SI-9029 Fix regression in extractor patterns

The unified treatment of classical and named-based pattern matching
does not correctly handle the generalization of "tuple capture".

By "tuple capture", I mean:

```
scala> object Extractor { def unapply(a: Any): Option[(Int, String)] = Some((1, "2")) }
defined object Extractor

scala> "" match { case Extractor(x: Int, y: String) => }

scala> "" match { case Extractor(xy : (Int, String)) => }
warning: there was one deprecation warning; re-run with -deprecation for details

scala> :warnings
<console>:9: warning: object Extractor expects 2 patterns to hold (Int, String) but crushing into 2-tuple to fit single pattern (SI-6675)
              "" match { case Extractor(xy : (Int, String)) => }
                              ^
```

Name based pattern matching, new in Scala 2.11, allows one to
deconstruct the elements that structurally resembles `ProductN`:

```
scala> class P2(val _1: Int, val _2: String)
defined class P2

scala> object Extractor { def unapply(a: Any): Option[P2] = Some(new P2(1, "2")) }
defined object Extractor

scala> "" match { case Extractor(x: Int, y: String) => }
```

However, attempting to extract the `P2` in its entirety leads to
an internal error:

```
scala> "" match { case Extractor(p2: P2) => }
<console>:10: warning: fruitless type test: a value of type (Int, String) cannot also be a P2
              "" match { case Extractor(p2: P2) => }
                                            ^
<console>:10: error: error during expansion of this match (this is a scalac bug).
The underlying error was: type mismatch;
 found   : P2
 required: (Int, String)
              "" match { case Extractor(p2: P2) => }
                 ^
```

Note that this match was legal and warning free in 2.10.

This commit avoids the hard-coded assumption that the "tuple capture"
results in a `TupleN`, and instead keeps track of the product-ish
type from which we extracted the element types. I have also opted not
to limit the deprecation warning to `TupleN` extractors.

1 files changed, 1 insertions, 0 deletions

diff --git a/test/files/run/t9029.flags b/test/files/run/t9029.flags
new file mode 100644
index 0000000000..dcc59ebe32
--- /dev/null
+++ b/test/files/run/t9029.flags
@@ -0,0 +1 @@
+-deprecation