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Add cyclic reference detection to TASTY unpickling #3842

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Merged
merged 1 commit into from
Jan 15, 2018
Merged

Add cyclic reference detection to TASTY unpickling #3842

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15 changes: 13 additions & 2 deletions compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -631,8 +631,16 @@ class TreeUnpickler(reader: TastyReader,
* or else read definition.
*/
def readIndexedDef()(implicit ctx: Context): Tree = treeAtAddr.remove(currentAddr) match {
case Some(tree) => skipTree(); tree
case none => readNewDef()
case Some(tree) =>
assert(tree != PoisonTree, s"Cyclic reference while unpickling definition at address ${currentAddr.index} in unit ${ctx.compilationUnit}")
skipTree()
tree
case none =>
val start = currentAddr
treeAtAddr(start) = PoisonTree
val tree = readNewDef()
treeAtAddr.remove(start)
tree
}

private def readNewDef()(implicit ctx: Context): Tree = {
Expand Down Expand Up @@ -1169,6 +1177,9 @@ class TreeUnpickler(reader: TastyReader,

object TreeUnpickler {

/** A marker value used to detect cyclic reference while unpickling definitions. */
@sharable val PoisonTree: tpd.Tree = Thicket(Nil)

/** An enumeration indicating which subtrees should be added to an OwnerTree. */
type MemberDefMode = Int
final val MemberDefsOnly = 0 // add only member defs; skip other statements
Expand Down