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};
52 use std::ops::ControlFlow;
55 pub use crate::ty::diagnostics::*;
56 pub use rustc_type_ir::InferTy::*;
57 pub use rustc_type_ir::RegionKind::*;
58 pub use rustc_type_ir::TyKind::*;
59 pub use rustc_type_ir::*;
61 pub use self::binding::BindingMode;
62 pub use self::binding::BindingMode::*;
63 pub use self::closure::{
64 is_ancestor_or_same_capture, place_to_string_for_capture, BorrowKind, CaptureInfo,
65 CapturedPlace, ClosureKind, MinCaptureInformationMap, MinCaptureList,
66 RootVariableMinCaptureList, UpvarCapture, UpvarCaptureMap, UpvarId, UpvarListMap, UpvarPath,
69 pub use self::consts::{
70 Const, ConstInt, ConstKind, ConstS, InferConst, ScalarInt, Unevaluated, ValTree,
72 pub use self::context::{
73 tls, CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations,
74 CtxtInterners, DelaySpanBugEmitted, FreeRegionInfo, GeneratorDiagnosticData,
75 GeneratorInteriorTypeCause, GlobalCtxt, Lift, OnDiskCache, TyCtxt, TypeckResults, UserType,
76 UserTypeAnnotationIndex,
78 pub use self::instance::{Instance, InstanceDef};
79 pub use self::list::List;
80 pub use self::parameterized::ParameterizedOverTcx;
81 pub use self::rvalue_scopes::RvalueScopes;
82 pub use self::sty::BoundRegionKind::*;
84 Article, Binder, BoundRegion, BoundRegionKind, BoundTy, BoundTyKind, BoundVar,
85 BoundVariableKind, CanonicalPolyFnSig, ClosureSubsts, ClosureSubstsParts, ConstVid,
86 EarlyBinder, EarlyBoundRegion, ExistentialPredicate, ExistentialProjection,
87 ExistentialTraitRef, FnSig, FreeRegion, GenSig, GeneratorSubsts, GeneratorSubstsParts,
88 InlineConstSubsts, InlineConstSubstsParts, ParamConst, ParamTy, PolyExistentialProjection,
89 PolyExistentialTraitRef, PolyFnSig, PolyGenSig, PolyTraitRef, ProjectionTy, Region, RegionKind,
90 RegionVid, TraitRef, TyKind, TypeAndMut, UpvarSubsts, VarianceDiagInfo,
92 pub use self::trait_def::TraitDef;
95 pub mod abstract_const;
104 pub mod inhabitedness;
106 pub mod normalize_erasing_regions;
130 mod structural_impls;
135 pub type RegisteredTools = FxHashSet<Ident>;
138 pub struct ResolverOutputs {
139 pub visibilities: FxHashMap<LocalDefId, Visibility>,
140 /// This field is used to decide whether we should make `PRIVATE_IN_PUBLIC` a hard error.
141 pub has_pub_restricted: bool,
142 /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
143 pub expn_that_defined: FxHashMap<LocalDefId, ExpnId>,
144 /// Reference span for definitions.
145 pub source_span: IndexVec<LocalDefId, Span>,
146 pub access_levels: AccessLevels,
147 pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
148 pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
149 pub maybe_unused_extern_crates: Vec<(LocalDefId, Span)>,
150 pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>,
151 pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,
152 /// Extern prelude entries. The value is `true` if the entry was introduced
153 /// via `extern crate` item and not `--extern` option or compiler built-in.
154 pub extern_prelude: FxHashMap<Symbol, bool>,
155 pub main_def: Option<MainDefinition>,
156 pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,
157 /// A list of proc macro LocalDefIds, written out in the order in which
158 /// they are declared in the static array generated by proc_macro_harness.
159 pub proc_macros: Vec<LocalDefId>,
160 /// Mapping from ident span to path span for paths that don't exist as written, but that
161 /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`.
162 pub confused_type_with_std_module: FxHashMap<Span, Span>,
163 pub registered_tools: RegisteredTools,
166 /// Resolutions that should only be used for lowering.
167 /// This struct is meant to be consumed by lowering.
169 pub struct ResolverAstLowering {
170 pub legacy_const_generic_args: FxHashMap<DefId, Option<Vec<usize>>>,
172 /// Resolutions for nodes that have a single resolution.
173 pub partial_res_map: NodeMap<hir::def::PartialRes>,
174 /// Resolutions for import nodes, which have multiple resolutions in different namespaces.
175 pub import_res_map: NodeMap<hir::def::PerNS<Option<Res<ast::NodeId>>>>,
176 /// Resolutions for labels (node IDs of their corresponding blocks or loops).
177 pub label_res_map: NodeMap<ast::NodeId>,
178 /// Resolutions for lifetimes.
179 pub lifetimes_res_map: NodeMap<LifetimeRes>,
180 /// Lifetime parameters that lowering will have to introduce.
181 pub extra_lifetime_params_map: NodeMap<Vec<(Ident, ast::NodeId, LifetimeRes)>>,
183 pub next_node_id: ast::NodeId,
185 pub node_id_to_def_id: FxHashMap<ast::NodeId, LocalDefId>,
186 pub def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>,
188 pub trait_map: NodeMap<Vec<hir::TraitCandidate>>,
189 /// A small map keeping true kinds of built-in macros that appear to be fn-like on
190 /// the surface (`macro` items in libcore), but are actually attributes or derives.
191 pub builtin_macro_kinds: FxHashMap<LocalDefId, MacroKind>,
194 #[derive(Clone, Copy, Debug)]
195 pub struct MainDefinition {
196 pub res: Res<ast::NodeId>,
201 impl MainDefinition {
202 pub fn opt_fn_def_id(self) -> Option<DefId> {
203 if let Res::Def(DefKind::Fn, def_id) = self.res { Some(def_id) } else { None }
207 /// The "header" of an impl is everything outside the body: a Self type, a trait
208 /// ref (in the case of a trait impl), and a set of predicates (from the
209 /// bounds / where-clauses).
210 #[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
211 pub struct ImplHeader<'tcx> {
212 pub impl_def_id: DefId,
213 pub self_ty: Ty<'tcx>,
214 pub trait_ref: Option<TraitRef<'tcx>>,
215 pub predicates: Vec<Predicate<'tcx>>,
218 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)]
219 pub enum ImplSubject<'tcx> {
220 Trait(TraitRef<'tcx>),
224 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable, Debug)]
225 #[derive(TypeFoldable, TypeVisitable)]
226 pub enum ImplPolarity {
227 /// `impl Trait for Type`
229 /// `impl !Trait for Type`
231 /// `#[rustc_reservation_impl] impl Trait for Type`
233 /// This is a "stability hack", not a real Rust feature.
234 /// See #64631 for details.
239 /// Flips polarity by turning `Positive` into `Negative` and `Negative` into `Positive`.
240 pub fn flip(&self) -> Option<ImplPolarity> {
242 ImplPolarity::Positive => Some(ImplPolarity::Negative),
243 ImplPolarity::Negative => Some(ImplPolarity::Positive),
244 ImplPolarity::Reservation => None,
249 impl fmt::Display for ImplPolarity {
250 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
252 Self::Positive => f.write_str("positive"),
253 Self::Negative => f.write_str("negative"),
254 Self::Reservation => f.write_str("reservation"),
259 #[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, Encodable, Decodable, HashStable)]
260 pub enum Visibility {
261 /// Visible everywhere (including in other crates).
263 /// Visible only in the given crate-local module.
265 /// Not visible anywhere in the local crate. This is the visibility of private external items.
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 // Private items from other crates are visible nowhere.
364 Visibility::Invisible => return false,
365 // Restricted items are visible in an arbitrary local module.
366 Visibility::Restricted(other) if other.krate != module.krate => return false,
367 Visibility::Restricted(module) => module,
370 tree.is_descendant_of(module, restriction)
373 /// Returns `true` if this visibility is at least as accessible as the given visibility
374 pub fn is_at_least<T: DefIdTree>(self, vis: Visibility, tree: T) -> bool {
375 let vis_restriction = match vis {
376 Visibility::Public => return self == Visibility::Public,
377 Visibility::Invisible => return true,
378 Visibility::Restricted(module) => module,
381 self.is_accessible_from(vis_restriction, tree)
384 // Returns `true` if this item is visible anywhere in the local crate.
385 pub fn is_visible_locally(self) -> bool {
387 Visibility::Public => true,
388 Visibility::Restricted(def_id) => def_id.is_local(),
389 Visibility::Invisible => false,
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,
593 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> {
594 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
598 // The other fields just provide fast access to information that is
599 // also contained in `kind`, so no need to hash them.
