trait Types extends AnyRef
EXPERIMENTAL
A trait that defines types and operations on them.
Type instances represent information about the type of a corresponding symbol. This includes its members (methods, fields, type parameters, nested classes, traits, etc.) either declared directly or inherited, its base types, its erasure and so on. Types also provide operations to test for type conformance or equivalence or for widening.
To instantiate a type, most of the time, the scala.reflect.api.TypeTags#typeOf method can be used. It takes
a type argument and produces a Type instance which represents that argument. For example:
scala> typeOf[List[Int]] res0: reflect.runtime.universe.Type = scala.List[Int]
In this example, a scala.reflect.api.Types#TypeRef is returned, which corresponds to the type constructor List
applied to the type argument Int.
Note: Method typeOf does not work for types with type parameters, such as typeOf[List[A]] where A is
a type parameter. In this case, use scala.reflect.api.TypeTags#weakTypeOf instead.
For other ways to instantiate types, see the corresponding section of the Reflection Guide.
Common Operations on Types
Types are typically used for type conformance tests or are queried for declarations of members or inner types.
- Subtyping Relationships can be tested using
<:<andweak_<:<. - Type Equality can be checked with
=:=. It's important to note that==should not be used to compare types for equality--==can't check for type equality in the presence of type aliases, while=:=can.
Types can be queried for members and declarations by using the members and declarations methods (along with
their singular counterparts member and declaration), which provide the list of definitions associated with that type.
For example, to look up the map method of List, one can do:
scala> typeOf[List[_]].member("map": TermName) res1: reflect.runtime.universe.Symbol = method map
For more information about Types, see the Reflection Guide: Symbols, Trees, and Types
- Self Type
- Universe
- Source
- Types.scala
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Type Members
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abstract
type
AnnotatedType >: Null <: Universe.AnnotatedTypeApi with Universe.Type
The
AnnotatedTypetype signature is used for annotated types of the for<type> @<annotation>. -
trait
AnnotatedTypeApi extends Universe.TypeApi
The API that all annotated types support.
The API that all annotated types support. The main source of information about types is the scala.reflect.api.Types page.
-
abstract
class
AnnotatedTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
AnnotatedType(annotations, underlying).An extractor class to create and pattern match with syntax
AnnotatedType(annotations, underlying). Here,annotationsare the annotations decorating the underlying typeunderlying.selfSymis a symbol representing the annotated type itself. -
abstract
type
BoundedWildcardType >: Null <: Universe.BoundedWildcardTypeApi with Universe.Type
BoundedWildcardTypes, used only during type inference, are created in two places:
BoundedWildcardTypes, used only during type inference, are created in two places:
- If the expected type of an expression is an existential type, its hidden symbols are replaced with bounded wildcards. 2. When an implicit conversion is being sought based in part on the name of a method in the converted type, a HasMethodMatching type is created: a MethodType with parameters typed as BoundedWildcardTypes.
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trait
BoundedWildcardTypeApi extends Universe.TypeApi
The API that all this types support.
The API that all this types support. The main source of information about types is the scala.reflect.api.Types page.
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abstract
class
BoundedWildcardTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
BoundedWildcardTypeExtractor(bounds)withboundsdenoting the type bounds. -
abstract
type
ClassInfoType >: Null <: Universe.ClassInfoTypeApi with Universe.CompoundType
The
ClassInfotype signature is used to define parents and declarations of classes, traits, and objects.The
ClassInfotype signature is used to define parents and declarations of classes, traits, and objects. If a class, trait, or object C is declared like thisC extends P_1 with ... with P_m { D_1; ...; D_n}
its
ClassInfotype has the following form:ClassInfo(List(P_1, ..., P_m), Scope(D_1, ..., D_n), C) -
trait
ClassInfoTypeApi extends Universe.TypeApi
The API that all class info types support.
The API that all class info types support. The main source of information about types is the scala.reflect.api.Types page.
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abstract
class
ClassInfoTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
ClassInfo(parents, decls, clazz)Here,parentsis the list of parent types of the class,declsis the scope containing all declarations in the class, andclazzis the symbol of the class itself. -
abstract
type
CompoundType >: Null <: Universe.CompoundTypeApi with Universe.Type
A subtype of Type representing refined types as well as
ClassInfosignatures. -
trait
CompoundTypeApi extends AnyRef
Has no special methods.
Has no special methods. Is here to provides erased identity for
CompoundType. -
abstract
type
ConstantType >: Null <: Universe.ConstantTypeApi with Universe.SingletonType
The
ConstantTypetype is not directly written in user programs, but arises as the type of a constant.The
ConstantTypetype is not directly written in user programs, but arises as the type of a constant. The REPL expresses constant types likeInt(11). Here are some constants with their types:1 ConstantType(Constant(1)) "abc" ConstantType(Constant("abc"))
-
trait
ConstantTypeApi extends Universe.TypeApi
The API that all constant types support.
