SI-5900 Fix pattern inference regression

This commit does not close SI-5900. It only addresses a regression
in 2.11 prereleases caused by SI-7886.

The fix for SI-7886 was incomplete (as shown by the last commit)
and incorrect (as shown by the regression in pos/t5900a.scala and
the fact it ended up inferring type parameters.)

I believe that the key to fixing this problem will be unifying
the inference of case class constructor patterns and extractor
patterns.

I've explored that idea:

  https://gist.github.com/retronym/7704153
  https://github.com/retronym/scala/compare/ticket/5900

But didn't quite get there.

2 files changed, 9 insertions, 29 deletions

diff --git a/test/files/pos/pattern-typing.scala b/test/files/pos/pattern-typing.scala
deleted file mode 100644
index 7286cc38af..0000000000
--- a/test/files/pos/pattern-typing.scala
+++ /dev/null
@@ -1,29 +0,0 @@
-import scala.language.higherKinds
-
-trait Bound[B]
-
-package p1 {
-  case class Sub[B <: Bound[B]](p: B)
-  object Test {
-    def g[A](x: Bound[A]) = ()
-    def f(x: Any) = x match { case Sub(p) => g(p) }
-  }
-}
-
-package p2 {
-  trait Traversable[+A] { def head: A = ??? }
-  trait Seq[+A] extends Traversable[A] { def length: Int = ??? }
-
-  case class SubHK[B <: Bound[B], CC[X] <: Traversable[X]](xs: CC[B])
-  class MyBound extends Bound[MyBound]
-  class MySeq extends Seq[MyBound]
-
-  object Test {
-    def g[B](x: Bound[B]) = ()
-
-    def f1(x: Any) = x match { case SubHK(xs) => xs }
-    def f2[B <: Bound[B], CC[X] <: Traversable[X]](sub: SubHK[B, CC]): CC[B] = sub match { case SubHK(xs) => xs }
-    def f3 = g(f1(SubHK(new MySeq)).head)
-    def f4 = g(f2(SubHK(new MySeq)).head)
-  }
-}
diff --git a/test/files/pos/t5900a.scala b/test/files/pos/t5900a.scala
new file mode 100644
index 0000000000..cb02f67fb2
--- /dev/null
+++ b/test/files/pos/t5900a.scala
@@ -0,0 +1,9 @@
+case class Transition[S](x: S)
+
+object C
+
+object Test {
+  (??? : Any) match {
+    case Transition(C) =>
+  }
+}