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Scala example source code file (Universe.scala)

This example Scala source code file (Universe.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

apis, classtag, list, position, symbol, t, tree, type, typetree, use

The Universe.scala Scala example source code

package scala
package reflect
package macros

import scala.language.implicitConversions
import scala.language.higherKinds

/**
 * <span class="badge badge-red" style="float: right;">EXPERIMENTAL</span>
 *
 *  The refinement of [[scala.reflect.api.Universe]] for the use by macro writers.
 *
 *  This universe provides mutability for reflection artifacts (e.g. macros can change types of compiler trees,
 *  add annotation to symbols representing definitions, etc) and exposes some internal compiler functionality
 *  such as `Symbol.deSkolemize` or `Tree.attachments`.
 *  @groupname Macros Macro Specific Additions
 *  @groupprio Macros -1
 *
 *  @contentDiagram hideNodes "*Api"
 */
abstract class Universe extends scala.reflect.api.Universe {

  /** @inheritdoc */
  override type Internal <: MacroInternalApi

  /** @inheritdoc */
  trait MacroInternalApi extends InternalApi { internal =>

    /** Adds a given symbol to the given scope.
     */
    def enter(scope: Scope, sym: Symbol): scope.type

    /** Removes a given symbol to the given scope.
     */
    def unlink(scope: Scope, sym: Symbol): scope.type

    /** Collects all the symbols defined by subtrees of `tree` that are owned by `prev`,
     *  and then changes their owner to point to `next`.
     *
     *  This is an essential tool to battle owner chain corruption when moving trees
     *  from one lexical context to another. Whenever you take an attributed tree that
     *  has been typechecked under the Context owned by some symbol (let's call it `x`)
     *  and splice it elsewhere, into the Context owned by another symbol (let's call it `y`),
     *  it is imperative that you either call `untypecheck` or do `changeOwner(tree, x, y)`.
     *
     *  Since at the moment `untypecheck` has fundamental problem that can sometimes lead to tree corruption,
     *  `changeOwner` becomes an indispensible tool in building 100% robust macros.
     *  Future versions of the reflection API might obviate the need in taking care of
     *  these low-level details, but at the moment this is what we've got.
     */
    def changeOwner(tree: Tree, prev: Symbol, next: Symbol): tree.type

    /** Advanced tree factories */
    val gen: TreeGen

    /** The attachment of the symbol. */
    def attachments(symbol: Symbol): Attachments { type Pos = Position }

    /** Updates the attachment with the payload slot of T added/updated with the provided value.
     *  Replaces an existing payload of the same type, if exists.
     *  Returns the symbol itself.
     */
    def updateAttachment[T: ClassTag](symbol: Symbol, attachment: T): symbol.type

    /** Update the attachment with the payload of the given class type `T` removed.
     *  Returns the symbol itself.
     */
    def removeAttachment[T: ClassTag](symbol: Symbol): symbol.type

    /** Sets the `owner` of the symbol. */
    def setOwner(symbol: Symbol, newowner: Symbol): symbol.type

    /** Sets the `info` of the symbol. */
    def setInfo(symbol: Symbol, tpe: Type): symbol.type

    /** Sets the `annotations` of the symbol. */
    def setAnnotations(symbol: Symbol, annots: Annotation*): symbol.type

    /** Sets the `name` of the symbol. */
    def setName(symbol: Symbol, name: Name): symbol.type

    /** Sets the `privateWithin` of the symbol. */
    def setPrivateWithin(symbol: Symbol, sym: Symbol): symbol.type

    /** Enables `flags` on the symbol. */
    def setFlag(symbol: Symbol, flags: FlagSet): symbol.type

    /** Disables `flags` on the symbol. */
    def resetFlag(symbol: Symbol, flags: FlagSet): symbol.type

    /** The attachment of the tree. */
    def attachments(tree: Tree): Attachments { type Pos = Position }

    /** Updates the attachment with the payload slot of T added/updated with the provided value.
     *  Replaces an existing payload of the same type, if exists.
     *  Returns the tree itself.
     */
    def updateAttachment[T: ClassTag](tree: Tree, attachment: T): tree.type

    /** Update the attachment with the payload of the given class type `T` removed.
     *  Returns the tree itself.
     */
    def removeAttachment[T: ClassTag](tree: Tree): tree.type

