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.

1 files changed, 4 insertions, 4 deletions

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