SI-9702 Fix backend crash with classOf[T] annotation argument

This commit fixes various issues with classOf literals and Java
annotations.

  - Ensure that a Type within a ConstantType (i.e., a classOf literal)
    is erased, so `classOf[List[Int]]` becomes `classOf[List]`.
  - Ensure that no non-erased types are passed to `typeToBType` in the
    backend. This happens for Java annotations: the annotation type and
    `classOf` annotation arguments are not erased, the annotationInfos
    of a symbol are not touched in the compiler pipeline.
  - If T is an alias to a value class, ensure that `classOf[T]` erases
    to the value class by calling `dealiasWiden` in erasure.

2 files changed, 4 insertions, 2 deletions

diff --git a/src/reflect/scala/reflect/internal/transform/Erasure.scala b/src/reflect/scala/reflect/internal/transform/Erasure.scala
index 32af6529ca..c069e2c198 100644
--- a/src/reflect/scala/reflect/internal/transform/Erasure.scala
+++ b/src/reflect/scala/reflect/internal/transform/Erasure.scala
@@ -112,8 +112,9 @@ trait Erasure {
     protected def eraseDerivedValueClassRef(tref: TypeRef): Type = erasedValueClassArg(tref)
 
     def apply(tp: Type): Type = tp match {
-      case ConstantType(_) =>
-        tp
+      case ConstantType(ct) =>
+        if (ct.tag == ClazzTag) ConstantType(Constant(apply(ct.typeValue)))
+        else tp
       case st: ThisType if st.sym.isPackageClass =>
         tp
       case st: SubType =>
diff --git a/src/reflect/scala/reflect/runtime/JavaMirrors.scala b/src/reflect/scala/reflect/runtime/JavaMirrors.scala
index 49799136de..bdcfcabdd5 100644
--- a/src/reflect/scala/reflect/runtime/JavaMirrors.scala
+++ b/src/reflect/scala/reflect/runtime/JavaMirrors.scala
@@ -1161,6 +1161,7 @@ private[scala] trait JavaMirrors extends internal.SymbolTable with api.JavaUnive
       propagatePackageBoundary(jmeth.javaFlags, meth)
       copyAnnotations(meth, jmeth)
       if (jmeth.javaFlags.isVarargs) meth modifyInfo arrayToRepeated
+      if (jmeth.getDefaultValue != null) meth.addAnnotation(AnnotationDefaultAttr)
       markAllCompleted(meth)
       meth
     }