The API that all constant types support. The main source of information about types is the scala.reflect.api.Types page.
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abstract
class
ConstantTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
ConstantType(constant)Here,constantis the constant value represented by the type. -
abstract
type
ExistentialType >: Null <: Universe.ExistentialTypeApi with Universe.Type
The
ExistentialTypetype signature is used for existential types and wildcard types. -
trait
ExistentialTypeApi extends Universe.TypeApi
The API that all existential types support.
The API that all existential types support. The main source of information about types is the scala.reflect.api.Types page.
-
abstract
class
ExistentialTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
ExistentialType(quantified, underlying).An extractor class to create and pattern match with syntax
ExistentialType(quantified, underlying). Here,quantifiedare the type variables bound by the existential type andunderlyingis the type that's existentially quantified. -
abstract
type
MethodType >: Null <: Universe.MethodTypeApi with Universe.Type
The
MethodTypetype signature is used to indicate parameters and result type of a method -
trait
MethodTypeApi extends Universe.TypeApi
The API that all method types support.
The API that all method types support. The main source of information about types is the scala.reflect.api.Types page.
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abstract
class
MethodTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
MethodType(params, restpe)Here,paramsis a potentially empty list of parameter symbols of the method, andrestpeis the result type of the method.An extractor class to create and pattern match with syntax
MethodType(params, restpe)Here,paramsis a potentially empty list of parameter symbols of the method, andrestpeis the result type of the method. If the method is curried,restpewould be anotherMethodType. Note:MethodType(Nil, Int)would be the type of a method defined with an empty parameter list.def f(): Int
If the method is completely parameterless, as in
def f: Int
its type is a
NullaryMethodType. -
abstract
type
NullaryMethodType >: Null <: Universe.NullaryMethodTypeApi with Universe.Type
The
NullaryMethodTypetype signature is used for parameterless methods with declarations of the formdef foo: T -
trait
NullaryMethodTypeApi extends Universe.TypeApi
The API that all nullary method types support.
The API that all nullary method types support. The main source of information about types is the scala.reflect.api.Types page.
-
abstract
class
NullaryMethodTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
NullaryMethodType(resultType).An extractor class to create and pattern match with syntax
NullaryMethodType(resultType). Here,resultTypeis the result type of the parameterless method. -
abstract
type
PolyType >: Null <: Universe.PolyTypeApi with Universe.Type
The
PolyTypetype signature is used for polymorphic methods that have at least one type parameter. -
trait
PolyTypeApi extends Universe.TypeApi
The API that all polymorphic types support.
The API that all polymorphic types support. The main source of information about types is the scala.reflect.api.Types page.
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abstract
class
PolyTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
PolyType(typeParams, resultType).An extractor class to create and pattern match with syntax
PolyType(typeParams, resultType). Here,typeParamsare the type parameters of the method andresultTypeis the type signature following the type parameters. -
abstract
type
RefinedType >: Null <: Universe.RefinedTypeApi with Universe.CompoundType
The
RefinedTypetype defines types of any of the forms on the left, with their RefinedType representations to the right.The
RefinedTypetype defines types of any of the forms on the left, with their RefinedType representations to the right.P_1 with ... with P_m { D_1; ...; D_n} RefinedType(List(P_1, ..., P_m), Scope(D_1, ..., D_n)) P_1 with ... with P_m RefinedType(List(P_1, ..., P_m), Scope()) { D_1; ...; D_n} RefinedType(List(AnyRef), Scope(D_1, ..., D_n))
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trait
RefinedTypeApi extends Universe.TypeApi
The API that all refined types support.
The API that all refined types support. The main source of information about types is the scala.reflect.api.Types page.
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abstract
class
RefinedTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
RefinedType(parents, decls)Here,parentsis the list of parent types of the class, anddeclsis the scope containing all declarations in the class. -
abstract
type
SingleType >: Null <: Universe.SingleTypeApi with Universe.SingletonType
The
SingleTypetype describes types of any of the forms on the left, with their TypeRef representations to the right.The
SingleTypetype describes types of any of the forms on the left, with their TypeRef representations to the right.(T # x).type SingleType(T, x) p.x.type SingleType(p.type, x) x.type SingleType(NoPrefix, x)
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trait
SingleTypeApi extends Universe.TypeApi
The API that all single types support.
The API that all single types support. The main source of information about types is the scala.reflect.api.Types page.
