SI-5919 TypeTags and Exprs should be serializable

- Make TypeCreator and TreeCreator extend Serializable.
- When replacing a SerializedTypeTag with a TypeTag or WeakTypeTag,
  do not use scala.reflect.runtime.universe.rootMirror, since
  it is unlikely to find user classes; instead, create a runtime
  mirror using the context ClassLoader of the current thread.
  Use the same logic for SerializedExpr.
- Remove writeObject/readObject methods from SerializedTypeTag
  and SerializedExpr since they are unused.
- Add @throws annotation on writeReplace and readResolve methods.
- Handle SecurityException if the current thread cannot access the
  context ClassLoader.
- To make type tags of primitive value classes serializable, make
  PredefTypeCreator a top-level class. Otherwise, it would
  retain a reference to the enclosing Universe,
  rendering the TypeCreator non-serializable.

Binary compatibility:

- Keep nested PredefTypeCreator class to avoid backward binary
  incompatible change.
- Keep `var` modifiers on the class parameters of
  SerializedTypeTag for backward binary compatibility.
- Adds filter rules to forward binary compatibility whitelist:
  - `TypeCreator`, `PredefTypeCreator`, and `TreeCreator` must now
    extend from `Serializable`.
  - Must have new class `scala.reflect.api.PredefTypeCreator`
    to avoid problematic outer reference.

1 files changed, 5 insertions, 0 deletions

diff --git a/test/files/run/typetags_serialize.scala b/test/files/run/typetags_serialize.scala
index 3c842e6cc9..a7a7845232 100644
--- a/test/files/run/typetags_serialize.scala
+++ b/test/files/run/typetags_serialize.scala
@@ -4,6 +4,10 @@ import scala.reflect.runtime.{universe => ru}
 import scala.reflect.runtime.{currentMirror => cm}
 
 object Test extends App {
+  class C[A] {
+    def m(a: A): Int = 5
+  }
+
   def test(tag: TypeTag[_]) =
     try {
       val fout = new ByteArrayOutputStream()
@@ -26,4 +30,5 @@ object Test extends App {
 
   test(implicitly[TypeTag[Int]])
   test(implicitly[TypeTag[String]])
+  test(implicitly[TypeTag[C[Double]]])
 }
\ No newline at end of file