Fix a NSDNHAO in extension methods.

A bridge method, created when we override a method from
a superclass and refine the return type, was appearing
as an overloaded alternative. (`erasure` doesn't create
new scopes, so the bridges it builds are visible at
earlier phases.)

The problem was masked when compiling with specialization,
which *does* create a new scope, shielding the code in
question from the artefacts of erasure.

To fix the problem, we filter out bridge methods from
the overloaded alternatives returned by `.decl`, as would
happen internally in `.member`.

1 files changed, 9 insertions, 0 deletions

diff --git a/test/files/pos/value-class-override-spec.scala b/test/files/pos/value-class-override-spec.scala
new file mode 100644
index 0000000000..79de5d9305
--- /dev/null
+++ b/test/files/pos/value-class-override-spec.scala
@@ -0,0 +1,9 @@
+// There are two versions of this tests: one with and one without specialization.
+// The bug was only exposed *without* specialization.
+trait T extends Any {
+  def x: Any
+}
+
+final class StringOps(val repr0: String) extends AnyVal with T {
+  def x = ()
+}