Symbols - Scala Reflection Library 2.11.6 - scala.reflect.api.Symbols
Keywords: Symbols Scala Reflection Library 2.11.6 scala.reflect.api.Symbols

scala.reflect.api

# Symbols

###
Related Doc: package api

#### 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(TermName("test")).asMethod
    test: reflect.runtime.universe.MethodSymbol = method test

    scala> test.info
    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, Universe, Universe
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Inherited

1. Symbols
2. AnyRef
3. Any

Implicitly

1. by any2stringadd
2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

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### Type Members

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

   The type of class symbols representing class and trait definitions.

2. #### trait ClassSymbolApi extends Universe.TypeSymbolApi

   The API of class symbols.

   The API of class symbols. The main source of information about symbols is the Symbols page.

   Class Symbol defines `isXXX` test methods such as `isPublic` or `isFinal`, `params` and `returnType` methods for method symbols, `baseClasses` for class symbols and so on. Some of these methods don't make sense for certain subclasses of `Symbol` and return `NoSymbol`, `Nil` or other empty values.

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

   The type of method symbols representing def declarations.

4. #### trait MethodSymbolApi extends Universe.TermSymbolApi

   The API of method symbols.

   The API of method symbols. The main source of information about symbols is the Symbols page.

   Class Symbol defines `isXXX` test methods such as `isPublic` or `isFinal`, `params` and `returnType` methods for method symbols, `baseClasses` for class symbols and so on. Some of these methods don't make sense for certain subclasses of `Symbol` and return `NoSymbol`, `Nil` or other empty values.

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

   The type of module symbols representing object declarations.

6. #### trait ModuleSymbolApi extends Universe.TermSymbolApi

   The API of module symbols.

   The API of module symbols. The main source of information about symbols is the Symbols page.

   Class Symbol defines `isXXX` test methods such as `isPublic` or `isFinal`, `params` and `returnType` methods for method symbols, `baseClasses` for class symbols and so on. Some of these methods don't make sense for certain subclasses of `Symbol` and return `NoSymbol`, `Nil` or other empty values.

7. #### abstract type Symbol >: Null <: Universe.SymbolApi

   The type of symbols representing declarations.

8. #### trait SymbolApi extends AnyRef

   The API of symbols.

   The API of symbols. The main source of information about symbols is the Symbols page.

   Class Symbol defines `isXXX` test methods such as `isPublic` or `isFinal`, `params` and `returnType` methods for method symbols, `baseClasses` for class symbols and so on. Some of these methods don't make sense for certain subclasses of `Symbol` and return `NoSymbol`, `Nil` or other empty values.

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

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

10. #### trait TermSymbolApi extends Universe.SymbolApi

    The API of term symbols.

    The API of term symbols. The main source of information about symbols is the Symbols page.

    Class Symbol defines `isXXX` test methods such as `isPublic` or `isFinal`, `params` and `returnType` methods for method symbols, `baseClasses` for class symbols and so on. Some of these methods don't make sense for certain subclasses of `Symbol` and return `NoSymbol`, `Nil` or other empty values.

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

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

12. #### trait TypeSymbolApi extends Universe.SymbolApi

    The API of type symbols.

    The API of type symbols. The main source of information about symbols is the Symbols page.

    Class Symbol defines `isXXX` test methods such as `isPublic` or `isFinal`, `params` and `returnType` methods for method symbols, `baseClasses` for class symbols and so on. Some of these methods don't make sense for certain subclasses of `Symbol` and return `NoSymbol`, `Nil` or other empty values.

### Abstract Value Members

1. #### 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.

### Concrete Value Members

1. #### final def !=(arg0: Any): Boolean

   Test two objects for inequality.

   Test two objects for inequality.

   returns

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

   Definition Classes
     AnyRef → Any

2. #### 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

3. #### def +(other: String): String

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

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

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

5. #### final def ==(arg0: Any): Boolean

   The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   The expression `x == that` is equivalent to `if (x eq null) that eq null else x.equals(that)`.

   arg0

     the object to compare against this object for equality.

   returns

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

   Definition Classes
     AnyRef → Any

6. #### 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`.

7. #### 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

8. #### 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 Ensuring in scala.Predef.
   Definition Classes
     Ensuring

9. #### def ensuring(cond: (Symbols) ⇒ Boolean): Symbols

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

10. #### 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 Ensuring in scala.Predef.
    Definition Classes
      Ensuring

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

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

12. #### 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

13. #### 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

14. #### 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

15. #### def formatted(fmtstr: String): String

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

16. #### 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

17. #### 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

18. #### 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

19. #### 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

20. #### 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

21. #### 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

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

    Definition Classes
      AnyRef

23. #### 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

24. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

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

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

26. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

27. #### def →[B](y: B): (Symbols, B)

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

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from Symbols to any2stringadd[Symbols]

### Inherited by implicit conversion StringFormat from Symbols to StringFormat[Symbols]

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

### Inherited by implicit conversion ArrowAssoc from Symbols to ArrowAssoc[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.

### Ungrouped