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Diffstat (limited to 'compiler/rustc_middle/src/ty/mod.rs')
| -rw-r--r-- | compiler/rustc_middle/src/ty/mod.rs | 2518 |
1 files changed, 2518 insertions, 0 deletions
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs new file mode 100644 index 000000000..02da02568 --- /dev/null +++ b/compiler/rustc_middle/src/ty/mod.rs @@ -0,0 +1,2518 @@ +//! Defines how the compiler represents types internally. +//! +//! Two important entities in this module are: +//! +//! - [`rustc_middle::ty::Ty`], used to represent the semantics of a type. +//! - [`rustc_middle::ty::TyCtxt`], the central data structure in the compiler. +//! +//! For more information, see ["The `ty` module: representing types"] in the rustc-dev-guide. +//! +//! ["The `ty` module: representing types"]: https://rustc-dev-guide.rust-lang.org/ty.html + +pub use self::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable}; +pub use self::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor}; +pub use self::AssocItemContainer::*; +pub use self::BorrowKind::*; +pub use self::IntVarValue::*; +pub use self::Variance::*; +use crate::metadata::ModChild; +use crate::middle::privacy::AccessLevels; +use crate::mir::{Body, GeneratorLayout}; +use crate::traits::{self, Reveal}; +use crate::ty; +use crate::ty::fast_reject::SimplifiedType; +use crate::ty::util::Discr; +pub use adt::*; +pub use assoc::*; +pub use generics::*; +use rustc_ast as ast; +use rustc_ast::node_id::NodeMap; +use rustc_attr as attr; +use rustc_data_structures::fingerprint::Fingerprint; +use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet}; +use rustc_data_structures::intern::{Interned, WithStableHash}; +use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; +use rustc_data_structures::tagged_ptr::CopyTaggedPtr; +use rustc_hir as hir; +use rustc_hir::def::{CtorKind, CtorOf, DefKind, LifetimeRes, Res}; +use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LocalDefIdMap}; +use rustc_hir::Node; +use rustc_index::vec::IndexVec; +use rustc_macros::HashStable; +use rustc_query_system::ich::StableHashingContext; +use rustc_span::hygiene::MacroKind; +use rustc_span::symbol::{kw, sym, Ident, Symbol}; +use rustc_span::{ExpnId, Span}; +use rustc_target::abi::{Align, VariantIdx}; +pub use subst::*; +pub use vtable::*; + +use std::fmt::Debug; +use std::hash::{Hash, Hasher}; +use std::ops::ControlFlow; +use std::{fmt, str}; + +pub use crate::ty::diagnostics::*; +pub use rustc_type_ir::InferTy::*; +pub use rustc_type_ir::RegionKind::*; +pub use rustc_type_ir::TyKind::*; +pub use rustc_type_ir::*; + +pub use self::binding::BindingMode; +pub use self::binding::BindingMode::*; +pub use self::closure::{ + is_ancestor_or_same_capture, place_to_string_for_capture, BorrowKind, CaptureInfo, + CapturedPlace, ClosureKind, MinCaptureInformationMap, MinCaptureList, + RootVariableMinCaptureList, UpvarCapture, UpvarCaptureMap, UpvarId, UpvarListMap, UpvarPath, + CAPTURE_STRUCT_LOCAL, +}; +pub use self::consts::{ + Const, ConstInt, ConstKind, ConstS, InferConst, ScalarInt, Unevaluated, ValTree, +}; +pub use self::context::{ + tls, CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, + CtxtInterners, DelaySpanBugEmitted, FreeRegionInfo, GeneratorDiagnosticData, + GeneratorInteriorTypeCause, GlobalCtxt, Lift, OnDiskCache, TyCtxt, TypeckResults, UserType, + UserTypeAnnotationIndex, +}; +pub use self::instance::{Instance, InstanceDef}; +pub use self::list::List; +pub use self::parameterized::ParameterizedOverTcx; +pub use self::rvalue_scopes::RvalueScopes; +pub use self::sty::BoundRegionKind::*; +pub use self::sty::{ + Article, Binder, BoundRegion, BoundRegionKind, BoundTy, BoundTyKind, BoundVar, + BoundVariableKind, CanonicalPolyFnSig, ClosureSubsts, ClosureSubstsParts, ConstVid, + EarlyBinder, EarlyBoundRegion, ExistentialPredicate, ExistentialProjection, + ExistentialTraitRef, FnSig, FreeRegion, GenSig, GeneratorSubsts, GeneratorSubstsParts, + InlineConstSubsts, InlineConstSubstsParts, ParamConst, ParamTy, PolyExistentialProjection, + PolyExistentialTraitRef, PolyFnSig, PolyGenSig, PolyTraitRef, ProjectionTy, Region, RegionKind, + RegionVid, TraitRef, TyKind, TypeAndMut, UpvarSubsts, VarianceDiagInfo, +}; +pub use self::trait_def::TraitDef; + +pub mod _match; +pub mod abstract_const; +pub mod adjustment; +pub mod binding; +pub mod cast; +pub mod codec; +pub mod error; +pub mod fast_reject; +pub mod flags; +pub mod fold; +pub mod inhabitedness; +pub mod layout; +pub mod normalize_erasing_regions; +pub mod print; +pub mod query; +pub mod relate; +pub mod subst; +pub mod trait_def; +pub mod util; +pub mod visit; +pub mod vtable; +pub mod walk; + +mod adt; +mod assoc; +mod closure; +mod consts; +mod context; +mod diagnostics; +mod erase_regions; +mod generics; +mod impls_ty; +mod instance; +mod list; +mod parameterized; +mod rvalue_scopes; +mod structural_impls; +mod sty; + +// Data types + +pub type RegisteredTools = FxHashSet<Ident>; + +#[derive(Debug)] +pub struct ResolverOutputs { + pub visibilities: FxHashMap<LocalDefId, Visibility>, + /// This field is used to decide whether we should make `PRIVATE_IN_PUBLIC` a hard error. + pub has_pub_restricted: bool, + /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`. + pub expn_that_defined: FxHashMap<LocalDefId, ExpnId>, + /// Reference span for definitions. + pub source_span: IndexVec<LocalDefId, Span>, + pub access_levels: AccessLevels, + pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>, + pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>, + pub maybe_unused_extern_crates: Vec<(LocalDefId, Span)>, + pub reexport_map: FxHashMap<LocalDefId, Vec<ModChild>>, + pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>, + /// Extern prelude entries. The value is `true` if the entry was introduced + /// via `extern crate` item and not `--extern` option or compiler built-in. + pub extern_prelude: FxHashMap<Symbol, bool>, + pub main_def: Option<MainDefinition>, + pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>, + /// A list of proc macro LocalDefIds, written out in the order in which + /// they are declared in the static array generated by proc_macro_harness. + pub proc_macros: Vec<LocalDefId>, + /// Mapping from ident span to path span for paths that don't exist as written, but that + /// exist under `std`. For example, wrote `str::from_utf8` instead of `std::str::from_utf8`. + pub confused_type_with_std_module: FxHashMap<Span, Span>, + pub registered_tools: RegisteredTools, +} + +/// Resolutions that should only be used for lowering. +/// This struct is meant to be consumed by lowering. +#[derive(Debug)] +pub struct ResolverAstLowering { + pub legacy_const_generic_args: FxHashMap<DefId, Option<Vec<usize>>>, + + /// Resolutions for nodes that have a single resolution. + pub partial_res_map: NodeMap<hir::def::PartialRes>, + /// Resolutions for import nodes, which have multiple resolutions in different namespaces. + pub import_res_map: NodeMap<hir::def::PerNS<Option<Res<ast::NodeId>>>>, + /// Resolutions for labels (node IDs of their corresponding blocks or loops). + pub label_res_map: NodeMap<ast::NodeId>, + /// Resolutions for lifetimes. + pub lifetimes_res_map: NodeMap<LifetimeRes>, + /// Mapping from generics `def_id`s to TAIT generics `def_id`s. + /// For each captured lifetime (e.g., 'a), we create a new lifetime parameter that is a generic + /// defined on the TAIT, so we have type Foo<'a1> = ... and we establish a mapping in this + /// field from the original parameter 'a to the new parameter 'a1. + pub generics_def_id_map: Vec<FxHashMap<LocalDefId, LocalDefId>>, + /// Lifetime parameters that lowering will have to introduce. + pub extra_lifetime_params_map: NodeMap<Vec<(Ident, ast::NodeId, LifetimeRes)>>, + + pub next_node_id: ast::NodeId, + + pub node_id_to_def_id: FxHashMap<ast::NodeId, LocalDefId>, + pub def_id_to_node_id: IndexVec<LocalDefId, ast::NodeId>, + + pub trait_map: NodeMap<Vec<hir::TraitCandidate>>, + /// A small map keeping true kinds of built-in macros that appear to be fn-like on + /// the surface (`macro` items in libcore), but are actually attributes or derives. + pub builtin_macro_kinds: FxHashMap<LocalDefId, MacroKind>, +} + +#[derive(Clone, Copy, Debug)] +pub struct MainDefinition { + pub res: Res<ast::NodeId>, + pub is_import: bool, + pub span: Span, +} + +impl MainDefinition { + pub fn opt_fn_def_id(self) -> Option<DefId> { + if let Res::Def(DefKind::Fn, def_id) = self.res { Some(def_id) } else { None } + } +} + +/// The "header" of an impl is everything outside the body: a Self type, a trait +/// ref (in the case of a trait impl), and a set of predicates (from the +/// bounds / where-clauses). +#[derive(Clone, Debug, TypeFoldable, TypeVisitable)] +pub struct ImplHeader<'tcx> { + pub impl_def_id: DefId, + pub self_ty: Ty<'tcx>, + pub trait_ref: Option<TraitRef<'tcx>>, + pub predicates: Vec<Predicate<'tcx>>, +} + +#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable)] +pub enum ImplSubject<'tcx> { + Trait(TraitRef<'tcx>), + Inherent(Ty<'tcx>), +} + +#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, HashStable, Debug)] +#[derive(TypeFoldable, TypeVisitable)] +pub enum ImplPolarity { + /// `impl Trait for Type` + Positive, + /// `impl !Trait for Type` + Negative, + /// `#[rustc_reservation_impl] impl Trait for Type` + /// + /// This is a "stability hack", not a real Rust feature. + /// See #64631 for details. + Reservation, +} + +impl ImplPolarity { + /// Flips polarity by turning `Positive` into `Negative` and `Negative` into `Positive`. + pub fn flip(&self) -> Option<ImplPolarity> { + match self { + ImplPolarity::Positive => Some(ImplPolarity::Negative), + ImplPolarity::Negative => Some(ImplPolarity::Positive), + ImplPolarity::Reservation => None, + } + } +} + +impl fmt::Display for ImplPolarity { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self { + Self::Positive => f.write_str("positive"), + Self::Negative => f.write_str("negative"), + Self::Reservation => f.write_str("reservation"), + } + } +} + +#[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, Encodable, Decodable, HashStable)] +pub enum Visibility { + /// Visible everywhere (including in other crates). + Public, + /// Visible only in the given crate-local module. + Restricted(DefId), + /// Not visible anywhere in the local crate. This is the visibility of private external items. + Invisible, +} + +#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable, TyEncodable, TyDecodable)] +pub enum BoundConstness { + /// `T: Trait` + NotConst, + /// `T: ~const Trait` + /// + /// Requires resolving to const only when we are in a const context. + ConstIfConst, +} + +impl BoundConstness { + /// Reduce `self` and `constness` to two possible combined states instead of four. + pub fn and(&mut self, constness: hir::Constness) -> hir::Constness { + match (constness, self) { + (hir::Constness::Const, BoundConstness::ConstIfConst) => hir::Constness::Const, + (_, this) => { + *this = BoundConstness::NotConst; + hir::Constness::NotConst + } + } + } +} + +impl fmt::Display for BoundConstness { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self { + Self::NotConst => f.write_str("normal"), + Self::ConstIfConst => f.write_str("`~const`"), + } + } +} + +#[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, TyEncodable, TyDecodable, HashStable)] +#[derive(TypeFoldable, TypeVisitable)] +pub struct ClosureSizeProfileData<'tcx> { + /// Tuple containing the types of closure captures before the feature `capture_disjoint_fields` + pub before_feature_tys: Ty<'tcx>, + /// Tuple containing the types of closure captures after the feature `capture_disjoint_fields` + pub after_feature_tys: Ty<'tcx>, +} + +pub trait DefIdTree: Copy { + fn opt_parent(self, id: DefId) -> Option<DefId>; + + #[inline] + #[track_caller] + fn parent(self, id: DefId) -> DefId { + match self.opt_parent(id) { + Some(id) => id, + // not `unwrap_or_else` to avoid breaking caller tracking + None => bug!