Scala example source code file (TreeGen.scala)

This example Scala source code file (TreeGen.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

block, collection, compiler, ident, import, list, mutable, name, nil, noposition, nsc, symbol, tree, type

The TreeGen.scala Scala example source code

/* NSC -- new Scala compiler
 * Copyright 2005-2013 LAMP/EPFL
 * @author  Martin Odersky
 */

package scala.tools.nsc
package ast

import scala.collection.mutable.ListBuffer
import symtab.Flags._
import scala.language.postfixOps

/** XXX to resolve: TreeGen only assumes global is a SymbolTable, but
 *  TreeDSL at the moment expects a Global.  Can we get by with SymbolTable?
 */
abstract class TreeGen extends scala.reflect.internal.TreeGen with TreeDSL {
  val global: Global

  import global._
  import definitions._

  /** Builds a fully attributed, synthetic wildcard import node.
   */
  def mkWildcardImport(pkg: Symbol): Import =
    mkImportFromSelector(pkg, ImportSelector.wildList)

  /** Builds a fully attributed, synthetic import node.
    * import `qualSym`.{`name` => `toName`}
    */
  def mkImport(qualSym: Symbol, name: Name, toName: Name): Import =
    mkImportFromSelector(qualSym, ImportSelector(name, 0, toName, 0) :: Nil)

  private def mkImportFromSelector(qualSym: Symbol, selector: List[ImportSelector]): Import = {
    assert(qualSym ne null, this)
    val qual = gen.mkAttributedStableRef(qualSym)
    val importSym = (
      NoSymbol
        newImport NoPosition
          setFlag SYNTHETIC
          setInfo ImportType(qual)
    )
    val importTree = (
      Import(qual, selector)
        setSymbol importSym
          setType NoType
    )
    importTree
  }

  // wrap the given expression in a SoftReference so it can be gc-ed
  def mkSoftRef(expr: Tree): Tree = atPos(expr.pos) {
    val constructor = SoftReferenceClass.info.nonPrivateMember(nme.CONSTRUCTOR).suchThat(_.paramss.flatten.size == 1)
    NewFromConstructor(constructor, expr)
  }

  // Builds a tree of the form "{ lhs = rhs ; lhs  }"
  def mkAssignAndReturn(lhs: Symbol, rhs: Tree): Tree = {
    def lhsRef = if (lhs.owner.isClass) Select(This(lhs.owner), lhs) else Ident(lhs)
    Block(Assign(lhsRef, rhs) :: Nil, lhsRef)
  }

  def newModule(accessor: Symbol, tpe: Type) = {
    val ps = tpe.typeSymbol.primaryConstructor.info.paramTypes
    if (ps.isEmpty) New(tpe)
    else New(tpe, This(accessor.owner.enclClass))
  }

  def mkRuntimeCall(meth: Name, args: List[Tree]): Tree =
    mkRuntimeCall(meth, Nil, args)

  def mkRuntimeCall(meth: Name, targs: List[Type], args: List[Tree]): Tree =
    mkMethodCall(ScalaRunTimeModule, meth, targs, args)

  def mkSysErrorCall(message: String): Tree =
    mkMethodCall(Sys_error, List(Literal(Constant(message))))

  /** A creator for a call to a scala.reflect.Manifest or ClassManifest factory method.
   *
   *  @param    full          full or partial manifest (target will be Manifest or ClassManifest)
   *  @param    constructor   name of the factory method (e.g. "classType")
   *  @param    tparg         the type argument
   *  @param    args          value arguments
   *  @return   the tree
   */
  def mkManifestFactoryCall(full: Boolean, constructor: String, tparg: Type, args: List[Tree]): Tree =
    mkMethodCall(
      if (full) FullManifestModule else PartialManifestModule,
      newTermName(constructor),
      List(tparg),
      args
    )

