Module ty

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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.

Re-exports§

pub use self::pattern::Pattern;
pub use self::pattern::PatternKind;
pub use self::trait_def::TraitDef;
pub use vtable::*;

Modules§

abstract_const: A subset of a mir body used for const evaluability checking.
adjustment
adt 🔒
assoc 🔒
cast
closure 🔒
codec: This module contains some shared code for encoding and decoding various things from the ty module, and in particular implements support for “shorthands” which allow to have pointers back into the already encoded stream instead of re-encoding the same thing twice.
consts 🔒
context 🔒: Type context book-keeping.
data_structures
diagnostics 🔒: Diagnostics related methods for Ty.
elaborate
elaborate_impl 🔒
erase_regions 🔒
error
fast_reject
flags
fold 🔒
generic_args 🔒
generics 🔒
impls_ty 🔒: This module contains HashStable implementations for various data types from rustc_middle::ty in no particular order.
inhabitedness: This module contains logic for determining whether a type is inhabited or uninhabited. The InhabitedPredicate type captures the minimum information needed to determine whether a type is inhabited given a ParamEnv and module ID.
inherent: Set of traits which are used to emulate the inherent impls that are present in rustc_middle. It is customary to glob-import rustc_type_ir::inherent::* to bring all of these traits into scope when programming in interner-agnostic settings, and to avoid importing any of these directly elsewhere (i.e. specify the full path for an implementation downstream).
instance 🔒
intrinsic 🔒
ir_print
lang_items
layout
lift
list 🔒
normalize_erasing_regions: Methods for normalizing when you don’t care about regions (and aren’t doing type inference). If either of those things don’t apply to you, use infcx.normalize(...).
opaque_types 🔒
outlives: The outlives relation T: 'a or 'a: 'b. This code frequently refers to rules defined in RFC 1214 (OutlivesFooBar), so see that RFC for reference.
parameterized 🔒
pattern
predicate 🔒
print
region 🔒
relate
rvalue_scopes 🔒
search_graph
significant_drop_order
size_asserts 🔒
solve
structural_impls 🔒: This module contains implementations of the Lift, TypeFoldable and TypeVisitable traits for various types in the Rust compiler. Most are written by hand, though we’ve recently added some macros and proc-macros to help with the tedium.
sty 🔒: This module contains TyKind and its major components.
tls
trait_def
typeck_results 🔒
util: Miscellaneous type-system utilities that are too small to deserve their own modules.
visit 🔒
vtable
walk: An iterator over the type substructure. WARNING: this does not keep track of the region depth.

Macros§

TrivialTypeTraversalImpls: Used for types that are Copy and which do not care arena allocated data (i.e., don’t need to be folded).
try_visit
walk_visitable_list

