Enum rustc_middle::ty::TyKind

pub enum TyKind<I>where
    I: Interner,{
    Bool,
    Char,
    Int(IntTy),
    Uint(UintTy),
    Float(FloatTy),
    Adt(<I as Interner>::AdtDef, <I as Interner>::SubstsRef),
    Foreign(<I as Interner>::DefId),
    Str,
    Array(<I as Interner>::Ty, <I as Interner>::Const),
    Slice(<I as Interner>::Ty),
    RawPtr(<I as Interner>::TypeAndMut),
    Ref(<I as Interner>::Region, <I as Interner>::Ty, <I as Interner>::Mutability),
    FnDef(<I as Interner>::DefId, <I as Interner>::SubstsRef),
    FnPtr(<I as Interner>::PolyFnSig),
    Dynamic(<I as Interner>::ListBinderExistentialPredicate, <I as Interner>::Region, DynKind),
    Closure(<I as Interner>::DefId, <I as Interner>::SubstsRef),
    Generator(<I as Interner>::DefId, <I as Interner>::SubstsRef, <I as Interner>::Movability),
    GeneratorWitness(<I as Interner>::BinderListTy),
    Never,
    Tuple(<I as Interner>::ListTy),
    Projection(<I as Interner>::ProjectionTy),
    Opaque(<I as Interner>::DefId, <I as Interner>::SubstsRef),
    Param(<I as Interner>::ParamTy),
    Bound(DebruijnIndex, <I as Interner>::BoundTy),
    Placeholder(<I as Interner>::PlaceholderType),
    Infer(<I as Interner>::InferTy),
    Error(<I as Interner>::DelaySpanBugEmitted),
}

Defines the kinds of types used by the type system.

Types written by the user start out as hir::TyKind and get converted to this representation using AstConv::ast_ty_to_ty.

Variants

Bool

The primitive boolean type. Written as bool.

Char

The primitive character type; holds a Unicode scalar value (a non-surrogate code point). Written as char.

Int(IntTy)

A primitive signed integer type. For example, i32.

Uint(UintTy)

A primitive unsigned integer type. For example, u32.

Float(FloatTy)

A primitive floating-point type. For example, f64.

Adt(<I as Interner>::AdtDef, <I as Interner>::SubstsRef)

Algebraic data types (ADT). For example: structures, enumerations and unions.

For example, the type List<i32> would be represented using the AdtDef for struct List<T> and the substs [i32].

Note that generic parameters in fields only get lazily substituted by using something like adt_def.all_fields().map(|field| field.ty(tcx, substs)).

Foreign(<I as Interner>::DefId)

An unsized FFI type that is opaque to Rust. Written as extern type T.

Str

The pointee of a string slice. Written as str.

Array(<I as Interner>::Ty, <I as Interner>::Const)

An array with the given length. Written as [T; N].

Slice(<I as Interner>::Ty)

The pointee of an array slice. Written as [T].

RawPtr(<I as Interner>::TypeAndMut)

A raw pointer. Written as *mut T or *const T

Ref(<I as Interner>::Region, <I as Interner>::Ty, <I as Interner>::Mutability)

A reference; a pointer with an associated lifetime. Written as &'a mut T or &'a T.

FnDef(<I as Interner>::DefId, <I as Interner>::SubstsRef)

The anonymous type of a function declaration/definition. Each function has a unique type.

For the function fn foo() -> i32 { 3 } this type would be shown to the user as fn() -> i32 {foo}.

For example the type of bar here:

fn foo() -> i32 { 1 }
let bar = foo; // bar: fn() -> i32 {foo}

FnPtr(<I as Interner>::PolyFnSig)

A pointer to a function. Written as fn() -> i32.

Note that both functions and closures start out as either FnDef or Closure which can be then be coerced to this variant.

For example the type of bar here:

fn foo() -> i32 { 1 }
let bar: fn() -> i32 = foo;

Dynamic(<I as Interner>::ListBinderExistentialPredicate, <I as Interner>::Region, DynKind)

A trait object. Written as dyn for<'b> Trait<'b, Assoc = u32> + Send + 'a.

Closure(<I as Interner>::DefId, <I as Interner>::SubstsRef)

The anonymous type of a closure. Used to represent the type of |a| a.

Closure substs contain both the - potentially substituted - generic parameters of its parent and some synthetic parameters. See the documentation for ClosureSubsts for more details.

Generator(<I as Interner>::DefId, <I as Interner>::SubstsRef, <I as Interner>::Movability)

The anonymous type of a generator. Used to represent the type of |a| yield a.

For more info about generator substs, visit the documentation for GeneratorSubsts.

GeneratorWitness(<I as Interner>::BinderListTy)

A type representing the types stored inside a generator. This should only appear as part of the GeneratorSubsts.

Note that the captured variables for generators are stored separately using a tuple in the same way as for closures.

Unlike upvars, the witness can reference lifetimes from inside of the generator itself. To deal with them in the type of the generator, we convert them to higher ranked lifetimes bound by the witness itself.

Looking at the following example, the witness for this generator may end up as something like for<'a> [Vec<i32>, &'a Vec<i32>]:

#![feature(generators)]
|a| {
    let x = &vec![3];
    yield a;
    yield x[0];
}

Never

The never type !.

Tuple(<I as Interner>::ListTy)

A tuple type. For example, (i32, bool).

Projection(<I as Interner>::ProjectionTy)

The projection of an associated type. For example, <T as Trait<..>>::N.

Opaque(<I as Interner>::DefId, <I as Interner>::SubstsRef)

Opaque (impl Trait) type found in a return type.

The DefId comes either from

• the impl Trait ast::Ty node,
• or the type Foo = impl Trait declaration

For RPIT the substitutions are for the generics of the function, while for TAIT it is used for the generic parameters of the alias.

During codegen, tcx.type_of(def_id) can be used to get the underlying type.

Param(<I as Interner>::ParamTy)

A type parameter; for example, T in fn f<T>(x: T) {}.

Bound(DebruijnIndex, <I as Interner>::BoundTy)

Bound type variable, used to represent the 'a in for<'a> fn(&'a ()).

For canonical queries, we replace inference variables with bound variables, so e.g. when checking whether &'_ (): Trait<_> holds, we canonicalize that to for<'a, T> &'a (): Trait<T> and then convert the introduced bound variables back to inference variables in a new inference context when inside of the query.

See the rustc-dev-guide for more details about higher-ranked trait bounds and canonical queries.

Placeholder(<I as Interner>::PlaceholderType)

A placeholder type, used during higher ranked subtyping to instantiate bound variables.

Infer(<I as Interner>::InferTy)

A type variable used during type checking.

Similar to placeholders, inference variables also live in a universe to correctly deal with higher ranked types. Though unlike placeholders, that universe is stored in the InferCtxt instead of directly inside of the type.

Error(<I as Interner>::DelaySpanBugEmitted)

A placeholder for a type which could not be computed; this is propagated to avoid useless error messages.

Trait Implementations

impl<'tcx> Borrow<TyKind<TyCtxt<'tcx>>> for InternedInSet<'tcx, WithStableHash<TyS<'tcx>>>

fn borrow<'a>(&'a self) -> &'a TyKind<'tcx>

Immutably borrows from an owned value.

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.