scala.reflect.api

Symbols

trait Symbols extends AnyRef

EXPERIMENTAL

This trait defines symbols and operations on them.

Symbols are used to establish bindings between a name and the entity it refers to, such as a class or a method. Anything you define and can give a name to in Scala has an associated symbol.

Symbols contain all available information about the declaration of an entity (class/object/trait etc.) or a member (vals/vars/defs etc.), and as such are an integral abstraction central to both runtime reflection and macros.

A symbol can provide a wealth of information ranging from the basic name method available on all symbols to other, more involved, concepts such as getting the baseClasses from ClassSymbol. Other common use cases of symbols include inspecting members' signatures, getting type parameters of a class, getting the parameter type of a method or finding out the type of a field.

Example usage of runtime reflection; getting a method's type signature:

scala> import scala.reflect.runtime.universe._
import scala.reflect.runtime.universe._

scala> class C[T] { def test[U](x: T)(y: U): Int = ??? }
defined class C

scala> val test = typeOf[C[Int]].member(newTermName("test")).asMethod
test: reflect.runtime.universe.MethodSymbol = method test

scala> test.typeSignature
res0: reflect.runtime.universe.Type = [U](x: T)(y: U)scala.Int

Symbols are organized in a hierarchy. For example, a symbol that represents a parameter of a method is owned by the corresponding method symbol, a method symbol is owned by its enclosing class, a class is owned by a containing package and so on.

Certain types of tree nodes, such as Ident (references to identifiers) and Select (references to members) expose method symbol to obtain the symbol that represents their declaration. During the typechecking phase, the compiler looks up the symbol based on the name and scope and sets the symbol field of tree nodes.

For more information about Symbol usage and attached intricacies, see the Reflection Guide: Symbols

Self Type
Universe
Source
Symbols.scala
Linear Supertypes
AnyRef, Any
Known Subclasses
JavaUniverse, JavaUniverse, Universe, Universe
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Inherited
  1. Symbols
  2. AnyRef
  3. Any
Implicitly
  1. by any2stringadd
  2. by any2stringfmt
  3. by any2ArrowAssoc
  4. by any2Ensuring
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Type Members

  1. abstract type ClassSymbol >: Null <: Universe.TypeSymbol with Universe.ClassSymbolApi

    The type of class symbols representing class and trait definitions.

  2. trait ClassSymbolApi extends Universe.TypeSymbolApi

    The API of class symbols.

  3. abstract type FreeTermSymbol >: Null <: Universe.TermSymbol with Universe.FreeTermSymbolApi

    The type of free terms introduced by reification.

  4. trait FreeTermSymbolApi extends Universe.TermSymbolApi

    The API of free term symbols.

  5. abstract type FreeTypeSymbol >: Null <: Universe.TypeSymbol with Universe.FreeTypeSymbolApi

    The type of free types introduced by reification.

  6. trait FreeTypeSymbolApi extends Universe.TypeSymbolApi

    The API of free type symbols.

  7. abstract type MethodSymbol >: Null <: Universe.TermSymbol with Universe.MethodSymbolApi

    The type of method symbols representing def declarations.

  8. trait MethodSymbolApi extends Universe.TermSymbolApi

    The API of method symbols.

  9. abstract type ModuleSymbol >: Null <: Universe.TermSymbol with Universe.ModuleSymbolApi

    The type of module symbols representing object declarations.

  10. trait ModuleSymbolApi extends Universe.TermSymbolApi

    The API of module symbols.

  11. abstract type Symbol >: Null <: Universe.SymbolApi

    The type of symbols representing declarations.

  12. trait SymbolApi extends AnyRef

    The API of symbols.

  13. abstract type TermSymbol >: Null <: Universe.Symbol with Universe.TermSymbolApi

    The type of term symbols representing val, var, def, and object declarations as well as packages and value parameters.

  14. trait TermSymbolApi extends Universe.SymbolApi

    The API of term symbols.

  15. abstract type TypeSymbol >: Null <: Universe.Symbol with Universe.TypeSymbolApi

    The type of type symbols representing type, class, and trait declarations, as well as type parameters.

  16. trait TypeSymbolApi extends Universe.SymbolApi

    The API of type symbols.

Abstract Value Members

  1. implicit abstract val ClassSymbolTag: ClassTag[Universe.ClassSymbol]

    A tag that preserves the identity of the ClassSymbol abstract type from erasure.