601 outer_exclusive_binder: _,
604 kind.hash_stable(hcx, hasher);
608 impl rustc_errors::IntoDiagnosticArg for Predicate<'_> {
609 fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
610 rustc_errors::DiagnosticArgValue::Str(std::borrow::Cow::Owned(self.to_string()))
614 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
615 #[derive(HashStable, TypeFoldable, TypeVisitable)]
616 pub enum PredicateKind<'tcx> {
617 /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be
618 /// the `Self` type of the trait reference and `A`, `B`, and `C`
619 /// would be the type parameters.
620 Trait(TraitPredicate<'tcx>),
623 RegionOutlives(RegionOutlivesPredicate<'tcx>),
626 TypeOutlives(TypeOutlivesPredicate<'tcx>),
628 /// `where <T as TraitRef>::Name == X`, approximately.
629 /// See the `ProjectionPredicate` struct for details.
630 Projection(ProjectionPredicate<'tcx>),
632 /// No syntax: `T` well-formed.
633 WellFormed(GenericArg<'tcx>),
635 /// Trait must be object-safe.
638 /// No direct syntax. May be thought of as `where T: FnFoo<...>`
639 /// for some substitutions `...` and `T` being a closure type.
640 /// Satisfied (or refuted) once we know the closure's kind.
641 ClosureKind(DefId, SubstsRef<'tcx>, ClosureKind),
645 /// This obligation is created most often when we have two
646 /// unresolved type variables and hence don't have enough
647 /// information to process the subtyping obligation yet.
648 Subtype(SubtypePredicate<'tcx>),
650 /// `T1` coerced to `T2`
652 /// Like a subtyping obligation, this is created most often
653 /// when we have two unresolved type variables and hence
654 /// don't have enough information to process the coercion
655 /// obligation yet. At the moment, we actually process coercions
656 /// very much like subtyping and don't handle the full coercion
658 Coerce(CoercePredicate<'tcx>),
660 /// Constant initializer must evaluate successfully.
661 ConstEvaluatable(ty::Unevaluated<'tcx, ()>),
663 /// Constants must be equal. The first component is the const that is expected.
664 ConstEquate(Const<'tcx>, Const<'tcx>),
666 /// Represents a type found in the environment that we can use for implied bounds.
668 /// Only used for Chalk.
669 TypeWellFormedFromEnv(Ty<'tcx>),
672 /// The crate outlives map is computed during typeck and contains the
673 /// outlives of every item in the local crate. You should not use it
674 /// directly, because to do so will make your pass dependent on the
675 /// HIR of every item in the local crate. Instead, use
676 /// `tcx.inferred_outlives_of()` to get the outlives for a *particular*
678 #[derive(HashStable, Debug)]
679 pub struct CratePredicatesMap<'tcx> {
680 /// For each struct with outlive bounds, maps to a vector of the
681 /// predicate of its outlive bounds. If an item has no outlives
682 /// bounds, it will have no entry.
683 pub predicates: FxHashMap<DefId, &'tcx [(Predicate<'tcx>, Span)]>,
686 impl<'tcx> Predicate<'tcx> {
687 /// Performs a substitution suitable for going from a
688 /// poly-trait-ref to supertraits that must hold if that
689 /// poly-trait-ref holds. This is slightly different from a normal
690 /// substitution in terms of what happens with bound regions. See
691 /// lengthy comment below for details.
692 pub fn subst_supertrait(
695 trait_ref: &ty::PolyTraitRef<'tcx>,
696 ) -> Predicate<'tcx> {
697 // The interaction between HRTB and supertraits is not entirely
698 // obvious. Let me walk you (and myself) through an example.
700 // Let's start with an easy case. Consider two traits:
702 // trait Foo<'a>: Bar<'a,'a> { }
703 // trait Bar<'b,'c> { }
705 // Now, if we have a trait reference `for<'x> T: Foo<'x>`, then
706 // we can deduce that `for<'x> T: Bar<'x,'x>`. Basically, if we
707 // knew that `Foo<'x>` (for any 'x) then we also know that
708 // `Bar<'x,'x>` (for any 'x). This more-or-less falls out from
709 // normal substitution.
711 // In terms of why this is sound, the idea is that whenever there
712 // is an impl of `T:Foo<'a>`, it must show that `T:Bar<'a,'a>`
713 // holds. So if there is an impl of `T:Foo<'a>` that applies to
714 // all `'a`, then we must know that `T:Bar<'a,'a>` holds for all
717 // Another example to be careful of is this:
719 // trait Foo1<'a>: for<'b> Bar1<'a,'b> { }
720 // trait Bar1<'b,'c> { }
722 // Here, if we have `for<'x> T: Foo1<'x>`, then what do we know?
723 // The answer is that we know `for<'x,'b> T: Bar1<'x,'b>`. The
724 // reason is similar to the previous example: any impl of
725 // `T:Foo1<'x>` must show that `for<'b> T: Bar1<'x, 'b>`. So
726 // basically we would want to collapse the bound lifetimes from
727 // the input (`trait_ref`) and the supertraits.
729 // To achieve this in practice is fairly straightforward. Let's
730 // consider the more complicated scenario:
732 // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x`
733 // has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`,
734 // where both `'x` and `'b` would have a DB index of 1.
735 // The substitution from the input trait-ref is therefore going to be
736 // `'a => 'x` (where `'x` has a DB index of 1).
737 // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an
738 // early-bound parameter and `'b' is a late-bound parameter with a
740 // - If we replace `'a` with `'x` from the input, it too will have
741 // a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>`
742 // just as we wanted.
744 // There is only one catch. If we just apply the substitution `'a
745 // => 'x` to `for<'b> Bar1<'a,'b>`, the substitution code will
746 // adjust the DB index because we substituting into a binder (it
747 // tries to be so smart...) resulting in `for<'x> for<'b>
748 // Bar1<'x,'b>` (we have no syntax for this, so use your
749 // imagination). Basically the 'x will have DB index of 2 and 'b
750 // will have DB index of 1. Not quite what we want. So we apply
751 // the substitution to the *contents* of the trait reference,
752 // rather than the trait reference itself (put another way, the
753 // substitution code expects equal binding levels in the values
754 // from the substitution and the value being substituted into, and
755 // this trick achieves that).
757 // Working through the second example:
758 // trait_ref: for<'x> T: Foo1<'^0.0>; substs: [T, '^0.0]
759 // predicate: for<'b> Self: Bar1<'a, '^0.0>; substs: [Self, 'a, '^0.0]
760 // We want to end up with:
761 // for<'x, 'b> T: Bar1<'^0.0, '^0.1>
763 // 1) We must shift all bound vars in predicate by the length
764 // of trait ref's bound vars. So, we would end up with predicate like
765 // Self: Bar1<'a, '^0.1>
766 // 2) We can then apply the trait substs to this, ending up with
767 // T: Bar1<'^0.0, '^0.1>
768 // 3) Finally, to create the final bound vars, we concatenate the bound
769 // vars of the trait ref with those of the predicate:
771 let bound_pred = self.kind();
772 let pred_bound_vars = bound_pred.bound_vars();
773 let trait_bound_vars = trait_ref.bound_vars();
774 // 1) Self: Bar1<'a, '^0.0> -> Self: Bar1<'a, '^0.1>
776 tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
777 // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
778 let new = EarlyBinder(shifted_pred).subst(tcx, trait_ref.skip_binder().substs);
779 // 3) ['x] + ['b] -> ['x, 'b]
781 tcx.mk_bound_variable_kinds(trait_bound_vars.iter().chain(pred_bound_vars));
782 tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars))
786 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
787 #[derive(HashStable, TypeFoldable, TypeVisitable)]
788 pub struct TraitPredicate<'tcx> {
789 pub trait_ref: TraitRef<'tcx>,
791 pub constness: BoundConstness,
793 /// If polarity is Positive: we are proving that the trait is implemented.
795 /// If polarity is Negative: we are proving that a negative impl of this trait
796 /// exists. (Note that coherence also checks whether negative impls of supertraits
797 /// exist via a series of predicates.)
799 /// If polarity is Reserved: that's a bug.
800 pub polarity: ImplPolarity,
803 pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>;
805 impl<'tcx> TraitPredicate<'tcx> {
806 pub fn remap_constness(&mut self, param_env: &mut ParamEnv<'tcx>) {
807 *param_env = param_env.with_constness(self.constness.and(param_env.constness()))
810 /// Remap the constness of this predicate before emitting it for diagnostics.
811 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
812 // this is different to `remap_constness` that callees want to print this predicate
813 // in case of selection errors. `T: ~const Drop` bounds cannot end up here when the
814 // param_env is not const because it is always satisfied in non-const contexts.