("{id:?} doesn't have a parent"), + } + } + + #[inline] + #[track_caller] + fn opt_local_parent(self, id: LocalDefId) -> Option<LocalDefId> { + self.opt_parent(id.to_def_id()).map(DefId::expect_local) + } + + #[inline] + #[track_caller] + fn local_parent(self, id: LocalDefId) -> LocalDefId { + self.parent(id.to_def_id()).expect_local() + } + + fn is_descendant_of(self, mut descendant: DefId, ancestor: DefId) -> bool { + if descendant.krate != ancestor.krate { + return false; + } + + while descendant != ancestor { + match self.opt_parent(descendant) { + Some(parent) => descendant = parent, + None => return false, + } + } + true + } +} + +impl<'tcx> DefIdTree for TyCtxt<'tcx> { + #[inline] + fn opt_parent(self, id: DefId) -> Option<DefId> { + self.def_key(id).parent.map(|index| DefId { index, ..id }) + } +} + +impl Visibility { + /// Returns `true` if an item with this visibility is accessible from the given block. + pub fn is_accessible_from<T: DefIdTree>(self, module: DefId, tree: T) -> bool { + let restriction = match self { + // Public items are visible everywhere. + Visibility::Public => return true, + // Private items from other crates are visible nowhere. + Visibility::Invisible => return false, + // Restricted items are visible in an arbitrary local module. + Visibility::Restricted(other) if other.krate != module.krate => return false, + Visibility::Restricted(module) => module, + }; + + tree.is_descendant_of(module, restriction) + } + + /// Returns `true` if this visibility is at least as accessible as the given visibility + pub fn is_at_least<T: DefIdTree>(self, vis: Visibility, tree: T) -> bool { + let vis_restriction = match vis { + Visibility::Public => return self == Visibility::Public, + Visibility::Invisible => return true, + Visibility::Restricted(module) => module, + }; + + self.is_accessible_from(vis_restriction, tree) + } + + // Returns `true` if this item is visible anywhere in the local crate. + pub fn is_visible_locally(self) -> bool { + match self { + Visibility::Public => true, + Visibility::Restricted(def_id) => def_id.is_local(), + Visibility::Invisible => false, + } + } + + pub fn is_public(self) -> bool { + matches!(self, Visibility::Public) + } +} + +/// The crate variances map is computed during typeck and contains the +/// variance of every item in the local crate. You should not use it +/// directly, because to do so will make your pass dependent on the +/// HIR of every item in the local crate. Instead, use +/// `tcx.variances_of()` to get the variance for a *particular* +/// item. +#[derive(HashStable, Debug)] +pub struct CrateVariancesMap<'tcx> { + /// For each item with generics, maps to a vector of the variance + /// of its generics. If an item has no generics, it will have no + /// entry. + pub variances: FxHashMap<DefId, &'tcx [ty::Variance]>, +} + +// Contains information needed to resolve types and (in the future) look up +// the types of AST nodes. +#[derive(Copy, Clone, PartialEq, Eq, Hash)] +pub struct CReaderCacheKey { + pub cnum: Option<CrateNum>, + pub pos: usize, +} + +/// Represents a type. +/// +/// IMPORTANT: +/// - This is a very "dumb" struct (with no derives and no `impls`). +/// - Values of this type are always interned and thus unique, and are stored +/// as an `Interned<TyS>`. +/// - `Ty` (which contains a reference to a `Interned<TyS>`) or `Interned<TyS>` +/// should be used everywhere instead of `TyS`. In particular, `Ty` has most +/// of the relevant methods. +#[derive(PartialEq, Eq, PartialOrd, Ord)] +#[allow(rustc::usage_of_ty_tykind)] +pub(crate) struct TyS<'tcx> { + /// This field shouldn't be used directly and may be removed in the future. + /// Use `Ty::kind()` instead. + kind: TyKind<'tcx>, + + /// This field provides fast access to information that is also contained + /// in `kind`. + /// + /// This field shouldn't be used directly and may be removed in the future. + /// Use `Ty::flags()` instead. + flags: TypeFlags, + + /// This field provides fast access to information that is also contained + /// in `kind`. + /// + /// This is a kind of confusing thing: it stores the smallest + /// binder such that + /// + /// (a) the binder itself captures nothing but + /// (b) all the late-bound things within the type are captured + /// by some sub-binder. + /// + /// So, for a type without any late-bound things, like `u32`, this + /// will be *innermost*, because that is the innermost binder that + /// captures nothing. But for a type `&'D u32`, where `'D` is a + /// late-bound region with De Bruijn index `D`, this would be `D + 1` + /// -- the binder itself does not capture `D`, but `D` is captured + /// by an inner binder. + /// + /// We call this concept an "exclusive" binder `D` because all + /// De Bruijn indices within the type are contained within `0..D` + /// (exclusive). + outer_exclusive_binder: ty::DebruijnIndex, +} + +// `TyS` is used a lot. Make sure it doesn't unintentionally get bigger. +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +static_assert_size!(TyS<'_>, 40); + +// We are actually storing a stable hash cache next to the type, so let's +// also check the full size +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +static_assert_size!(WithStableHash<TyS<'_>>, 56); + +/// Use this rather than `TyS`, whenever possible. +#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, HashStable)] +#[rustc_diagnostic_item = "Ty"] +#[rustc_pass_by_value] +pub struct Ty<'tcx>(Interned<'tcx, WithStableHash<TyS<'tcx>>>); + +impl<'tcx> TyCtxt<'tcx> { + /// A "bool" type used in rustc_mir_transform unit tests when we + /// have not spun up a TyCtxt. + pub const BOOL_TY_FOR_UNIT_TESTING: Ty<'tcx> = Ty(Interned::new_unchecked(&WithStableHash { + internee: TyS { + kind: ty::Bool, + flags: TypeFlags::empty(), + outer_exclusive_binder: DebruijnIndex::from_usize(0), + }, + stable_hash: Fingerprint::ZERO, + })); +} + +impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for TyS<'tcx> { + #[inline] + fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) { + let TyS { + kind, + + // The other fields just provide fast access to information that is + // also contained in `kind`, so no need to hash them. + flags: _, + + outer_exclusive_binder: _, + } = self; + + kind.hash_stable(hcx, hasher) + } +} + +impl ty::EarlyBoundRegion { + /// Does this early bound region have a name? Early bound regions normally + /// always have names except when using anonymous lifetimes (`'_`). + pub fn has_name(&self) -> bool { + self.name != kw::UnderscoreLifetime + } +} + +/// Represents a predicate. +/// +/// See comments on `TyS`, which apply here too (albeit for +/// `PredicateS`/`Predicate` rather than `TyS`/`Ty`). +#[derive(Debug)] +pub(crate) struct PredicateS<'tcx> { + kind: Binder<'tcx, PredicateKind<'tcx>>, + flags: TypeFlags, + /// See the comment for the corresponding field of [TyS]. + outer_exclusive_binder: ty::DebruijnIndex, +} + +// This type is used a lot. Make sure it doesn't unintentionally get bigger. +#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] +static_assert_size!(PredicateS<'_>, 56); + +/// Use this rather than `PredicateS`, whenever possible. +#[derive(Clone, Copy, PartialEq, Eq, Hash)] +#[rustc_pass_by_value] +pub struct Predicate<'tcx>(Interned<'tcx, PredicateS<'tcx>>); + +impl<'tcx> Predicate<'tcx> { + /// Gets the inner `Binder<'tcx, PredicateKind<'tcx>>`. + #[inline] + pub fn kind(self) -> Binder<'tcx, PredicateKind<'tcx>> { + self.0.kind + } + + #[inline(always)] + pub fn flags(self) -> TypeFlags { + self.0.flags + } + + #[inline(always)] + pub fn outer_exclusive_binder(self) -> DebruijnIndex { + self.0.outer_exclusive_binder + } + + /// Flips the polarity of a Predicate. + /// + /// Given `T: Trait` predicate it returns `T: !Trait` and given `T: !Trait` returns `T: Trait`. + pub fn flip_polarity(self, tcx: TyCtxt<'tcx>) -> Option<Predicate<'tcx>> { + let kind = self + .kind() + .map_bound(|kind| match kind { + PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) => { + Some(PredicateKind::Trait(TraitPredicate { + trait_ref, + constness, + polarity: polarity.flip()?, + })) + } + + _ => None, + }) + .transpose()?; + + Some(tcx.mk_predicate(kind)) + } + + pub fn without_const(mut self, tcx: TyCtxt<'tcx>) -> Self { + if let PredicateKind::Trait(TraitPredicate { trait_ref, constness, polarity }) = self.kind().skip_binder() + && constness != BoundConstness::NotConst + { + self = tcx.mk_predicate(self.kind().rebind(PredicateKind::Trait(TraitPredicate { + trait_ref, + constness: BoundConstness::NotConst, + polarity, + }))); + } + self + } +} + +impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for Predicate<'tcx> { + fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) { + let PredicateS { + ref kind, + + // The other fields just provide fast access to information that is + // also contained in `kind`, so no need to hash them. + flags: _, + outer_exclusive_binder: _, + } = self.0.0; + + kind.hash_stable(hcx, hasher); + } +} + +impl rustc_errors::IntoDiagnosticArg for Predicate<'_> { + fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> { + rustc_errors::DiagnosticArgValue::Str(std::borrow::Cow::Owned(self.to_string())) + } +} + +#[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable)] +pub enum PredicateKind<'tcx> { + /// Corresponds to `where Foo: Bar<A, B, C>`. `Foo` here would be + /// the `Self` type of the trait reference and `A`, `B`, and `C` + /// would be the type parameters. + Trait(TraitPredicate<'tcx>), + + /// `where 'a: 'b` + RegionOutlives(RegionOutlivesPredicate<'tcx>), + + /// `where T: 'a` + TypeOutlives(TypeOutlivesPredicate<'tcx>), + + /// `where <T as TraitRef>::Name == X`, approximately. + /// See the `ProjectionPredicate` struct for details. + Projection(ProjectionPredicate<'tcx>), + + /// No syntax: `T` well-formed. + WellFormed(GenericArg<'tcx>), + + /// Trait must be object-safe. + ObjectSafe(DefId), + + /// No direct syntax. May be thought of as `where T: FnFoo<...