From 333ec27c9e503f428c86a155351d11f332f2892d Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Sun, 4 Sep 2016 15:01:05 +0200
Subject: 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.
---
 .../tools/dotc/core/tasty/PositionPickler.scala    | 92 +++++++++-------------
 1 file changed, 38 insertions(+), 54 deletions(-)

(limited to 'src/dotty/tools/dotc/core/tasty/PositionPickler.scala')

diff --git a/src/dotty/tools/dotc/core/tasty/PositionPickler.scala b/src/dotty/tools/dotc/core/tasty/PositionPickler.scala
index b0550b70a..63bb00a71 100644
--- a/src/dotty/tools/dotc/core/tasty/PositionPickler.scala
+++ b/src/dotty/tools/dotc/core/tasty/PositionPickler.scala
@@ -3,7 +3,8 @@ package dotc
 package core
 package tasty
 
-import ast.tpd._
+import ast._
+import ast.Trees._
 import ast.Trees.WithLazyField
 import TastyFormat._
 import core._
@@ -12,64 +13,47 @@ import collection.mutable
 import TastyBuffer._
 import util.Positions._
 
-object PositionPickler {
-
-  trait DeferredPosition {
-    var parentPos: Position = NoPosition
-  }
-
-  def traverse(x: Any, parentPos: Position, op: (Tree, Position) => Unit)(implicit ctx: Context): Unit =
-    if (parentPos.exists)
-      x match {
-        case x: Tree @unchecked =>
-          op(x, parentPos)
-          x match {
-            case x: MemberDef @unchecked => traverse(x.symbol.annotations, x.pos, op)
-            case _ =>
-          }
-          traverse(x.productIterator, x.pos, op)
-        case x: DeferredPosition =>
-          x.parentPos = parentPos
-        case xs: TraversableOnce[_] =>
-          xs.foreach(traverse(_, parentPos, op))
-        case _ =>
-      }
-}
-import PositionPickler._
-
-class PositionPickler(pickler: TastyPickler, addrOfTree: Tree => Option[Addr]) {
+class PositionPickler(pickler: TastyPickler, addrOfTree: tpd.Tree => Option[Addr]) {
   val buf = new TastyBuffer(5000)
   pickler.newSection("Positions", buf)
   import buf._
+  import ast.tpd._
+
+  def header(addrDelta: Int, hasStartDelta: Boolean, hasEndDelta: Boolean) = {
+    def toInt(b: Boolean) = if (b) 1 else 0
+    (addrDelta << 2) | (toInt(hasStartDelta) << 1) | toInt(hasEndDelta)
+  }
 
-  def picklePositions(roots: List[Tree], totalRange: Position)(implicit ctx: Context) = {
+  def picklePositions(roots: List[Tree])(implicit ctx: Context) = {
     var lastIndex = 0
-    def record(tree: Tree, parentPos: Position): Unit =
-      if (tree.pos.exists) {
-        def msg = s"failure to pickle $tree at ${tree.pos}, parent = $parentPos"
-        val endPos = tree.pos.end min parentPos.end
-          // end positions can be larger than their parents
-          // e.g. in the case of synthetic empty ranges, which are placed at the next token after
-          // the current construct.
-        val endDelta = endPos - parentPos.end
-        val startPos =
-          if (endDelta == 0) tree.pos.start max parentPos.start else tree.pos.start min endPos
-          // Since end positions are corrected above, start positions have to follow suit.
-        val startDelta = startPos - parentPos.start
-        if (startDelta != 0 || endDelta != 0)
-          for (addr <- addrOfTree(tree)) {
-            buf.writeInt(addr.index - lastIndex)
-            lastIndex = addr.index
-            if (startDelta != 0) buf.writeInt(startDelta)
-            if (endDelta != 0) {
-              assert(endDelta < 0, msg)
-              buf.writeInt(endDelta)
-            } else
-              assert(startDelta >= 0, msg)
+    var lastPos = Position(0, 0)
+    def pickleDeltas(index: Int, pos: Position) = {
+      val addrDelta = index - lastIndex
+      val startDelta = pos.start - lastPos.start
+      val endDelta = pos.end - lastPos.end
+      buf.writeInt(header(addrDelta, startDelta != 0, endDelta != 0))
+      if (startDelta != 0) buf.writeInt(startDelta)
+      if (endDelta != 0) buf.writeInt(endDelta)
+      lastIndex = index
+      lastPos = pos
+    }
+    def traverse(x: Any, parentPos: Position): Unit = x match {
+      case x: Tree @unchecked =>
+        if (x.pos.exists && x.pos.toSynthetic != parentPos.toSynthetic) {
+          addrOfTree(x) match {
+            case Some(addr) => pickleDeltas(addr.index, x.pos)
+            case _ =>
           }
-      }
-
-    buf.writeNat(totalRange.end)
-    traverse(roots, totalRange, record)
+        }
+        x match {
+          case x: MemberDef @unchecked => traverse(x.symbol.annotations, x.pos)
+          case _ =>
+        }
+        traverse(x.productIterator, x.pos)
+      case xs: TraversableOnce[_] =>
+        xs.foreach(traverse(_, parentPos))
+      case _ =>
+    }
+    traverse(roots, NoPosition)
   }
 }
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