815 if let hir::Constness::NotConst = param_env.constness() {
816 self.constness = ty::BoundConstness::NotConst;
820 pub fn def_id(self) -> DefId {
821 self.trait_ref.def_id
824 pub fn self_ty(self) -> Ty<'tcx> {
825 self.trait_ref.self_ty()
829 pub fn is_const_if_const(self) -> bool {
830 self.constness == BoundConstness::ConstIfConst
833 pub fn is_constness_satisfied_by(self, constness: hir::Constness) -> bool {
834 match (self.constness, constness) {
835 (BoundConstness::NotConst, _)
836 | (BoundConstness::ConstIfConst, hir::Constness::Const) => true,
837 (BoundConstness::ConstIfConst, hir::Constness::NotConst) => false,
842 impl<'tcx> PolyTraitPredicate<'tcx> {
843 pub fn def_id(self) -> DefId {
844 // Ok to skip binder since trait `DefId` does not care about regions.
845 self.skip_binder().def_id()
848 pub fn self_ty(self) -> ty::Binder<'tcx, Ty<'tcx>> {
849 self.map_bound(|trait_ref| trait_ref.self_ty())
852 /// Remap the constness of this predicate before emitting it for diagnostics.
853 pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) {
854 *self = self.map_bound(|mut p| {
855 p.remap_constness_diag(param_env);
861 pub fn is_const_if_const(self) -> bool {
862 self.skip_binder().is_const_if_const()
866 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
867 #[derive(HashStable, TypeFoldable, TypeVisitable)]
868 pub struct OutlivesPredicate<A, B>(pub A, pub B); // `A: B`
869 pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>;
870 pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>;
871 pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>;
872 pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>;
874 /// Encodes that `a` must be a subtype of `b`. The `a_is_expected` flag indicates
875 /// whether the `a` type is the type that we should label as "expected" when
876 /// presenting user diagnostics.
877 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
878 #[derive(HashStable, TypeFoldable, TypeVisitable)]
879 pub struct SubtypePredicate<'tcx> {
880 pub a_is_expected: bool,
884 pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>;
886 /// Encodes that we have to coerce *from* the `a` type to the `b` type.
887 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
888 #[derive(HashStable, TypeFoldable, TypeVisitable)]
889 pub struct CoercePredicate<'tcx> {
893 pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
895 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, TyEncodable, TyDecodable)]
896 #[derive(HashStable, TypeFoldable, TypeVisitable)]
897 pub enum Term<'tcx> {
902 impl<'tcx> From<Ty<'tcx>> for Term<'tcx> {
903 fn from(ty: Ty<'tcx>) -> Self {
908 impl<'tcx> From<Const<'tcx>> for Term<'tcx> {
909 fn from(c: Const<'tcx>) -> Self {
914 impl<'tcx> Term<'tcx> {
915 pub fn ty(&self) -> Option<Ty<'tcx>> {
916 if let Term::Ty(ty) = self { Some(*ty) } else { None }
919 pub fn ct(&self) -> Option<Const<'tcx>> {
920 if let Term::Const(c) = self { Some(*c) } else { None }
923 pub fn into_arg(self) -> GenericArg<'tcx> {
925 Term::Ty(ty) => ty.into(),
926 Term::Const(c) => c.into(),
931 /// This kind of predicate has no *direct* correspondent in the
932 /// syntax, but it roughly corresponds to the syntactic forms:
934 /// 1. `T: TraitRef<..., Item = Type>`
935 /// 2. `<T as TraitRef<...>>::Item == Type` (NYI)
937 /// In particular, form #1 is "desugared" to the combination of a
938 /// normal trait predicate (`T: TraitRef<...>`) and one of these
939 /// predicates. Form #2 is a broader form in that it also permits
940 /// equality between arbitrary types. Processing an instance of
941 /// Form #2 eventually yields one of these `ProjectionPredicate`
942 /// instances to normalize the LHS.
943 #[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
944 #[derive(HashStable, TypeFoldable, TypeVisitable)]
945 pub struct ProjectionPredicate<'tcx> {
946 pub projection_ty: ProjectionTy<'tcx>,
947 pub term: Term<'tcx>,
950 pub type PolyProjectionPredicate<'tcx> = Binder<'tcx, ProjectionPredicate<'tcx>>;
952 impl<'tcx> PolyProjectionPredicate<'tcx> {
953 /// Returns the `DefId` of the trait of the associated item being projected.
955 pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId {
956 self.skip_binder().projection_ty.trait_def_id(tcx)
959 /// Get the [PolyTraitRef] required for this projection to be well formed.
960 /// Note that for generic associated types the predicates of the associated
961 /// type also need to be checked.
963 pub fn required_poly_trait_ref(&self, tcx: TyCtxt<'tcx>) -> PolyTraitRef<'tcx> {
964 // Note: unlike with `TraitRef::to_poly_trait_ref()`,
965 // `self.0.trait_ref` is permitted to have escaping regions.
966 // This is because here `self` has a `Binder` and so does our
967 // return value, so we are preserving the number of binding
969 self.map_bound(|predicate| predicate.projection_ty.trait_ref(tcx))
972 pub fn term(&self) -> Binder<'tcx, Term<'tcx>> {
973 self.map_bound(|predicate| predicate.term)
976 /// The `DefId` of the `TraitItem` for the associated type.
978 /// Note that this is not the `DefId` of the `TraitRef` containing this
979 /// associated type, which is in `tcx.associated_item(projection_def_id()).container`.
980 pub fn projection_def_id(&self) -> DefId {
981 // Ok to skip binder since trait `DefId` does not care about regions.
982 self.skip_binder().projection_ty.item_def_id
986 pub trait ToPolyTraitRef<'tcx> {
987 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx>;
990 impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> {
991 fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> {
992 self.map_bound_ref(|trait_pred| trait_pred.trait_ref)
996 pub trait ToPredicate<'tcx> {
997 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx>;
1000 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> {
1002 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1003 tcx.mk_predicate(self)
1007 impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
1008 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1009 self.map_bound(PredicateKind::Trait).to_predicate(tcx)
1013 impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
1014 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1015 self.map_bound(PredicateKind::RegionOutlives).to_predicate(tcx)
1019 impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> {
1020 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1021 self.map_bound(PredicateKind::TypeOutlives).to_predicate(tcx)
1025 impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
1026 fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
1027 self.map_bound(PredicateKind::Projection).to_predicate(tcx)
1031 impl<'tcx> Predicate<'tcx> {
1032 pub fn to_opt_poly_trait_pred(self) -> Option<PolyTraitPredicate<'tcx>> {
1033 let predicate = self.kind();
1034 match predicate.skip_binder() {
1035 PredicateKind::Trait(t) => Some(predicate.rebind(t)),
1036 PredicateKind::Projection(..)
1037 | PredicateKind::Subtype(..)
1038 | PredicateKind::Coerce(..)
1039 | PredicateKind::RegionOutlives(..)
1040 | PredicateKind::WellFormed(..)
1041 | PredicateKind::ObjectSafe(..)
1042 | PredicateKind::ClosureKind(..)
1043 | PredicateKind::TypeOutlives(..)
1044 | PredicateKind::ConstEvaluatable(..)
1045 | PredicateKind::ConstEquate(..)
1046 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1050 pub fn to_opt_poly_projection_pred(self) -> Option<PolyProjectionPredicate<'tcx>> {
1051 let predicate = self.kind();
1052 match predicate.skip_binder() {
1053 PredicateKind::Projection(t) => Some(predicate.rebind(t)),
1054 PredicateKind::Trait(..)
1055 | PredicateKind::Subtype(..)
1056 | PredicateKind::Coerce(..)
1057 | PredicateKind::RegionOutlives(..)
1058 | PredicateKind::WellFormed(..)
1059 | PredicateKind::ObjectSafe(..)
1060 | PredicateKind::ClosureKind(..)
1061 | PredicateKind::TypeOutlives(..)
1062 | PredicateKind::ConstEvaluatable(..)
1063 | PredicateKind::ConstEquate(..)
1064 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1068 pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> {
1069 let predicate = self.kind();
1070 match predicate.skip_binder() {
1071 PredicateKind::TypeOutlives(data) => Some(predicate.rebind(data)),
1072 PredicateKind::Trait(..)
1073 | PredicateKind::Projection(..)
1074 | PredicateKind::Subtype(..)
1075 | PredicateKind::Coerce(..)
1076 | PredicateKind::RegionOutlives(..)
1077 | PredicateKind::WellFormed(..)
1078 | PredicateKind::ObjectSafe(..)
1079 | PredicateKind::ClosureKind(..)
1080 | PredicateKind::ConstEvaluatable(..)
1081 | PredicateKind::ConstEquate(..)
1082 | PredicateKind::TypeWellFormedFromEnv(..) => None,
1087 /// Represents the bounds declared on a particular set of type
1088 /// parameters. Should eventually be generalized into a flag list of
1089 /// where-clauses. You can obtain an `InstantiatedPredicates` list from a
1090 /// `GenericPredicates` by using the `instantiate` method. Note that this method
1091 /// reflects an important semantic invariant of `InstantiatedPredicates`: while
1092 /// the `GenericPredicates` are expressed in terms of the bound type
1093 /// parameters of the impl/trait/whatever, an `InstantiatedPredicates` instance
1094 /// represented a set of bounds for some particular instantiation,
1095 /// meaning that the generic parameters have been substituted with
1099 /// ```ignore (illustrative)
1100 /// struct Foo<T, U: Bar<T>> { ... }
1102 /// Here, the `GenericPredicates` for `Foo` would contain a list of bounds like
1103 /// `[[], [U:Bar<T>]]`. Now if there were some particular reference
1104 /// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[],
1105 /// [usize:Bar<isize>]]`.
