SI-7329 duplicate default getters for specialized parameters.

The default getter is generated with @specialized annotation if the
type parameter corresponding to the type of the parameter is
specialized. Consequently specialize pass tries to generate overloads.

Rather than pruning overloads to exclude duplicates, let's notice
that default getter specialization is not needed at all:
  - The dynamic scope of default getter doesn't include specialized
    method or class constructor.
  - generic default getter is called even when calling specialized
    method:
    object V {
      @specialized def foo[@specialized B](b: B = (??? : B)) = {}
      foo[Int]()
    }
    gives:
      invokevirtual Method V$.foo$default$1:()Ljava/lang/Object;
      invokestatic (unboxToInt)
      invokevirtual Method V$.foo$mIc$sp:(I)V

2 files changed, 6 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
index a71920f787..d91ea4707d 100644
--- a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
+++ b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
@@ -796,7 +796,11 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
   private def normalizeMember(owner: Symbol, sym: Symbol, outerEnv: TypeEnv): List[Symbol] = {
     sym :: (
       if (!sym.isMethod || beforeTyper(sym.typeParams.isEmpty)) Nil
-      else {
+      else if (sym.hasDefault) {
+        /* Specializing default getters is useless, also see SI-7329 . */
+        sym.resetFlag(SPECIALIZED)
+        Nil
+      } else {
         // debuglog("normalizeMember: " + sym.fullNameAsName('.').decode)
         var specializingOn = specializedParams(sym)
         val unusedStvars   = specializingOn filterNot specializedTypeVars(sym.info)
diff --git a/test/files/pos/t7329.scala b/test/files/pos/t7329.scala
new file mode 100644
index 0000000000..76bf1fb9f5
--- /dev/null
+++ b/test/files/pos/t7329.scala
@@ -0,0 +1 @@
+class TwoParamSpecializedWithDefault[@specialized A, @specialized B](a: A, b: B = (??? : B))
\ No newline at end of file