Packages

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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  3. By Inheritance
Inherited
  1. Printers
  2. AnyRef
  3. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
  1. Hide All
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Visibility
  1. Public
  2. Protected

Type Members

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

  2. trait TreePrinter extends AnyRef

    Attributes
    protected

Abstract Value Members

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

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

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

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

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

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

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

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

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

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

    Renders a prettified representation of a position.

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

    Renders a prettified representation of a flag set.

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

    Renders a prettified representation of a name.

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

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

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##: Int
    Definition Classes
    AnyRef → Any
  3. def +(other: String): String
    Implicit
    This member is added by an implicit conversion from Printers toany2stringadd[Printers] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (Printers, B)
    Implicit
    This member is added by an implicit conversion from Printers toArrowAssoc[Printers] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  5. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  6. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  7. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
  8. def ensuring(cond: (Printers) => Boolean, msg: => Any): Printers
    Implicit
    This member is added by an implicit conversion from Printers toEnsuring[Printers] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  9. def ensuring(cond: (Printers) => Boolean): Printers
    Implicit
    This member is added by an implicit conversion from Printers toEnsuring[Printers] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  10. def ensuring(cond: Boolean, msg: => Any): Printers
    Implicit
    This member is added by an implicit conversion from Printers toEnsuring[Printers] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: Boolean): Printers
    Implicit
    This member is added by an implicit conversion from Printers toEnsuring[Printers] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  13. def equals(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef → Any
  14. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.Throwable])
  15. final def getClass(): Class[_ <: AnyRef]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  16. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  17. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  18. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  19. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  20. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  21. 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

    Attributes
    protected
  22. 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

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

  23. 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

    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.

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

    Renders internal structure of a position.

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

    Renders internal structure of a flag set.

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

    Renders internal structure of a name.

  27. 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

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

  28. final def synchronized[T0](arg0: => T0): T0
    Definition Classes
    AnyRef
  29. def toString(): String
    Definition Classes
    AnyRef → Any
  30. def treeToString(tree: Universe.Tree): String

    By default trees are printed with show

    By default trees are printed with show

    Attributes
    protected
  31. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  32. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  33. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()
  34. object BooleanFlag extends java.io.Serializable

Deprecated Value Members

  1. def formatted(fmtstr: String): String
    Implicit
    This member is added by an implicit conversion from Printers toStringFormat[Printers] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @deprecated @inline()
    Deprecated

    (Since version 2.12.16) Use formatString.format(value) instead of value.formatted(formatString), or use the f"" string interpolator. In Java 15 and later, formatted resolves to the new method in String which has reversed parameters.

  2. def [B](y: B): (Printers, B)
    Implicit
    This member is added by an implicit conversion from Printers toArrowAssoc[Printers] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use -> instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd fromPrinters to any2stringadd[Printers]

Inherited by implicit conversion StringFormat fromPrinters to StringFormat[Printers]

Inherited by implicit conversion Ensuring fromPrinters to Ensuring[Printers]

Inherited by implicit conversion ArrowAssoc fromPrinters to ArrowAssoc[Printers]

Printers

Ungrouped