1106 #[derive(Clone, Debug, TypeFoldable, TypeVisitable)]
1107 pub struct InstantiatedPredicates<'tcx> {
1108 pub predicates: Vec<Predicate<'tcx>>,
1109 pub spans: Vec<Span>,
1112 impl<'tcx> InstantiatedPredicates<'tcx> {
1113 pub fn empty() -> InstantiatedPredicates<'tcx> {
1114 InstantiatedPredicates { predicates: vec![], spans: vec![] }
1117 pub fn is_empty(&self) -> bool {
1118 self.predicates.is_empty()
1122 #[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable, Lift)]
1123 #[derive(TypeFoldable, TypeVisitable)]
1124 pub struct OpaqueTypeKey<'tcx> {
1125 pub def_id: LocalDefId,
1126 pub substs: SubstsRef<'tcx>,
1129 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
1130 pub struct OpaqueHiddenType<'tcx> {
1131 /// The span of this particular definition of the opaque type. So
1134 /// ```ignore (incomplete snippet)
1135 /// type Foo = impl Baz;
1136 /// fn bar() -> Foo {
1137 /// // ^^^ This is the span we are looking for!
1141 /// In cases where the fn returns `(impl Trait, impl Trait)` or
1142 /// other such combinations, the result is currently
1143 /// over-approximated, but better than nothing.
1146 /// The type variable that represents the value of the opaque type
1147 /// that we require. In other words, after we compile this function,
1148 /// we will be created a constraint like:
1149 /// ```ignore (pseudo-rust)
1152 /// where `?C` is the value of this type variable. =) It may
1153 /// naturally refer to the type and lifetime parameters in scope
1154 /// in this function, though ultimately it should only reference
1155 /// those that are arguments to `Foo` in the constraint above. (In
1156 /// other words, `?C` should not include `'b`, even though it's a
1157 /// lifetime parameter on `foo`.)
1161 impl<'tcx> OpaqueHiddenType<'tcx> {
1162 pub fn report_mismatch(&self, other: &Self, tcx: TyCtxt<'tcx>) {
1163 // Found different concrete types for the opaque type.
1164 let mut err = tcx.sess.struct_span_err(
1166 "concrete type differs from previous defining opaque type use",
1168 err.span_label(other.span, format!("expected `{}`, got `{}`", self.ty, other.ty));
1169 if self.span == other.span {
1172 "this expression supplies two conflicting concrete types for the same opaque type",
1175 err.span_note(self.span, "previous use here");
1181 /// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are
1182 /// identified by both a universe, as well as a name residing within that universe. Distinct bound
1183 /// regions/types/consts within the same universe simply have an unknown relationship to one
1185 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
1186 #[derive(HashStable, TyEncodable, TyDecodable)]
1187 pub struct Placeholder<T> {
1188 pub universe: UniverseIndex,
1192 pub type PlaceholderRegion = Placeholder<BoundRegionKind>;
1194 pub type PlaceholderType = Placeholder<BoundVar>;
1196 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
1197 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
1198 pub struct BoundConst<'tcx> {
1203 pub type PlaceholderConst<'tcx> = Placeholder<BoundConst<'tcx>>;
1205 /// A `DefId` which, in case it is a const argument, is potentially bundled with
1206 /// the `DefId` of the generic parameter it instantiates.
1208 /// This is used to avoid calls to `type_of` for const arguments during typeck
1209 /// which cause cycle errors.
1214 /// fn foo<const N: usize>(&self) -> [u8; N] { [0; N] }
1215 /// // ^ const parameter
1219 /// fn foo<const M: u8>(&self) -> usize { 42 }
1220 /// // ^ const parameter
1225 /// let _b = a.foo::<{ 3 + 7 }>();
1226 /// // ^^^^^^^^^ const argument
1230 /// Let's look at the call `a.foo::<{ 3 + 7 }>()` here. We do not know
1231 /// which `foo` is used until we know the type of `a`.
1233 /// We only know the type of `a` once we are inside of `typeck(main)`.
1234 /// We also end up normalizing the type of `_b` during `typeck(main)` which
1235 /// requires us to evaluate the const argument.
1237 /// To evaluate that const argument we need to know its type,
1238 /// which we would get using `type_of(const_arg)`. This requires us to
1239 /// resolve `foo` as it can be either `usize` or `u8` in this example.
1240 /// However, resolving `foo` once again requires `typeck(main)` to get the type of `a`,
1241 /// which results in a cycle.
1243 /// In short we must not call `type_of(const_arg)` during `typeck(main)`.
1245 /// When first creating the `ty::Const` of the const argument inside of `typeck` we have
1246 /// already resolved `foo` so we know which const parameter this argument instantiates.
1247 /// This means that we also know the expected result of `type_of(const_arg)` even if we
1248 /// aren't allowed to call that query: it is equal to `type_of(const_param)` which is
1249 /// trivial to compute.
1251 /// If we now want to use that constant in a place which potentially needs its type
1252 /// we also pass the type of its `const_param`. This is the point of `WithOptConstParam`,
1253 /// except that instead of a `Ty` we bundle the `DefId` of the const parameter.
1254 /// Meaning that we need to use `type_of(const_param_did)` if `const_param_did` is `Some`
1255 /// to get the type of `did`.
1256 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, Lift, TyEncodable, TyDecodable)]
1257 #[derive(PartialEq, Eq, PartialOrd, Ord)]
1258 #[derive(Hash, HashStable)]
1259 pub struct WithOptConstParam<T> {
1261 /// The `DefId` of the corresponding generic parameter in case `did` is
1262 /// a const argument.
1264 /// Note that even if `did` is a const argument, this may still be `None`.
1265 /// All queries taking `WithOptConstParam` start by calling `tcx.opt_const_param_of(def.did)`
1266 /// to potentially update `param_did` in the case it is `None`.
1267 pub const_param_did: Option<DefId>,
1270 impl<T> WithOptConstParam<T> {
1271 /// Creates a new `WithOptConstParam` setting `const_param_did` to `None`.
1273 pub fn unknown(did: T) -> WithOptConstParam<T> {
1274 WithOptConstParam { did, const_param_did: None }
1278 impl WithOptConstParam<LocalDefId> {
1279 /// Returns `Some((did, param_did))` if `def_id` is a const argument,
1280 /// `None` otherwise.
1282 pub fn try_lookup(did: LocalDefId, tcx: TyCtxt<'_>) -> Option<(LocalDefId, DefId)> {
1283 tcx.opt_const_param_of(did).map(|param_did| (did, param_did))
1286 /// In case `self` is unknown but `self.did` is a const argument, this returns
1287 /// a `WithOptConstParam` with the correct `const_param_did`.
1289 pub fn try_upgrade(self, tcx: TyCtxt<'_>) -> Option<WithOptConstParam<LocalDefId>> {
1290 if self.const_param_did.is_none() {
1291 if let const_param_did @ Some(_) = tcx.opt_const_param_of(self.did) {
1292 return Some(WithOptConstParam { did: self.did, const_param_did });
1299 pub fn to_global(self) -> WithOptConstParam<DefId> {
1300 WithOptConstParam { did: self.did.to_def_id(), const_param_did: self.const_param_did }
1303 pub fn def_id_for_type_of(self) -> DefId {
1304 if let Some(did) = self.const_param_did { did } else { self.did.to_def_id() }
1308 impl WithOptConstParam<DefId> {
1309 pub fn as_local(self) -> Option<WithOptConstParam<LocalDefId>> {
1312 .map(|did| WithOptConstParam { did, const_param_did: self.const_param_did })
1315 pub fn as_const_arg(self) -> Option<(LocalDefId, DefId)> {
1316 if let Some(param_did) = self.const_param_did {
1317 if let Some(did) = self.did.as_local() {
1318 return Some((did, param_did));
1325 pub fn is_local(self) -> bool {
1329 pub fn def_id_for_type_of(self) -> DefId {
1330 self.const_param_did.unwrap_or(self.did)
1334 /// When type checking, we use the `ParamEnv` to track
1335 /// details about the set of where-clauses that are in scope at this
1336 /// particular point.
1337 #[derive(Copy, Clone, Hash, PartialEq, Eq)]
1338 pub struct ParamEnv<'tcx> {
1339 /// This packs both caller bounds and the reveal enum into one pointer.
1341 /// Caller bounds are `Obligation`s that the caller must satisfy. This is
1342 /// basically the set of bounds on the in-scope type parameters, translated
1343 /// into `Obligation`s, and elaborated and normalized.
