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package scala.tools.nsc.interactive
import ast.Trees
import scala.tools.nsc.util.{SourceFile, Position, RangePosition, OffsetPosition, 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, then singleton consisting of the node itself.
*/
trait Positions extends Trees {
self: Global =>
case class Range(val pos: Position, val tree: Tree) {
def isFree = tree == EmptyTree
}
class TransparentPosition(source0: SourceFile, start: Int, point: Int, end: Int) extends RangePosition(source0, start, point, end) {
override def toString = "<"+super.toString+">"
}
def isTransparent(pos: Position) = pos.isInstanceOf[TransparentPosition]
def isRange(pos: Position) = pos.isInstanceOf[RangePosition]
// -------------- ensuring no overlaps -------------------------------
def solidDescendants(tree: Tree): List[Tree] =
if (isTransparent(tree.pos)) 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 val maxFree: Range = free(0, Math.MAX_INT)
/** 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(!isTransparent(t.pos))
if (r.isFree && (r.pos includes 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 list of trees has mutually non-overlapping positions,
* by assinging TransparentPositions to some of them, if necessary
*/
def ensureNonOverlapping(cts: List[Tree]): Unit = {
/** Do a pass over all child trees `cts`, where `ranges` reflects positions previously
* encountered. If there are overlaps, break up one node by making its position a TransparentPosition
* and do another pass of `ensureOverlapping`.
* @param ranges The current list of non-overlapping ranges,
* both occupied and free, sorted from later to earlier.
* No TransparentPositions allowed here!
* @param trees The list of trees to insert in ranges.
*/
def iterate(ranges: List[Range], trees: List[Tree]): Unit = trees match {
case List() =>
;
case ct :: trees1 =>
if (isTransparent(ct.pos))
iterate(ranges, solidDescendants(ct) ::: trees1)
else if (ct.pos.isDefined) {
val conflicting = new ListBuffer[Tree]
val ranges1 = insert(ranges, ct, conflicting)
if (conflicting.isEmpty) {
iterate(ranges1, trees1)
} else {
val splitNode =
if (conflicting.size == 1 && (conflicting.head.pos includes ct.pos)) conflicting.head
else ct
splitNode setPos new TransparentPosition(splitNode.pos.source.get, splitNode.pos.start, splitNode.pos.point, splitNode.pos.end)
ensureNonOverlapping(replace(cts, splitNode, solidDescendants(splitNode)))
}
}
}
iterate(List(maxFree), cts)
}
/** Does given list of trees have mutually non-overlapping positions? */
def findOverlapping(cts: List[Tree]): List[(Tree, Tree)] = {
var ranges = List(maxFree)
for (ct <- cts) {
val conflicting = new ListBuffer[Tree]
ranges = insert(ranges, ct, conflicting)
if (conflicting.nonEmpty) return conflicting.toList map (t => (t, ct))
}
List()
}
// -------------- setting positions -------------------------------
/** The sorted list of descendant nodes, a long 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
*/
private def setChildrenPos(pos: Position, trees: List[Tree]) {
var currentPos = pos
for (tree <- trees) {
if (tree != EmptyTree && tree.pos == NoPosition) {
val children = tree.children
if (children.isEmpty)
tree setPos OffsetPosition(pos.source.get, currentPos.start)
else {
setChildrenPos(currentPos, children)
tree setPos new RangePosition(
pos.source.get, (children map (_.pos.start)).min, pos.point, (children map (_.pos.end)).max)
}
currentPos = new RangePosition(pos.source.get, tree.pos.end, pos.point, pos.end)
}
// println("set children pos "+pos+" of "+trees)
}
ensureNonOverlapping(trees)
}
/** 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 (isRange(pos)) {
if (tree != EmptyTree && 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 ----------------------------------
def validatePositions(tree: Tree) {
def error(msg: String) {
inform("**** bad positions:")
inform(msg)
inform("================= in =================")
inform(tree.toString)
}
def validate(tree: Tree, encltree: Tree) {
if (encltree.pos.isSynthetic && !tree.pos.isSynthetic)
error("synthetic "+encltree+" contains nonsynthetic" + tree)
if (!(encltree.pos includes tree.pos))
error(encltree+" does not include "+tree)
for ((t1, t2) <- findOverlapping(tree.children flatMap solidDescendants))
error("overlapping trees: "+t1+" === and === "+t2)
}
validate(tree, tree)
}
// ---------------- 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
}
override def traverse(t: Tree) {
if (!t.pos.isSynthetic && (t.pos includes pos)) {
if (!isTransparent(t.pos)) last = t
super.traverse(t)
}
}
}
}
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