Structs§

AdtDef
AdtDefData: The definition of a user-defined type, e.g., a struct, enum, or union.
AdtFlags
AssocItem: Information about an associated item
AssocItems: A list of ty::AssocItems in definition order that allows for efficient lookup by name.
AsyncDestructor
BottomUpFolder
BoundConst
BoundRegion
BoundTy
BoundVar
CReaderCacheKey
Canonical: A “canonicalized” type V is one where all free inference variables have been rewritten to “canonical vars”. These are numbered starting from 0 in order of first appearance.
CanonicalQueryInput
CanonicalUserTypeAnnotation
CanonicalVarInfo: Information about a canonical variable that is included with the canonical value. This is sufficient information for code to create a copy of the canonical value in some other inference context, with fresh inference variables replacing the canonical values.
CanonicalVarValues: A set of values corresponding to the canonical variables from some Canonical. You can give these values to canonical_value.instantiate to instantiate them into the canonical value at the right places.
CaptureInfo: Part of MinCaptureInformationMap; describes the capture kind (&, &mut, move) for a particular capture as well as identifying the part of the source code that triggered this capture to occur.
CapturedPlace: A composite describing a Place that is captured by a closure.
Clause: A subset of predicates which can be assumed by the trait solver. They show up in an item’s where clauses, hence the name Clause, and may either be user-written (such as traits) or may be inserted during lowering.
ClosureArgs: A closure can be modeled as a struct that looks like:
ClosureArgsParts: Struct returned by split().
ClosureSizeProfileData
ClosureTypeInfo
Const
ConstConditions: ~const bounds for a given item. This is represented using a struct much like GenericPredicates, where you can either choose to only instantiate the “own” bounds or all of the bounds including those from the parent. This distinction is necessary for code like compare_method_predicate_entailment.
ConstInt: A type for representing any integer. Only used for printing.
ConstVid: A const variable ID.
CoroutineArgs: Similar to ClosureArgs; see the above documentation for more.
CoroutineArgsParts
CoroutineClosureArgs
CoroutineClosureArgsParts: See docs for explanation of how each argument is used.
CoroutineClosureSignature
CrateInherentImpls: 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).
CratePredicatesMap: 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.
CrateVariancesMap: 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.
CtxtInterners
CurrentGcx: This is used to get a reference to a GlobalCtxt if one is available.
DebruijnIndex: A De Bruijn index is a standard means of representing regions (and perhaps later types) in a higher-ranked setting. In particular, imagine a type like this:
DeducedParamAttrs: Parameter attributes that can only be determined by examining the body of a function instead of just its signature.
DelegationFnSig
Destructor
DestructuredConst: The constituent parts of a type level constant of kind ADT or array.
EarlyBinderIter
EarlyParamRegion
Expr
Feed: The same as TyCtxtFeed, but does not contain a TyCtxt. Use this to pass around when you have a TyCtxt elsewhere. Just an optimization to save space and not store hundreds of TyCtxtFeed in the resolver.
FieldDef
FloatVid: A floating-point (f32 or f64) type variable ID.
FnHeader
FnMutDelegate: A simple delegate taking 3 mutable functions. The used functions must always return the same result for each bound variable, no matter how frequently they are called.
FnSigTys
FreeRegionInfo: This struct contains information regarding a free parameter region, either a ReEarlyParam or ReLateParam.
GenSig
GenericArg: An entity in the Rust type system, which can be one of several kinds (types, lifetimes, and consts). To reduce memory usage, a GenericArg is an interned pointer, with the lowest 2 bits being reserved for a tag to indicate the type (Ty, Region, or Const) it points to.
GenericParamCount
GenericParamDef
GenericPredicates: Bounds on generics.
Generics: Information about the formal type/lifetime parameters associated with an item or method. Analogous to hir::Generics.
GlobalCtxt: See TyCtxt for details about this type.
ImplHeader: 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).
ImplTraitHeader
InferVarInfo
InlineConstArgs: An inline const is modeled like
InlineConstArgsParts: Struct returned by split().
Instance: An InstanceKind along with the args that are needed to substitute the instance.
InstantiatedPredicates: 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 instantiated with their values.
IntVid: An integral (u32, i32, usize, etc.) type variable ID.
IntrinsicDef
IsSuggestableVisitor
IterIdentityCopied
IterInstantiated
IterInstantiatedCopied
LateParamRegion: The parameter representation of late-bound function parameters, “some region at least as big as the scope fr.scope”.
MainDefinition
MakeSuggestableFolder
MaxUniverse: Finds the max universe present
OpaqueHiddenType
ParamConst
ParamEnv: When interacting with the type system we must provide information about the environment. ParamEnv is the type that represents this information. See the dev guide chapter for more information.
ParamEnvAnd
ParamTy
Placeholder: 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.
Predicate: A statement that can be proven by a trait solver. This includes things that may show up in where clauses, such as trait predicates and projection predicates, and also things that are emitted as part of type checking such as DynCompatible predicate which is emitted when a type is coerced to a trait object.
PseudoCanonicalInput: Similar to CanonicalInput, this carries the typing_mode and the environment necessary to do any kind of trait solving inside of nested queries.
Region: Use this rather than RegionKind, whenever possible.
RegionFolder: Folds over the substructure of a type, visiting its component types and all regions that occur free within it.
RegionVid: A region variable ID.
ResolverAstLowering: Resolutions that should only be used for lowering. This struct is meant to be consumed by lowering.
ResolverGlobalCtxt
ResolverOutputs
Rust2024IncompatiblePatInfo: Information on a pattern incompatible with Rust 2024, for use by the error/migration diagnostic emitted during THIR construction.
RvalueScopes: RvalueScopes is a mapping from sub-expressions to extended lifetime as determined by rules laid out in rustc_hir_analysis::check::rvalue_scopes.
ScalarInt: The raw bytes of a simple value.
ShortInstance
StaticLifetimeVisitor: Collect al types that have an implicit 'static obligation that we could suggest '_ for.
SymbolName
Term
TraitObjectVisitor: Collect al types that have an implicit 'static obligation that we could suggest '_ for.
Ty: Use this rather than TyKind, whenever possible.
TyCtxt: The central data structure of the compiler. It stores references to the various arenas and also houses the results of the various compiler queries that have been performed. See the rustc dev guide for more details.
TyCtxtFeed: This struct should only be created by create_def.
TyVid: A type variable ID.
TypeFlags: Flags that we track on types. These flags are propagated upwards through the type during type construction, so that we can quickly check whether the type has various kinds of types in it without recursing over the type itself.
TypeckResults
TypingEnv: The environment in which to do trait solving.
UniverseIndex: “Universes” are used during type- and trait-checking in the presence of for<..> binders to control what sets of names are visible. Universes are arranged into a tree: the root universe contains names that are always visible. Each child then adds a new set of names that are visible, in addition to those of its parent. We say that the child universe “extends” the parent universe with new names.
UnsafeBinderInner
UnusedGenericParams
UpvarId: Upvars do not get their own NodeId. Instead, we use the pair of the original var ID (that is, the root variable that is referenced by the upvar) and the ID of the closure expression.
UpvarPath
UserArgs: Stores the user-given args to reach some fully qualified path (e.g., <T>::Item or <T as Trait>::Item).
UserSelfTy: Specifies the user-given self type. In the case of a path that refers to a member in an inherent impl, this self type is sometimes needed to constrain the type parameters on the impl. For example, in this code:
UserType
UserTypeAnnotationIndex
ValTree: An interned valtree. Use this rather than ValTreeKind, whenever possible.
ValidateBoundVars
Value: A type-level constant value.
VariantDef: Definition of a variant – a struct’s fields or an enum variant.
VariantFlags
WithCachedTypeInfo: A helper type that you can wrap round your own type in order to automatically cache the stable hash, type flags and debruijn index on creation and not recompute it whenever the information is needed. This is only done in incremental mode. You can also opt out of caching by using StableHash::ZERO for the hash, in which case the hash gets computed each time. This is useful if you have values that you intern but never (can?) use for stable hashing.