  /** Make a synchronized block on 'monitor'. */
  def mkSynchronized(monitor: Tree, body: Tree): Tree =
    Apply(Select(monitor, Object_synchronized), List(body))

  def mkAppliedTypeForCase(clazz: Symbol): Tree = {
    val numParams = clazz.typeParams.size
    if (clazz.typeParams.isEmpty) Ident(clazz)
    else AppliedTypeTree(Ident(clazz), 1 to numParams map (_ => Bind(tpnme.WILDCARD, EmptyTree)) toList)
  }
  def mkBindForCase(patVar: Symbol, clazz: Symbol, targs: List[Type]): Tree = {
    Bind(patVar, Typed(Ident(nme.WILDCARD),
      if (targs.isEmpty) mkAppliedTypeForCase(clazz)
      else AppliedTypeTree(Ident(clazz), targs map TypeTree)
    ))
  }

  def wildcardStar(tree: Tree) =
    atPos(tree.pos) { Typed(tree, Ident(tpnme.WILDCARD_STAR)) }

  def paramToArg(vparam: Symbol): Tree =
    paramToArg(Ident(vparam), isRepeatedParamType(vparam.tpe))

  def paramToArg(vparam: ValDef): Tree =
    paramToArg(Ident(vparam.name), treeInfo.isRepeatedParamType(vparam.tpt))

  def paramToArg(arg: Ident, isRepeatedParam: Boolean): Tree  =
    if (isRepeatedParam) wildcardStar(arg) else arg

  /** Make forwarder to method `target`, passing all parameters in `params` */
  def mkForwarder(target: Tree, vparamss: List[List[Symbol]]) =
    (target /: vparamss)((fn, vparams) => Apply(fn, vparams map paramToArg))

  /** Applies a wrapArray call to an array, making it a WrappedArray.
   *  Don't let a reference type parameter be inferred, in case it's a singleton:
   *  apply the element type directly.
   */
  def mkWrapArray(tree: Tree, elemtp: Type) = {
    mkMethodCall(
      PredefModule,
      wrapArrayMethodName(elemtp),
      if (isPrimitiveValueType(elemtp)) Nil else List(elemtp),
      List(tree)
    )
  }

  /** Cast `tree` to type `pt` by creating
   *  one of the calls of the form
   *
   *    x.asInstanceOf[`pt`]     up to phase uncurry
   *    x.asInstanceOf[`pt`]()   if after uncurry but before erasure
   *    x.$asInstanceOf[`pt`]()  if at or after erasure
   */
  override def mkCast(tree: Tree, pt: Type): Tree = {
    debuglog("casting " + tree + ":" + tree.tpe + " to " + pt + " at phase: " + phase)
    assert(!tree.tpe.isInstanceOf[MethodType], tree)
    assert(pt eq pt.normalize, tree +" : "+ debugString(pt) +" ~>"+ debugString(pt.normalize))
    atPos(tree.pos) {
      mkAsInstanceOf(tree, pt, any = !phase.next.erasedTypes, wrapInApply = isAtPhaseAfter(currentRun.uncurryPhase))
    }
  }

  // drop annotations generated by CPS plugin etc, since its annotationchecker rejects T @cps[U] <: Any
  // let's assume for now annotations don't affect casts, drop them there, and bring them back using the outer Typed tree
  def mkCastPreservingAnnotations(tree: Tree, pt: Type) =
    Typed(mkCast(tree, pt.withoutAnnotations.dealias), TypeTree(pt))

  /** Generate a cast for tree Tree representing Array with
   *  elem type elemtp to expected type pt.
   */
  def mkCastArray(tree: Tree, elemtp: Type, pt: Type) =
    if (elemtp.typeSymbol == AnyClass && isPrimitiveValueType(tree.tpe.typeArgs.head))
      mkCast(mkRuntimeCall(nme.toObjectArray, List(tree)), pt)
    else
      mkCast(tree, pt)

  /** Translate names in Select/Ident nodes to type names.
   */
  def convertToTypeName(tree: Tree): Option[RefTree] = tree match {
    case Select(qual, name) => Some(Select(qual, name.toTypeName))
    case Ident(name)        => Some(Ident(name.toTypeName))
    case _                  => None
  }

  /** Try to convert Select(qual, name) to a SelectFromTypeTree.
   */
  def convertToSelectFromType(qual: Tree, origName: Name) = convertToTypeName(qual) match {
    case Some(qual1)  => SelectFromTypeTree(qual1 setPos qual.pos, origName.toTypeName)
    case _            => EmptyTree
  }

  /** Create a ValDef initialized to the given expression, setting the
   *  symbol to its packed type, and an function for creating Idents
   *  which refer to it.
   */
  private def mkPackedValDef(expr: Tree, owner: Symbol, name: Name): (ValDef, () => Ident) = {
    val packedType = typer.packedType(expr, owner)
    val sym = owner.newValue(name.toTermName, expr.pos.makeTransparent, SYNTHETIC) setInfo packedType

