Fix for one of the oldest open soundness bugs.

Closes SI-963, since it was one of my random 30 it won the prize.
The trick after adding the stability check (which has been sitting
there commented out for 3+ years) was that implicit search depended
on the wrongness, because memberWildcardType would create scopes
with members of the form

  ?{ val name: tp }

And since a def shouldn't match that, fixing it broke everything
until I flipped it around: memberWildcardType should be seeking

  ?{ def name: tp }

It could also search for a mutable value: the relevant quality
is that it not be stable so it doesn't have a tighter type than
the members it hopes to match.

4 files changed, 36 insertions, 6 deletions

diff --git a/test/files/buildmanager/t2556_3/t2556_3.check b/test/files/buildmanager/t2556_3/t2556_3.check
index 37808d2b31..34f90f7f9b 100644
--- a/test/files/buildmanager/t2556_3/t2556_3.check
+++ b/test/files/buildmanager/t2556_3/t2556_3.check
@@ -9,10 +9,10 @@ invalidate B.scala because it references invalid (no longer inherited) definitio
 compiling Set(B.scala, C.scala)
 B.scala:3: error: type mismatch;
  found   : C
- required: ?{val x: ?}
+ required: ?{def x: ?}
 Note that implicit conversions are not applicable because they are ambiguous:
  both method any2Ensuring in object Predef of type [A](x: A)Ensuring[A]
  and method any2ArrowAssoc in object Predef of type [A](x: A)ArrowAssoc[A]
- are possible conversion functions from C to ?{val x: ?}
+ are possible conversion functions from C to ?{def x: ?}
     println( (new C).x )
               ^
diff --git a/test/files/neg/logImplicits.check b/test/files/neg/logImplicits.check
index d98422dacb..54afc6f86d 100644
--- a/test/files/neg/logImplicits.check
+++ b/test/files/neg/logImplicits.check
@@ -1,16 +1,16 @@
-logImplicits.scala:2: applied implicit conversion from xs.type to ?{val size: ?} = implicit def byteArrayOps(xs: Array[Byte]): scala.collection.mutable.ArrayOps[Byte]
+logImplicits.scala:2: applied implicit conversion from xs.type to ?{def size: ?} = implicit def byteArrayOps(xs: Array[Byte]): scala.collection.mutable.ArrayOps[Byte]
   def f(xs: Array[Byte]) = xs.size
                            ^
-logImplicits.scala:7: applied implicit conversion from String("abc") to ?{val map: ?} = implicit def augmentString(x: String): scala.collection.immutable.StringOps
+logImplicits.scala:7: applied implicit conversion from String("abc") to ?{def map: ?} = implicit def augmentString(x: String): scala.collection.immutable.StringOps
   def f = "abc" map (_ + 1)
           ^
 logImplicits.scala:15: inferred view from String("abc") to Int = C.this.convert:(p: String("abc"))Int
   math.max(122, x: Int)
                 ^
-logImplicits.scala:19: applied implicit conversion from Int(1) to ?{val ->: ?} = implicit def any2ArrowAssoc[A](x: A): ArrowAssoc[A]
+logImplicits.scala:19: applied implicit conversion from Int(1) to ?{def ->: ?} = implicit def any2ArrowAssoc[A](x: A): ArrowAssoc[A]
   def f = (1 -> 2) + "c"
            ^
-logImplicits.scala:19: applied implicit conversion from (Int, Int) to ?{val +: ?} = implicit def any2stringadd(x: Any): scala.runtime.StringAdd
+logImplicits.scala:19: applied implicit conversion from (Int, Int) to ?{def +: ?} = implicit def any2stringadd(x: Any): scala.runtime.StringAdd
   def f = (1 -> 2) + "c"
              ^
 logImplicits.scala:22: error: class Un needs to be abstract, since method unimplemented is not defined
diff --git a/test/files/neg/t963.check b/test/files/neg/t963.check
new file mode 100644
index 0000000000..1f2d0687b3
--- /dev/null
+++ b/test/files/neg/t963.check
@@ -0,0 +1,12 @@
+t963.scala:14: error: stable identifier required, but Test.this.y3.x found.
+  val w3 : y3.x.type = y3.x
+              ^
+t963.scala:17: error: stable identifier required, but Test.this.y4.x found.
+  val w4 : y4.x.type = y4.x
+              ^
+t963.scala:10: error: type mismatch;
+ found   : Object{def x: Integer}
+ required: AnyRef{val x: Integer}
+  val y2 : { val x : java.lang.Integer  } = new { def x = new java.lang.Integer(r.nextInt) }
+                                            ^
+three errors found
diff --git a/test/files/neg/t963.scala b/test/files/neg/t963.scala
new file mode 100644
index 0000000000..0cc2034299
--- /dev/null
+++ b/test/files/neg/t963.scala
@@ -0,0 +1,18 @@
+import scala.util.Random
+
+// Only y1 (val/val) should actually compile.
+object Test {
+  val r = new Random()
+
+  val y1 : { val x : java.lang.Integer  } = new { val x = new java.lang.Integer(r.nextInt) }
+  val w1 : y1.x.type = y1.x
+
+  val y2 : { val x : java.lang.Integer  } = new { def x = new java.lang.Integer(r.nextInt) }
+  val w2 : y2.x.type = y2.x
+
+  val y3 : { def x : java.lang.Integer  } = new { val x = new java.lang.Integer(r.nextInt) }
+  val w3 : y3.x.type = y3.x
+
+  val y4 : { def x : java.lang.Integer  } = new { def x = new java.lang.Integer(r.nextInt) }
+  val w4 : y4.x.type = y4.x
+}