Expand description
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§
- A subset of a mir body used for const evaluability checking.
- adt 🔒
- assoc 🔒
- closure 🔒
- This module contains some shared code for encoding and decoding various things from the
tymodule, 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.
- Diagnostics related methods for
Ty. - generics 🔒
- impls_
ty 🔒This module containsHashStableimplementations for various data types fromrustc_middle::tyin no particular order. - This module contains logic for determining whether a type is inhabited or uninhabited. The
InhabitedPredicatetype captures the minimum information needed to determine whether a type is inhabited given aParamEnvand module ID. - Set of traits which are used to emulate the inherent impls that are present in
rustc_middle. It is customary to glob-importrustc_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 🔒
- list 🔒
- 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(...). - The outlives relation
T: 'aor'a: 'b. This code frequently refers to rules defined in RFC 1214 (OutlivesFooBar), so see that RFC for reference. - region 🔒
- This module contains implementations of the
Lift,TypeFoldableandTypeVisitabletraits 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
TyKindand its major components. - Miscellaneous type-system utilities that are too small to deserve their own modules.
- An iterator over the type substructure. WARNING: this does not keep track of the region depth.
Macros§
Structs§
- The definition of a user-defined type, e.g., a
struct,enum, orunion. - Information about an associated item
- A list of
ty::AssocItems in definition order that allows for efficient lookup by name. - A “canonicalized” type
Vis one where all free inference variables have been rewritten to “canonical vars”. These are numbered starting from 0 in order of first appearance. - 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.
- A set of values corresponding to the canonical variables from some
Canonical. You can give these values tocanonical_value.instantiateto instantiate them into the canonical value at the right places. - 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. - A composite describing a
Placethat is captured by a closure. - 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. - A closure can be modeled as a struct that looks like:
- Struct returned by
split(). ~constbounds for a given item. This is represented using a struct much likeGenericPredicates, 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 likecompare_method_predicate_entailment.- A type for representing any integer. Only used for printing.
- A
constvariable ID. - Similar to
ClosureArgs; see the above documentation for more. - See docs for explanation of how each argument is used.
- 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). - 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. - 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. - This is used to get a reference to a
GlobalCtxtif one is available. - 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:
- Parameter attributes that can only be determined by examining the body of a function instead of just its signature.
- The constituent parts of a type level constant of kind ADT or array.
- The same as
TyCtxtFeed, but does not contain aTyCtxt. Use this to pass around when you have aTyCtxtelsewhere. Just an optimization to save space and not store hundreds ofTyCtxtFeedin the resolver. - A floating-point (
f32orf64) type variable ID. - This struct contains information regarding a free parameter region, either a
ReEarlyParamorReLateParam. - An entity in the Rust type system, which can be one of several kinds (types, lifetimes, and consts). To reduce memory usage, a
GenericArgis an interned pointer, with the lowest 2 bits being reserved for a tag to indicate the type (Ty,Region, orConst) it points to. - Bounds on generics.
- Information about the formal type/lifetime parameters associated with an item or method. Analogous to
hir::Generics. - See TyCtxt for details about this type.
- 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).
- An inline const is modeled like
- Struct returned by
split(). - An
InstanceKindalong with the args that are needed to substitute the instance. - 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
InstantiatedPredicateslist from aGenericPredicatesby using theinstantiatemethod. Note that this method reflects an important semantic invariant ofInstantiatedPredicates: while theGenericPredicatesare expressed in terms of the bound type parameters of the impl/trait/whatever, anInstantiatedPredicatesinstance represented a set of bounds for some particular instantiation, meaning that the generic parameters have been instantiated with their values. - An integral (
u32,i32,usize, etc.) type variable ID. - The parameter representation of late-bound function parameters, “some region at least as big as the scope
fr.scope”. - When interacting with the type system we must provide information about the environment.
ParamEnvis the type that represents this information. See the dev guide chapter for more information. - 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.
- 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
DynCompatiblepredicate which is emitted when a type is coerced to a trait object. - Similar to
CanonicalInput, this carries thetyping_modeand the environment necessary to do any kind of trait solving inside of nested queries. - Use this rather than
RegionKind, whenever possible. - A region variable ID.