-
abstract
class
SingleTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
SingleType(pre, sym)Here,preis the prefix of the single-type, andsymis the stable value symbol referred to by the single-type. -
abstract
type
SingletonType >: Null <: Universe.SingletonTypeApi with Universe.Type
The type of Scala singleton types, i.e., types that are inhabited by only one nun-null value.
The type of Scala singleton types, i.e., types that are inhabited by only one nun-null value. These include types of the forms
C.this.type C.super.type x.type
as well as constant types.
-
trait
SingletonTypeApi extends AnyRef
Has no special methods.
Has no special methods. Is here to provides erased identity for
SingletonType. -
abstract
type
SuperType >: Null <: Universe.SuperTypeApi with Universe.SingletonType
The
SuperTypetype is not directly written, but arises whenC.superis used as a prefix in aTypeReforSingleType.The
SuperTypetype is not directly written, but arises whenC.superis used as a prefix in aTypeReforSingleType. It's internal presentation isSuperType(thistpe, supertpe)
Here,
thistpeis the type of the corresponding this-type. For instance, in the type arising from C.super, thethistpepart would beThisType(C).supertpeis the type of the super class referred to by thesuper. -
trait
SuperTypeApi extends Universe.TypeApi
The API that all super types support.
The API that all super types support. The main source of information about types is the scala.reflect.api.Types page.
-
abstract
class
SuperTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
SingleType(thistpe, supertpe) -
abstract
type
ThisType >: Null <: Universe.ThisTypeApi with Universe.SingletonType
A singleton type that describes types of the form on the left with the corresponding
ThisTyperepresentation to the right:A singleton type that describes types of the form on the left with the corresponding
ThisTyperepresentation to the right:C.this.type ThisType(C)
-
trait
ThisTypeApi extends Universe.TypeApi
The API that all this types support.
The API that all this types support. The main source of information about types is the scala.reflect.api.Types page.
-
abstract
class
ThisTypeExtractor extends AnyRef
An extractor class to create and pattern match with syntax
ThisType(sym)wheresymis the class prefix of the this type. -
abstract
type
Type >: Null <: Universe.TypeApi
The type of Scala types, and also Scala type signatures.
The type of Scala types, and also Scala type signatures. (No difference is internally made between the two).
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abstract
class
TypeApi extends AnyRef
The API of types.
The API of types. The main source of information about types is the scala.reflect.api.Types page.
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abstract
type
TypeBounds >: Null <: Universe.TypeBoundsApi with Universe.Type
The
TypeBoundstype signature is used to indicate lower and upper type bounds of type parameters and abstract types.The
TypeBoundstype signature is used to indicate lower and upper type bounds of type parameters and abstract types. It is not a first-class type. If an abstract type or type parameter is declared with any of the forms on the left, its type signature is the TypeBounds type on the right.T >: L <: U TypeBounds(L, U) T >: L TypeBounds(L, Any) T <: U TypeBounds(Nothing, U)
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trait
TypeBoundsApi extends Universe.TypeApi
The API that all type bounds support.
The API that all type bounds support. The main source of information about types is the scala.reflect.api.Types page.
-
abstract
class
TypeBoundsExtractor extends AnyRef
An extractor class to create and pattern match with syntax
TypeBound(lower, upper)Here,loweris the lower bound of theTypeBoundspair, andupperis the upper bound. -
abstract
type
TypeRef >: Null <: Universe.TypeRefApi with Universe.Type
The
TypeReftype describes types of any of the forms on the left, with their TypeRef representations to the right.The
TypeReftype describes types of any of the forms on the left, with their TypeRef representations to the right.T # C[T_1, ..., T_n] TypeRef(T, C, List(T_1, ..., T_n)) p.C[T_1, ..., T_n] TypeRef(p.type, C, List(T_1, ..., T_n)) C[T_1, ..., T_n] TypeRef(NoPrefix, C, List(T_1, ..., T_n)) T # C TypeRef(T, C, Nil) p.C TypeRef(p.type, C, Nil) C TypeRef(NoPrefix, C, Nil)
-
trait
TypeRefApi extends Universe.TypeApi
The API that all type refs support.
The API that all type refs support. The main source of information about types is the scala.reflect.api.Types page.
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abstract
class
TypeRefExtractor extends AnyRef
An extractor class to create and pattern match with syntax
TypeRef(pre, sym, args)Here,preis the prefix of the type reference,symis the symbol referred to by the type reference, andargsis a possible empty list of type arguments.
