Scala example source code file (RangePositions.scala)

This example Scala source code file (RangePositions.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

emptytree, enclosing, int, int, list, list, noposition, position, position, range, string, tree, tree, unit

The Scala RangePositions.scala source code

/* NSC -- new Scala compiler
 * Copyright 2009-2011 Scala Solutions and LAMP/EPFL
 * @author Martin Odersky
 */
package scala.tools.nsc
package interactive

import ast.Trees
import symtab.Positions
import scala.tools.nsc.util.{SourceFile, Position, RangePosition, NoPosition, WorkScheduler}
import scala.collection.mutable.ListBuffer

/** Handling range positions
 *  atPos, the main method in this trait, will add positions to a tree,
 *  and will ensure the following properties:
 *
 *    1. All nodes between the root of the tree and nodes that already have positions
 *       will be assigned positions.
 *    2. No node which already has a position will be assigned a different range; however
 *       a RangePosition might become a TransparentPosition.
 *    3. The position of each assigned node includes the positions of each of its children.
 *    4. The positions of all solid descendants of children of an assigned node
 *       are mutually non-overlapping.
 *
 * Here, the solid descendant of a node are:
 *
 *   If the node has a TransparentPosition, the solid descendants of all its children
 *   Otherwise, the singleton consisting of the node itself.
 */
trait RangePositions extends Trees with Positions { 
self: scala.tools.nsc.Global =>

  case class Range(pos: Position, tree: Tree) {
    def isFree = tree == EmptyTree
  }

  override def rangePos(source: SourceFile, start: Int, point: Int, end: Int) = 
    new RangePosition(source, start, point, end)

  /** A position that wraps a set of trees.
   *  The point of the wrapping position is the point of the default position.
   *  If some of the trees are ranges, returns a range position enclosing all ranges
   *  Otherwise returns default position.
   */
  override def wrappingPos(default: Position, trees: List[Tree]): Position = {
    val ranged = trees filter (_.pos.isRange)
    if (ranged.isEmpty) default.focus
    else new RangePosition(default.source, (ranged map (_.pos.start)).min, default.point, (ranged map (_.pos.end)).max)
  }

  /** A position that wraps a non-empty set of trees.
   *  The point of the wrapping position is the point of the first trees' position.
   *  If some of the trees are ranges, returns a range position enclosing all ranges
   *  Otherwise returns first tree's position.
   */
  override def wrappingPos(trees: List[Tree]): Position = {
    val headpos = trees.head.pos
    if (headpos.isDefined) wrappingPos(headpos, trees) else headpos
  }

/*
  override def integratePos(tree: Tree, pos: Position) = 
    if (pos.isSynthetic && !tree.pos.isSynthetic) tree.syntheticDuplicate 
    else tree
*/

  // -------------- ensuring no overlaps -------------------------------

  def solidDescendants(tree: Tree): List[Tree] = 
    if (tree.pos.isTransparent) tree.children flatMap solidDescendants 
    else List(tree)

  /** A free range from `lo` to `hi` */
  private def free(lo: Int, hi: Int): Range = 
    Range(new RangePosition(null, lo, lo, hi), EmptyTree)

  /** The maximal free range */
  private lazy val maxFree: Range = free(0, Int.MaxValue)

  /** A singleton list of a non-empty range from `lo` to `hi`, or else the empty List */ 
  private def maybeFree(lo: Int, hi: Int) = 
    if (lo < hi) List(free(lo, hi)) 
    else List()

  /** Insert `pos` into ranges `rs` if possible;
   *  otherwise add conflicting trees to `conflicting`.
   */
  private def insert(rs: List[Range], t: Tree, conflicting: ListBuffer[Tree]): List[Range] = rs match {
    case List() =>
      assert(conflicting.nonEmpty)
      rs
    case r :: rs1 =>
      assert(!t.pos.isTransparent)
      if (r.isFree && (r.pos includes t.pos)) {
//      println("subdividing "+r+"/"+t.pos)
        maybeFree(t.pos.end, r.pos.end) ::: List(Range(t.pos, t)) ::: maybeFree(r.pos.start, t.pos.start) ::: rs1
      } else {
        if (!r.isFree && (r.pos overlaps t.pos)) conflicting += r.tree 
        r :: insert(rs1, t, conflicting)
      }
  }

  /** Replace elem `t` of `ts` by `replacement` list. */
  private def replace(ts: List[Tree], t: Tree, replacement: List[Tree]): List[Tree] = 
    if (ts.head == t) replacement ::: ts.tail
    else ts.head :: replace(ts.tail, t, replacement)

  /** Ensure that given tree has no positions that overlap with
   *  any of the positions of `others`. This is done by
   *  shortening the range or assigning TransparentPositions
   *  to some of the nodes in `tree`.
   */
  override def ensureNonOverlapping(tree: Tree, others: List[Tree]) {
    def isOverlapping(pos: Position) = 
      pos.isRange && (others exists (pos overlaps _.pos))
    if (isOverlapping(tree.pos)) {
      val children = tree.children
      children foreach (ensureNonOverlapping(_, others))
      if (tree.pos.isOpaqueRange) {
        val wpos = wrappingPos(tree.pos.focus, children)
        tree setPos (if (isOverlapping(wpos)) tree.pos.makeTransparent else wpos)
      }
    }
  }

