moves Expr from api to base

This is the first step in supporting serialization for exprs and type tags.

Generally speaking universes and mirrors cannot be serialized (even not taking
into account all the amount of scalac-specific transient stuff, java mirrors
use classloaders, which are not serializable).

Hence we can only serialize tree and type creators, and deserialize them into
the mirror we surely know will be there - the scala.reflect.basis.rootMirror.

To do that we need to have exprs in scala.reflect.base. Luckily all the trees
are already in base, we only need to move a single file to scala-library.jar.
Another good news is that reification logic is simplified, because we don't
have to special case exprs as being defined in ApiUniverseClass.

1 files changed, 0 insertions, 49 deletions

diff --git a/src/reflect/scala/reflect/api/Universe.scala b/src/reflect/scala/reflect/api/Universe.scala
index da05b5ba46..3dce0f218e 100644
--- a/src/reflect/scala/reflect/api/Universe.scala
+++ b/src/reflect/scala/reflect/api/Universe.scala
@@ -14,53 +14,4 @@ abstract class Universe extends base.Universe
                            with StandardDefinitions
                            with StandardNames
                            with Importers
-                           with Exprs
                            with AnnotationInfos
-{
-
-  /** Given an expression, generate a tree that when compiled and executed produces the original tree.
-   *  The produced tree will be bound to the Universe it was called from.
-   *
-   *  For instance, given the abstract syntax tree representation of the <[ x + 1 ]> expression:
-   *
-   *  {{{
-   *    Apply(Select(Ident("x"), "+"), List(Literal(Constant(1))))
-   *  }}}
-   *
-   *  The reifier transforms it to the following expression:
-   *
-   *  {{{
-   *    <[
-   *      val $u: u.type = u // where u is a reference to the Universe that calls the reify
-   *      $u.Expr[Int]($u.Apply($u.Select($u.Ident($u.newFreeVar("x", <Int>, x), "+"), List($u.Literal($u.Constant(1))))))
-   *    ]>
-   *  }}}
-   *
-   *  Reification performs expression splicing (when processing Expr.splice)
-   *  and type splicing (for every type T that has a TypeTag[T] implicit in scope):
-   *
-   *  {{{
-   *    val two = mirror.reify(2)                         // Literal(Constant(2))
-   *    val four = mirror.reify(two.splice + two.splice)  // Apply(Select(two.tree, newTermName("$plus")), List(two.tree))
-   *
-   *    def macroImpl[T](c: Context) = {
-   *      ...
-   *      // T here is just a type parameter, so the tree produced by reify won't be of much use in a macro expansion
-   *      // however, if T were annotated with c.TypeTag (which would declare an implicit parameter for macroImpl)
-   *      // then reification would subtitute T with the TypeTree that was used in a TypeApply of this particular macro invocation
-   *      val factory = c.reify{ new Queryable[T] }
-   *      ...
-   *    }
-   *  }}}
-   *
-   *  The transformation looks mostly straightforward, but it has its tricky parts:
-   *    * Reifier retains symbols and types defined outside the reified tree, however
-   *      locally defined entities get erased and replaced with their original trees
-   *    * Free variables are detected and wrapped in symbols of the type FreeVar
-   *    * Mutable variables that are accessed from a local function are wrapped in refs
-   *    * Since reified trees can be compiled outside of the scope they've been created in,
-   *      special measures are taken to ensure that all members accessed in the reifee remain visible
-   */
-  // implementation is magically hardwired to `scala.reflect.reify.Taggers`
-  def reify[T](expr: T): Expr[T] = ??? // macro
-}
\ No newline at end of file