>` + /// for some substitutions `...` and `T` being a closure type. + /// Satisfied (or refuted) once we know the closure's kind. + ClosureKind(DefId, SubstsRef<'tcx>, ClosureKind), + + /// `T1 <: T2` + /// + /// This obligation is created most often when we have two + /// unresolved type variables and hence don't have enough + /// information to process the subtyping obligation yet. + Subtype(SubtypePredicate<'tcx>), + + /// `T1` coerced to `T2` + /// + /// Like a subtyping obligation, this is created most often + /// when we have two unresolved type variables and hence + /// don't have enough information to process the coercion + /// obligation yet. At the moment, we actually process coercions + /// very much like subtyping and don't handle the full coercion + /// logic. + Coerce(CoercePredicate<'tcx>), + + /// Constant initializer must evaluate successfully. + ConstEvaluatable(ty::Unevaluated<'tcx, ()>), + + /// Constants must be equal. The first component is the const that is expected. + ConstEquate(Const<'tcx>, Const<'tcx>), + + /// Represents a type found in the environment that we can use for implied bounds. + /// + /// Only used for Chalk. + TypeWellFormedFromEnv(Ty<'tcx>), +} + +/// The crate outlives map is computed during typeck and contains the +/// outlives of every item in the local crate. You should not use it +/// directly, because to do so will make your pass dependent on the +/// HIR of every item in the local crate. Instead, use +/// `tcx.inferred_outlives_of()` to get the outlives for a *particular* +/// item. +#[derive(HashStable, Debug)] +pub struct CratePredicatesMap<'tcx> { + /// For each struct with outlive bounds, maps to a vector of the + /// predicate of its outlive bounds. If an item has no outlives + /// bounds, it will have no entry. + pub predicates: FxHashMap<DefId, &'tcx [(Predicate<'tcx>, Span)]>, +} + +impl<'tcx> Predicate<'tcx> { + /// Performs a substitution suitable for going from a + /// poly-trait-ref to supertraits that must hold if that + /// poly-trait-ref holds. This is slightly different from a normal + /// substitution in terms of what happens with bound regions. See + /// lengthy comment below for details. + pub fn subst_supertrait( + self, + tcx: TyCtxt<'tcx>, + trait_ref: &ty::PolyTraitRef<'tcx>, + ) -> Predicate<'tcx> { + // The interaction between HRTB and supertraits is not entirely + // obvious. Let me walk you (and myself) through an example. + // + // Let's start with an easy case. Consider two traits: + // + // trait Foo<'a>: Bar<'a,'a> { } + // trait Bar<'b,'c> { } + // + // Now, if we have a trait reference `for<'x> T: Foo<'x>`, then + // we can deduce that `for<'x> T: Bar<'x,'x>`. Basically, if we + // knew that `Foo<'x>` (for any 'x) then we also know that + // `Bar<'x,'x>` (for any 'x). This more-or-less falls out from + // normal substitution. + // + // In terms of why this is sound, the idea is that whenever there + // is an impl of `T:Foo<'a>`, it must show that `T:Bar<'a,'a>` + // holds. So if there is an impl of `T:Foo<'a>` that applies to + // all `'a`, then we must know that `T:Bar<'a,'a>` holds for all + // `'a`. + // + // Another example to be careful of is this: + // + // trait Foo1<'a>: for<'b> Bar1<'a,'b> { } + // trait Bar1<'b,'c> { } + // + // Here, if we have `for<'x> T: Foo1<'x>`, then what do we know? + // The answer is that we know `for<'x,'b> T: Bar1<'x,'b>`. The + // reason is similar to the previous example: any impl of + // `T:Foo1<'x>` must show that `for<'b> T: Bar1<'x, 'b>`. So + // basically we would want to collapse the bound lifetimes from + // the input (`trait_ref`) and the supertraits. + // + // To achieve this in practice is fairly straightforward. Let's + // consider the more complicated scenario: + // + // - We start out with `for<'x> T: Foo1<'x>`. In this case, `'x` + // has a De Bruijn index of 1. We want to produce `for<'x,'b> T: Bar1<'x,'b>`, + // where both `'x` and `'b` would have a DB index of 1. + // The substitution from the input trait-ref is therefore going to be + // `'a => 'x` (where `'x` has a DB index of 1). + // - The supertrait-ref is `for<'b> Bar1<'a,'b>`, where `'a` is an + // early-bound parameter and `'b' is a late-bound parameter with a + // DB index of 1. + // - If we replace `'a` with `'x` from the input, it too will have + // a DB index of 1, and thus we'll have `for<'x,'b> Bar1<'x,'b>` + // just as we wanted. + // + // There is only one catch. If we just apply the substitution `'a + // => 'x` to `for<'b> Bar1<'a,'b>`, the substitution code will + // adjust the DB index because we substituting into a binder (it + // tries to be so smart...) resulting in `for<'x> for<'b> + // Bar1<'x,'b>` (we have no syntax for this, so use your + // imagination). Basically the 'x will have DB index of 2 and 'b + // will have DB index of 1. Not quite what we want. So we apply + // the substitution to the *contents* of the trait reference, + // rather than the trait reference itself (put another way, the + // substitution code expects equal binding levels in the values + // from the substitution and the value being substituted into, and + // this trick achieves that). + + // Working through the second example: + // trait_ref: for<'x> T: Foo1<'^0.0>; substs: [T, '^0.0] + // predicate: for<'b> Self: Bar1<'a, '^0.0>; substs: [Self, 'a, '^0.0] + // We want to end up with: + // for<'x, 'b> T: Bar1<'^0.0, '^0.1> + // To do this: + // 1) We must shift all bound vars in predicate by the length + // of trait ref's bound vars. So, we would end up with predicate like + // Self: Bar1<'a, '^0.1> + // 2) We can then apply the trait substs to this, ending up with + // T: Bar1<'^0.0, '^0.1> + // 3) Finally, to create the final bound vars, we concatenate the bound + // vars of the trait ref with those of the predicate: + // ['x, 'b] + let bound_pred = self.kind(); + let pred_bound_vars = bound_pred.bound_vars(); + let trait_bound_vars = trait_ref.bound_vars(); + // 1) Self: Bar1<'a, '^0.0> -> Self: Bar1<'a, '^0.1> + let shifted_pred = + tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder()); + // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1> + let new = EarlyBinder(shifted_pred).subst(tcx, trait_ref.skip_binder().substs); + // 3) ['x] + ['b] -> ['x, 'b] + let bound_vars = + tcx.mk_bound_variable_kinds(trait_bound_vars.iter().chain(pred_bound_vars)); + tcx.reuse_or_mk_predicate(self, ty::Binder::bind_with_vars(new, bound_vars)) + } +} + +#[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable)] +pub struct TraitPredicate<'tcx> { + pub trait_ref: TraitRef<'tcx>, + + pub constness: BoundConstness, + + /// If polarity is Positive: we are proving that the trait is implemented. + /// + /// If polarity is Negative: we are proving that a negative impl of this trait + /// exists. (Note that coherence also checks whether negative impls of supertraits + /// exist via a series of predicates.) + /// + /// If polarity is Reserved: that's a bug. + pub polarity: ImplPolarity, +} + +pub type PolyTraitPredicate<'tcx> = ty::Binder<'tcx, TraitPredicate<'tcx>>; + +impl<'tcx> TraitPredicate<'tcx> { + pub fn remap_constness(&mut self, param_env: &mut ParamEnv<'tcx>) { + *param_env = param_env.with_constness(self.constness.and(param_env.constness())) + } + + /// Remap the constness of this predicate before emitting it for diagnostics. + pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) { + // this is different to `remap_constness` that callees want to print this predicate + // in case of selection errors. `T: ~const Drop` bounds cannot end up here when the + // param_env is not const because it is always satisfied in non-const contexts. + if let hir::Constness::NotConst = param_env.constness() { + self.constness = ty::BoundConstness::NotConst; + } + } + + pub fn def_id(self) -> DefId { + self.trait_ref.def_id + } + + pub fn self_ty(self) -> Ty<'tcx> { + self.trait_ref.self_ty() + } + + #[inline] + pub fn is_const_if_const(self) -> bool { + self.constness == BoundConstness::ConstIfConst + } + + pub fn is_constness_satisfied_by(self, constness: hir::Constness) -> bool { + match (self.constness, constness) { + (BoundConstness::NotConst, _) + | (BoundConstness::ConstIfConst, hir::Constness::Const) => true, + (BoundConstness::ConstIfConst, hir::Constness::NotConst) => false, + } + } +} + +impl<'tcx> PolyTraitPredicate<'tcx> { + pub fn def_id(self) -> DefId { + // Ok to skip binder since trait `DefId` does not care about regions. + self.skip_binder().def_id() + } + + pub fn self_ty(self) -> ty::Binder<'tcx, Ty<'tcx>> { + self.map_bound(|trait_ref| trait_ref.self_ty()) + } + + /// Remap the constness of this predicate before emitting it for diagnostics. + pub fn remap_constness_diag(&mut self, param_env: ParamEnv<'tcx>) { + *self = self.map_bound(|mut p| { + p.remap_constness_diag(param_env); + p + }); + } + + #[inline] + pub fn is_const_if_const(self) -> bool { + self.skip_binder().is_const_if_const() + } +} + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable)] +pub struct OutlivesPredicate<A, B>(pub A, pub B); // `A: B` +pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>, ty::Region<'tcx>>; +pub type TypeOutlivesPredicate<'tcx> = OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>; +pub type PolyRegionOutlivesPredicate<'tcx> = ty::Binder<'tcx, RegionOutlivesPredicate<'tcx>>; +pub type PolyTypeOutlivesPredicate<'tcx> = ty::Binder<'tcx, TypeOutlivesPredicate<'tcx>>; + +/// Encodes that `a` must be a subtype of `b`. The `a_is_expected` flag indicates +/// whether the `a` type is the type that we should label as "expected" when +/// presenting user diagnostics. +#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable)] +pub struct SubtypePredicate<'tcx> { + pub a_is_expected: bool, + pub a: Ty<'tcx>, + pub b: Ty<'tcx>, +} +pub type PolySubtypePredicate<'tcx> = ty::Binder<'tcx, SubtypePredicate<'tcx>>; + +/// Encodes that we have to coerce *from* the `a` type to the `b` type. +#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable)] +pub struct CoercePredicate<'tcx> { + pub a: Ty<'tcx>, + pub b: Ty<'tcx>, +} +pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>; + +#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable)] +pub enum Term<'tcx> { + Ty(Ty<'tcx>), + Const(Const<'tcx>), +} + +impl<'tcx> From<Ty<'tcx>> for Term<'tcx> { + fn from(ty: Ty<'tcx>) -> Self { + Term::Ty(ty) + } +} + +impl<'tcx> From<Const<'tcx>> for Term<'tcx> { + fn from(c: Const<'tcx>) -> Self { + Term::Const(c) + } +} + +impl<'tcx> Term<'tcx> { + pub fn ty(&self) -> Option<Ty<'tcx>> { + if let Term::Ty(ty) = self { Some(*ty) } else { None } + } + + pub fn ct(&self) -> Option<Const<'tcx>> { + if let Term::Const(c) = self { Some(*c) } else { None } + } + + pub fn into_arg(self) -> GenericArg<'tcx> { + match self { + Term::Ty(ty) => ty.into(), + Term::Const(c) => c.into(), + } + } +} + +/// This kind of predicate has no *direct* correspondent in the +/// syntax, but it roughly corresponds to the syntactic forms: +/// +/// 1. `T: TraitRef<..., Item = Type>` +/// 2. `<T as TraitRef<...