  /** Does given list of trees have mutually non-overlapping positions?
   *  pre: None of the trees is transparent
   */
  def findOverlapping(cts: List[Tree]): List[(Tree, Tree)] = {
    var ranges = List(maxFree)
    for (ct <- cts) {
      if (ct.pos.isOpaqueRange) {
        val conflicting = new ListBuffer[Tree]
        ranges = insert(ranges, ct, conflicting)
        if (conflicting.nonEmpty) return conflicting.toList map (t => (t, ct))
      }
    }
    List()
  }

  // -------------- setting positions -------------------------------

  /** Set position of all children of a node
   *  @param  pos   A target position.
   *                Uses the point of the position as the point of all positions it assigns.
   *                Uses the start of this position as an Offset position for unpositioed trees
   *                without children.
   *  @param  trees  The children to position. All children must be positionable. 
   */
  private def setChildrenPos(pos: Position, trees: List[Tree]): Unit = try {
    for (tree <- trees) {
      if (!tree.isEmpty && tree.pos == NoPosition) {
        val children = tree.children
        if (children.isEmpty) {
          tree setPos pos.focus
        } else {
          setChildrenPos(pos, children)
          tree setPos wrappingPos(pos, children)
        }
      }
    }
  } catch {
    case ex: Exception =>
      println("error while set children pos "+pos+" of "+trees)
      throw ex
  }

  /** Position a tree.
   *  This means: Set position of a node and position all its unpositioned children.
   */
  override def atPos[T <: Tree](pos: Position)(tree: T): T =
    if (pos.isOpaqueRange) {
      if (!tree.isEmpty && tree.pos == NoPosition) {
        tree.setPos(pos)
        val children = tree.children
        if (children.nonEmpty) {
          if (children.tail.isEmpty) atPos(pos)(children.head)
          else setChildrenPos(pos, children)
        }
      }
      tree
    } else {
      super.atPos(pos)(tree)
    }

  // ---------------- Validating positions ----------------------------------

  override def validatePositions(tree: Tree) {
    def reportTree(prefix : String, tree : Tree) {
      val source = if (tree.pos.isDefined) tree.pos.source else ""
      inform("== "+prefix+" tree ["+tree.id+"] of type "+tree.productPrefix+" at "+tree.pos.show+source)
      inform("")
      inform(tree.toString)
      inform("")
    }
    
    def positionError(msg: String)(body : => Unit) {
      inform("======= Bad positions: "+msg)
      inform("")
      body
      inform("=== While validating")
      inform("")
      inform(tree.toString)
      inform("")
      inform("=======")
      throw new ValidateException(msg)
    }
    
    def validate(tree: Tree, encltree: Tree): Unit = {
      if (!tree.isEmpty) {
        if (!tree.pos.isDefined) 
          positionError("Unpositioned tree ["+tree.id+"]") { reportTree("Unpositioned", tree) }
        if (tree.pos.isRange) {
          if (!encltree.pos.isRange)
            positionError("Synthetic tree ["+encltree.id+"] contains nonsynthetic tree ["+tree.id+"]") {
            reportTree("Enclosing", encltree)
            reportTree("Enclosed", tree)
            }
          if (!(encltree.pos includes tree.pos))
            positionError("Enclosing tree ["+encltree.id+"] does not include tree ["+tree.id+"]") {
              reportTree("Enclosing", encltree)
              reportTree("Enclosed", tree)
            }
          
          findOverlapping(tree.children flatMap solidDescendants) match {
            case List() => ;
            case xs => {
              positionError("Overlapping trees "+xs.map { case (x, y) => (x.id, y.id) }.mkString("", ", ", "")) {
                reportTree("Ancestor", tree)
                for((x, y) <- xs) {
                  reportTree("First overlapping", x)
                  reportTree("Second overlapping", y)
                }
              }
            }
          }
        }
        for (ct <- tree.children flatMap solidDescendants) validate(ct, tree)
      }
    }

    validate(tree, tree)
  }

  class ValidateException(msg : String) extends Exception(msg)

  // ---------------- Locating trees ----------------------------------

  /** A locator for trees with given positions.
   *  Given a position `pos`, locator.apply returns
   *  the smallest tree that encloses `pos`.
   */
  class Locator(pos: Position) extends Traverser {
    var last: Tree = _
    def locateIn(root: Tree): Tree = {
      this.last = EmptyTree
      traverse(root)
      this.last
    }
    protected def isEligible(t: Tree) = !t.pos.isTransparent
    override def traverse(t: Tree) {
      t match {
        case tt : TypeTree if tt.original != null => traverse(tt.original)
        case _ =>
          if (t.pos includes pos) {
            if (isEligible(t)) last = t
            super.traverse(t)
          } else t match {
            case mdef: MemberDef =>
              traverseTrees(mdef.mods.annotations)
            case _ =>
          }
      }
    }
  }

  class TypedLocator(pos: Position) extends Locator(pos) {
    override protected def isEligible(t: Tree) = super.isEligible(t) && t.tpe != null
  }
}