Scala example source code file (TreeBuilder.scala)

This example Scala source code file (TreeBuilder.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

apply, collection, compiler, emptytree, if, int, list, mutable, name, nil, nsc, reflection, termname, tree, utilities, valdef

The TreeBuilder.scala Scala example source code

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

package scala.tools.nsc
package ast.parser

import symtab.Flags._
import scala.collection.mutable.ListBuffer
import scala.reflect.internal.util.{Position, SourceFile, FreshNameCreator}

/** Methods for building trees, used in the parser.  All the trees
 *  returned by this class must be untyped.
 */
abstract class TreeBuilder {
  val global: Global
  import global._

  def unit: CompilationUnit
  def source: SourceFile

  implicit def fresh: FreshNameCreator              = unit.fresh
  def o2p(offset: Int): Position                    = Position.offset(source, offset)
  def r2p(start: Int, mid: Int, end: Int): Position = rangePos(source, start, mid, end)

  def rootScalaDot(name: Name) = gen.rootScalaDot(name)
  def scalaDot(name: Name)     = gen.scalaDot(name)
  def scalaAnyRefConstr        = scalaDot(tpnme.AnyRef)
  def scalaUnitConstr          = scalaDot(tpnme.Unit)

  def convertToTypeName(t: Tree) = gen.convertToTypeName(t)

  def byNameApplication(tpe: Tree): Tree =
    AppliedTypeTree(rootScalaDot(tpnme.BYNAME_PARAM_CLASS_NAME), List(tpe))
  def repeatedApplication(tpe: Tree): Tree =
    AppliedTypeTree(rootScalaDot(tpnme.REPEATED_PARAM_CLASS_NAME), List(tpe))

  def makeImportSelector(name: Name, nameOffset: Int): ImportSelector =
    ImportSelector(name, nameOffset, name, nameOffset)

  def makeTupleTerm(elems: List[Tree]) = gen.mkTuple(elems)

  def makeTupleType(elems: List[Tree]) = gen.mkTupleType(elems)

  def stripParens(t: Tree) = t match {
    case Parens(ts) => atPos(t.pos) { makeTupleTerm(ts) }
    case _ => t
  }

  def makeAnnotated(t: Tree, annot: Tree): Tree =
    atPos(annot.pos union t.pos)(Annotated(annot, t))

  def makeSelfDef(name: TermName, tpt: Tree): ValDef =
    ValDef(Modifiers(PRIVATE), name, tpt, EmptyTree)

  /** Create tree representing (unencoded) binary operation expression or pattern. */
  def makeBinop(isExpr: Boolean, left: Tree, op: TermName, right: Tree, opPos: Position, targs: List[Tree] = Nil): Tree = {
    require(isExpr || targs.isEmpty || targs.exists(_.isErroneous), s"Incompatible args to makeBinop: !isExpr but targs=$targs")

    def mkSelection(t: Tree) = {
      def sel = atPos(opPos union t.pos)(Select(stripParens(t), op.encode))
      if (targs.isEmpty) sel else atPos(left.pos)(TypeApply(sel, targs))
    }
    def mkNamed(args: List[Tree]) = if (isExpr) args map treeInfo.assignmentToMaybeNamedArg else args
    val arguments = right match {
      case Parens(args) => mkNamed(args)
      case _            => List(right)
    }
    if (isExpr) {
      if (treeInfo.isLeftAssoc(op)) {
        Apply(mkSelection(left), arguments)
      } else {
        val x = freshTermName()
        Block(
          List(ValDef(Modifiers(SYNTHETIC | ARTIFACT), x, TypeTree(), stripParens(left))),
          Apply(mkSelection(right), List(Ident(x))))
      }
    } else {
      Apply(Ident(op.encode), stripParens(left) :: arguments)
    }
  }

  /** Tree for `od op`, start is start0 if od.pos is borked. */
  def makePostfixSelect(start0: Int, end: Int, od: Tree, op: Name): Tree = {
    val start = if (od.pos.isDefined) od.pos.start else start0
    atPos(r2p(start, end, end + op.length)) { new PostfixSelect(od, op.encode) }
  }