>>::Item == Type` (NYI) +/// +/// In particular, form #1 is "desugared" to the combination of a +/// normal trait predicate (`T: TraitRef<...>`) and one of these +/// predicates. Form #2 is a broader form in that it also permits +/// equality between arbitrary types. Processing an instance of +/// Form #2 eventually yields one of these `ProjectionPredicate` +/// instances to normalize the LHS. +#[derive(Copy, Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable)] +#[derive(HashStable, TypeFoldable, TypeVisitable)] +pub struct ProjectionPredicate<'tcx> { + pub projection_ty: ProjectionTy<'tcx>, + pub term: Term<'tcx>, +} + +pub type PolyProjectionPredicate<'tcx> = Binder<'tcx, ProjectionPredicate<'tcx>>; + +impl<'tcx> PolyProjectionPredicate<'tcx> { + /// Returns the `DefId` of the trait of the associated item being projected. + #[inline] + pub fn trait_def_id(&self, tcx: TyCtxt<'tcx>) -> DefId { + self.skip_binder().projection_ty.trait_def_id(tcx) + } + + /// Get the [PolyTraitRef] required for this projection to be well formed. + /// Note that for generic associated types the predicates of the associated + /// type also need to be checked. + #[inline] + pub fn required_poly_trait_ref(&self, tcx: TyCtxt<'tcx>) -> PolyTraitRef<'tcx> { + // Note: unlike with `TraitRef::to_poly_trait_ref()`, + // `self.0.trait_ref` is permitted to have escaping regions. + // This is because here `self` has a `Binder` and so does our + // return value, so we are preserving the number of binding + // levels. + self.map_bound(|predicate| predicate.projection_ty.trait_ref(tcx)) + } + + pub fn term(&self) -> Binder<'tcx, Term<'tcx>> { + self.map_bound(|predicate| predicate.term) + } + + /// The `DefId` of the `TraitItem` for the associated type. + /// + /// Note that this is not the `DefId` of the `TraitRef` containing this + /// associated type, which is in `tcx.associated_item(projection_def_id()).container`. + pub fn projection_def_id(&self) -> DefId { + // Ok to skip binder since trait `DefId` does not care about regions. + self.skip_binder().projection_ty.item_def_id + } +} + +pub trait ToPolyTraitRef<'tcx> { + fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx>; +} + +impl<'tcx> ToPolyTraitRef<'tcx> for PolyTraitPredicate<'tcx> { + fn to_poly_trait_ref(&self) -> PolyTraitRef<'tcx> { + self.map_bound_ref(|trait_pred| trait_pred.trait_ref) + } +} + +pub trait ToPredicate<'tcx> { + fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx>; +} + +impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, PredicateKind<'tcx>> { + #[inline(always)] + fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> { + tcx.mk_predicate(self) + } +} + +impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> { + fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> { + self.map_bound(PredicateKind::Trait).to_predicate(tcx) + } +} + +impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> { + fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> { + self.map_bound(PredicateKind::RegionOutlives).to_predicate(tcx) + } +} + +impl<'tcx> ToPredicate<'tcx> for PolyTypeOutlivesPredicate<'tcx> { + fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> { + self.map_bound(PredicateKind::TypeOutlives).to_predicate(tcx) + } +} + +impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> { + fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> { + self.map_bound(PredicateKind::Projection).to_predicate(tcx) + } +} + +impl<'tcx> Predicate<'tcx> { + pub fn to_opt_poly_trait_pred(self) -> Option<PolyTraitPredicate<'tcx>> { + let predicate = self.kind(); + match predicate.skip_binder() { + PredicateKind::Trait(t) => Some(predicate.rebind(t)), + PredicateKind::Projection(..) + | PredicateKind::Subtype(..) + | PredicateKind::Coerce(..) + | PredicateKind::RegionOutlives(..) + | PredicateKind::WellFormed(..) + | PredicateKind::ObjectSafe(..) + | PredicateKind::ClosureKind(..) + | PredicateKind::TypeOutlives(..) + | PredicateKind::ConstEvaluatable(..) + | PredicateKind::ConstEquate(..) + | PredicateKind::TypeWellFormedFromEnv(..) => None, + } + } + + pub fn to_opt_poly_projection_pred(self) -> Option<PolyProjectionPredicate<'tcx>> { + let predicate = self.kind(); + match predicate.skip_binder() { + PredicateKind::Projection(t) => Some(predicate.rebind(t)), + PredicateKind::Trait(..) + | PredicateKind::Subtype(..) + | PredicateKind::Coerce(..) + | PredicateKind::RegionOutlives(..) + | PredicateKind::WellFormed(..) + | PredicateKind::ObjectSafe(..) + | PredicateKind::ClosureKind(..) + | PredicateKind::TypeOutlives(..) + | PredicateKind::ConstEvaluatable(..) + | PredicateKind::ConstEquate(..) + | PredicateKind::TypeWellFormedFromEnv(..) => None, + } + } + + pub fn to_opt_type_outlives(self) -> Option<PolyTypeOutlivesPredicate<'tcx>> { + let predicate = self.kind(); + match predicate.skip_binder() { + PredicateKind::TypeOutlives(data) => Some(predicate.rebind(data)), + PredicateKind::Trait(..) + | PredicateKind::Projection(..) + | PredicateKind::Subtype(..) + | PredicateKind::Coerce(..) + | PredicateKind::RegionOutlives(..) + | PredicateKind::WellFormed(..) + | PredicateKind::ObjectSafe(..) + | PredicateKind::ClosureKind(..) + | PredicateKind::ConstEvaluatable(..) + | PredicateKind::ConstEquate(..) + | PredicateKind::TypeWellFormedFromEnv(..) => None, + } + } +} + +/// Represents the bounds declared on a particular set of type +/// parameters. Should eventually be generalized into a flag list of +/// where-clauses. You can obtain an `InstantiatedPredicates` list from a +/// `GenericPredicates` by using the `instantiate` method. Note that this method +/// reflects an important semantic invariant of `InstantiatedPredicates`: while +/// the `GenericPredicates` are expressed in terms of the bound type +/// parameters of the impl/trait/whatever, an `InstantiatedPredicates` instance +/// represented a set of bounds for some particular instantiation, +/// meaning that the generic parameters have been substituted with +/// their values. +/// +/// Example: +/// ```ignore (illustrative) +/// struct Foo<T, U: Bar<T>> { ... } +/// ``` +/// Here, the `GenericPredicates` for `Foo` would contain a list of bounds like +/// `[[], [U:Bar<T>]]`. Now if there were some particular reference +/// like `Foo<isize,usize>`, then the `InstantiatedPredicates` would be `[[], +/// [usize:Bar<isize>]]`. +#[derive(Clone, Debug, TypeFoldable, TypeVisitable)] +pub struct InstantiatedPredicates<'tcx> { + pub predicates: Vec<Predicate<'tcx>>, + pub spans: Vec<Span>, +} + +impl<'tcx> InstantiatedPredicates<'tcx> { + pub fn empty() -> InstantiatedPredicates<'tcx> { + InstantiatedPredicates { predicates: vec![], spans: vec![] } + } + + pub fn is_empty(&self) -> bool { + self.predicates.is_empty() + } +} + +#[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable, Lift)] +#[derive(TypeFoldable, TypeVisitable)] +pub struct OpaqueTypeKey<'tcx> { + pub def_id: LocalDefId, + pub substs: SubstsRef<'tcx>, +} + +#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)] +pub struct OpaqueHiddenType<'tcx> { + /// The span of this particular definition of the opaque type. So + /// for example: + /// + /// ```ignore (incomplete snippet) + /// type Foo = impl Baz; + /// fn bar() -> Foo { + /// // ^^^ This is the span we are looking for! + /// } + /// ``` + /// + /// In cases where the fn returns `(impl Trait, impl Trait)` or + /// other such combinations, the result is currently + /// over-approximated, but better than nothing. + pub span: Span, + + /// The type variable that represents the value of the opaque type + /// that we require. In other words, after we compile this function, + /// we will be created a constraint like: + /// ```ignore (pseudo-rust) + /// Foo<'a, T> = ?C + /// ``` + /// where `?C` is the value of this type variable. =) It may + /// naturally refer to the type and lifetime parameters in scope + /// in this function, though ultimately it should only reference + /// those that are arguments to `Foo` in the constraint above. (In + /// other words, `?C` should not include `'b`, even though it's a + /// lifetime parameter on `foo`.) + pub ty: Ty<'tcx>, +} + +impl<'tcx> OpaqueHiddenType<'tcx> { + pub fn report_mismatch(&self, other: &Self, tcx: TyCtxt<'tcx>) { + // Found different concrete types for the opaque type. + let mut err = tcx.sess.struct_span_err( + other.span, + "concrete type differs from previous defining opaque type use", + ); + err.span_label(other.span, format!