Scala example source code file (TraceSymbolActivity.scala)

This example Scala source code file (TraceSymbolActivity.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

any, collection, int, list, nil, nophase, string, symbol, t, traversable, u

The TraceSymbolActivity.scala Scala example source code

package scala
package reflect.internal
package util

import scala.collection.{ mutable, immutable }
import scala.language.postfixOps

trait TraceSymbolActivity {
  val global: SymbolTable
  import global._

  private[this] var enabled = traceSymbolActivity
  if (enabled && global.isCompilerUniverse)
    scala.sys addShutdownHook showAllSymbols()

  val allSymbols  = mutable.Map[Int, Symbol]()
  val allChildren = mutable.Map[Int, List[Int]]() withDefaultValue Nil
  val prevOwners  = mutable.Map[Int, List[(Int, Phase)]]() withDefaultValue Nil
  val allTrees    = mutable.Set[Tree]()

  def recordSymbolsInTree(tree: Tree) {
    if (enabled)
      allTrees += tree
  }

  def recordNewSymbol(sym: Symbol) {
    if (enabled && sym.id > 1) {
      allSymbols(sym.id) = sym
      allChildren(sym.owner.id) ::= sym.id
    }
  }
  def recordNewSymbolOwner(sym: Symbol, newOwner: Symbol) {
    if (enabled) {
      val sid = sym.id
      val oid = sym.owner.id
      val nid = newOwner.id

      prevOwners(sid) ::= (oid -> phase)
      allChildren(oid) = allChildren(oid) filterNot (_ == sid)
      allChildren(nid) ::= sid
    }
  }

  private lazy val erasurePhase = findPhaseWithName("erasure")
  private def signature(id: Int) = enteringPhase(erasurePhase)(allSymbols(id).defString)

  private def dashes(s: Any): String = ("" + s) map (_ => '-')
  private def show(s1: Any, ss: Any*) {
    println("%-12s".format(s1) +: ss mkString " ")
  }
  private def showHeader(s1: Any, ss: Any*) {
    show(s1, ss: _*)
    show(dashes(s1), ss map dashes: _*)
  }
  private def showSym(sym: Symbol) {
    def prefix = ("  " * (sym.ownerChain.length - 1)) + sym.id
    try println("%s#%s %s".format(prefix, sym.accurateKindString, sym.name.decode))
    catch {
      case x: Throwable => println(prefix + " failed: " + x)
    }
    allChildren(sym.id).sorted foreach showIdAndRemove
  }
  private def showIdAndRemove(id: Int) {
    allSymbols remove id foreach showSym
  }
  private def symbolStr(id: Int): String = {
    if (id == 1) "NoSymbol" else {
      val sym = allSymbols(id)
      sym.accurateKindString + " " + sym.name.decode
    }
  }
  private def ownerStr(id: Int): String = {
    val sym = allSymbols(id)
    sym.name.decode + "#" + sym.id
  }

  private def freq[T, U](xs: scala.collection.Traversable[T])(fn: T => U): List[(U, Int)] = {
    val ys = xs groupBy fn mapValues (_.size)
    ys.toList sortBy (-_._2)
  }

  private def showMapFreq[T](xs: scala.collection.Map[T, Traversable[_]])(showFn: T => String) {
    xs.mapValues(_.size).toList.sortBy(-_._2) take 100 foreach { case (k, size) =>
      show(size, showFn(k))
    }
    println("\n")
  }
  private def showFreq[T, U](xs: Traversable[T])(groupFn: T => U, showFn: U => String) = {
    showMapFreq(xs.toList groupBy groupFn)(showFn)
  }

  def showAllSymbols() {
    if (!enabled) return
    enabled = false
    allSymbols(1) = NoSymbol

    println("" + allSymbols.size + " symbols created.")
    println("")

    showHeader("descendants", "symbol")
    showFreq(allSymbols.values flatMap (_.ownerChain drop 1))(_.id, symbolStr)

    showHeader("children", "symbol")
    showMapFreq(allChildren)(symbolStr)

    if (prevOwners.nonEmpty) {
      showHeader("prev owners", "symbol")
      showMapFreq(prevOwners) { k =>
        val owners = (((allSymbols(k).owner.id, NoPhase)) :: prevOwners(k)) map {
          case (oid, NoPhase) => "-> owned by " + ownerStr(oid)
          case (oid, ph)      => "-> owned by %s (until %s)".format(ownerStr(oid), ph)
        }
        signature(k) :: owners mkString "\n                "
      }
    }

    val nameFreq = allSymbols.values.toList groupBy (_.name)
    showHeader("frequency", "%-15s".format("name"), "owners")
    showMapFreq(nameFreq) { name =>
      "%-15s %s".format(name.decode, {
        val owners = freq(nameFreq(name))(_.owner)

        "%4s owners (%s)".format(
          owners.size,
          owners.take(3).map({ case (k, v) => v + "/" + k }).mkString(", ") + ", ..."
        )
      })
    }

    allSymbols.keys.toList.sorted foreach showIdAndRemove
  }
}