    (ValDef(sym, expr), () => Ident(sym) setPos sym.pos.focus setType expr.tpe)
  }

  /** Used in situations where you need to access value of an expression several times
   */
  def evalOnce(expr: Tree, owner: Symbol, unit: CompilationUnit)(within: (() => Tree) => Tree): Tree = {
    var used = false
    if (treeInfo.isExprSafeToInline(expr)) {
      within(() => if (used) expr.duplicate else { used = true; expr })
    }
    else {
      val (valDef, identFn) = mkPackedValDef(expr, owner, unit.freshTermName("ev$"))
      val containing = within(identFn)
      ensureNonOverlapping(containing, List(expr))
      Block(List(valDef), containing) setPos (containing.pos union expr.pos)
    }
  }

  def evalOnceAll(exprs: List[Tree], owner: Symbol, unit: CompilationUnit)(within: (List[() => Tree]) => Tree): Tree = {
    val vdefs = new ListBuffer[ValDef]
    val exprs1 = new ListBuffer[() => Tree]
    val used = new Array[Boolean](exprs.length)
    var i = 0
    for (expr <- exprs) {
      if (treeInfo.isExprSafeToInline(expr)) {
        exprs1 += {
          val idx = i
          () => if (used(idx)) expr.duplicate else { used(idx) = true; expr }
        }
      }
      else {
        val (valDef, identFn) = mkPackedValDef(expr, owner, unit.freshTermName("ev$"))
        vdefs += valDef
        exprs1 += identFn
      }
      i += 1
    }
    val prefix = vdefs.toList
    val containing = within(exprs1.toList)
    ensureNonOverlapping(containing, exprs)
    if (prefix.isEmpty) containing
    else Block(prefix, containing) setPos (prefix.head.pos union containing.pos)
  }

  /** Return the synchronized part of the double-checked locking idiom around the syncBody tree. It guards with `cond` and
   *  synchronizez on `clazz.this`. Additional statements can be included after initialization,
   *  (outside the synchronized block).
   *
   *  The idiom works only if the condition is using a volatile field.
   *  @see http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
   */
  def mkSynchronizedCheck(clazz: Symbol, cond: Tree, syncBody: List[Tree], stats: List[Tree]): Tree =
    mkSynchronizedCheck(mkAttributedThis(clazz), cond, syncBody, stats)

  def mkSynchronizedCheck(attrThis: Tree, cond: Tree, syncBody: List[Tree], stats: List[Tree]): Tree =
    Block(mkSynchronized(
      attrThis,
      If(cond, Block(syncBody: _*), EmptyTree)) ::
      stats: _*)

  /** Creates a tree representing new Object { stats }.
   *  To make sure an anonymous subclass of Object is created,
   *  if there are no stats, a () is added.
   */
  def mkAnonymousNew(stats: List[Tree]): Tree = {
    val stats1 = if (stats.isEmpty) List(Literal(Constant(()))) else stats
    mkNew(Nil, noSelfType, stats1, NoPosition, NoPosition)
  }

  /**
   * Create a method based on a Function
   *
   * Used both to under `-Ydelambdafy:method` create a lifted function and
   * under `-Ydelamdafy:inline` to create the apply method on the anonymous
   * class.
   *
   * It creates a method definition with value params cloned from the
   * original lambda. Then it calls a supplied function to create
   * the body and types the result. Finally
   * everything is wrapped up in a DefDef
   *
   * @param owner The owner for the new method
   * @param name name for the new method
   * @param additionalFlags flags to be put on the method in addition to FINAL
   */
  def mkMethodFromFunction(localTyper: analyzer.Typer)
                          (fun: Function, owner: Symbol, name: TermName, additionalFlags: FlagSet = NoFlags) = {
    val funParams = fun.vparams map (_.symbol)
    val formals :+ restpe = fun.tpe.typeArgs

    val methSym = owner.newMethod(name, fun.pos, FINAL | additionalFlags)

    val paramSyms = map2(formals, fun.vparams) {
      (tp, vparam) => methSym.newSyntheticValueParam(tp, vparam.name)
    }

    methSym setInfo MethodType(paramSyms, restpe.deconst)

    fun.body.substituteSymbols(funParams, paramSyms)
    fun.body changeOwner (fun.symbol -> methSym)

    val methDef = DefDef(methSym, fun.body)

    // Have to repack the type to avoid mismatches when existentials
    // appear in the result - see SI-4869.
    methDef.tpt setType localTyper.packedType(fun.body, methSym).deconst
    methDef
  }
}