Set the positions of inlined trees wehn read form Tasty

This required a major change in the way positions are handled, as the
previous scheme did not allow to read the positions of arbitrary subtrees
selectively.

Fortunately, it's altogether a major simplification.

Also, this fixed a bug in the previous scheme, where positions were
generated before compactification, resulting in addresses being wrong.

1 files changed, 19 insertions, 21 deletions

diff --git a/src/dotty/tools/dotc/core/tasty/PositionUnpickler.scala b/src/dotty/tools/dotc/core/tasty/PositionUnpickler.scala
index fa80a2769..c29aeba70 100644
--- a/src/dotty/tools/dotc/core/tasty/PositionUnpickler.scala
+++ b/src/dotty/tools/dotc/core/tasty/PositionUnpickler.scala
@@ -6,33 +6,31 @@ package tasty
 
 import util.Positions._
 import collection.mutable
-import TastyBuffer.Addr
-
-object PositionUnpickler {
-  type AddrToPosition = mutable.HashMap[Addr, Position]
-}
+import TastyBuffer.{Addr, NoAddr}
 
 /** Unpickler for tree positions */
 class PositionUnpickler(reader: TastyReader) {
-  import PositionUnpickler._
   import reader._
 
-  def unpickle(): (Position, AddrToPosition) = {
-    val positions = new mutable.HashMap[Addr, Position] // Dotty deviation: Can't use new AddrToPosition here. TODO: fix this!
-    val sourceLength = readNat()
-    def readDelta() = if (isAtEnd) 0 else readInt()
-    var curIndex: Addr = Addr(readDelta())
+  private[tasty] lazy val positions = {
+    val positions = new mutable.HashMap[Addr, Position]
+    var curIndex = 0
+    var curStart = 0
+    var curEnd = 0
     while (!isAtEnd) {
-      val delta1 = readDelta()
-      val delta2 = readDelta()
-      val (startDelta, endDelta, indexDelta) =
-        if (delta2 <= 0) (delta1, -delta2, readDelta())
-        else if (delta1 < 0) (0, -delta1, delta2)
-        else (delta1, 0, delta2)
-      positions(curIndex) = Position(startDelta, endDelta, startDelta)
-        // make non-synthetic position; will be made synthetic by normalization.
-      curIndex += indexDelta
+      val header = readInt()
+      val addrDelta = header >> 2
+      val hasStart = (header & 2) != 0
+      val hasEnd = (header & 1) != 0
+      curIndex += addrDelta
+      assert(curIndex >= 0)
+      if (hasStart) curStart += readInt()
+      if (hasEnd) curEnd += readInt()
+      positions(Addr(curIndex)) = Position(curStart, curEnd)
     }
-    (Position(0, sourceLength), positions)
+    positions
   }
+
+  def posAt(addr: Addr) = positions.getOrElse(addr, NoPosition)
 }
+