426 ast::UintTy::U16 => UintTy::U16,
2427 ast::UintTy::U32 => UintTy::U32,
2428 ast::UintTy::U64 => UintTy::U64,
2429 ast::UintTy::U128 => UintTy::U128,
2433 pub fn float_ty(fty: ast::FloatTy) -> FloatTy {
2435 ast::FloatTy::F32 => FloatTy::F32,
2436 ast::FloatTy::F64 => FloatTy::F64,
2440 pub fn ast_int_ty(ity: IntTy) -> ast::IntTy {
2442 IntTy::Isize => ast::IntTy::Isize,
2443 IntTy::I8 => ast::IntTy::I8,
2444 IntTy::I16 => ast::IntTy::I16,
2445 IntTy::I32 => ast::IntTy::I32,
2446 IntTy::I64 => ast::IntTy::I64,
2447 IntTy::I128 => ast::IntTy::I128,
2451 pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy {
2453 UintTy::Usize => ast::UintTy::Usize,
2454 UintTy::U8 => ast::UintTy::U8,
2455 UintTy::U16 => ast::UintTy::U16,
2456 UintTy::U32 => ast::UintTy::U32,
2457 UintTy::U64 => ast::UintTy::U64,
2458 UintTy::U128 => ast::UintTy::U128,
2462 pub fn provide(providers: &mut ty::query::Providers) {
2463 closure::provide(providers);
2464 context::provide(providers);
2465 erase_regions::provide(providers);
2466 layout::provide(providers);
2467 util::provide(providers);
2468 print::provide(providers);
2469 super::util::bug::provide(providers);
2470 super::middle::provide(providers);
2471 *providers = ty::query::Providers {
2472 trait_impls_of: trait_def::trait_impls_of_provider,
2473 incoherent_impls: trait_def::incoherent_impls_provider,
2474 type_uninhabited_from: inhabitedness::type_uninhabited_from,
2475 const_param_default: consts::const_param_default,
2476 vtable_allocation: vtable::vtable_allocation_provider,
2481 /// A map for the local crate mapping each type to a vector of its
2482 /// inherent impls. This is not meant to be used outside of coherence;
2483 /// rather, you should request the vector for a specific type via
2484 /// `tcx.inherent_impls(def_id)` so as to minimize your dependencies
2485 /// (constructing this map requires touching the entire crate).
2486 #[derive(Clone, Debug, Default, HashStable)]
2487 pub struct CrateInherentImpls {
2488 pub inherent_impls: LocalDefIdMap<Vec<DefId>>,
2489 pub incoherent_impls: FxHashMap<SimplifiedType, Vec<LocalDefId>>,
2492 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, HashStable)]
2493 pub struct SymbolName<'tcx> {
2494 /// `&str` gives a consistent ordering, which ensures reproducible builds.
2495 pub name: &'tcx str,
2498 impl<'tcx> SymbolName<'tcx> {
2499 pub fn new(tcx: TyCtxt<'tcx>, name: &str) -> SymbolName<'tcx> {
2501 name: unsafe { str::from_utf8_unchecked(tcx.arena.alloc_slice(name.as_bytes())) },
2506 impl<'tcx> fmt::Display for SymbolName<'tcx> {
2507 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2508 fmt::Display::fmt(&self.name, fmt)
2512 impl<'tcx> fmt::Debug for SymbolName<'tcx> {
2513 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2514 fmt::Display::fmt(&self.name, fmt)
2518 #[derive(Debug, Default, Copy, Clone)]
2519 pub struct FoundRelationships {
2520 /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
2521 /// obligation, where:
2523 /// * `Foo` is not `Sized`
2524 /// * `(): Foo` may be satisfied
2525 pub self_in_trait: bool,
2526 /// This is true if we identified that this Ty (`?T`) is found in a `<_ as
2527 /// _>::AssocType = ?T`
2531 /// The constituent parts of a type level constant of kind ADT or array.
2532 #[derive(Copy, Clone, Debug, HashStable)]
2533 pub struct DestructuredConst<'tcx> {
2534 pub variant: Option<VariantIdx>,
2535 pub fields: &'tcx [ty::Const<'tcx>],