    /** Sets the `pos` of the tree. Returns the tree itself. */
    def setPos(tree: Tree, newpos: Position): tree.type

    /** Sets the `tpe` of the tree. Returns the tree itself. */
    def setType(tree: Tree, tp: Type): tree.type

    /** Like `setType`, but if this is a previously empty TypeTree that
     *  fact is remembered so that `untypecheck` will snap back.
     *
     *  \@PP: Attempting to elaborate on the above, I find: If defineType
     *  is called on a TypeTree whose type field is null or NoType,
     *  this is recorded as "wasEmpty = true". That value is used in
     *  ResetAttrsTraverser, which nulls out the type field of TypeTrees
     *  for which wasEmpty is true, leaving the others alone.
     *
     *  `untypecheck` (or `resetAttrs` in compiler parlance) is used
     *  in situations where some speculative
     *  typing of a tree takes place, fails, and the tree needs to be
     *  returned to its former state to try again. So according to me:
     *  using `defineType` instead of `setType` is how you communicate
     *  that the type being set does not depend on any previous state,
     *  and therefore should be abandoned if the current line of type
     *  inquiry doesn't work out.
     */
    def defineType(tree: Tree, tp: Type): tree.type

    /** Sets the `symbol` of the tree. Returns the tree itself. */
    def setSymbol(tree: Tree, sym: Symbol): tree.type

    /** Sets the `original` field of the type tree. */
    def setOriginal(tt: TypeTree, original: Tree): TypeTree

    /** Mark a variable as captured; i.e. force boxing in a *Ref type.
     *  @group Macros
     */
    def captureVariable(vble: Symbol): Unit

    /** Mark given identifier as a reference to a captured variable itself
     *  suppressing dereferencing with the `elem` field.
     *  @group Macros
     */
    def referenceCapturedVariable(vble: Symbol): Tree

    /** Convert type of a captured variable to *Ref type.
     *  @group Macros
     */
    def capturedVariableType(vble: Symbol): Type

    /** Retrieves the untyped list of subpatterns attached to selector dummy of an UnApply node.
     *  Useful in writing quasiquoting macros that do pattern matching.
     */
    def subpatterns(tree: Tree): Option[List[Tree]]

    /** @inheritdoc */
    override type Decorators <: MacroDecoratorApi

    /** @inheritdoc */
    trait MacroDecoratorApi extends DecoratorApi {
      /** Extension methods for scopes */
      type ScopeDecorator[T <: Scope] <: MacroScopeDecoratorApi[T]

      /** @see [[ScopeDecorator]] */
      implicit def scopeDecorator[T <: Scope](tree: T): ScopeDecorator[T]

      /** @see [[ScopeDecorator]] */
      class MacroScopeDecoratorApi[T <: Scope](val scope: T) {
        /** @see [[internal.enter]] */
        def enter(sym: Symbol): T = internal.enter(scope, sym)

        /** @see [[internal.unlink]] */
        def unlink(sym: Symbol): T = internal.unlink(scope, sym)
      }

      /** @inheritdoc */
      override type TreeDecorator[T <: Tree] <: MacroTreeDecoratorApi[T]

      /** @see [[TreeDecorator]] */
      class MacroTreeDecoratorApi[T <: Tree](override val tree: T) extends TreeDecoratorApi[T](tree) {
        /** @see [[internal.changeOwner]] */
        def changeOwner(prev: Symbol, next: Symbol): tree.type = internal.changeOwner(tree, prev, next)

        /** @see [[internal.attachments]] */
        def attachments: Attachments { type Pos = Position } = internal.attachments(tree)

        /** @see [[internal.updateAttachment]] */
        def updateAttachment[A: ClassTag](attachment: A): tree.type = internal.updateAttachment(tree, attachment)

        /** @see [[internal.removeAttachment]] */
        def removeAttachment[A: ClassTag]: T = internal.removeAttachment[A](tree)

        /** @see [[internal.setPos]] */
        def setPos(newpos: Position): T = internal.setPos(tree, newpos)

        /** @see [[internal.setType]] */
        def setType(tp: Type): T = internal.setType(tree, tp)