1345 /// Use the `caller_bounds()` method to access.
1347 /// Typically, this is `Reveal::UserFacing`, but during codegen we
1348 /// want `Reveal::All`.
1350 /// Note: This is packed, use the reveal() method to access it.
1351 packed: CopyTaggedPtr<&'tcx List<Predicate<'tcx>>, ParamTag, true>,
1354 #[derive(Copy, Clone)]
1356 reveal: traits::Reveal,
1357 constness: hir::Constness,
1360 unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag {
1361 const BITS: usize = 2;
1363 fn into_usize(self) -> usize {
1365 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0,
1366 Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1,
1367 Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2,
1368 Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3,
1372 unsafe fn from_usize(ptr: usize) -> Self {
1374 0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst },
1375 1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst },
1376 2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const },
1377 3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const },
1378 _ => std::hint::unreachable_unchecked(),
1383 impl<'tcx> fmt::Debug for ParamEnv<'tcx> {
1384 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1385 f.debug_struct("ParamEnv")
1386 .field("caller_bounds", &self.caller_bounds())
1387 .field("reveal", &self.reveal())
1388 .field("constness", &self.constness())
1393 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
1394 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
1395 self.caller_bounds().hash_stable(hcx, hasher);
1396 self.reveal().hash_stable(hcx, hasher);
1397 self.constness().hash_stable(hcx, hasher);
1401 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
1402 fn try_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>(
1405 ) -> Result<Self, F::Error> {
1407 self.caller_bounds().try_fold_with(folder)?,
1408 self.reveal().try_fold_with(folder)?,
1409 self.constness().try_fold_with(folder)?,
1414 impl<'tcx> TypeVisitable<'tcx> for ParamEnv<'tcx> {
1415 fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
1416 self.caller_bounds().visit_with(visitor)?;
1417 self.reveal().visit_with(visitor)?;
1418 self.constness().visit_with(visitor)
1422 impl<'tcx> ParamEnv<'tcx> {
1423 /// Construct a trait environment suitable for contexts where
1424 /// there are no where-clauses in scope. Hidden types (like `impl
1425 /// Trait`) are left hidden, so this is suitable for ordinary
1428 pub fn empty() -> Self {
1429 Self::new(List::empty(), Reveal::UserFacing, hir::Constness::NotConst)
1433 pub fn caller_bounds(self) -> &'tcx List<Predicate<'tcx>> {
1434 self.packed.pointer()
1438 pub fn reveal(self) -> traits::Reveal {
1439 self.packed.tag().reveal
1443 pub fn constness(self) -> hir::Constness {
1444 self.packed.tag().constness
1448 pub fn is_const(self) -> bool {
1449 self.packed.tag().constness == hir::Constness::Const
1452 /// Construct a trait environment with no where-clauses in scope
1453 /// where the values of all `impl Trait` and other hidden types
1454 /// are revealed. This is suitable for monomorphized, post-typeck
1455 /// environments like codegen or doing optimizations.
1457 /// N.B., if you want to have predicates in scope, use `ParamEnv::new`,
1458 /// or invoke `param_env.with_reveal_all()`.
1460 pub fn reveal_all() -> Self {
1461 Self::new(List::empty(), Reveal::All, hir::Constness::NotConst)
1464 /// Construct a trait environment with the given set of predicates.
1467 caller_bounds: &'tcx List<Predicate<'tcx>>,
1469 constness: hir::Constness,
1471 ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal, constness }) }
1474 pub fn with_user_facing(mut self) -> Self {
1475 self.packed.set_tag(ParamTag { reveal: Reveal::UserFacing, ..self.packed.tag() });
1480 pub fn with_constness(mut self, constness: hir::Constness) -> Self {
1481 self.packed.set_tag(ParamTag { constness, ..self.packed.tag() });
1486 pub fn with_const(mut self) -> Self {
1487 self.packed.set_tag(ParamTag { constness: hir::Constness::Const, ..self.packed.tag() });
1492 pub fn without_const(mut self) -> Self {
1493 self.packed.set_tag(ParamTag { constness: hir::Constness::NotConst, ..self.packed.tag() });
1498 pub fn remap_constness_with(&mut self, mut constness: ty::BoundConstness) {
1499 *self = self.with_constness(constness.and(self.constness()))
1502 /// Returns a new parameter environment with the same clauses, but
1503 /// which "reveals" the true results of projections in all cases
1504 /// (even for associated types that are specializable). This is
1505 /// the desired behavior during codegen and certain other special
1506 /// contexts; normally though we want to use `Reveal::UserFacing`,
1507 /// which is the default.
1508 /// All opaque types in the caller_bounds of the `ParamEnv`
1509 /// will be normalized to their underlying types.
1510 /// See PR #65989 and issue #65918 for more details
1511 pub fn with_reveal_all_normalized(self, tcx: TyCtxt<'tcx>) -> Self {
1512 if self.packed.tag().reveal == traits::Reveal::All {
1517 tcx.normalize_opaque_types(self.caller_bounds()),
1523 /// Returns this same environment but with no caller bounds.
1525 pub fn without_caller_bounds(self) -> Self {
1526 Self::new(List::empty(), self.reveal(), self.constness())
1529 /// Creates a suitable environment in which to perform trait
1530 /// queries on the given value. When type-checking, this is simply
1531 /// the pair of the environment plus value. But when reveal is set to
1532 /// All, then if `value` does not reference any type parameters, we will
1533 /// pair it with the empty environment. This improves caching and is generally
1536 /// N.B., we preserve the environment when type-checking because it
1537 /// is possible for the user to have wacky where-clauses like
1538 /// `where Box<u32>: Copy`, which are clearly never
1539 /// satisfiable. We generally want to behave as if they were true,
1540 /// although the surrounding function is never reachable.
1541 pub fn and<T: TypeVisitable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> {
1542 match self.reveal() {
1543 Reveal::UserFacing => ParamEnvAnd { param_env: self, value },
1546 if value.is_global() {
1547 ParamEnvAnd { param_env: self.without_caller_bounds(), value }
1549 ParamEnvAnd { param_env: self, value }
1556 // FIXME(ecstaticmorse): Audit all occurrences of `without_const().to_predicate(tcx)` to ensure that
1557 // the constness of trait bounds is being propagated correctly.
1558 impl<'tcx> PolyTraitRef<'tcx> {
1560 pub fn with_constness(self, constness: BoundConstness) -> PolyTraitPredicate<'tcx> {
1561 self.map_bound(|trait_ref| ty::TraitPredicate {
1564 polarity: ty::ImplPolarity::Positive,
1569 pub fn without_const(self) -> PolyTraitPredicate<'tcx> {
1570 self.with_constness(BoundConstness::NotConst)
1574 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
1575 #[derive(HashStable)]
1576 pub struct ParamEnvAnd<'tcx, T> {
1577 pub param_env: ParamEnv<'tcx>,
1581 impl<'tcx, T> ParamEnvAnd<'tcx, T> {
1582 pub fn into_parts(self) -> (ParamEnv<'tcx>, T) {
1583 (self.param_env, self.value)
1587 pub fn without_const(mut self) -> Self {
1588 self.param_env = self.param_env.without_const();
1593 #[derive(Copy, Clone, Debug, HashStable, Encodable, Decodable)]
1594 pub struct Destructor {
1595 /// The `DefId` of the destructor method
1597 /// The constness of the destructor method
1598 pub constness: hir::Constness,
1602 #[derive(HashStable, TyEncodable, TyDecodable)]
1603 pub struct VariantFlags: u32 {
1604 const NO_VARIANT_FLAGS = 0;
1605 /// Indicates whether the field list of this variant is `#[non_exhaustive]`.
1606 const IS_FIELD_LIST_NON_EXHAUSTIVE = 1 << 0;
1607 /// Indicates whether this variant was obtained as part of recovering from
1608 /// a syntactic error. May be incomplete or bogus.
1609 const IS_RECOVERED = 1 << 1;
1613 /// Definition of a variant -- a struct's fields or an enum variant.
1614 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1615 pub struct VariantDef {
1616 /// `DefId` that identifies the variant itself.
1617 /// If this variant belongs to a struct or union, then this is a copy of its `DefId`.
1619 /// `DefId` that identifies the variant's constructor.
1620 /// If this variant is a struct variant, then this is `None`.
1621 pub ctor_def_id: Option<DefId>,
1622 /// Variant or struct name.
1624 /// Discriminant of this variant.
1625 pub discr: VariantDiscr,
1626 /// Fields of this variant.
1627 pub fields: Vec<FieldDef>,
1628 /// Type of constructor of variant.
1629 pub ctor_kind: CtorKind,
1630 /// Flags of the variant (e.g. is field list non-exhaustive)?
1631 flags: VariantFlags,
1635 /// Creates a new `VariantDef`.