Abstract Value Members
-
abstract
val
AnnotatedType: Universe.AnnotatedTypeExtractor
The constructor/extractor for
AnnotatedTypeinstances. -
abstract
val
BoundedWildcardType: Universe.BoundedWildcardTypeExtractor
The constructor/extractor for
BoundedWildcardTypeinstances. -
abstract
val
ClassInfoType: Universe.ClassInfoTypeExtractor
The constructor/extractor for
ClassInfoTypeinstances. -
abstract
val
ConstantType: Universe.ConstantTypeExtractor
The constructor/extractor for
ConstantTypeinstances. -
abstract
val
ExistentialType: Universe.ExistentialTypeExtractor
The constructor/extractor for
ExistentialTypeinstances. -
abstract
val
MethodType: Universe.MethodTypeExtractor
The constructor/extractor for
MethodTypeinstances. -
abstract
val
NoPrefix: Universe.Type
This constant is used as a special value denoting the empty prefix in a path dependent type.
This constant is used as a special value denoting the empty prefix in a path dependent type. For instance
x.typeis represented asSingleType(NoPrefix, <x>), where<x>stands for the symbol forx. -
abstract
val
NoType: Universe.Type
This constant is used as a special value that indicates that no meaningful type exists.
-
abstract
val
NullaryMethodType: Universe.NullaryMethodTypeExtractor
The constructor/extractor for
NullaryMethodTypeinstances. -
abstract
val
PolyType: Universe.PolyTypeExtractor
The constructor/extractor for
PolyTypeinstances. -
abstract
val
RefinedType: Universe.RefinedTypeExtractor
The constructor/extractor for
RefinedTypeinstances. -
abstract
val
SingleType: Universe.SingleTypeExtractor
The constructor/extractor for
SingleTypeinstances. -
abstract
val
SuperType: Universe.SuperTypeExtractor
The constructor/extractor for
SuperTypeinstances. -
abstract
val
ThisType: Universe.ThisTypeExtractor
The constructor/extractor for
ThisTypeinstances. -
abstract
val
TypeBounds: Universe.TypeBoundsExtractor
The constructor/extractor for
TypeBoundsinstances. -
abstract
val
TypeRef: Universe.TypeRefExtractor
The constructor/extractor for
TypeRefinstances. -
abstract
val
WildcardType: Universe.Type
An object representing an unknown type, used during type inference.
An object representing an unknown type, used during type inference. If you see WildcardType outside of inference it is almost certainly a bug.
-
abstract
def
appliedType(sym: Universe.Symbol, args: Universe.Type*): Universe.Type
- See also
-
abstract
def
appliedType(sym: Universe.Symbol, args: List[Universe.Type]): Universe.Type
- See also
-
abstract
def
appliedType(tycon: Universe.Type, args: Universe.Type*): Universe.Type
- See also
-
abstract
def
appliedType(tycon: Universe.Type, args: List[Universe.Type]): Universe.Type
A creator for type applications
-
abstract
def
glb(ts: List[Universe.Type]): Universe.Type
The greatest lower bound of a list of types, as determined by
<:<. -
abstract
def
lub(xs: List[Universe.Type]): Universe.Type
The least upper bound of a list of types, as determined by
<:<.
Concrete Value Members
-
final
def
!=(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
##(): Int
- Definition Classes
- AnyRef → Any
- def +(other: String): String
- def ->[B](y: B): (Types, B)
-
final
def
==(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
asInstanceOf[T0]: T0
- Definition Classes
- Any
-
def
clone(): AnyRef
- Attributes
- protected[java.lang]
- Definition Classes
- AnyRef
- Annotations
- @native() @throws( ... )
- def ensuring(cond: (Types) ⇒ Boolean, msg: ⇒ Any): Types
- def ensuring(cond: (Types) ⇒ Boolean): Types
- def ensuring(cond: Boolean, msg: ⇒ Any): Types
- def ensuring(cond: Boolean): Types
-
final
def
eq(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
def
equals(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
def
finalize(): Unit
- Attributes
- protected[java.lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( classOf[java.lang.Throwable] )
- def formatted(fmtstr: String): String
-
final
def
getClass(): Class[_]
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
def
hashCode(): Int
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
final
def
isInstanceOf[T0]: Boolean
- Definition Classes
- Any
-
final
def
ne(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
final
def
notify(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
final
def
notifyAll(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
def
toString(): String
- Definition Classes
- AnyRef → Any
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @native() @throws( ... )
- def →[B](y: B): (Types, B)
Inherited from AnyRef
Inherited from Any
Types - Operations
Types
API
The methods available for each reflection entity, without the implementation. Since the reflection entities are later overridden by runtime reflection and macros, their API counterparts guarantee a minimum set of methods that are implemented.
Extractors
Extractors provide the machinery necessary to allow pattern matching and construction of reflection entities that is similar to case classes, although the entities are only abstract types that are later overridden.