Enums§

AdtKind
AliasRelationDirection
AliasTermKind
AliasTyKind
AssocItemContainer
AssocKind
Asyncness
BorrowKind
BoundConstness
BoundRegionKind
BoundTyKind
BoundVariableKind
CanonicalTyVarKind: Rust actually has more than one category of type variables; notably, the type variables we create for literals (e.g., 22 or 22.) can only be instantiated with integral/float types (e.g., usize or f32). In order to faithfully reproduce a type, we need to know what set of types a given type variable can be unified with.
CanonicalVarKind: Describes the “kind” of the canonical variable. This is a “kind” in the type-theory sense of the term – i.e., a “meta” type system that analyzes type-like values.
ClosureKind: Represents the various closure traits in the language. This will determine the type of the environment (self, in the desugaring) argument that the closure expects.
DynKind: Specifies how a trait object is represented.
ExprKind
FloatTy
FloatVarValue
GenericParamDefKind
ImplOverlapKind
ImplPolarity
ImplSubject
ImplTraitInTraitData: Useful source information about where a desugared associated type for an RPITIT originated from.
InferConst: An inference variable for a const, for use in const generics.
InferTy: A placeholder for a type that hasn’t been inferred yet.
InstanceKind
IntTy
IntVarValue
LateParamRegionKind: When liberating bound regions, we map their BoundRegionKind to this as we need to track the index of anonymous regions. We otherwise end up liberating multiple bound regions to the same late-bound region.
Movability: The movability of a coroutine / closure literal: whether a coroutine contains self-references, causing it to be !Unpin.
Mutability
ParamTerm
Pinnedness
PredicatePolarity: Polarity for a trait predicate. May either be negative or positive. Distinguished from ImplPolarity since we never compute goals with “reservation” level.
ReifyReason: Describes why a ReifyShim was created. This is needed to distinguish a ReifyShim created to adjust for things like #[track_caller] in a vtable from a ReifyShim created to produce a function pointer from a vtable entry. Currently, this is only used when KCFI is enabled, as only KCFI needs to treat those two ReifyShims differently.
Representability
TermVid
UintTy
UpvarArgs
UpvarCapture: Information describing the capture of an upvar. This is computed during typeck, specifically by regionck.
UserTypeKind: A user-given type annotation attached to a constant. These arise from constants that are named via paths, like Foo::<A>::new and so forth.
ValTreeKind: This datastructure is used to represent the value of constants used in the type system.
Variance
VarianceDiagInfo: Extra information about why we ended up with a particular variance. This is only used to add more information to error messages, and has no effect on soundness. While choosing the ‘wrong’ VarianceDiagInfo may lead to confusing notes in error messages, it will never cause a miscompilation or unsoundness.
VariantDiscr
Visibility

