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Fix #3544: Better cache invalidation of uninstVars #3726

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Merged
merged 2 commits into from
Jan 14, 2018
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Fix #3544: Better cache invalidation of uninstVars #3726

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a3b0f45
Fix #3544: Better cache invalidation of uninstVars
odersky Jan 1, 2018
2744447
Add test case for #3470
odersky Jan 1, 2018
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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/core/OrderingConstraint.scala
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Expand Up @@ -548,7 +548,7 @@ class OrderingConstraint(private val boundsMap: ParamBounds,

/** The uninstantiated typevars of this constraint */
def uninstVars: collection.Seq[TypeVar] = {
if (myUninstVars == null) {
if (myUninstVars == null || myUninstVars.exists(_.inst.exists)) {
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Shouldn't this use instanceOpt instead of inst? Otherwise this will still return instantiated type variables whose inst field has not yet been set.

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I wonder if it wouldn't be simpler and more efficient to clear the cache everytime we instantiate a typevar instead.

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Anything in the constraint is already taken into account in uninstVars. After all, constraints are immutable. So we only need to make sure there are no instantiations not mirrored in the constraint. We can't clear the cache when we instantiate a typevar because there is no 1-1 mapping between constraints and typevars. So there could me multiple constraints that become invalid.

myUninstVars = new mutable.ArrayBuffer[TypeVar]
boundsMap.foreachBinding { (poly, entries) =>
for (i <- 0 until paramCount(entries)) {
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6 changes: 6 additions & 0 deletions tests/neg/i3470.scala
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@@ -0,0 +1,6 @@
object Main {
abstract class Factory[T <: Int] {
def size: T
def create: Array[T] = Array.ofDim(size) // error: No ClassTag available
}
}
6 changes: 6 additions & 0 deletions tests/pos/i3544.scala
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@@ -0,0 +1,6 @@
object Test {
case class Tuple2K[F[_], G[_], A](f: F[A], g: G[A])

val p0: Tuple2K[[X] => Int, [X] => String, Any] = Tuple2K(1, "s")
p0 == Tuple2K(List(1), Option("s"))
}