Scala example source code file (SyntaxAnalyzer.scala)

This example Scala source code file (SyntaxAnalyzer.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

compilationunit, compiler, memberdef, memberdeftraverser, memberposreporter, nsc, parserphase, phase, stdphase, string, tree, unit

The SyntaxAnalyzer.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 javac._

/** An nsc sub-component.
 */
abstract class SyntaxAnalyzer extends SubComponent with Parsers with MarkupParsers with Scanners with JavaParsers with JavaScanners {
  import global._

  val phaseName = "parser"
  def newPhase(prev: Phase): StdPhase = new ParserPhase(prev)

  abstract class MemberDefTraverser extends Traverser {
    def onMember(defn: MemberDef): Unit

    private var depth: Int = 0
    private def lower[T](body: => T): T = {
      depth += 1
      try body finally depth -= 1
    }
    def currentDepth = depth

    /** Prune this tree and all trees beneath it. Can be overridden. */
    def prune(md: MemberDef): Boolean = (
         md.mods.isSynthetic
      || md.mods.isParamAccessor
      || nme.isConstructorName(md.name)
      || (md.name containsName nme.ANON_CLASS_NAME)
    )

    override def traverse(t: Tree): Unit = t match {
      case md: MemberDef if prune(md) =>
      case md @ PackageDef(_, stats)  => traverseTrees(stats)
      case md: ImplDef                => onMember(md) ; lower(traverseTrees(md.impl.body))
      case md: ValOrDefDef            => onMember(md) ; lower(traverse(md.rhs))
      case _                          => super.traverse(t)
    }
  }

  class MemberPosReporter(unit: CompilationUnit) extends MemberDefTraverser {
    private var outputFn: MemberDef => String = outputForScreen
    val path = unit.source.file.path

    // If a single line, outputs the line; if it spans multiple lines
    // outputs NN,NN with start and end lines, e.g. 15,25.
    def outputPos(md: MemberDef): String = {
      val pos   = md.pos
      val start = pos.focusStart.line
      val end   = pos.focusEnd.line

      if (start == end) "" + start else s"$start,$end"
    }
    def outputForSed(md: MemberDef): String = {
      val pos_s = "%-12s" format outputPos(md) + "p"
      s"$pos_s $path    # ${md.keyword} ${md.name}"
    }
    def outputForScreen(md: MemberDef): String = {
      val pos_s = "%-20s" format " " * currentDepth + outputPos(md)
      s"$pos_s ${md.keyword} ${md.name}"
    }

    def onMember(md: MemberDef) = println(outputFn(md))
    // It recognizes "sed" and "anything else".
    def show(style: String) {
      if (style == "sed") {
        outputFn = outputForSed
        traverse(unit.body)
      }
      else {
        outputFn = outputForScreen
        println(path)
        traverse(unit.body)
      }
      println("")
    }
  }

  private def initialUnitBody(unit: CompilationUnit): Tree = {
    if (unit.isJava) new JavaUnitParser(unit).parse()
    else if (global.reporter.incompleteHandled) newUnitParser(unit).parse()
    else newUnitParser(unit).smartParse()
  }

  class ParserPhase(prev: Phase) extends StdPhase(prev) {
    override val checkable = false
    override val keepsTypeParams = false

    def apply(unit: CompilationUnit) {
      informProgress("parsing " + unit)
      // if the body is already filled in, don't overwrite it
      // otherwise compileLate is going to overwrite bodies of synthetic source files
      if (unit.body == EmptyTree)
        unit.body = initialUnitBody(unit)

      if (settings.Yrangepos && !reporter.hasErrors)
        validatePositions(unit.body)

      if (settings.Ymemberpos.isSetByUser)
        new MemberPosReporter(unit) show (style = settings.Ymemberpos.value)
    }
  }
}