("expected `{}`, got `{}`", self.ty, other.ty)); + if self.span == other.span { + err.span_label( + self.span, + "this expression supplies two conflicting concrete types for the same opaque type", + ); + } else { + err.span_note(self.span, "previous use here"); + } + err.emit(); + } +} + +/// The "placeholder index" fully defines a placeholder region, type, or const. Placeholders are +/// identified by both a universe, as well as a name residing within that universe. Distinct bound +/// regions/types/consts within the same universe simply have an unknown relationship to one +/// another. +#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)] +#[derive(HashStable, TyEncodable, TyDecodable)] +pub struct Placeholder<T> { + pub universe: UniverseIndex, + pub name: T, +} + +pub type PlaceholderRegion = Placeholder<BoundRegionKind>; + +pub type PlaceholderType = Placeholder<BoundVar>; + +#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)] +#[derive(TyEncodable, TyDecodable, PartialOrd, Ord)] +pub struct BoundConst<'tcx> { + pub var: BoundVar, + pub ty: Ty<'tcx>, +} + +pub type PlaceholderConst<'tcx> = Placeholder<BoundVar>; + +/// A `DefId` which, in case it is a const argument, is potentially bundled with +/// the `DefId` of the generic parameter it instantiates. +/// +/// This is used to avoid calls to `type_of` for const arguments during typeck +/// which cause cycle errors. +/// +/// ```rust +/// struct A; +/// impl A { +/// fn foo<const N: usize>(&self) -> [u8; N] { [0; N] } +/// // ^ const parameter +/// } +/// struct B; +/// impl B { +/// fn foo<const M: u8>(&self) -> usize { 42 } +/// // ^ const parameter +/// } +/// +/// fn main() { +/// let a = A; +/// let _b = a.foo::<{ 3 + 7 }>(); +/// // ^^^^^^^^^ const argument +/// } +/// ``` +/// +/// Let's look at the call `a.foo::<{ 3 + 7 }>()` here. We do not know +/// which `foo` is used until we know the type of `a`. +/// +/// We only know the type of `a` once we are inside of `typeck(main)`. +/// We also end up normalizing the type of `_b` during `typeck(main)` which +/// requires us to evaluate the const argument. +/// +/// To evaluate that const argument we need to know its type, +/// which we would get using `type_of(const_arg)`. This requires us to +/// resolve `foo` as it can be either `usize` or `u8` in this example. +/// However, resolving `foo` once again requires `typeck(main)` to get the type of `a`, +/// which results in a cycle. +/// +/// In short we must not call `type_of(const_arg)` during `typeck(main)`. +/// +/// When first creating the `ty::Const` of the const argument inside of `typeck` we have +/// already resolved `foo` so we know which const parameter this argument instantiates. +/// This means that we also know the expected result of `type_of(const_arg)` even if we +/// aren't allowed to call that query: it is equal to `type_of(const_param)` which is +/// trivial to compute. +/// +/// If we now want to use that constant in a place which potentially needs its type +/// we also pass the type of its `const_param`. This is the point of `WithOptConstParam`, +/// except that instead of a `Ty` we bundle the `DefId` of the const parameter. +/// Meaning that we need to use `type_of(const_param_did)` if `const_param_did` is `Some` +/// to get the type of `did`. +#[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, Lift, TyEncodable, TyDecodable)] +#[derive(PartialEq, Eq, PartialOrd, Ord)] +#[derive(Hash, HashStable)] +pub struct WithOptConstParam<T> { + pub did: T, + /// The `DefId` of the corresponding generic parameter in case `did` is + /// a const argument. + /// + /// Note that even if `did` is a const argument, this may still be `None`. + /// All queries taking `WithOptConstParam` start by calling `tcx.opt_const_param_of(def.did)` + /// to potentially update `param_did` in the case it is `None`. + pub const_param_did: Option<DefId>, +} + +impl<T> WithOptConstParam<T> { + /// Creates a new `WithOptConstParam` setting `const_param_did` to `None`. + #[inline(always)] + pub fn unknown(did: T) -> WithOptConstParam<T> { + WithOptConstParam { did, const_param_did: None } + } +} + +impl WithOptConstParam<LocalDefId> { + /// Returns `Some((did, param_did))` if `def_id` is a const argument, + /// `None` otherwise. + #[inline(always)] + pub fn try_lookup(did: LocalDefId, tcx: TyCtxt<'_>) -> Option<(LocalDefId, DefId)> { + tcx.opt_const_param_of(did).map(|param_did| (did, param_did)) + } + + /// In case `self` is unknown but `self.did` is a const argument, this returns + /// a `WithOptConstParam` with the correct `const_param_did`. + #[inline(always)] + pub fn try_upgrade(self, tcx: TyCtxt<'_>) -> Option<WithOptConstParam<LocalDefId>> { + if self.const_param_did.is_none() { + if let const_param_did @ Some(_) = tcx.opt_const_param_of(self.did) { + return Some(WithOptConstParam { did: self.did, const_param_did }); + } + } + + None + } + + pub fn to_global(self) -> WithOptConstParam<DefId> { + WithOptConstParam { did: self.did.to_def_id(), const_param_did: self.const_param_did } + } + + pub fn def_id_for_type_of(self) -> DefId { + if let Some(did) = self.const_param_did { did } else { self.did.to_def_id() } + } +} + +impl WithOptConstParam<DefId> { + pub fn as_local(self) -> Option<WithOptConstParam<LocalDefId>> { + self.did + .as_local() + .map(|did| WithOptConstParam { did, const_param_did: self.const_param_did }) + } + + pub fn as_const_arg(self) -> Option<(LocalDefId, DefId)> { + if let Some(param_did) = self.const_param_did { + if let Some(did) = self.did.as_local() { + return Some((did, param_did)); + } + } + + None + } + + pub fn is_local(self) -> bool { + self.did.is_local() + } + + pub fn def_id_for_type_of(self) -> DefId { + self.const_param_did.unwrap_or(self.did) + } +} + +/// When type checking, we use the `ParamEnv` to track +/// details about the set of where-clauses that are in scope at this +/// particular point. +#[derive(Copy, Clone, Hash, PartialEq, Eq)] +pub struct ParamEnv<'tcx> { + /// This packs both caller bounds and the reveal enum into one pointer. + /// + /// Caller bounds are `Obligation`s that the caller must satisfy. This is + /// basically the set of bounds on the in-scope type parameters, translated + /// into `Obligation`s, and elaborated and normalized. + /// + /// Use the `caller_bounds()` method to access. + /// + /// Typically, this is `Reveal::UserFacing`, but during codegen we + /// want `Reveal::All`. + /// + /// Note: This is packed, use the reveal() method to access it. + packed: CopyTaggedPtr<&'tcx List<Predicate<'tcx>>, ParamTag, true>, +} + +#[derive(Copy, Clone)] +struct ParamTag { + reveal: traits::Reveal, + constness: hir::Constness, +} + +unsafe impl rustc_data_structures::tagged_ptr::Tag for ParamTag { + const BITS: usize = 2; + #[inline] + fn into_usize(self) -> usize { + match self { + Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst } => 0, + Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst } => 1, + Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const } => 2, + Self { reveal: traits::Reveal::All, constness: hir::Constness::Const } => 3, + } + } + #[inline] + unsafe fn from_usize(ptr: usize) -> Self { + match ptr { + 0 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::NotConst }, + 1 => Self { reveal: traits::Reveal::All, constness: hir::Constness::NotConst }, + 2 => Self { reveal: traits::Reveal::UserFacing, constness: hir::Constness::Const }, + 3 => Self { reveal: traits::Reveal::All, constness: hir::Constness::Const }, + _ => std::hint::unreachable_unchecked(), + } + } +} + +impl<'tcx> fmt::Debug for ParamEnv<'tcx> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("ParamEnv") + .field("caller_bounds", &self.caller_bounds()) + .field("reveal", &self.reveal()) + .field("constness", &self.constness()) + .finish() + } +} + +impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> { + fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) { + self.caller_bounds().hash_stable(hcx, hasher); + self.reveal().hash_stable(hcx, hasher); + self.constness().hash_stable(hcx, hasher); + } +} + +impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> { + fn try_fold_with<F: ty::fold::FallibleTypeFolder<'tcx>>( + self, + folder: &mut F, + ) -> Result<Self, F::Error> { + Ok(ParamEnv::new( + self.caller_bounds().try_fold_with(folder)?, + self.reveal().try_fold_with(folder)?, + self.constness().try_fold_with(folder)?, + )) + } +} + +impl<'tcx> TypeVisitable<'tcx> for ParamEnv<'tcx> { + fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> { + self.caller_bounds().visit_with(visitor)?; + self.reveal().visit_with(visitor)?; + self.constness().visit_with(visitor) + } +} + +impl<'tcx> ParamEnv<'tcx> { + /// Construct a trait environment suitable for contexts where + /// there are no where-clauses in scope. Hidden types (like `impl + /// Trait`) are left hidden, so this is suitable for ordinary + /// type-checking. + #[inline] + pub fn empty() -> Self { + Self::new(List::empty(), Reveal::UserFacing, hir::Constness::NotConst) + } + + #[inline] + pub fn caller_bounds(self) -> &'tcx List<Predicate<'tcx>> { + self.packed.pointer() + } + + #[inline] + pub fn reveal(self) -> traits::Reveal { + self.packed.tag().reveal + } + + #[inline] + pub fn constness(self) -> hir::Constness { + self.packed.tag().constness + } + + #[inline] + pub fn is_const(self) -> bool { + self.packed.tag().constness == hir::Constness::Const + } + + /// Construct a trait environment with no where-clauses in scope + /// where the values of all `impl Trait` and other hidden types + /// are revealed. This is suitable for monomorphized, post-typeck + /// environments like codegen or doing optimizations. + /// + /// N.B., if you want to have predicates in scope, use `ParamEnv::new`, + /// or invoke `param_env.with_reveal_all()`. + #[inline] + pub fn reveal_all() -> Self { + Self::new(List::empty(), Reveal::All, hir::Constness::NotConst) + } + + /// Construct a trait environment with the given set of predicates. + #[inline] + pub fn new( + caller_bounds: &'tcx List<Predicate<'tcx>>, + reveal: Reveal, + constness: hir::Constness, + ) -> Self { + ty::ParamEnv { packed: CopyTaggedPtr::new(caller_bounds, ParamTag { reveal, constness }) } + } + + pub fn with_user_facing(mut self) -> Self { + self.packed.set_tag(ParamTag { reveal: Reveal::UserFacing, ..self.packed.tag() }); + self + } + + #[inline] + pub fn with_constness(mut self, constness: hir::Constness) -> Self { + self.packed.set_tag(ParamTag { constness, ..self.packed.tag() }); + self + } + + #[inline] + pub fn with_const(mut self) -> Self { + self.packed.set_tag(ParamTag { constness: hir::Constness::Const, ..self.packed.tag() }); + self + } + + #[inline] + pub fn without_const(mut self) -> Self { + self.packed.set_tag(ParamTag { constness: hir::Constness::NotConst, ..self.packed.tag() }); + self + } + + #[inline] + pub fn remap_constness_with(&mut self, mut constness: ty::BoundConstness) { + *self = self.with_constness(constness.and(self.constness())) + } + + /// Returns a new parameter environment with the same clauses, but + /// which "reveals" the true results of projections in all cases + /// (even for associated types that are specializable). This is + /// the desired behavior during codegen and certain other special + /// contexts; normally though we want to use `Reveal::UserFacing`, + /// which is the default. + /// All opaque types in the caller_bounds of the `ParamEnv` + /// will be normalized to their underlying types. + /// See PR #65989 and issue #65918 for more details + pub fn with_reveal_all_normalized(self, tcx: TyCtxt<'tcx>) -> Self { + if self.packed.tag().reveal == traits::Reveal::All { + return self; + } + + ParamEnv::new( + tcx.normalize_opaque_types(self.caller_bounds()), + Reveal::All, + self.constness(), + ) + } + + /// Returns this same environment but with no caller bounds. + #[inline] + pub fn without_caller_bounds(self) -> Self { + Self::new(List::empty(), self.reveal(), self.constness()) + } + + /// Creates a suitable environment in which to perform trait + /// queries on the given value. When type-checking, this is simply + /// the pair of the environment plus value. But when reveal is set to + /// All, then if `value` does not reference any type parameters, we will + /// pair