        /** @see [[internal.defineType]] */
        def defineType(tp: Type): T = internal.defineType(tree, tp)

        /** @see [[internal.setSymbol]] */
        def setSymbol(sym: Symbol): T = internal.setSymbol(tree, sym)
      }

      /** Extension methods for typetrees */
      type TypeTreeDecorator[T <: TypeTree] <: MacroTypeTreeDecoratorApi[T]

      /** @see [[TypeTreeDecorator]] */
      implicit def typeTreeDecorator[T <: TypeTree](tt: T): TypeTreeDecorator[T]

      /** @see [[TypeTreeDecorator]] */
      class MacroTypeTreeDecoratorApi[T <: TypeTree](val tt: T) {
        /** @see [[internal.setOriginal]] */
        def setOriginal(tree: Tree): TypeTree = internal.setOriginal(tt, tree)
      }

      /** @inheritdoc */
      override type SymbolDecorator[T <: Symbol] <: MacroSymbolDecoratorApi[T]

      /** @see [[TreeDecorator]] */
      class MacroSymbolDecoratorApi[T <: Symbol](override val symbol: T) extends SymbolDecoratorApi[T](symbol) {
        /** @see [[internal.attachments]] */
        def attachments: Attachments { type Pos = Position } = internal.attachments(symbol)

        /** @see [[internal.updateAttachment]] */
        def updateAttachment[A: ClassTag](attachment: A): T = internal.updateAttachment(symbol, attachment)

        /** @see [[internal.removeAttachment]] */
        def removeAttachment[A: ClassTag]: T = internal.removeAttachment[A](symbol)

        /** @see [[internal.setOwner]] */
        def setOwner(newowner: Symbol): T = internal.setOwner(symbol, newowner)

        /** @see [[internal.setInfo]] */
        def setInfo(tpe: Type): T = internal.setInfo(symbol, tpe)

        /** @see [[internal.setAnnotations]] */
        def setAnnotations(annots: Annotation*): T = internal.setAnnotations(symbol, annots: _*)

        /** @see [[internal.setName]] */
        def setName(name: Name): T = internal.setName(symbol, name)

        /** @see [[internal.setPrivateWithin]] */
        def setPrivateWithin(sym: Symbol): T = internal.setPrivateWithin(symbol, sym)

        /** @see [[internal.setFlag]] */
        def setFlag(flags: FlagSet): T = internal.setFlag(symbol, flags)

        /** @see [[internal.setFlag]] */
        def resetFlag(flags: FlagSet): T = internal.resetFlag(symbol, flags)
      }
    }
  }

  /** @group Internal */
  trait TreeGen {
    /** Builds a reference to value whose type is given stable prefix.
     *  The type must be suitable for this.  For example, it
     *  must not be a TypeRef pointing to an abstract type variable.
     */
    def mkAttributedQualifier(tpe: Type): Tree

    /** Builds a reference to value whose type is given stable prefix.
     *  If the type is unsuitable, e.g. it is a TypeRef for an
     *  abstract type variable, then an Ident will be made using
     *  termSym as the Ident's symbol.  In that case, termSym must
     *  not be NoSymbol.
     */
    def mkAttributedQualifier(tpe: Type, termSym: Symbol): Tree

    /** Builds a typed reference to given symbol with given stable prefix. */
    def mkAttributedRef(pre: Type, sym: Symbol): RefTree

    /** Builds a typed reference to given symbol. */
    def mkAttributedRef(sym: Symbol): RefTree

    def stabilize(tree: Tree): Tree

    def mkAttributedStableRef(pre: Type, sym: Symbol): Tree

    def mkAttributedStableRef(sym: Symbol): Tree

    /** Builds an untyped reference to given symbol. Requires the symbol to be static. */
    def mkUnattributedRef(sym: Symbol): RefTree

    /** Builds an untyped reference to symbol with given name. Requires the symbol to be static. */
    def mkUnattributedRef(fullName: Name): RefTree

    /** Builds a typed This reference to given symbol. */
    def mkAttributedThis(sym: Symbol): This

    /** Builds a typed Ident with an underlying symbol. */
    def mkAttributedIdent(sym: Symbol): RefTree

    /** Builds a typed Select with an underlying symbol. */
    def mkAttributedSelect(qual: Tree, sym: Symbol): RefTree