Constants§

CAPTURE_STRUCT_LOCAL: Captures are represented using fields inside a structure. This represents accessing self in the closure structure
CONST_TAG 🔒
INNERMOST
TAG_MASK 🔒
TYPE_TAG 🔒

Traits§

Article
BoundVarReplacerDelegate: A delegate used when instantiating bound vars.
CollectAndApply: Imagine you have a function F: FnOnce(&[T]) -> R, plus an iterator iter that produces T items. You could combine them with f(&iter.collect::<Vec<_>>()), but this requires allocating memory for the Vec.
CoroutineArgsExt
ExistentialPredicateStableCmpExt
FallibleTypeFolder: This trait is implemented for every folding traversal. There is a fold method defined for every type of interest. Each such method has a default that does an “identity” fold.
Flags
InferCtxtLike
Interner
IsIdentity
IsSuggestable
Lift: A trait implemented for all X<'a> types that can be safely and efficiently converted to X<'tcx> as long as they are part of the provided TyCtxt<'tcx>. This can be done, for example, for Ty<'tcx> or GenericArgsRef<'tcx> by looking them up in their respective interners.
ParameterizedOverTcx
TermKindPackExt
TypeFoldable: This trait is implemented for every type that can be folded, providing the skeleton of the traversal.
TypeFolder: This trait is implemented for every infallible folding traversal. There is a fold method defined for every type of interest. Each such method has a default that does an “identity” fold. Implementations of these methods often fall back to a super_fold_with method if the primary argument doesn’t satisfy a particular condition.
TypeSuperFoldable
TypeSuperVisitable
TypeVisitable: This trait is implemented for every type that can be visited, providing the skeleton of the traversal.
TypeVisitableExt
TypeVisitor: This trait is implemented for every visiting traversal. There is a visit method defined for every type of interest. Each such method has a default that recurses into the type’s fields in a non-custom fashion.
Upcast: An Into-like trait that takes TyCtxt to perform interner-specific transformations.
UpcastFrom: A From-like trait that takes TyCtxt to perform interner-specific transformations.
VisitorResult: Similar to the Try trait, but also implemented for ().

Functions§

analyze_coroutine_closure_captures
ast_int_ty
ast_uint_ty
debug_bound_var
float_ty
fold_regions
int_ty
is_ancestor_or_same_capture: Return true if the proj_possible_ancestor represents an ancestor path to proj_capture or proj_possible_ancestor is same as proj_capture, assuming they both start off of the same root variable.
place_to_string_for_capture
provide
shift_region
shift_vars
suggest_arbitrary_trait_bound
suggest_constraining_type_param: Suggest restricting a type param with a new bound.
suggest_constraining_type_params: Suggest restricting a type param with a new bound.
uint_ty

Type Aliases§

AliasTerm
AliasTy
Binder
CanonicalPolyFnSig
CanonicalUserType: Canonical user type annotation.
CanonicalUserTypeAnnotations: Mapping of type annotation indices to canonical user type annotations.
ClauseKind
Clauses
CoercePredicate
ConstKind
EarlyBinder
ExistentialPredicate
ExistentialProjection
ExistentialTraitRef
FnSig
GenericArgKind
GenericArgs: List of generic arguments that are gonna be used to replace generic parameters.
GenericArgsRef
HostEffectPredicate
List: List<T> is a bit like &[T], but with some critical differences.
ListWithCachedTypeInfo: A List that additionally stores type information inline to speed up TypeVisitableExt operations.
MinCaptureInformationMap: Given the closure DefId this map provides a map of root variables to minimum set of CapturedPlaces that need to be tracked to support all captures of that closure.
MinCaptureList: Part of MinCaptureInformationMap; List of CapturePlaces.
NormalizesTo
OpaqueTypeKey
OutlivesPredicate
PlaceholderConst
PlaceholderRegion
PlaceholderType
PolyCoercePredicate
PolyExistentialPredicate
PolyExistentialProjection
PolyExistentialTraitRef
PolyFnSig
PolyProjectionPredicate
PolyRegionOutlivesPredicate
PolySubtypePredicate
PolyTraitPredicate
PolyTraitRef
PolyTypeOutlivesPredicate
PredicateKind
ProjectionPredicate
RegionKind
RegionOutlivesPredicate
RegisteredTools
RootVariableMinCaptureList: Part of MinCaptureInformationMap; Maps a root variable to the list of CapturedPlace. Used to track the minimum set of Places that need to be captured to support all Places captured by the closure starting at a given root variable.
SubtypePredicate
TermKind
TraitPredicate
TraitRef
TyKind
TypeAndMut
TypeOutlivesPredicate
TypingMode
UnevaluatedConst

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