    A tag that preserves the identity of the ClassSymbol abstract type from erasure. Can be used for pattern matching, instance tests, serialization and likes.

  2. implicit abstract val FreeTermSymbolTag: ClassTag[Universe.FreeTermSymbol]

    A tag that preserves the identity of the FreeTermSymbol abstract type from erasure.

    A tag that preserves the identity of the FreeTermSymbol abstract type from erasure. Can be used for pattern matching, instance tests, serialization and likes.

  3. implicit abstract val FreeTypeSymbolTag: ClassTag[Universe.FreeTypeSymbol]

    A tag that preserves the identity of the FreeTypeSymbol abstract type from erasure.

    A tag that preserves the identity of the FreeTypeSymbol abstract type from erasure. Can be used for pattern matching, instance tests, serialization and likes.

  4. implicit abstract val MethodSymbolTag: ClassTag[Universe.MethodSymbol]

    A tag that preserves the identity of the MethodSymbol abstract type from erasure.

    A tag that preserves the identity of the MethodSymbol abstract type from erasure. Can be used for pattern matching, instance tests, serialization and likes.

  5. implicit abstract val ModuleSymbolTag: ClassTag[Universe.ModuleSymbol]

    A tag that preserves the identity of the ModuleSymbol abstract type from erasure.

    A tag that preserves the identity of the ModuleSymbol abstract type from erasure. Can be used for pattern matching, instance tests, serialization and likes.

  6. abstract val NoSymbol: Universe.Symbol

    A special "missing" symbol.

    A special "missing" symbol. Commonly used in the API to denote a default or empty value.

  7. implicit abstract val SymbolTag: ClassTag[Universe.Symbol]

    A tag that preserves the identity of the Symbol abstract type from erasure.

    A tag that preserves the identity of the Symbol abstract type from erasure. Can be used for pattern matching, instance tests, serialization and likes.

  8. implicit abstract val TermSymbolTag: ClassTag[Universe.TermSymbol]

    A tag that preserves the identity of the TermSymbol abstract type from erasure.

    A tag that preserves the identity of the TermSymbol abstract type from erasure. Can be used for pattern matching, instance tests, serialization and likes.

  9. implicit abstract val TypeSymbolTag: ClassTag[Universe.TypeSymbol]

    A tag that preserves the identity of the TypeSymbol abstract type from erasure.

    A tag that preserves the identity of the TypeSymbol abstract type from erasure. Can be used for pattern matching, instance tests, serialization and likes.

Concrete Value Members

  1. final def !=(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  2. final def !=(arg0: Any): Boolean

    Test two objects for inequality.

    Test two objects for inequality.

    returns

    true if !(this == that), false otherwise.

    Definition Classes
    Any

  3. final def ##(): Int

    Equivalent to x.hashCode except for boxed numeric types and null.

    Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.

    returns

    a hash value consistent with ==

    Definition Classes
    AnyRef → Any

  4. def +(other: String): String

    Implicit information
    This member is added by an implicit conversion from Symbols to StringAdd performed by method any2stringadd in scala.Predef.
    Definition Classes
    StringAdd

  5. def ->[B](y: B): (Symbols, B)

    Implicit information
    This member is added by an implicit conversion from Symbols to ArrowAssoc[Symbols] performed by method any2ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()

  6. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  7. final def ==(arg0: Any): Boolean

    Test two objects for equality.

    Test two objects for equality. The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    Any

  8. final def asInstanceOf[T0]: T0

    Cast the receiver object to be of type T0.

    Cast the receiver object to be of type T0.

    Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

    returns

    the receiver object.

    Definition Classes
    Any
    Exceptions thrown
    ClassCastException

    if the receiver object is not an instance of the erasure of type T0.

  9. def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the clone method is platform dependent.

    returns

    a copy of the receiver object.