it with the empty environment. This improves caching and is generally + /// invisible. + /// + /// N.B., we preserve the environment when type-checking because it + /// is possible for the user to have wacky where-clauses like + /// `where Box<u32>: Copy`, which are clearly never + /// satisfiable. We generally want to behave as if they were true, + /// although the surrounding function is never reachable. + pub fn and<T: TypeVisitable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T> { + match self.reveal() { + Reveal::UserFacing => ParamEnvAnd { param_env: self, value }, + + Reveal::All => { + if value.is_global() { + ParamEnvAnd { param_env: self.without_caller_bounds(), value } + } else { + ParamEnvAnd { param_env: self, value } + } + } + } + } +} + +// FIXME(ecstaticmorse): Audit all occurrences of `without_const().to_predicate(tcx)` to ensure that +// the constness of trait bounds is being propagated correctly. +impl<'tcx> PolyTraitRef<'tcx> { + #[inline] + pub fn with_constness(self, constness: BoundConstness) -> PolyTraitPredicate<'tcx> { + self.map_bound(|trait_ref| ty::TraitPredicate { + trait_ref, + constness, + polarity: ty::ImplPolarity::Positive, + }) + } + + #[inline] + pub fn without_const(self) -> PolyTraitPredicate<'tcx> { + self.with_constness(BoundConstness::NotConst) + } +} + +#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)] +#[derive(HashStable)] +pub struct ParamEnvAnd<'tcx, T> { + pub param_env: ParamEnv<'tcx>, + pub value: T, +} + +impl<'tcx, T> ParamEnvAnd<'tcx, T> { + pub fn into_parts(self) -> (ParamEnv<'tcx>, T) { + (self.param_env, self.value) + } + + #[inline] + pub fn without_const(mut self) -> Self { + self.param_env = self.param_env.without_const(); + self + } +} + +#[derive(Copy, Clone, Debug, HashStable, Encodable, Decodable)] +pub struct Destructor { + /// The `DefId` of the destructor method + pub did: DefId, + /// The constness of the destructor method + pub constness: hir::Constness, +} + +bitflags! { + #[derive(HashStable, TyEncodable, TyDecodable)] + pub struct VariantFlags: u32 { + const NO_VARIANT_FLAGS = 0; + /// Indicates whether the field list of this variant is `#[non_exhaustive]`. + const IS_FIELD_LIST_NON_EXHAUSTIVE = 1 << 0; + /// Indicates whether this variant was obtained as part of recovering from + /// a syntactic error. May be incomplete or bogus. + const IS_RECOVERED = 1 << 1; + } +} + +/// Definition of a variant -- a struct's fields or an enum variant. +#[derive(Debug, HashStable, TyEncodable, TyDecodable)] +pub struct VariantDef { + /// `DefId` that identifies the variant itself. + /// If this variant belongs to a struct or union, then this is a copy of its `DefId`. + pub def_id: DefId, + /// `DefId` that identifies the variant's constructor. + /// If this variant is a struct variant, then this is `None`. + pub ctor_def_id: Option<DefId>, + /// Variant or struct name. + pub name: Symbol, + /// Discriminant of this variant. + pub discr: VariantDiscr, + /// Fields of this variant. + pub fields: Vec<FieldDef>, + /// Type of constructor of variant. + pub ctor_kind: CtorKind, + /// Flags of the variant (e.g. is field list non-exhaustive)? + flags: VariantFlags, +} + +impl VariantDef { + /// Creates a new `VariantDef`. + /// + /// `variant_did` is the `DefId` that identifies the enum variant (if this `VariantDef` + /// represents an enum variant). + /// + /// `ctor_did` is the `DefId` that identifies the constructor of unit or + /// tuple-variants/structs. If this is a `struct`-variant then this should be `None`. + /// + /// `parent_did` is the `DefId` of the `AdtDef` representing the enum or struct that + /// owns this variant. It is used for checking if a struct has `#[non_exhaustive]` w/out having + /// to go through the redirect of checking the ctor's attributes - but compiling a small crate + /// requires loading the `AdtDef`s for all the structs in the universe (e.g., coherence for any + /// built-in trait), and we do not want to load attributes twice. + /// + /// If someone speeds up attribute loading to not be a performance concern, they can + /// remove this hack and use the constructor `DefId` everywhere. + pub fn new( + name: Symbol, + variant_did: Option<DefId>, + ctor_def_id: Option<DefId>, + discr: VariantDiscr, + fields: Vec<FieldDef>, + ctor_kind: CtorKind, + adt_kind: AdtKind, + parent_did: DefId, + recovered: bool, + is_field_list_non_exhaustive: bool, + ) -> Self { + debug!( + "VariantDef::new(name = {:?}, variant_did = {:?}, ctor_def_id = {:?}, discr = {:?}, + fields = {:?}, ctor_kind = {:?}, adt_kind = {:?}, parent_did = {:?})", + name, variant_did, ctor_def_id, discr, fields, ctor_kind, adt_kind, parent_did, + ); + + let mut flags = VariantFlags::NO_VARIANT_FLAGS; + if is_field_list_non_exhaustive { + flags |= VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE; + } + + if recovered { + flags |= VariantFlags::IS_RECOVERED; + } + + VariantDef { + def_id: variant_did.unwrap_or(parent_did), + ctor_def_id, + name, + discr, + fields, + ctor_kind, + flags, + } + } + + /// Is this field list non-exhaustive? + #[inline] + pub fn is_field_list_non_exhaustive(&self) -> bool { + self.flags.intersects(VariantFlags::IS_FIELD_LIST_NON_EXHAUSTIVE) + } + + /// Was this variant obtained as part of recovering from a syntactic error? + #[inline] + pub fn is_recovered(&self) -> bool { + self.flags.intersects(VariantFlags::IS_RECOVERED) + } + + /// Computes the `Ident` of this variant by looking up the `Span` + pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident { + Ident::new(self.name, tcx.def_ident_span(self.def_id).unwrap()) + } +} + +impl PartialEq for VariantDef { + #[inline] + fn eq(&self, other: &Self) -> bool { + // There should be only one `VariantDef` for each `def_id`, therefore + // it is fine to implement `PartialEq` only based on `def_id`. + // + // Below, we exhaustively destructure `self` and `other` so that if the + // definition of `VariantDef` changes, a compile-error will be produced, + // reminding us to revisit this assumption. + + let Self { + def_id: lhs_def_id, + ctor_def_id: _, + name: _, + discr: _, + fields: _, + ctor_kind: _, + flags: _, + } = &self; + + let Self { + def_id: rhs_def_id, + ctor_def_id: _, + name: _, + discr: _, + fields: _, + ctor_kind: _, + flags: _, + } = other; + + lhs_def_id == rhs_def_id + } +} + +impl Eq for VariantDef {} + +impl Hash for VariantDef { + #[inline] + fn hash<H: Hasher>(&self, s: &mut H) { + // There should be only one `VariantDef` for each `def_id`, therefore + // it is fine to implement `Hash` only based on `def_id`. + // + // Below, we exhaustively destructure `self` so that if the definition + // of `VariantDef` changes, a compile-error will be produced, reminding + // us to revisit this assumption. + + let Self { def_id, ctor_def_id: _, name: _, discr: _, fields: _, ctor_kind: _, flags: _ } = + &self; + + def_id.hash(s) + } +} + +#[derive(Copy, Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, HashStable)] +pub enum VariantDiscr { + /// Explicit value for this variant, i.e., `X = 123`. + /// The `DefId` corresponds to the embedded constant. + Explicit(DefId), + + /// The previous variant's discriminant plus one. + /// For efficiency reasons, the distance from the + /// last `Explicit` discriminant is being stored, + /// or `0` for the first variant, if it has none. + Relative(u32), +} + +#[derive(Debug, HashStable, TyEncodable, TyDecodable)] +pub struct FieldDef { + pub did: DefId, + pub name: Symbol, + pub vis: Visibility, +} + +impl PartialEq for FieldDef { + #[inline] + fn eq(&self, other: &Self) -> bool { + // There should be only one `FieldDef` for each `did`, therefore it is + // fine to implement `PartialEq` only based on `did`. + // + // Below, we exhaustively destructure `self` so that if the definition + // of `FieldDef` changes, a compile-error will be produced, reminding + // us to revisit this assumption. + + let Self { did: lhs_did, name: _, vis: _ } = &self; + + let Self { did: rhs_did, name: _, vis: _ } = other; + + lhs_did == rhs_did + } +} + +impl Eq for FieldDef {} + +impl Hash for FieldDef { + #[inline] + fn hash<H: Hasher>(&self, s: &mut H) { + // There should be only one `FieldDef` for each `did`, therefore it is + // fine to implement `Hash` only based on `did`. + // + // Below, we exhaustively destructure `self` so that if the definition + // of `FieldDef` changes, a compile-error will be produced, reminding + // us to revisit this assumption. + + let Self { did, name: _, vis: _ } = &self; + + did.hash(s) + } +} + +bitflags! { + #[derive(TyEncodable, TyDecodable, Default, HashStable)] + pub struct ReprFlags: u8 { + const IS_C = 1 << 0; + const IS_SIMD = 1 << 1; + const IS_TRANSPARENT = 1 << 2; + // Internal only for now. If true, don't reorder fields. + const IS_LINEAR = 1 << 3; + // If true, the type's layout can be randomized using + // the seed stored in `ReprOptions.layout_seed` + const RANDOMIZE_LAYOUT = 1 << 4; + // Any of these flags being set prevent field reordering optimisation. + const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits + | ReprFlags::IS_SIMD.bits + | ReprFlags::IS_LINEAR.bits; + } +} + +/// Represents the repr options provided by the user, +#[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Default, HashStable)] +pub struct ReprOptions { + pub int: Option<attr::IntType>, + pub align: Option<Align>, + pub pack: Option<Align>, + pub flags: ReprFlags, + /// The seed to be used for randomizing a type's layout + /// + /// Note: This could technically be a `[u8; 16]` (a `u128`) which would + /// be the "most accurate" hash as it'd encompass the item and crate + /// hash without loss, but it does pay the price of being larger. + /// Everything's a tradeoff, a `u64` seed should be sufficient for our + /// purposes (primarily `-Z randomize-layout`) + pub field_shuffle_seed: u64, +} + +impl ReprOptions { + pub fn new(tcx: TyCtxt<'_>, did: DefId) -> ReprOptions { + let mut flags = ReprFlags::empty(); + let mut size = None; + let mut max_align: Option<Align> = None; + let mut min_pack: Option<Align> = None; + + // Generate a deterministically-derived seed from the item's path hash + // to allow for cross-crate compilation to actually work + let mut field_shuffle_seed = tcx.def_path_hash(did).0.to_smaller_hash(); + + // If the user defined a custom seed for layout randomization, xor the item's + // path hash with the user defined seed, this will allowing determinism while + // still allowing users to further randomize layout generation for e.g. fuzzing + if let Some(user_seed) = tcx.sess.opts.unstable_opts.layout_seed { + field_shuffle_seed ^= user_seed; + } + + for attr in tcx.get_attrs(did, sym::repr) { + for r in attr::parse_repr_attr(&tcx.sess, attr) { + flags.insert(match