    /** A creator for method calls, e.g. fn[T1, T2, ...](v1, v2, ...)
     *  There are a number of variations.
     *
     *  @param    receiver    symbol of the method receiver
     *  @param    methodName  name of the method to call
     *  @param    targs       type arguments (if Nil, no TypeApply node will be generated)
     *  @param    args        value arguments
     *  @return               the newly created trees.
     */
    def mkMethodCall(receiver: Symbol, methodName: Name, targs: List[Type], args: List[Tree]): Tree

    def mkMethodCall(method: Symbol, targs: List[Type], args: List[Tree]): Tree

    def mkMethodCall(method: Symbol, args: List[Tree]): Tree

    def mkMethodCall(target: Tree, args: List[Tree]): Tree

    def mkMethodCall(receiver: Symbol, methodName: Name, args: List[Tree]): Tree

    def mkMethodCall(receiver: Tree, method: Symbol, targs: List[Type], args: List[Tree]): Tree

    def mkMethodCall(target: Tree, targs: List[Type], args: List[Tree]): Tree

    def mkNullaryCall(method: Symbol, targs: List[Type]): Tree

    /** A tree that refers to the runtime reflexive universe, `scala.reflect.runtime.universe`. */
    def mkRuntimeUniverseRef: Tree

    def mkZero(tp: Type): Tree

    def mkCast(tree: Tree, pt: Type): Tree
  }

  /** @see [[internal.gen]] */
  @deprecated("Use `internal.gen` instead", "2.11.0")
  val treeBuild: TreeGen

  /** @inheritdoc */
  type Compat <: MacroCompatApi

  /** @see [[compat]]
   *  @group Internal
   */
  trait MacroCompatApi extends CompatApi {
    /** Scala 2.10 compatibility enrichments for Symbol. */
    implicit class MacroCompatibleSymbol(symbol: Symbol) {
      /** @see [[InternalMacroApi.attachments]] */
      @deprecated("Use `internal.attachments` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def attachments: Attachments { type Pos = Position } = internal.attachments(symbol)

      /** @see [[InternalMacroApi.updateAttachment]] */
      @deprecated("Use `internal.updateAttachment` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def updateAttachment[T: ClassTag](attachment: T): Symbol = internal.updateAttachment[T](symbol, attachment)

      /** @see [[InternalMacroApi.removeAttachment]] */
      @deprecated("Use `internal.removeAttachment` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def removeAttachment[T: ClassTag]: Symbol = internal.removeAttachment[T](symbol)

      /** @see [[InternalMacroApi.setInfo]] */
      @deprecated("Use `internal.setInfo` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def setTypeSignature(tpe: Type): Symbol = internal.setInfo(symbol, tpe)

      /** @see [[InternalMacroApi.setAnnotations]] */
      @deprecated("Use `internal.setAnnotations` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def setAnnotations(annots: Annotation*): Symbol = internal.setAnnotations(symbol, annots: _*)

      /** @see [[InternalMacroApi.setName]] */
      @deprecated("Use `internal.setName` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def setName(name: Name): Symbol = internal.setName(symbol, name)

      /** @see [[InternalMacroApi.setPrivateWithin]] */
      @deprecated("Use `internal.setPrivateWithin` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def setPrivateWithin(sym: Symbol): Symbol = internal.setPrivateWithin(symbol, sym)
    }

    /** Scala 2.10 compatibility enrichments for TypeTree. */
    implicit class MacroCompatibleTree(tree: Tree) {
      /** @see [[InternalMacroApi.attachments]] */
      @deprecated("Use `internal.attachments` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def attachments: Attachments { type Pos = Position } = internal.attachments(tree)

      /** @see [[InternalMacroApi.updateAttachment]] */
      @deprecated("Use `internal.updateAttachment` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def updateAttachment[T: ClassTag](attachment: T): Tree = internal.updateAttachment[T](tree, attachment)

      /** @see [[InternalMacroApi.removeAttachment]] */
      @deprecated("Use `internal.removeAttachment` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def removeAttachment[T: ClassTag]: Tree = internal.removeAttachment[T](tree)

      /** @see [[InternalMacroApi.setPos]] */
      @deprecated("Use `internal.setPos` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def pos_=(pos: Position): Unit = internal.setPos(tree, pos)

