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, 0 insertions, 13 deletions

diff --git a/test/files/run/t4574.scala b/test/files/run/t4574.scala
deleted file mode 100644
index 1dde496aca..0000000000
--- a/test/files/run/t4574.scala
+++ /dev/null
@@ -1,13 +0,0 @@
-object Test {
-  val xs: List[(Int, Int)] = List((2, 2), null)
-  
-  def expectMatchError[T](msg: String)(body: => T) {
-    try { body ; assert(false, "Should not succeed.") }
-    catch { case _: MatchError => println(msg) }
-  }
-
-  def main(args: Array[String]): Unit = {
-    expectMatchError("I hereby refute null!")( for ((x, y) <- xs) yield x )
-    expectMatchError("I denounce null as unListLike!")( (null: Any) match { case List(_*) => true } )
-  }
-}