r { + attr::ReprC => ReprFlags::IS_C, + attr::ReprPacked(pack) => { + let pack = Align::from_bytes(pack as u64).unwrap(); + min_pack = Some(if let Some(min_pack) = min_pack { + min_pack.min(pack) + } else { + pack + }); + ReprFlags::empty() + } + attr::ReprTransparent => ReprFlags::IS_TRANSPARENT, + attr::ReprSimd => ReprFlags::IS_SIMD, + attr::ReprInt(i) => { + size = Some(i); + ReprFlags::empty() + } + attr::ReprAlign(align) => { + max_align = max_align.max(Some(Align::from_bytes(align as u64).unwrap())); + ReprFlags::empty() + } + }); + } + } + + // If `-Z randomize-layout` was enabled for the type definition then we can + // consider performing layout randomization + if tcx.sess.opts.unstable_opts.randomize_layout { + flags.insert(ReprFlags::RANDOMIZE_LAYOUT); + } + + // This is here instead of layout because the choice must make it into metadata. + if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) { + flags.insert(ReprFlags::IS_LINEAR); + } + + Self { int: size, align: max_align, pack: min_pack, flags, field_shuffle_seed } + } + + #[inline] + pub fn simd(&self) -> bool { + self.flags.contains(ReprFlags::IS_SIMD) + } + + #[inline] + pub fn c(&self) -> bool { + self.flags.contains(ReprFlags::IS_C) + } + + #[inline] + pub fn packed(&self) -> bool { + self.pack.is_some() + } + + #[inline] + pub fn transparent(&self) -> bool { + self.flags.contains(ReprFlags::IS_TRANSPARENT) + } + + #[inline] + pub fn linear(&self) -> bool { + self.flags.contains(ReprFlags::IS_LINEAR) + } + + /// Returns the discriminant type, given these `repr` options. + /// This must only be called on enums! + pub fn discr_type(&self) -> attr::IntType { + self.int.unwrap_or(attr::SignedInt(ast::IntTy::Isize)) + } + + /// Returns `true` if this `#[repr()]` should inhabit "smart enum + /// layout" optimizations, such as representing `Foo<&T>` as a + /// single pointer. + pub fn inhibit_enum_layout_opt(&self) -> bool { + self.c() || self.int.is_some() + } + + /// Returns `true` if this `#[repr()]` should inhibit struct field reordering + /// optimizations, such as with `repr(C)`, `repr(packed(1))`, or `repr(<int>)`. + pub fn inhibit_struct_field_reordering_opt(&self) -> bool { + if let Some(pack) = self.pack { + if pack.bytes() == 1 { + return true; + } + } + + self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some() + } + + /// Returns `true` if this type is valid for reordering and `-Z randomize-layout` + /// was enabled for its declaration crate + pub fn can_randomize_type_layout(&self) -> bool { + !self.inhibit_struct_field_reordering_opt() + && self.flags.contains(ReprFlags::RANDOMIZE_LAYOUT) + } + + /// Returns `true` if this `#[repr()]` should inhibit union ABI optimisations. + pub fn inhibit_union_abi_opt(&self) -> bool { + self.c() + } +} + +impl<'tcx> FieldDef { + /// Returns the type of this field. The resulting type is not normalized. The `subst` is + /// typically obtained via the second field of [`TyKind::Adt`]. + pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> { + tcx.bound_type_of(self.did).subst(tcx, subst) + } + + /// Computes the `Ident` of this variant by looking up the `Span` + pub fn ident(&self, tcx: TyCtxt<'_>) -> Ident { + Ident::new(self.name, tcx.def_ident_span(self.did).unwrap()) + } +} + +pub type Attributes<'tcx> = impl Iterator<Item = &'tcx ast::Attribute>; +#[derive(Debug, PartialEq, Eq)] +pub enum ImplOverlapKind { + /// These impls are always allowed to overlap. + Permitted { + /// Whether or not the impl is permitted due to the trait being a `#[marker]` trait + marker: bool, + }, + /// These impls are allowed to overlap, but that raises + /// an issue #33140 future-compatibility warning. + /// + /// Some background: in Rust 1.0, the trait-object types `Send + Sync` (today's + /// `dyn Send + Sync`) and `Sync + Send` (now `dyn Sync + Send`) were different. + /// + /// The widely-used version 0.1.0 of the crate `traitobject` had accidentally relied + /// that difference, making what reduces to the following set of impls: + /// + /// ```compile_fail,(E0119) + /// trait Trait {} + /// impl Trait for dyn Send + Sync {} + /// impl Trait for dyn Sync + Send {} + /// ``` + /// + /// Obviously, once we made these types be identical, that code causes a coherence + /// error and a fairly big headache for us. However, luckily for us, the trait + /// `Trait` used in this case is basically a marker trait, and therefore having + /// overlapping impls for it is sound. + /// + /// To handle this, we basically regard the trait as a marker trait, with an additional + /// future-compatibility warning. To avoid accidentally "stabilizing" this feature, + /// it has the following restrictions: + /// + /// 1. The trait must indeed be a marker-like trait (i.e., no items), and must be + /// positive impls. + /// 2. The trait-ref of both impls must be equal. + /// 3. The trait-ref of both impls must be a trait object type consisting only of + /// marker traits. + /// 4. Neither of the impls can have any where-clauses. + /// + /// Once `traitobject` 0.1.0 is no longer an active concern, this hack can be removed. + Issue33140, +} + +impl<'tcx> TyCtxt<'tcx> { + pub fn typeck_body(self, body: hir::BodyId) -> &'tcx TypeckResults<'tcx> { + self.typeck(self.hir().body_owner_def_id(body)) + } + + pub fn provided_trait_methods(self, id: DefId) -> impl 'tcx + Iterator<Item = &'tcx AssocItem> { + self.associated_items(id) + .in_definition_order() + .filter(move |item| item.kind == AssocKind::Fn && item.defaultness(self).has_value()) + } + + /// Look up the name of a definition across crates. This does not look at HIR. + pub fn opt_item_name(self, def_id: DefId) -> Option<Symbol> { + if let Some(cnum) = def_id.as_crate_root() { + Some(self.crate_name(cnum)) + } else { + let def_key = self.def_key(def_id); + match def_key.disambiguated_data.data { + // The name of a constructor is that of its parent. + rustc_hir::definitions::DefPathData::Ctor => self + .opt_item_name(DefId { krate: def_id.krate, index: def_key.parent.unwrap() }), + // The name of opaque types only exists in HIR. + rustc_hir::definitions::DefPathData::ImplTrait + if let Some(def_id) = def_id.as_local() => + self.hir().opt_name(self.hir().local_def_id_to_hir_id(def_id)), + _ => def_key.get_opt_name(), + } + } + } + + /// Look up the name of a definition across crates. This does not look at HIR. + /// + /// This method will ICE if the corresponding item does not have a name. In these cases, use + /// [`opt_item_name`] instead. + /// + /// [`opt_item_name`]: Self::opt_item_name + pub fn item_name(self, id: DefId) -> Symbol { + self.opt_item_name(id).unwrap_or_else(|| { + bug!("item_name: no name for {:?}", self.def_path(id)); + }) + } + + /// Look up the name and span of a definition. + /// + /// See [`item_name`][Self::item_name] for more information. + pub fn opt_item_ident(self, def_id: DefId) -> Option<Ident> { + let def = self.opt_item_name(def_id)?; + let span = def_id + .as_local() + .and_then(|id| self.def_ident_span(id)) + .unwrap_or(rustc_span::DUMMY_SP); + Some(Ident::new(def, span)) + } + + pub fn opt_associated_item(self, def_id: DefId) -> Option<&'tcx AssocItem> { + if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) { + Some(self.associated_item(def_id)) + } else { + None + } + } + + pub fn field_index(self, hir_id: hir::HirId, typeck_results: &TypeckResults<'_>) -> usize { + typeck_results.field_indices().get(hir_id).cloned().expect("no index for a field") + } + + pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> { + variant + .fields + .iter() + .position(|field| self.hygienic_eq(ident, field.ident(self), variant.def_id)) + } + + /// Returns `true` if the impls are the same polarity and the trait either + /// has no items or is annotated `#[marker]` and prevents item overrides. + pub fn impls_are_allowed_to_overlap( + self, + def_id1: DefId, + def_id2: DefId, + ) -> Option<ImplOverlapKind> { + // If either trait impl references an error, they're allowed to overlap, + // as one of them essentially doesn't exist. + if self.impl_trait_ref(def_id1).map_or(false, |tr| tr.references_error()) + || self.impl_trait_ref(def_id2).map_or(false, |tr| tr.references_error()) + { + return Some(ImplOverlapKind::Permitted { marker: false }); + } + + match (self.impl_polarity(def_id1), self.impl_polarity(def_id2)) { + (ImplPolarity::Reservation, _) | (_, ImplPolarity::Reservation) => { + // `#[rustc_reservation_impl]` impls don't overlap with anything + debug!( + "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (reservations)", + def_id1, def_id2 + ); + return Some(ImplOverlapKind::Permitted { marker: false }); + } + (ImplPolarity::Positive, ImplPolarity::Negative) + | (ImplPolarity::Negative, ImplPolarity::Positive) => { + // `impl AutoTrait for Type` + `impl !AutoTrait for Type` + debug!( + "impls_are_allowed_to_overlap({:?}, {:?}) - None (differing polarities)", + def_id1, def_id2 + ); + return None; + } + (ImplPolarity::Positive, ImplPolarity::Positive) + | (ImplPolarity::Negative, ImplPolarity::Negative) => {} + }; + + let is_marker_overlap = { + let is_marker_impl = |def_id: DefId| -> bool { + let trait_ref = self.impl_trait_ref(def_id); + trait_ref.map_or(false, |tr| self.trait_def(tr.def_id).is_marker) + }; + is_marker_impl(def_id1) && is_marker_impl(def_id2) + }; + + if is_marker_overlap { + debug!( + "impls_are_allowed_to_overlap({:?}, {:?}) = Some(Permitted) (marker overlap)", + def_id1, def_id2 + ); + Some(ImplOverlapKind::Permitted { marker: true }) + } else { + if let Some(self_ty1) = self.issue33140_self_ty(def_id1) { + if let Some(self_ty2) = self.issue33140_self_ty(def_id2) { + if self_ty1 == self_ty2 { + debug!( + "impls_are_allowed_to_overlap({:?}, {:?}) - issue #33140 HACK", + def_id1, def_id2 + ); + return Some(ImplOverlapKind::Issue33140); + } else { + debug!( + "impls_are_allowed_to_overlap({:?}, {:?}) - found {:?} != {:?}", + def_id1, def_id2, self_ty1, self_ty2 + ); + } + } + } + + debug!("impls_are_allowed_to_overlap({:?}, {:?}) = None", def_id1, def_id2); + None + } + } + + /// Returns `ty::VariantDef` if `res` refers to a struct, + /// or variant or their constructors, panics otherwise. + pub fn expect_variant_res(self, res: Res) -> &'tcx VariantDef { + match res { + Res::Def(DefKind::Variant, did) => { + let enum_did = self.parent(did); + self.adt_def(enum_did).variant_with_id(did) + } + Res::Def(DefKind::Struct | DefKind::Union, did) => self.adt_def(did).non_enum_variant(), + Res::Def(DefKind::Ctor(CtorOf::Variant, ..), variant_ctor_did) => { + let variant_did = self.parent(variant_ctor_did); + let enum_did = self.parent(variant_did); + self.adt_def(enum_did).variant_with_ctor_id(variant_ctor_did) + } + Res::Def(DefKind::Ctor(CtorOf::Struct, ..), ctor_did) => { + let struct_did = self.parent(ctor_did); + self.adt_def(struct_did).non_enum_variant() + } + _ => bug!