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
    Note

    not specified by SLS as a member of AnyRef

  10. def ensuring(cond: (Symbols) ⇒ Boolean, msg: ⇒ Any): Symbols

    Implicit information
    This member is added by an implicit conversion from Symbols to Ensuring[Symbols] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring

  11. def ensuring(cond: (Symbols) ⇒ Boolean): Symbols

    Implicit information
    This member is added by an implicit conversion from Symbols to Ensuring[Symbols] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring

  12. def ensuring(cond: Boolean, msg: ⇒ Any): Symbols

    Implicit information
    This member is added by an implicit conversion from Symbols to Ensuring[Symbols] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring

  13. def ensuring(cond: Boolean): Symbols

    Implicit information
    This member is added by an implicit conversion from Symbols to Ensuring[Symbols] performed by method any2Ensuring in scala.Predef.
    Definition Classes
    Ensuring

  14. final def eq(arg0: AnyRef): Boolean

    Tests whether the argument (arg0) is a reference to the receiver object (this).

    Tests whether the argument (arg0) is a reference to the receiver object (this).

    The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

    returns

    true if the argument is a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef

  15. def equals(arg0: Any): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to eq.

    See also equals in scala.Any.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any

  16. def finalize(): Unit

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
    Note

    not specified by SLS as a member of AnyRef

  17. def formatted(fmtstr: String): String

    Returns string formatted according to given format string.

    Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).

    Implicit information
    This member is added by an implicit conversion from Symbols to StringFormat performed by method any2stringfmt in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()

  18. final def getClass(): Class[_]

    A representation that corresponds to the dynamic class of the receiver object.

    A representation that corresponds to the dynamic class of the receiver object.

    The nature of the representation is platform dependent.

    returns

    a representation that corresponds to the dynamic class of the receiver object.

    Definition Classes
    AnyRef → Any
    Note

    not specified by SLS as a member of AnyRef

  19. def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

    the hash code value for this object.

    Definition Classes
    AnyRef → Any

  20. final def isInstanceOf[T0]: Boolean

    Test whether the dynamic type of the receiver object is T0.

    Test whether the dynamic type of the receiver object is T0.

    Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

    returns

    true if the receiver object is an instance of erasure of type T0; false otherwise.

    Definition Classes
    Any

  21. final def ne(arg0: AnyRef): Boolean

    Equivalent to !(this eq that).

    Equivalent to !(this eq that).

    returns

    true if the argument is not a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef

  22. final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Note

    not specified by SLS as a member of AnyRef

  23. final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Note

    not specified by SLS as a member of AnyRef

  24. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef

  25. def toString(): String

    Creates a String representation of this object.

    Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

    returns

    a String representation of the object.

    Definition Classes
    AnyRef → Any

  26. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )

  27. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )

  28. final def wait(arg0: Long): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws( ... )

  29. def →[B](y: B): (Symbols, B)

    Implicit information
    This member is added by an implicit conversion from Symbols to ArrowAssoc[Symbols] performed by method any2ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc

Shadowed Implicit Value Members

  1. val self: Any

    Implicit information
    This member is added by an implicit conversion from Symbols to StringAdd performed by method any2stringadd in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (symbols: StringAdd).self
    Definition Classes
    StringAdd

  2. val self: Any

    Implicit information
    This member is added by an implicit conversion from Symbols to StringFormat performed by method any2stringfmt in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (symbols: StringFormat).self
    Definition Classes
    StringFormat

Deprecated Value Members

  1. def x: Symbols

    Implicit information
    This member is added by an implicit conversion from Symbols to ArrowAssoc[Symbols] performed by method any2ArrowAssoc in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (symbols: ArrowAssoc[Symbols]).x
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use leftOfArrow instead

  2. def x: Symbols

    Implicit information
    This member is added by an implicit conversion from Symbols to Ensuring[Symbols] performed by method any2Ensuring in scala.Predef.
    Shadowing
    This implicitly inherited member is ambiguous. One or more implicitly inherited members have similar signatures, so calling this member may produce an ambiguous implicit conversion compiler error.
    To access this member you can use a type ascription:
    (symbols: Ensuring[Symbols]).x
    Definition Classes
    Ensuring
    Annotations
    @deprecated
    Deprecated

    (Since version 2.10.0) Use resultOfEnsuring instead

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from Symbols to StringAdd

Inherited by implicit conversion any2stringfmt from Symbols to StringFormat

Inherited by implicit conversion any2ArrowAssoc from Symbols to ArrowAssoc[Symbols]

Inherited by implicit conversion any2Ensuring from Symbols to Ensuring[Symbols]

Symbols

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.

Tags

Implicit values that provide ClassTags for the reflection classes. These are abstract in the interface but are later filled in to provide ClassTags for the either the runtime reflection or macros entities, depending on the use.

Ungrouped