The AnnotatedType
type signature is used for annotated types of the
for <type> @<annotation>
.
The API that all annotated types support.
An extractor class to create and pattern match with syntax
AnnotatedType(annotations, underlying)
.
BoundedWildcardTypes, used only during type inference, are created in two places:
The API that all this types support.
An extractor class to create and pattern match with syntax BoundedWildcardTypeExtractor(bounds)
with bounds
denoting the type bounds.
The ClassInfo
type signature is used to define parents and declarations
of classes, traits, and objects.
The API that all class info types support.
An extractor class to create and pattern match with syntax ClassInfo(parents, decls, clazz)
Here, parents
is the list of parent types of the class, decls
is the scope
containing all declarations in the class, and clazz
is the symbol of the class
itself.
A subtype of Type representing refined types as well as ClassInfo
signatures.
Has no special methods.
The ConstantType
type is not directly written in user programs, but arises as the type of a constant.
The API that all constant types support.
An extractor class to create and pattern match with syntax ConstantType(constant)
Here, constant
is the constant value represented by the type.
The ExistentialType
type signature is used for existential types and
wildcard types.
The API that all existential types support.
An extractor class to create and pattern match with syntax
ExistentialType(quantified, underlying)
.
The MethodType
type signature is used to indicate parameters and result type of a method
The API that all method types support.
An extractor class to create and pattern match with syntax MethodType(params, respte)
Here, params
is a potentially empty list of parameter symbols of the method,
and restpe
is the result type of the method.
The NullaryMethodType
type signature is used for parameterless methods
with declarations of the form def foo: T
The API that all nullary method types support.
An extractor class to create and pattern match with syntax NullaryMethodType(resultType)
.
The PolyType
type signature is used for polymorphic methods
that have at least one type parameter.
The API that all polymorphic types support.
An extractor class to create and pattern match with syntax PolyType(typeParams, resultType)
.
The RefinedType
type defines types of any of the forms on the left,
with their RefinedType representations to the right.
The API that all refined types support.
An extractor class to create and pattern match with syntax RefinedType(parents, decls)
Here, parents
is the list of parent types of the class, and decls
is the scope
containing all declarations in the class.
The SingleType
type describes types of any of the forms on the left,
with their TypeRef representations to the right.
The API that all single types support.
An extractor class to create and pattern match with syntax SingleType(pre, sym)
Here, pre
is the prefix of the single-type, and sym
is the stable value symbol
referred to by the single-type.
The type of Scala singleton types, i.
Has no special methods.
The SuperType
type is not directly written, but arises when C.super
is used
as a prefix in a TypeRef
or SingleType
.
The API that all super types support.
An extractor class to create and pattern match with syntax SingleType(thistpe, supertpe)
A singleton type that describes types of the form on the left with the
corresponding ThisType
representation to the right:
The API that all this types support.
An extractor class to create and pattern match with syntax ThisType(sym)
where sym
is the class prefix of the this type.
The type of Scala types, and also Scala type signatures.
The API of types.
The TypeBounds
type signature is used to indicate lower and upper type bounds
of type parameters and abstract types.
The API that all type bounds support.
An extractor class to create and pattern match with syntax TypeBound(lower, upper)
Here, lower
is the lower bound of the TypeBounds
pair, and upper
is
the upper bound.
The TypeRef
type describes types of any of the forms on the left,
with their TypeRef representations to the right.
The API that all type refs support.
An extractor class to create and pattern match with syntax TypeRef(pre, sym, args)
Here, pre
is the prefix of the type reference, sym
is the symbol
referred to by the type reference, and args
is a possible empty list of
type argumenrts.
The constructor/extractor for AnnotatedType
instances.
The constructor/extractor for BoundedWildcardType
instances.
The constructor/extractor for ClassInfoType
instances.
The constructor/extractor for ConstantType
instances.
The constructor/extractor for ExistentialType
instances.
The constructor/extractor for MethodType
instances.
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.type
is represented as SingleType(NoPrefix, <x>)
, where <x>
stands for
the symbol for x
.
This constant is used as a special value that indicates that no meaningful type exists.
The constructor/extractor for NullaryMethodType
instances.
The constructor/extractor for PolyType
instances.
The constructor/extractor for RefinedType
instances.
The constructor/extractor for SingleType
instances.
The constructor/extractor for SuperType
instances.
The constructor/extractor for ThisType
instances.
The constructor/extractor for TypeBounds
instances.
The constructor/extractor for TypeRef
instances.
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.
A creator for type applications
The greatest lower bound of a list of types, as determined by <:<
.
The least upper bound of a list of types, as determined by <:<
.
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 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.
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:In this example, a scala.reflect.api.Types#TypeRef is returned, which corresponds to the type constructor
List
applied to the type argumentInt
.Note: Method
typeOf
does not work for types with type parameters, such astypeOf[List[A]]
whereA
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.
<:<
andweak_<:<
.=:=
. 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
anddeclarations
methods (along with their singular counterpartsmember
anddeclaration
), which provide the list of definitions associated with that type. For example, to look up themap
method ofList
, one can do:For more information about
Type
s, see the Reflection Guide: Symbols, Trees, and Types