SI-6677 Insert required cast in `new qual.foo.T`

Short version: we sometimes need to rewrite this as

    new T(qual.asInstanceOf[OwnerOfFoo].foo)

Long version:

`adaptMember` in Erasure performs a few tasks, among them:

1. adding an empty argument list to qualifiers in `new qual.T`
    for which `qual` is a val template member that has
    (post uncurry) a MethodType with an empty parameter list.

    The same rewriting was already applied in uncurry for such
    qualifiers appearing in other contexts, e.g. `qual.foo` was
    already rewritten to `qual().foo`.
2. casting, if necessary, the qualifier in `Select(qual, name)`
    to the type of owner of the symbol that this selection
    references.

    This can be neccesary with compound types:
     - some val class member has type `A with B`;
     - we instantiate `new ab.valMemberOfB.T`
     - we must pass `ab.valMemberOfB` to the constructor of `T`
       as the `$outer` pointer
     - we must cast `ab` to `B` before calling `valMemberOfB`.

    Failure to insert this cast can lead to a LinkageError or
    a VerifyError.

However, if 1) was performed, 2) was not.

The error is pretty easy to trigger with the new reflection
API:

    class Test {
      val cm: reflect.runtime.universe.Mirror
          = reflect.runtime.currentMirror
      def error {
        new cm.universe.Traverser // java.lang.VerifyError
      }

      def okay1 {
        val cm: reflect.runtime.universe.Mirror = reflect.runtime.currentMirror
        new cm.universe.Traverser
      }
    }

The fix applied here to `adaptMember` mirrors the existing
implementation of `adaptType`.

1 files changed, 28 insertions, 0 deletions

diff --git a/test/files/run/t6677.scala b/test/files/run/t6677.scala
new file mode 100644
index 0000000000..e6eaf6a498
--- /dev/null
+++ b/test/files/run/t6677.scala
@@ -0,0 +1,28 @@
+
+class Test {
+  val cm: reflect.runtime.universe.Mirror = reflect.runtime.currentMirror
+  def error {
+    new cm.universe.Traverser // java.lang.VerifyError: (class: Test, method: error signature: ()V) Incompatible object argument for function call
+
+  }
+
+  def okay1 {
+    val cm: reflect.runtime.universe.Mirror = reflect.runtime.currentMirror
+
+    new cm.universe.Traverser
+  }
+
+  def okay2 {
+    val cm: reflect.runtime.universe.Mirror = reflect.runtime.currentMirror
+    val u: reflect.runtime.universe.type = cm.universe
+    new u.Traverser
+  }
+}
+
+object Test {
+  def main(args: Array[String]) {
+    new Test().error
+    new Test().okay1
+    new Test().okay2
+  }
+}