1637 /// `variant_did` is the `DefId` that identifies the enum variant (if this `VariantDef`
1638 /// represents an enum variant).
1640 /// `ctor_did` is the `DefId` that identifies the constructor of unit or
1641 /// tuple-variants/structs. If this is a `struct`-variant then this should be `None`.
1643 /// `parent_did` is the `DefId` of the `AdtDef` representing the enum or struct that
1644 /// owns this variant. It is used for checking if a struct has `#[non_exhaustive]` w/out having
1645 /// to go through the redirect of checking the ctor's attributes - but compiling a small crate
1646 /// requires loading the `AdtDef`s for all the structs in the universe (e.g., coherence for any
1647 /// built-in trait), and we do not want to load attributes twice.
1649 /// If someone speeds up attribute loading to not be a performance concern, they can
1650 /// remove this hack and use the constructor `DefId` everywhere.
1653 variant_did: Option<DefId>,
1654 ctor_def_id: Option<DefId>,
1655 discr: VariantDiscr,
1656 fields: Vec<FieldDef>,
1657 ctor_kind: CtorKind,
1661 is_field_list_non_exhaustive: bool,
1664 "VariantDef::new(name = {:?}, variant_did = {:?}, ctor_def_id = {:?}, discr = {:?},
1665 fields = {:?}, ctor_kind = {:?}, adt_kind = {:?}, parent_did = {:?})",
1666 name, variant_did, ctor_def_id, discr, fields, ctor_kind, adt_kind, parent_did,
1669 let mut flags = VariantFlags::NO_VARIANT_FLAGS;
1670 if is_field_list_non_exhaustive {
1671 flags |= VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE;
1675 flags |= VariantFlags::IS_RECOVERED;
1679 def_id: variant_did.unwrap_or(parent_did),
1689 /// Is this field list non-exhaustive?
1691 pub fn is_field_list_non_exhaustive(&self) -> bool {
1692 self.flags.intersects(VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE)
1695 /// Was this variant obtained as part of recovering from a syntactic error?
1697 pub fn is_recovered(&self) -> bool {
1698 self.flags.intersects(VariantFlags::IS_RECOVERED)
1701 /// Computes the `Ident` of this variant by looking up the `Span`
1702 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1703 Ident::new(self.name, tcx.def_ident_span(self.def_id).unwrap())
1707 #[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)]
1708 pub enum VariantDiscr {
1709 /// Explicit value for this variant, i.e., `X = 123`.
1710 /// The `DefId` corresponds to the embedded constant.
1713 /// The previous variant's discriminant plus one.
1714 /// For efficiency reasons, the distance from the
1715 /// last `Explicit` discriminant is being stored,
1716 /// or `0` for the first variant, if it has none.
1720 #[derive(Debug, HashStable, TyEncodable, TyDecodable)]
1721 pub struct FieldDef {
1724 pub vis: Visibility,
1728 #[derive(TyEncodable, TyDecodable, Default, HashStable)]
1729 pub struct ReprFlags: u8 {
1730 const IS_C = 1 << 0;
1731 const IS_SIMD = 1 << 1;
1732 const IS_TRANSPARENT = 1 << 2;
1733 // Internal only for now. If true, don't reorder fields.
1734 const IS_LINEAR = 1 << 3;
1735 // If true, the type's layout can be randomized using
1736 // the seed stored in `ReprOptions.layout_seed`
1737 const RANDOMIZE_LAYOUT = 1 << 4;
1738 // Any of these flags being set prevent field reordering optimisation.
1739 const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits
1740 | ReprFlags::IS_SIMD.bits
1741 | ReprFlags::IS_LINEAR.bits;
1745 /// Represents the repr options provided by the user,
1746 #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Default, HashStable)]
1747 pub struct ReprOptions {
1748 pub int: Option<attr::IntType>,
1749 pub align: Option<Align>,
1750 pub pack: Option<Align>,
1751 pub flags: ReprFlags,
1752 /// The seed to be used for randomizing a type's layout
1754 /// Note: This could technically be a `[u8; 16]` (a `u128`) which would
1755 /// be the "most accurate" hash as it'd encompass the item and crate
1756 /// hash without loss, but it does pay the price of being larger.
1757 /// Everything's a tradeoff, a `u64` seed should be sufficient for our
1758 /// purposes (primarily `-Z randomize-layout`)
1759 pub field_shuffle_seed: u64,
1763 pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions {
1764 let mut flags = ReprFlags::empty();
1765 let mut size = None;
1766 let mut max_align: Option<Align> = None;
1767 let mut min_pack: Option<Align> = None;
1769 // Generate a deterministically-derived seed from the item's path hash
1770 // to allow for cross-crate compilation to actually work
1771 let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash();
1773 // If the user defined a custom seed for layout randomization, xor the item's
1774 // path hash with the user defined seed, this will allowing determinism while
1775 // still allowing users to further randomize layout generation for e.g. fuzzing
1776 if let Some(user_seed) = tcx.sess.opts.unstable_opts.layout_seed {
1777 field_shuffle_seed ^= user_seed;
1780 for attr in tcx.get_attrs(did, sym::repr) {
1781 for r in attr::parse_repr_attr(&tcx.sess, attr) {
1782 flags.insert(match r {
1783 attr::ReprC => ReprFlags::IS_C,
1784 attr::ReprPacked(pack) => {
1785 let pack = Align::from_bytes(pack as u64).unwrap();
1786 min_pack = Some(if let Some(min_pack) = min_pack {
1793 attr::ReprTransparent => ReprFlags::IS_TRANSPARENT,
1794 attr::ReprSimd => ReprFlags::IS_SIMD,
1795 attr::ReprInt(i) => {
1799 attr::ReprAlign(align) => {
1800 max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap()));
1807 // If `-Z randomize-layout` was enabled for the type definition then we can
1808 // consider performing layout randomization
1809 if tcx.sess.opts.unstable_opts.randomize_layout {
1810 flags.insert(ReprFlags::RANDOMIZE_LAYOUT);
1813 // This is here instead of layout because the choice must make it into metadata.
1814 if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) {
1815 flags.insert(ReprFlags::IS_LINEAR);
1818 Self { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed }
1822 pub fn simd(&self) -> bool {
1823 self.flags.contains(ReprFlags::IS_SIMD)
1827 pub fn c(&self) -> bool {
1828 self.flags.contains(ReprFlags::IS_C)
1832 pub fn packed(&self) -> bool {
1837 pub fn transparent(&self) -> bool {
1838 self.flags.contains(ReprFlags::IS_TRANSPARENT)
1842 pub fn linear(&self) -> bool {
1843 self.flags.contains(ReprFlags::IS_LINEAR)
1846 /// Returns the discriminant type, given these `repr` options.
1847 /// This must only be called on enums!
1848 pub fn discr_type(&self) -> attr::IntType {
1849 self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize))
1852 /// Returns `true` if this `#[repr()]` should inhabit "smart enum
1853 /// layout" optimizations, such as representing `Foo<&T>` as a
1855 pub fn inhibit_enum_layout_opt(&self) -> bool {
1856 self.c() || self.int.is_some()
1859 /// Returns `true` if this `#[repr()]` should inhibit struct field reordering
1860 /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`.
1861 pub fn inhibit_struct_field_reordering_opt(&self) -> bool {
1862 if let Some(pack) = self.pack {
1863 if pack.bytes() == 1 {
1868 self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some()
1871 /// Returns `true` if this type is valid for reordering and `-Z randomize-layout`
1872 /// was enabled for its declaration crate
1873 pub fn can_randomize_type_layout(&self) -> bool {
1874 !self.inhibit_struct_field_reordering_opt()
1875 && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT)
1878 /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations.
1879 pub fn inhibit_union_abi_opt(&self) -> bool {
1884 impl<'tcx> FieldDef {
1885 /// Returns the type of this field. The resulting type is not normalized. The `subst` is
1886 /// typically obtained via the second field of [`TyKind::Adt`].
1887 pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
1888 tcx.bound_type_of(self.did).subst(tcx, subst)
1891 /// Computes the `Ident` of this variant by looking up the `Span`
1892 pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident {
1893 Ident::new(self.name, tcx.def_ident_span(self.did).unwrap())
1897 pub type Attributes<'tcx> = impl Iterator<Item = &'tcx ast::Attribute>;
1898 #[derive(Debug, PartialEq, Eq)]
1899 pub enum ImplOverlapKind {
1900 /// These impls are always allowed to overlap.
1902 /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait
1905 /// These impls are allowed to overlap, but that raises
1906 /// an issue #33140 future-compatibility warning.
1908 /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's
1909 /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different.
1911 /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied
1912 /// that difference, making what reduces to the following set of impls:
1914 /// ```compile_fail,(E0119)
1916 /// impl Trait for dyn Send + Sync {}
1917 /// impl Trait for dyn Sync + Send {}
1920 /// Obviously, once we made these types be identical, that code causes a coherence
1921 /// error and a fairly big headache for us. However, luckily for us, the trait
1922 /// `Trait` used in this case is basically a marker trait, and therefore having
1923 /// overlapping impls for it is sound.
