SI-6680 unsoundness in gadt typing.

Introduces -Xstrict-inference to deal with the significant
gap between soundness and what presently compiles. I'm hopeful
that it's TOO strict, because it finds e.g. 75 errors compiling
immutable/IntMap.scala, but it might be that bad.

1 files changed, 18 insertions, 0 deletions

diff --git a/test/files/neg/t6680a.scala b/test/files/neg/t6680a.scala
new file mode 100644
index 0000000000..93b796438f
--- /dev/null
+++ b/test/files/neg/t6680a.scala
@@ -0,0 +1,18 @@
+case class Cell[A](var x: A)
+object Test {
+  def f1(x: Any)        = x match { case y @ Cell(_) => y } // Inferred type is Cell[Any]
+  def f2(x: Cell[_])    = x match { case y @ Cell(_) => y } // Inferred type is Cell[_]
+  def f3[A](x: Cell[A]) = x match { case y @ Cell(_) => y } // Inferred type is Cell[A]
+
+  def main(args: Array[String]): Unit = {
+    val x = new Cell(1)
+    val y = f1(x)
+    y.x = "abc"
+    println(x.x + 1)
+  }
+}
+
+// The tweetable variation
+object Tweet {
+  case class C[A](f:A=>A);def f(x:Any)=x match { case C(f)=>f("") };f(C[Int](x=>x))
+}