Merge pull request #946 from dotty-staging/more-predictable-hashes

Make hash codes on type more predictable.

Author: DarkDimius

src/dotty/tools/dotc/core/Hashable.scala

@@ -28,7 +28,7 @@ object Hashable {
 trait Hashable {
   import Hashable._
 
-  protected def hashSeed: Int = getClass.hashCode
+  protected def hashSeed: Int = getClass.getSimpleName.hashCode
 
   protected final def finishHash(hashCode: Int, arity: Int): Int =
     avoidNotCached(hashing.finalizeHash(hashCode, arity))

src/dotty/tools/dotc/core/Uniques.scala

@@ -92,7 +92,7 @@ object Uniques {
   }
 
   final class RefinedUniques extends HashSet[RefinedType](Config.initialUniquesCapacity) with Hashable {
-    override val hashSeed = classOf[CachedRefinedType].hashCode // some types start life as CachedRefinedTypes, need to have same hash seed
+    override val hashSeed = "CachedRefinedType".hashCode // some types start life as CachedRefinedTypes, need to have same hash seed
     override def hash(x: RefinedType): Int = x.hash
 
     private def findPrevious(h: Int, parent: Type, refinedName: Name, refinedInfo: Type): RefinedType = {