1925 /// To handle this, we basically regard the trait as a marker trait, with an additional
1926 /// future-compatibility warning. To avoid accidentally "stabilizing" this feature,
1927 /// it has the following restrictions:
1929 /// 1. The trait must indeed be a marker-like trait (i.e., no items), and must be
1931 /// 2. The trait-ref of both impls must be equal.
1932 /// 3. The trait-ref of both impls must be a trait object type consisting only of
1934 /// 4. Neither of the impls can have any where-clauses.
1936 /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed.
1940 impl<'tcx> TyCtxt<'tcx> {
1941 pub fn typeck_body(self, body: hir::BodyId) -> &'tcx TypeckResults<'tcx> {
1942 self.typeck(self.hir().body_owner_def_id(body))
1945 pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> {
1946 self.associated_items(id)
1947 .in_definition_order()
1948 .filter(|item| item.kind == AssocKind::Fn && item.defaultness.has_value())
1951 /// Look up the name of a definition across crates. This does not look at HIR.
1952 pub fn opt_item_name(self, def_id: DefId) -> Option<Symbol> {
1953 if let Some(cnum) = def_id.as_crate_root() {
1954 Some(self.crate_name(cnum))
1956 let def_key = self.def_key(def_id);
1957 match def_key.disambiguated_data.data {
1958 // The name of a constructor is that of its parent.
1959 rustc_hir::definitions::DefPathData::Ctor => self
1960 .opt_item_name(DefId { krate: def_id.krate, index: def_key.parent.unwrap() }),
1961 // The name of opaque types only exists in HIR.
1962 rustc_hir::definitions::DefPathData::ImplTrait
1963 if let Some(def_id) = def_id.as_local() =>
1964 self.hir().opt_name(self.hir().local_def_id_to_hir_id(def_id)),
1965 _ => def_key.get_opt_name(),
1970 /// Look up the name of a definition across crates. This does not look at HIR.
1972 /// This method will ICE if the corresponding item does not have a name. In these cases, use
1973 /// [`opt_item_name`] instead.
1975 /// [`opt_item_name`]: Self::opt_item_name
1976 pub fn item_name(self, id: DefId) -> Symbol {
1977 self.opt_item_name(id).unwrap_or_else(|| {
1978 bug!("item_name: no name for {:?}", self.def_path(id));
1982 /// Look up the name and span of a definition.
1984 /// See [`item_name`][Self::item_name] for more information.
1985 pub fn opt_item_ident(self, def_id: DefId) -> Option<Ident> {
1986 let def = self.opt_item_name(def_id)?;
1989 .and_then(|id| self.def_ident_span(id))
1990 .unwrap_or(rustc_span::DUMMY_SP);
1991 Some(Ident::new(def, span))
1994 pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> {
1995 if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
1996 Some(self.associated_item(def_id))
2002 pub fn field_index(self, hir_id: hir::HirId, typeck_results: &TypeckResults<'_>) -> usize {
2003 typeck_results.field_indices().get(hir_id).cloned().expect("no index for a field")
2006 pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
2010 .position(|field| self.hygienic_eq(ident, field.ident(self), variant.def_id))
2013 /// Returns `true` if the impls are the same polarity and the trait either
2014 /// has no items or is annotated `#[marker]` and prevents item overrides.
2015 pub fn impls_are_allowed_to_overlap(
2019 ) -> Option<ImplOverlapKind> {
2020 // If either trait impl references an error, they're allowed to overlap,
2021 // as one of them essentially doesn't exist.
2022 if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.references_error())
2023 || self.impl_trait_ref(def_id2).map_or(false, |tr| tr.references_error())
2025 return Some(ImplOverlapKind::Permitted { marker: false });
2028 match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) {
2029 (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => {
2030 // `#[rustc_reservation_impl]` impls don't overlap with anything
2032 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (reservations)",
2035 return Some(ImplOverlapKind::Permitted { marker: false });
2037 (ImplPolarity::Positive, ImplPolarity::Negative)
2038 | (ImplPolarity::Negative, ImplPolarity::Positive) => {
2039 // `impl AutoTrait for Type` + `impl !AutoTrait for Type`
2041 "impls_are_allowed_to_overlap({:?}, {:?}) - None (differing polarities)",
2046 (ImplPolarity::Positive, ImplPolarity::Positive)
2047 | (ImplPolarity::Negative, ImplPolarity::Negative) => {}
2050 let is_marker_overlap = {
2051 let is_marker_impl = |def_id: DefId| -> bool {
2052 let trait_ref = self.impl_trait_ref(def_id);
2053 trait_ref.map_or(false, |tr| self.trait_def(tr.def_id).is_marker)
2055 is_marker_impl(def_id1) && is_marker_impl(def_id2)
2058 if is_marker_overlap {
2060 "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (marker overlap)",
2063 Some(ImplOverlapKind::Permitted { marker: true })
2065 if let Some(self_ty1) = self.issue33140_self_ty(def_id1) {
2066 if let Some(self_ty2) = self.issue33140_self_ty(def_id2) {
2067 if self_ty1 == self_ty2 {
2069 "impls_are_allowed_to_overlap({:?}, {:?}) - issue #33140 HACK",
2072 return Some(ImplOverlapKind::Issue33140);
2075 "impls_are_allowed_to_overlap({:?}, {:?}) - found {:?} != {:?}",
2076 def_id1, def_id2, self_ty1, self_ty2
2082 debug!("impls_are_allowed_to_overlap({:?}, {:?}) = None", def_id1, def_id2);
2087 /// Returns `ty::VariantDef` if `res` refers to a struct,
2088 /// or variant or their constructors, panics otherwise.
2089 pub fn expect_variant_res(self, res: Res) -> &'tcx VariantDef {
2091 Res::Def(DefKind::Variant, did) => {
2092 let enum_did = self.parent(did);
2093 self.adt_def(enum_did).variant_with_id(did)
2095 Res::Def(DefKind::Struct | DefKind::Union, did) => self.adt_def(did).non_enum_variant(),
2096 Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => {
2097 let variant_did = self.parent(variant_ctor_did);
2098 let enum_did = self.parent(variant_did);
2099 self.adt_def(enum_did).variant_with_ctor_id(variant_ctor_did)
2101 Res::Def(DefKind::Ctor(CtorOf::Struct, ..), ctor_did) => {
2102 let struct_did = self.parent(ctor_did);
2103 self.adt_def(struct_did).non_enum_variant()
2105 _ => bug!("expect_variant_res used with unexpected res {:?}", res),
2109 /// Returns the possibly-auto-generated MIR of a `(DefId, Subst)` pair.
2110 #[instrument(skip(self), level = "debug")]
2111 pub fn instance_mir(self, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> {
2113 ty::InstanceDef::Item(def) => {
2114 debug!("calling def_kind on def: {:?}", def);
2115 let def_kind = self.def_kind(def.did);
2116 debug!("returned from def_kind: {:?}", def_kind);
2119 | DefKind::Static(..)
2120 | DefKind::AssocConst
2122 | DefKind::AnonConst
2123 | DefKind::InlineConst => self.mir_for_ctfe_opt_const_arg(def),
2124 // If the caller wants `mir_for_ctfe` of a function they should not be using
2125 // `instance_mir`, so we'll assume const fn also wants the optimized version.
2127 assert_eq!(def.const_param_did, None);
2128 self.optimized_mir(def.did)
2132 ty::InstanceDef::VTableShim(..)
2133 | ty::InstanceDef::ReifyShim(..)
2134 | ty::InstanceDef::Intrinsic(..)
2135 | ty::InstanceDef::FnPtrShim(..)
2136 | ty::InstanceDef::Virtual(..)
2137 | ty::InstanceDef::ClosureOnceShim { .. }
2138 | ty::InstanceDef::DropGlue(..)
2139 | ty::InstanceDef::CloneShim(..) => self.mir_shims(instance),
2143 // FIXME(@lcnr): Remove this function.
2144 pub fn get_attrs_unchecked(self, did: DefId) -> &'tcx [ast::Attribute] {
2145 if let Some(did) = did.as_local() {
2146 self.hir().attrs(self.hir().local_def_id_to_hir_id(did))
2148 self.item_attrs(did)
2152 /// Gets all attributes with the given name.
2153 pub fn get_attrs(self, did: DefId, attr: Symbol) -> ty::Attributes<'tcx> {
2154 let filter_fn = move |a: &&ast::Attribute| a.has_name(attr);
2155 if let Some(did) = did.as_local() {
2156 self.hir().attrs(self.hir().local_def_id_to_hir_id(did)).iter().filter(filter_fn)
2157 } else if cfg!(debug_assertions) && rustc_feature::is_builtin_only_local(attr) {
2158 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2160 self.item_attrs(did).iter().filter(filter_fn)
2164 pub fn get_attr(self, did: DefId, attr: Symbol) -> Option<&'tcx ast::Attribute> {
2165 self.get_attrs(did, attr).next()
2168 /// Determines whether an item is annotated with an attribute.
