Trait

scala.reflect.api

Printers

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trait Printers extends AnyRef

EXPERIMENTAL

Utilities for nicely printing scala.reflect.api.Trees and scala.reflect.api.Types.

Printing Trees

The method show displays the "prettified" representation of reflection artifacts. This representation provides one with the desugared Java representation of Scala code. For example:

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

scala> def tree = reify{ final class C { def x = 2 } }.tree
tree: reflect.runtime.universe.Tree

scala> show(tree)
res0: String =
{
  final class C extends AnyRef {
    def <init>() = {
      super.<init>();
      ()
    };
    def x = 2
  };
  ()
}

The method showRaw displays internal structure of a given reflection object as a Scala abstract syntax tree (AST), the representation that the Scala typechecker operates on.

Note, that while this representation appears to generate correct trees that one might think would be possible to use in a macro implementation, this is not usually the case. Symbols aren't fully represented (only their names are). Thus, this method is best-suited for use simply inspecting ASTs given some valid Scala code.

scala> showRaw(tree)
res1: String = Block(List(
  ClassDef(Modifiers(FINAL), TypeName("C"), List(), Template(
    List(Ident(TypeName("AnyRef"))),
    noSelfType,
    List(
      DefDef(Modifiers(), nme.CONSTRUCTOR, List(), List(List()), TypeTree(),
        Block(List(
          Apply(Select(Super(This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR), List())),
          Literal(Constant(())))),
      DefDef(Modifiers(), TermName("x"), List(), List(), TypeTree(),
        Literal(Constant(2))))))),
  Literal(Constant(())))

The method showRaw can also print scala.reflect.api.Types next to the artifacts being inspected

scala> import scala.tools.reflect.ToolBox // requires scala-compiler.jar
import scala.tools.reflect.ToolBox

scala> import scala.reflect.runtime.{currentMirror => cm}
import scala.reflect.runtime.{currentMirror=>cm}

scala> showRaw(cm.mkToolBox().typecheck(tree), printTypes = true)
res2: String = Block[1](List(
  ClassDef[2](Modifiers(FINAL), TypeName("C"), List(), Template[3](
    List(Ident[4](TypeName("AnyRef"))),
    noSelfType,
    List(
      DefDef[2](Modifiers(), nme.CONSTRUCTOR, List(), List(List()), TypeTree[3](),
        Block[1](List(
          Apply[4](Select[5](Super[6](This[3](TypeName("C")), tpnme.EMPTY), ...))),
          Literal[1](Constant(())))),
      DefDef[2](Modifiers(), TermName("x"), List(), List(), TypeTree[7](),
        Literal[8](Constant(2))))))),
  Literal[1](Constant(())))
[1] TypeRef(ThisType(scala), scala.Unit, List())
[2] NoType
[3] TypeRef(NoPrefix, TypeName("C"), List())
[4] TypeRef(ThisType(java.lang), java.lang.Object, List())
[5] MethodType(List(), TypeRef(ThisType(java.lang), java.lang.Object, List()))
[6] SuperType(ThisType(TypeName("C")), TypeRef(... java.lang.Object ...))
[7] TypeRef(ThisType(scala), scala.Int, List())
[8] ConstantType(Constant(2))
Printing Types

The method show

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

scala> def tpe = typeOf[{ def x: Int; val y: List[Int] }]
tpe: reflect.runtime.universe.Type

scala> show(tpe)
res0: String = scala.AnyRef{def x: Int; val y: scala.List[Int]}

Like the method showRaw for scala.reflect.api.Trees, showRaw for scala.reflect.api.Types provides a visualization of the Scala AST operated on by the Scala typechecker.

// showRaw has already been discussed above
scala> showRaw(tpe)
res1: String = RefinedType(
  List(TypeRef(ThisType(scala), TypeName("AnyRef"), List())),
  Scope(
    TermName("x"),
    TermName("y")))

printIds and/or printKinds can additionally be supplied as arguments in a call to showRaw which additionally shows the unique identifiers of symbols.

scala> showRaw(tpe, printIds = true, printKinds = true)
res2: String = RefinedType(
  List(TypeRef(ThisType(scala#2043#PK), TypeName("AnyRef")#691#TPE, List())),
  Scope(
    TermName("x")#2540#METH,
    TermName("y")#2541#GET))

For more details about Printers and other aspects of Scala reflection, see the Reflection Guide

Self Type
Universe
Source
Printers.scala
Linear Supertypes
Known Subclasses
Type Hierarchy
Ordering
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  2. Alphabetic
  3. By Inheritance
Inherited
  1. Printers
  2. AnyRef
  3. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
  1. Public
  2. All

Type Members

  1. case class BooleanFlag(value: Option[Boolean]) extends Product with Serializable

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  2. trait TreePrinter extends AnyRef

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    Attributes
    protected

Abstract Value Members

  1. abstract def newCodePrinter(out: PrintWriter, tree: Universe.Tree, printRootPkg: Boolean): Universe.TreePrinter

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    Hook to define what showCode(...) means.

    Hook to define what showCode(...) means.

    Attributes
    protected
  2. abstract def newRawTreePrinter(out: PrintWriter): Universe.TreePrinter

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    Hook to define what showRaw(...) means.

    Hook to define what showRaw(...) means.

    Attributes
    protected
  3. abstract def newTreePrinter(out: PrintWriter): Universe.TreePrinter

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    Hook to define what show(...) means.

