Check that we are keeping the same exception while shrinking

Author: AurelienRichez

core/shared/src/main/scala/org/scalacheck/Prop.scala

@@ -772,10 +772,13 @@ object Prop {
     /*
      * Returns the first failed result in Left or success in Right.
      */
-    def getFirstFailure(xs: Stream[T]): Either[(T,Result),(T,Result)] = {
+    def getFirstFailure(xs: Stream[T], exceptionFilter: Option[Class[_]]): Either[(T,Result),(T,Result)] = {
       assert(!xs.isEmpty, "Stream cannot be empty")
       val results = xs.map(x => (x, result(x)))
-      results.dropWhile(!_._2.failure).headOption match {
+      results.dropWhile { 
+        case (_, Result(Exception(e), _, _, _)) => !exceptionFilter.contains(e.getClass)
+        case (_, r) => !r.failure 
+      }.headOption match {
         case None => Right(results.head)
         case Some(xr) => Left(xr)
       }
@@ -784,7 +787,8 @@ object Prop {
     def shrinker(x: T, r: Result, shrinks: Int, orig: T): Result = {
       val xs = shrink(x)
       val res = r.addArg(Arg(labels,x,shrinks,orig,pp(x),pp(orig)))
-      if(xs.isEmpty) res else getFirstFailure(xs) match {
+      val originalException = Some(r.status).collect { case Exception(e) => e.getClass() }
+      if(xs.isEmpty) res else getFirstFailure(xs, originalException) match {
         case Right((x2,r2)) => res
         case Left((x2,r2)) => shrinker(x2, replOrig(r,r2), shrinks+1, orig)
       }