2169 pub fn has_attr(self, did: DefId, attr: Symbol) -> bool {
2170 if cfg!(debug_assertions) && !did.is_local() && rustc_feature::is_builtin_only_local(attr) {
2171 bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr);
2173 self.get_attrs(did, attr).next().is_some()
2177 /// Returns `true` if this is an `auto trait`.
2178 pub fn trait_is_auto(self, trait_def_id: DefId) -> bool {
2179 self.trait_def(trait_def_id).has_auto_impl
2182 /// Returns layout of a generator. Layout might be unavailable if the
2183 /// generator is tainted by errors.
2184 pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> {
2185 self.optimized_mir(def_id).generator_layout()
2188 /// Given the `DefId` of an impl, returns the `DefId` of the trait it implements.
2189 /// If it implements no trait, returns `None`.
2190 pub fn trait_id_of_impl(self, def_id: DefId) -> Option<DefId> {
2191 self.impl_trait_ref(def_id).map(|tr| tr.def_id)
2194 /// If the given `DefId` describes a method belonging to an impl, returns the
2195 /// `DefId` of the impl that the method belongs to; otherwise, returns `None`.
2196 pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> {
2197 self.opt_associated_item(def_id).and_then(|trait_item| match trait_item.container {
2198 TraitContainer(_) => None,
2199 ImplContainer(def_id) => Some(def_id),
2203 /// If the given `DefId` belongs to a trait that was automatically derived, returns `true`.
2204 pub fn is_builtin_derive(self, def_id: DefId) -> bool {
2205 self.has_attr(def_id, sym::automatically_derived)
2208 /// Looks up the span of `impl_did` if the impl is local; otherwise returns `Err`
2209 /// with the name of the crate containing the impl.
2210 pub fn span_of_impl(self, impl_did: DefId) -> Result<Span, Symbol> {
2211 if let Some(impl_did) = impl_did.as_local() {
2212 Ok(self.def_span(impl_did))
2214 Err(self.crate_name(impl_did.krate))
2218 /// Hygienically compares a use-site name (`use_name`) for a field or an associated item with
2219 /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
2220 /// definition's parent/scope to perform comparison.
2221 pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
2222 // We could use `Ident::eq` here, but we deliberately don't. The name
2223 // comparison fails frequently, and we want to avoid the expensive
2224 // `normalize_to_macros_2_0()` calls required for the span comparison whenever possible.
2225 use_name.name == def_name.name
2229 .hygienic_eq(def_name.span.ctxt(), self.expn_that_defined(def_parent_def_id))
2232 pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident {
2233 ident.span.normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope));
2237 pub fn adjust_ident_and_get_scope(
2242 ) -> (Ident, DefId) {
2245 .normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope))
2246 .and_then(|actual_expansion| actual_expansion.expn_data().parent_module)
2247 .unwrap_or_else(|| self.parent_module(block).to_def_id());
2251 pub fn is_object_safe(self, key: DefId) -> bool {
2252 self.object_safety_violations(key).is_empty()
2256 pub fn is_const_fn_raw(self, def_id: DefId) -> bool {
2257 matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..))
2258 && self.constness(def_id) == hir::Constness::Const
2262 pub fn is_const_default_method(self, def_id: DefId) -> bool {
2263 matches!(self.trait_of_item(def_id), Some(trait_id) if self.has_attr(trait_id, sym::const_trait))
2267 /// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition.
2268 pub fn is_impl_trait_defn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<LocalDefId> {
2269 let def_id = def_id.as_local()?;
2270 if let Node::Item(item) = tcx.hir().get_by_def_id(def_id) {
2271 if let hir::ItemKind::OpaqueTy(ref opaque_ty) = item.kind {
2272 return match opaque_ty.origin {
2273 hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) => {
2276 hir::OpaqueTyOrigin::TyAlias => None,
2283 pub fn int_ty(ity: ast::IntTy) -> IntTy {
2285 ast::IntTy::Isize => IntTy::Isize,
2286 ast::IntTy::I8 => IntTy::I8,
2287 ast::IntTy::I16 => IntTy::I16,
2288 ast::IntTy::I32 => IntTy::I32,
2289 ast::IntTy::I64 => IntTy::I64,
2290 ast::IntTy::I128 => IntTy::I128,
2294 pub fn uint_ty(uty: ast::UintTy) -> UintTy {
2296 ast::UintTy::Usize => UintTy::Usize,
2297 ast::UintTy::U8 => UintTy::U8,
2298 ast::UintTy::U16 => UintTy::U16,
2299 ast::UintTy::U32 => UintTy::U32,
2300 ast::UintTy::U64 => UintTy::U64,
2301 ast::UintTy::U128 => UintTy::U128,
2305 pub fn float_ty(fty: ast::FloatTy) -> FloatTy {
2307 ast::FloatTy::F32 => FloatTy::F32,
2308 ast::FloatTy::F64 => FloatTy::F64,
2312 pub fn ast_int_ty(ity: IntTy) -> ast::IntTy {
2314 IntTy::Isize => ast::IntTy::Isize,
2315 IntTy::I8 => ast::IntTy::I8,
2316 IntTy::I16 => ast::IntTy::I16,
2317 IntTy::I32 => ast::IntTy::I32,
2318 IntTy::I64 => ast::IntTy::I64,
2319 IntTy::I128 => ast::IntTy::I128,
2323 pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy {
2325 UintTy::Usize => ast::UintTy::Usize,
2326 UintTy::U8 => ast::UintTy::U8,
2327 UintTy::U16 => ast::UintTy::U16,
2328 UintTy::U32 => ast::UintTy::U32,
2329 UintTy::U64 => ast::UintTy::U64,
2330 UintTy::U128 => ast::UintTy::U128,
2334 pub fn provide(providers: &mut ty::query::Providers) {
2335 closure::provide(providers);
2336 context::provide(providers);
2337 erase_regions::provide(providers);
2338 layout::provide(providers);
2339 util::provide(providers);
2340 print::provide(providers);
2341 super::util::bug::provide(providers);
2342 super::middle::provide(providers);
2343 *providers = ty::query::Providers {
2344 trait_impls_of: trait_def::trait_impls_of_provider,
2345 incoherent_impls: trait_def::incoherent_impls_provider,
2346 type_uninhabited_from: inhabitedness::type_uninhabited_from,
2347 const_param_default: consts::const_param_default,
2348 vtable_allocation: vtable::vtable_allocation_provider,
2353 /// A map for the local crate mapping each type to a vector of its
2354 /// inherent impls. This is not meant to be used outside of coherence;
2355 /// rather, you should request the vector for a specific type via
2356 /// `tcx.inherent_impls(def_id)` so as to minimize your dependencies
2357 /// (constructing this map requires touching the entire crate).
2358 #[derive(Clone, Debug, Default, HashStable)]
2359 pub struct CrateInherentImpls {
2360 pub inherent_impls: LocalDefIdMap<Vec<DefId>>,
2361 pub incoherent_impls: FxHashMap<SimplifiedType, Vec<LocalDefId>>,
2364 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, HashStable)]
2365 pub struct SymbolName<'tcx> {
2366 /// `&str` gives a consistent ordering, which ensures reproducible builds.
2367 pub name: &'tcx str,
2370 impl<'tcx> SymbolName<'tcx> {
2371 pub fn new(tcx: TyCtxt<'tcx>, name: &str) -> SymbolName<'tcx> {
2373 name: unsafe { str::from_utf8_unchecked(tcx.arena.alloc_slice(name.as_bytes())) },
2378 impl<'tcx> fmt::Display for SymbolName<'tcx> {
2379 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2380 fmt::Display::fmt(&self.name, fmt)
2384 impl<'tcx> fmt::Debug for SymbolName<'tcx> {
2385 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
2386 fmt::Display::fmt(&self.name, fmt)
2390 #[derive(Debug, Default, Copy, Clone)]
2391 pub struct FoundRelationships {
2392 /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo`
2393 /// obligation, where:
2395 /// * `Foo` is not `Sized`
2396 /// * `(): Foo` may be satisfied
2397 pub self_in_trait: bool,
2398 /// This is true if we identified that this Ty (`?T`) is found in a `<_ as
2399 /// _>::AssocType = ?T`
2403 /// The constituent parts of a type level constant of kind ADT or array.
2404 #[derive(Copy, Clone, Debug, HashStable)]
2405 pub struct DestructuredConst<'tcx> {
2406 pub variant: Option<VariantIdx>,
2407 pub fields: &'tcx [ty::Const<'tcx>],