    Hook to define what show(...) means.

    Attributes
    protected
  4. abstract def show(position: Universe.Position): String

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    Renders a prettified representation of a position.

  5. abstract def show(flags: Universe.FlagSet): String

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    Renders a prettified representation of a flag set.

  6. abstract def show(name: Universe.Name): String

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    Renders a prettified representation of a name.

  7. abstract def showDecl(sym: Universe.Symbol): String

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    Renders a string that represents a declaration of this symbol written in Scala.

Concrete Value Members

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

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    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

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    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

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    Implicit information
    This member is added by an implicit conversion from Printers to any2stringadd[Printers] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (Printers, B)

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    Implicit information
    This member is added by an implicit conversion from Printers to ArrowAssoc[Printers] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  5. final def ==(arg0: Any): Boolean

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    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).

    returns

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

    Definition Classes
    AnyRef → Any
  6. object BooleanFlag extends Serializable

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  7. final def asInstanceOf[T0]: T0

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    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.

  8. def clone(): AnyRef

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    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

  9. def ensuring(cond: (Printers) ⇒ Boolean, msg: ⇒ Any): Printers

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    Implicit information
    This member is added by an implicit conversion from Printers to Ensuring[Printers] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  10. def ensuring(cond: (Printers) ⇒ Boolean): Printers

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    Implicit information
    This member is added by an implicit conversion from Printers to Ensuring[Printers] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: Boolean, msg: ⇒ Any): Printers

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    Implicit information
    This member is added by an implicit conversion from Printers to Ensuring[Printers] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. def ensuring(cond: Boolean): Printers

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    Implicit information
    This member is added by an implicit conversion from Printers to Ensuring[Printers] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  13. final def eq(arg0: AnyRef): Boolean

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

    Tests whether the argument (that) 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
  14. def equals(arg0: Any): Boolean

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    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
  15. def finalize(): Unit

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    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

  16. def formatted(fmtstr: String): String

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    Implicit information
    This member is added by an implicit conversion from Printers to StringFormat[Printers] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  17. final def getClass(): Class[_]

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    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

  18. def hashCode(): Int

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    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
  19. final def isInstanceOf[T0]: Boolean

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

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    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
  21. final def notify(): Unit

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    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

  22. final def notifyAll(): Unit

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    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

  23. def render(what: Any, mkPrinter: (PrintWriter) ⇒ Universe.TreePrinter, printTypes: Universe.BooleanFlag = None, printIds: Universe.BooleanFlag = None, printOwners: Universe.BooleanFlag = None, printKinds: Universe.BooleanFlag = None, printMirrors: Universe.BooleanFlag = None, printPositions: Universe.BooleanFlag = None): String

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    Attributes
    protected
  24. def show(any: Any, printTypes: Universe.BooleanFlag = None, printIds: Universe.BooleanFlag = None, printOwners: Universe.BooleanFlag = None, printKinds: Universe.BooleanFlag = None, printMirrors: Universe.BooleanFlag = None, printPositions: Universe.BooleanFlag = None): String

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    Renders a representation of a reflection artifact as desugared Scala code.

  25. def showCode(tree: Universe.Tree, printTypes: Universe.BooleanFlag = None, printIds: Universe.BooleanFlag = None, printOwners: Universe.BooleanFlag = None, printPositions: Universe.BooleanFlag = None, printRootPkg: Boolean = false): String

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    Renders the code of the passed tree, so that: 1) it can be later compiled by scalac retaining the same meaning, 2) it looks pretty.

    Renders the code of the passed tree, so that: 1) it can be later compiled by scalac retaining the same meaning, 2) it looks pretty. #1 is available for unattributed trees and attributed trees #2 is more or less okay indentation-wise, but at the moment there's a lot of desugaring left in place, and that's what we plan to improve in the future. printTypes, printIds, printPositions options have the same meaning as for TreePrinter printRootPkg option is available only for attributed trees.

  26. def showRaw(position: Universe.Position): String

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    Renders internal structure of a position.

  27. def showRaw(flags: Universe.FlagSet): String

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    Renders internal structure of a flag set.

  28. def showRaw(name: Universe.Name): String

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    Renders internal structure of a name.

  29. def showRaw(any: Any, printTypes: Universe.BooleanFlag = None, printIds: Universe.BooleanFlag = None, printOwners: Universe.BooleanFlag = None, printKinds: Universe.BooleanFlag = None, printMirrors: Universe.BooleanFlag = None, printPositions: Universe.BooleanFlag = None): String

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    Renders internal structure of a reflection artifact as the visualization of a Scala syntax tree.

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

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    Definition Classes
    AnyRef
  31. def toString(): String

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    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
  32. def treeToString(tree: Universe.Tree): String

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    By default trees are printed with show

    By default trees are printed with show

    Attributes
    protected
  33. final def wait(): Unit

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    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  34. final def wait(arg0: Long, arg1: Int): Unit

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    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  35. final def wait(arg0: Long): Unit

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    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  36. def [B](y: B): (Printers, B)

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

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd from Printers to any2stringadd[Printers]

Inherited by implicit conversion StringFormat from Printers to StringFormat[Printers]

Inherited by implicit conversion Ensuring from Printers to Ensuring[Printers]

Inherited by implicit conversion ArrowAssoc from Printers to ArrowAssoc[Printers]

Printers

Ungrouped