  /** Create tree representing a while loop */
  def makeWhile(startPos: Int, cond: Tree, body: Tree): Tree = {
    val lname = freshTermName(nme.WHILE_PREFIX)
    def default = wrappingPos(List(cond, body)) match {
      case p if p.isDefined => p.end
      case _                => startPos
    }
    val continu = atPos(o2p(body.pos pointOrElse default)) { Apply(Ident(lname), Nil) }
    val rhs = If(cond, Block(List(body), continu), Literal(Constant(())))
    LabelDef(lname, Nil, rhs)
  }

  /** Create tree representing a do-while loop */
  def makeDoWhile(lname: TermName, body: Tree, cond: Tree): Tree = {
    val continu = Apply(Ident(lname), Nil)
    val rhs = Block(List(body), If(cond, continu, Literal(Constant(()))))
    LabelDef(lname, Nil, rhs)
  }

  /** Create block of statements `stats`  */
  def makeBlock(stats: List[Tree]): Tree = gen.mkBlock(stats)

  def makeParam(pname: TermName, tpe: Tree) =
    ValDef(Modifiers(PARAM), pname, tpe, EmptyTree)

  def makeSyntheticTypeParam(pname: TypeName, bounds: Tree) =
    TypeDef(Modifiers(DEFERRED | SYNTHETIC), pname, Nil, bounds)

  /** Create tree for a pattern alternative */
  def makeAlternative(ts: List[Tree]): Tree = {
    def alternatives(t: Tree): List[Tree] = t match {
      case Alternative(ts)  => ts
      case _                => List(t)
    }
    Alternative(ts flatMap alternatives)
  }

  /** Create tree for case definition <case pat if guard => rhs> */
  def makeCaseDef(pat: Tree, guard: Tree, rhs: Tree): CaseDef =
    CaseDef(gen.patvarTransformer.transform(pat), guard, rhs)

  /** Creates tree representing:
   *    { case x: Throwable =>
   *        val catchFn = catchExpr
   *        if (catchFn isDefinedAt x) catchFn(x) else throw x
   *    }
   */
  def makeCatchFromExpr(catchExpr: Tree): CaseDef = {
    val binder   = freshTermName()
    val pat      = Bind(binder, Typed(Ident(nme.WILDCARD), Ident(tpnme.Throwable)))
    val catchDef = ValDef(Modifiers(ARTIFACT), freshTermName("catchExpr"), TypeTree(), catchExpr)
    val catchFn  = Ident(catchDef.name)
    val body     = atPos(catchExpr.pos.makeTransparent)(Block(
      List(catchDef),
      If(
        Apply(Select(catchFn, nme.isDefinedAt), List(Ident(binder))),
        Apply(Select(catchFn, nme.apply), List(Ident(binder))),
        Throw(Ident(binder))
      )
    ))
    makeCaseDef(pat, EmptyTree, body)
  }

  /** Create a tree representing the function type (argtpes) => restpe */
  def makeFunctionTypeTree(argtpes: List[Tree], restpe: Tree): Tree = gen.mkFunctionTypeTree(argtpes, restpe)

  /** Append implicit parameter section if `contextBounds` nonempty */
  def addEvidenceParams(owner: Name, vparamss: List[List[ValDef]], contextBounds: List[Tree]): List[List[ValDef]] = {
    if (contextBounds.isEmpty) vparamss
    else {
      val mods = Modifiers(if (owner.isTypeName) PARAMACCESSOR | LOCAL | PRIVATE else PARAM)
      def makeEvidenceParam(tpt: Tree) = ValDef(mods | IMPLICIT | SYNTHETIC, freshTermName(nme.EVIDENCE_PARAM_PREFIX), tpt, EmptyTree)
      val evidenceParams = contextBounds map makeEvidenceParam

      val vparamssLast = if(vparamss.nonEmpty) vparamss.last else Nil
      if(vparamssLast.nonEmpty && vparamssLast.head.mods.hasFlag(IMPLICIT))
        vparamss.init ::: List(evidenceParams ::: vparamssLast)
      else
        vparamss ::: List(evidenceParams)
    }
  }

  def makePatDef(mods: Modifiers, pat: Tree, rhs: Tree) = gen.mkPatDef(mods, pat, rhs)
}