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, 37 deletions

diff --git a/test/files/neg/t5589neg.check b/test/files/neg/t5589neg.check
deleted file mode 100644
index f1dad94df3..0000000000
--- a/test/files/neg/t5589neg.check
+++ /dev/null
@@ -1,37 +0,0 @@
-t5589neg.scala:2: warning: `withFilter' method does not yet exist on scala.util.Either.RightProjection[Int,String], using `filter' method instead
-  def f5(x: Either[Int, String])        = for ((y1, y2: String) <- x.right) yield ((y1, y2))
-                                                                     ^
-t5589neg.scala:2: error: constructor cannot be instantiated to expected type;
- found   : (T1, T2)
- required: String
-  def f5(x: Either[Int, String])        = for ((y1, y2: String) <- x.right) yield ((y1, y2))
-                                               ^
-t5589neg.scala:3: warning: `withFilter' method does not yet exist on scala.util.Either.RightProjection[Int,String], using `filter' method instead
-  def f6(x: Either[Int, String])        = for ((y1, y2: Any) <- x.right) yield ((y1, y2))
-                                                                  ^
-t5589neg.scala:3: error: constructor cannot be instantiated to expected type;
- found   : (T1, T2)
- required: String
-  def f6(x: Either[Int, String])        = for ((y1, y2: Any) <- x.right) yield ((y1, y2))
-                                               ^
-t5589neg.scala:4: error: constructor cannot be instantiated to expected type;
- found   : (T1,)
- required: (String, Int)
-  def f7(x: Either[Int, (String, Int)]) = for (y1 @ Tuple1(y2) <- x.right) yield ((y1, y2))
-                                                    ^
-t5589neg.scala:4: error: not found: value y2
-  def f7(x: Either[Int, (String, Int)]) = for (y1 @ Tuple1(y2) <- x.right) yield ((y1, y2))
-                                                                                       ^
-t5589neg.scala:5: error: constructor cannot be instantiated to expected type;
- found   : (T1, T2, T3)
- required: (String, Int)
-  def f8(x: Either[Int, (String, Int)]) = for ((y1, y2, y3) <- x.right) yield ((y1, y2))
-                                               ^
-t5589neg.scala:5: error: not found: value y1
-  def f8(x: Either[Int, (String, Int)]) = for ((y1, y2, y3) <- x.right) yield ((y1, y2))
-                                                                                ^
-t5589neg.scala:5: error: not found: value y2
-  def f8(x: Either[Int, (String, Int)]) = for ((y1, y2, y3) <- x.right) yield ((y1, y2))
-                                                                                    ^
-two warnings found
-7 errors found