      /** @see [[InternalMacroApi.setPos]] */
      @deprecated("Use `internal.setPos` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def setPos(newpos: Position): Tree = internal.setPos(tree, newpos)

      /** @see [[InternalMacroApi.setType]] */
      @deprecated("Use `internal.setType` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def tpe_=(t: Type): Unit = internal.setType(tree, t)

      /** @see [[InternalMacroApi.setType]] */
      @deprecated("Use `internal.setType` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def setType(tp: Type): Tree = internal.setType(tree, tp)

      /** @see [[InternalMacroApi.defineType]] */
      @deprecated("Use `internal.defineType` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def defineType(tp: Type): Tree = internal.defineType(tree, tp)

      /** @see [[InternalMacroApi.setSymbol]] */
      @deprecated("Use `internal.setSymbol` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def symbol_=(sym: Symbol): Unit = internal.setSymbol(tree, sym)

      /** @see [[InternalMacroApi.setSymbol]] */
      @deprecated("Use `internal.setSymbol` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def setSymbol(sym: Symbol): Tree = internal.setSymbol(tree, sym)
    }

    /** Scala 2.10 compatibility enrichments for TypeTree. */
    implicit class CompatibleTypeTree(tt: TypeTree) {
      /** @see [[InternalMacroApi.setOriginal]] */
      @deprecated("Use `internal.setOriginal` instead or import `internal.decorators._` for infix syntax", "2.11.0")
      def setOriginal(tree: Tree): TypeTree = internal.setOriginal(tt, tree)
    }

    /** @see [[InternalMacroApi.captureVariable]] */
    @deprecated("Use `internal.captureVariable` instead", "2.11.0")
    def captureVariable(vble: Symbol): Unit = internal.captureVariable(vble)

    /** @see [[InternalMacroApi.captureVariable]] */
    @deprecated("Use `internal.referenceCapturedVariable` instead", "2.11.0")
    def referenceCapturedVariable(vble: Symbol): Tree = internal.referenceCapturedVariable(vble)

    /** @see [[InternalMacroApi.captureVariable]] */
    @deprecated("Use `internal.capturedVariableType` instead", "2.11.0")
    def capturedVariableType(vble: Symbol): Type = internal.capturedVariableType(vble)
  }

  /** The type of compilation runs.
   *  @see [[scala.reflect.macros.Enclosures]]
   *  @template
   *  @group Macros
   */
  @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0")
  type Run <: RunContextApi

  /** Compilation run uniquely identifies current invocation of the compiler
   *  (e.g. can be used to implement per-run caches for macros) and provides access to units of work
   *  of the invocation (currently processed unit of work and the list of all units).
   *  @see [[scala.reflect.macros.Enclosures]]
   *  @group API
   */
  @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0")
  trait RunContextApi {
    /** Currently processed unit of work (a real or a virtual file). */
    @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0")
    def currentUnit: CompilationUnit

    /** All units of work comprising this compilation run. */
    @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0")
    def units: Iterator[CompilationUnit]
  }

  /** The type of compilation units.
   *  @see [[scala.reflect.macros.Enclosures]]
   *  @template
   *  @group Macros
   */
  @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0")
  type CompilationUnit <: CompilationUnitContextApi

  /** Compilation unit describes a unit of work of the compilation run.
   *  It provides such information as file name, textual representation of the unit and the underlying AST.
   *  @see [[scala.reflect.macros.Enclosures]]
   *  @group API
   */
  @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0")
  trait CompilationUnitContextApi {
    /** Source file corresponding to this compilation unit.
     *
     *  Exposes information about the file as a part of a real or virtual file system
     *  along with the contents of that file.
     *
     *  The return type is `scala.reflect.io.AbstractFile`, which belongs to an experimental part of Scala reflection.
     *  It should not be used unless you know what you are doing. In subsequent releases, this API will be refined
     *  and exposed as a part of scala.reflect.api.
     */
    @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0")
    def source: scala.reflect.internal.util.SourceFile

    /** The AST that corresponds to this compilation unit. */
    @deprecated("c.enclosingTree-style APIs are now deprecated; consult the scaladoc for more information", "2.11.0")
    def body: Tree
  }
}

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