SI-6968 Simple Tuple patterns aren't irrefutable

Reverts part of c82ecab. The parser can't assume that
a pattern `(a, b)` will match, as results of
`.isInstanceOf[Tuple2]` can't be statically known until
after the typer.

The reopens SI-1336, SI-5589 and SI-4574, in exchange for fixing
this regression SI-6968. Keeping all of those fixed will require
a better definition of irrefutability, and some acrobatics to
ensure safe passage to the ambiguous trees through typechecking.

1 files changed, 1 insertions, 1 deletions

diff --git a/test/files/scalacheck/parallel-collections/ParallelMapCheck1.scala b/test/files/scalacheck/parallel-collections/ParallelMapCheck1.scala
index 05237bace8..b6af8f41bd 100644
--- a/test/files/scalacheck/parallel-collections/ParallelMapCheck1.scala
+++ b/test/files/scalacheck/parallel-collections/ParallelMapCheck1.scala
@@ -20,7 +20,7 @@ abstract class ParallelMapCheck[K, V](collname: String) extends ParallelIterable
   property("gets iterated keys") = forAll(collectionPairs) {
     case (t, coll) =>
     val containsT = for ((k, v) <- t) yield (coll.get(k) == Some(v))
-    val containsSelf = for ((k, v) <- coll) yield (coll.get(k) == Some(v))
+    val containsSelf = coll.map { case (k, v) => coll.get(k) == Some(v) }
     ("Par contains elements of seq map" |: containsT.forall(_ == true)) &&
     ("Par contains elements of itself" |: containsSelf.forall(_ == true))
   }