- Resolutions that should only be used for lowering. This struct is meant to be consumed by lowering.
RvalueScopesis a mapping from sub-expressions to extended lifetime as determined by rules laid out inrustc_hir_analysis::check::rvalue_scopes.- The raw bytes of a simple value.
- Collect al types that have an implicit
'staticobligation that we could suggest'_for. - Collect al types that have an implicit
'staticobligation that we could suggest'_for. - Use this rather than
TyKind, whenever possible. - 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.
- This struct should only be created by
create_def. - A type variable ID.
- 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.
- The environment in which to do trait solving.
- “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. - 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. - Stores the user-given args to reach some fully qualified path (e.g.,
<T>::Itemor<T as Trait>::Item). - 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:
- Definition of a variant – a struct’s fields or an enum variant.
- 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§
- 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.
- 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.
- 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. - Specifies how a trait object is represented.
- Useful source information about where a desugared associated type for an RPITIT originated from.
- An inference variable for a const, for use in const generics.
- A placeholder for a type that hasn’t been inferred yet.
- When liberating bound regions, we map their
BoundRegionKindto 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. - The movability of a coroutine / closure literal: whether a coroutine contains self-references, causing it to be
!Unpin. - Polarity for a trait predicate. May either be negative or positive. Distinguished from
ImplPolaritysince we never compute goals with “reservation” level. - Describes why a
ReifyShimwas created. This is needed to distinguish a ReifyShim created to adjust for things like#[track_caller]in a vtable from aReifyShimcreated 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 twoReifyShims differently. - Information describing the capture of an upvar. This is computed during
typeck, specifically byregionck. - A user-given type annotation attached to a constant. These arise from constants that are named via paths, like
Foo::<A>::newand so forth. - This datastructure is used to represent the value of constants used in the type system.
- 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’
VarianceDiagInfomay lead to confusing notes in error messages, it will never cause a miscompilation or unsoundness.
Constants§
- Captures are represented using fields inside a structure. This represents accessing self in the closure structure
- The shorthand encoding uses an enum’s variant index
usizeand is offset by this value so it never matches a real variant. This offset is also chosen so that the first byte is never < 0x80. - TAG_
MASK 🔒 - TYPE_
TAG 🔒
Traits§
- Imagine you have a function
F: FnOnce(&[T]) -> R, plus an iteratoriterthat producesTitems. You could combine them withf(&iter.collect::<Vec<_>>()), but this requires allocating memory for theVec. - 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.
- A trait implemented for all
X<'a>types that can be safely and efficiently converted toX<'tcx>as long as they are part of the providedTyCtxt<'tcx>. This can be done, for example, forTy<'tcx>orGenericArgsRef<'tcx>by looking them up in their respective interners. - Trait for decoding to a reference.
- This trait is implemented for every type that can be folded, providing the skeleton of the traversal.
- 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_withmethod if the primary argument doesn’t satisfy a particular condition. - This trait is implemented for every type that can be visited, providing the skeleton of the traversal.
- 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.
- An
Into-like trait that takesTyCtxtto perform interner-specific transformations. - A
From-like trait that takesTyCtxtto perform interner-specific transformations.
Functions§
- Return true if the
proj_possible_ancestorrepresents an ancestor path toproj_captureorproj_possible_ancestoris same asproj_capture, assuming they both start off of the same root variable. - Suggest restricting a type param with a new bound.
- Suggest restricting a type param with a new bound.
Type Aliases§
- Canonical user type annotation.
- Mapping of type annotation indices to canonical user type annotations.
- List of generic arguments that are gonna be used to replace generic parameters.
List<T>is a bit like&[T], but with some critical differences.- A
Listthat additionally stores type information inline to speed upTypeVisitableExtoperations. - 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. - Part of
MinCaptureInformationMap; List ofCapturePlaces. - Part of
MinCaptureInformationMap; Maps a root variable to the list ofCapturedPlace. Used to track the minimum set ofPlaces that need to be captured to support all Places captured by the closure starting at a given root variable.