("expect_variant_res used with unexpected res {:?}", res), + } + } + + /// Returns the possibly-auto-generated MIR of a `(DefId, Subst)` pair. + #[instrument(skip(self), level = "debug")] + pub fn instance_mir(self, instance: ty::InstanceDef<'tcx>) -> &'tcx Body<'tcx> { + match instance { + ty::InstanceDef::Item(def) => { + debug!("calling def_kind on def: {:?}", def); + let def_kind = self.def_kind(def.did); + debug!("returned from def_kind: {:?}", def_kind); + match def_kind { + DefKind::Const + | DefKind::Static(..) + | DefKind::AssocConst + | DefKind::Ctor(..) + | DefKind::AnonConst + | DefKind::InlineConst => self.mir_for_ctfe_opt_const_arg(def), + // If the caller wants `mir_for_ctfe` of a function they should not be using + // `instance_mir`, so we'll assume const fn also wants the optimized version. + _ => { + assert_eq!(def.const_param_did, None); + self.optimized_mir(def.did) + } + } + } + ty::InstanceDef::VTableShim(..) + | ty::InstanceDef::ReifyShim(..) + | ty::InstanceDef::Intrinsic(..) + | ty::InstanceDef::FnPtrShim(..) + | ty::InstanceDef::Virtual(..) + | ty::InstanceDef::ClosureOnceShim { .. } + | ty::InstanceDef::DropGlue(..) + | ty::InstanceDef::CloneShim(..) => self.mir_shims(instance), + } + } + + // FIXME(@lcnr): Remove this function. + pub fn get_attrs_unchecked(self, did: DefId) -> &'tcx [ast::Attribute] { + if let Some(did) = did.as_local() { + self.hir().attrs(self.hir().local_def_id_to_hir_id(did)) + } else { + self.item_attrs(did) + } + } + + /// Gets all attributes with the given name. + pub fn get_attrs(self, did: DefId, attr: Symbol) -> ty::Attributes<'tcx> { + let filter_fn = move |a: &&ast::Attribute| a.has_name(attr); + if let Some(did) = did.as_local() { + self.hir().attrs(self.hir().local_def_id_to_hir_id(did)).iter().filter(filter_fn) + } else if cfg!(debug_assertions) && rustc_feature::is_builtin_only_local(attr) { + bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr); + } else { + self.item_attrs(did).iter().filter(filter_fn) + } + } + + pub fn get_attr(self, did: DefId, attr: Symbol) -> Option<&'tcx ast::Attribute> { + self.get_attrs(did, attr).next() + } + + /// Determines whether an item is annotated with an attribute. + pub fn has_attr(self, did: DefId, attr: Symbol) -> bool { + if cfg!(debug_assertions) && !did.is_local() && rustc_feature::is_builtin_only_local(attr) { + bug!("tried to access the `only_local` attribute `{}` from an extern crate", attr); + } else { + self.get_attrs(did, attr).next().is_some() + } + } + + /// Returns `true` if this is an `auto trait`. + pub fn trait_is_auto(self, trait_def_id: DefId) -> bool { + self.trait_def(trait_def_id).has_auto_impl + } + + /// Returns layout of a generator. Layout might be unavailable if the + /// generator is tainted by errors. + pub fn generator_layout(self, def_id: DefId) -> Option<&'tcx GeneratorLayout<'tcx>> { + self.optimized_mir(def_id).generator_layout() + } + + /// Given the `DefId` of an impl, returns the `DefId` of the trait it implements. + /// If it implements no trait, returns `None`. + pub fn trait_id_of_impl(self, def_id: DefId) -> Option<DefId> { + self.impl_trait_ref(def_id).map(|tr| tr.def_id) + } + + /// If the given `DefId` describes an item belonging to a trait, + /// returns the `DefId` of the trait that the trait item belongs to; + /// otherwise, returns `None`. + pub fn trait_of_item(self, def_id: DefId) -> Option<DefId> { + if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) { + let parent = self.parent(def_id); + if let DefKind::Trait | DefKind::TraitAlias = self.def_kind(parent) { + return Some(parent); + } + } + None + } + + /// If the given `DefId` describes a method belonging to an impl, returns the + /// `DefId` of the impl that the method belongs to; otherwise, returns `None`. + pub fn impl_of_method(self, def_id: DefId) -> Option<DefId> { + if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) { + let parent = self.parent(def_id); + if let DefKind::Impl = self.def_kind(parent) { + return Some(parent); + } + } + None + } + + /// If the given `DefId` belongs to a trait that was automatically derived, returns `true`. + pub fn is_builtin_derive(self, def_id: DefId) -> bool { + self.has_attr(def_id, sym::automatically_derived) + } + + /// Looks up the span of `impl_did` if the impl is local; otherwise returns `Err` + /// with the name of the crate containing the impl. + pub fn span_of_impl(self, impl_did: DefId) -> Result<Span, Symbol> { + if let Some(impl_did) = impl_did.as_local() { + Ok(self.def_span(impl_did)) + } else { + Err(self.crate_name(impl_did.krate)) + } + } + + /// Hygienically compares a use-site name (`use_name`) for a field or an associated item with + /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed + /// definition's parent/scope to perform comparison. + pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool { + // We could use `Ident::eq` here, but we deliberately don't. The name + // comparison fails frequently, and we want to avoid the expensive + // `normalize_to_macros_2_0()` calls required for the span comparison whenever possible. + use_name.name == def_name.name + && use_name + .span + .ctxt() + .hygienic_eq(def_name.span.ctxt(), self.expn_that_defined(def_parent_def_id)) + } + + pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident { + ident.span.normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope)); + ident + } + + pub fn adjust_ident_and_get_scope( + self, + mut ident: Ident, + scope: DefId, + block: hir::HirId, + ) -> (Ident, DefId) { + let scope = ident + .span + .normalize_to_macros_2_0_and_adjust(self.expn_that_defined(scope)) + .and_then(|actual_expansion| actual_expansion.expn_data().parent_module) + .unwrap_or_else(|| self.parent_module(block).to_def_id()); + (ident, scope) + } + + pub fn is_object_safe(self, key: DefId) -> bool { + self.object_safety_violations(key).is_empty() + } + + #[inline] + pub fn is_const_fn_raw(self, def_id: DefId) -> bool { + matches!(self.def_kind(def_id), DefKind::Fn | DefKind::AssocFn | DefKind::Ctor(..)) + && self.constness(def_id) == hir::Constness::Const + } + + #[inline] + pub fn is_const_default_method(self, def_id: DefId) -> bool { + matches!(self.trait_of_item(def_id), Some(trait_id) if self.has_attr(trait_id, sym::const_trait)) + } +} + +/// Yields the parent function's `LocalDefId` if `def_id` is an `impl Trait` definition. +pub fn is_impl_trait_defn(tcx: TyCtxt<'_>, def_id: DefId) -> Option<LocalDefId> { + let def_id = def_id.as_local()?; + if let Node::Item(item) = tcx.hir().get_by_def_id(def_id) { + if let hir::ItemKind::OpaqueTy(ref opaque_ty) = item.kind { + return match opaque_ty.origin { + hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) => { + Some(parent) + } + hir::OpaqueTyOrigin::TyAlias => None, + }; + } + } + None +} + +pub fn int_ty(ity: ast::IntTy) -> IntTy { + match ity { + ast::IntTy::Isize => IntTy::Isize, + ast::IntTy::I8 => IntTy::I8, + ast::IntTy::I16 => IntTy::I16, + ast::IntTy::I32 => IntTy::I32, + ast::IntTy::I64 => IntTy::I64, + ast::IntTy::I128 => IntTy::I128, + } +} + +pub fn uint_ty(uty: ast::UintTy) -> UintTy { + match uty { + ast::UintTy::Usize => UintTy::Usize, + ast::UintTy::U8 => UintTy::U8, + ast::UintTy::U16 => UintTy::U16, + ast::UintTy::U32 => UintTy::U32, + ast::UintTy::U64 => UintTy::U64, + ast::UintTy::U128 => UintTy::U128, + } +} + +pub fn float_ty(fty: ast::FloatTy) -> FloatTy { + match fty { + ast::FloatTy::F32 => FloatTy::F32, + ast::FloatTy::F64 => FloatTy::F64, + } +} + +pub fn ast_int_ty(ity: IntTy) -> ast::IntTy { + match ity { + IntTy::Isize => ast::IntTy::Isize, + IntTy::I8 => ast::IntTy::I8, + IntTy::I16 => ast::IntTy::I16, + IntTy::I32 => ast::IntTy::I32, + IntTy::I64 => ast::IntTy::I64, + IntTy::I128 => ast::IntTy::I128, + } +} + +pub fn ast_uint_ty(uty: UintTy) -> ast::UintTy { + match uty { + UintTy::Usize => ast::UintTy::Usize, + UintTy::U8 => ast::UintTy::U8, + UintTy::U16 => ast::UintTy::U16, + UintTy::U32 => ast::UintTy::U32, + UintTy::U64 => ast::UintTy::U64, + UintTy::U128 => ast::UintTy::U128, + } +} + +pub fn provide(providers: &mut ty::query::Providers) { + closure::provide(providers); + context::provide(providers); + erase_regions::provide(providers); + layout::provide(providers); + util::provide(providers); + print::provide(providers); + super::util::bug::provide(providers); + super::middle::provide(providers); + *providers = ty::query::Providers { + trait_impls_of: trait_def::trait_impls_of_provider, + incoherent_impls: trait_def::incoherent_impls_provider, + type_uninhabited_from: inhabitedness::type_uninhabited_from, + const_param_default: consts::const_param_default, + vtable_allocation: vtable::vtable_allocation_provider, + ..*providers + }; +} + +/// A map for the local crate mapping each type to a vector of its +/// inherent impls. This is not meant to be used outside of coherence; +/// rather, you should request the vector for a specific type via +/// `tcx.inherent_impls(def_id)` so as to minimize your dependencies +/// (constructing this map requires touching the entire crate). +#[derive(Clone, Debug, Default, HashStable)] +pub struct CrateInherentImpls { + pub inherent_impls: LocalDefIdMap<Vec<DefId>>, + pub incoherent_impls: FxHashMap<SimplifiedType, Vec<LocalDefId>>, +} + +#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, TyEncodable, HashStable)] +pub struct SymbolName<'tcx> { + /// `&str` gives a consistent ordering, which ensures reproducible builds. + pub name: &'tcx str, +} + +impl<'tcx> SymbolName<'tcx> { + pub fn new(tcx: TyCtxt<'tcx>, name: &str) -> SymbolName<'tcx> { + SymbolName { + name: unsafe { str::from_utf8_unchecked(tcx.arena.alloc_slice(name.as_bytes())) }, + } + } +} + +impl<'tcx> fmt::Display for SymbolName<'tcx> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt::Display::fmt(&self.name, fmt) + } +} + +impl<'tcx> fmt::Debug for SymbolName<'tcx> { + fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { + fmt::Display::fmt(&self.name, fmt) + } +} + +#[derive(Debug, Default, Copy, Clone)] +pub struct FoundRelationships { + /// This is true if we identified that this Ty (`?T`) is found in a `?T: Foo` + /// obligation, where: + /// + /// * `Foo` is not `Sized` + /// * `(): Foo` may be satisfied + pub self_in_trait: bool, + /// This is true if we identified that this Ty (`?T`) is found in a `<_ as + /// _>::AssocType = ?T` + pub output: bool, +} + +/// The constituent parts of a type level constant of kind ADT or array. +#[derive(Copy, Clone, Debug, HashStable)] +pub struct DestructuredConst<'tcx> { + pub variant: Option<VariantIdx>, + pub fields: &'tcx [ty::Const<'tcx>], +} |