Simplify type bounds.

I started out looking to limit the noise from empty type
bounds, i.e. the endless repetition of

  class A[T >: _root_.scala.Nothing <: _root_.scala.Any]

This led me to be reminded of all the unnecessary and
in fact damaging overreaches which are performed during parsing.
Why should a type parameter for which no bounds are
specified be immediately encoded with this giant tree:

  TypeBounds(
    Select(Select(Ident(nme.ROOTPKG), tpnme.scala_), tpnme.Nothing),
    Select(Select(Ident(nme.ROOTPKG), tpnme.scala_), tpnme.Any)
  )

...which must then be manually recognized as empty type bounds?
Truly, this is madness.

 - It deftly eliminates the possibility of recognizing
   whether the user wrote "class A[T]" or "class A[T >: Nothing]"
   or "class A[T <: Any]" or specified both bounds. The fact
   that these work out the same internally does not imply the
   information should be exterminated even before parsing completes.
 - It burdens everyone who must recognize type bounds trees,
   such as this author
 - It is far less efficient than the obvious encoding
 - It offers literally no advantage whatsoever

Encode empty type bounds as

  TypeBounds(EmptyTree, EmptyTree)

What could be simpler.

1 files changed, 2 insertions, 2 deletions

diff --git a/test/files/run/macro-typecheck-macrosdisabled.check b/test/files/run/macro-typecheck-macrosdisabled.check
index 29a881f8b1..e0e880ab66 100644
--- a/test/files/run/macro-typecheck-macrosdisabled.check
+++ b/test/files/run/macro-typecheck-macrosdisabled.check
@@ -7,7 +7,7 @@
         $treecreator1.super.<init>();
         ()
       };
-      def apply[U >: Nothing <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Tree = {
+      def apply[U <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Tree = {
         val $u: U = $m$untyped.universe;
         val $m: $u.Mirror = $m$untyped.asInstanceOf[$u.Mirror];
         $u.Literal.apply($u.Constant.apply(2))
@@ -20,7 +20,7 @@
         $typecreator2.super.<init>();
         ()
       };
-      def apply[U >: Nothing <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Type = {
+      def apply[U <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Type = {
         val $u: U = $m$untyped.universe;
         val $m: $u.Mirror = $m$untyped.asInstanceOf[$u.Mirror];
         $u.ConstantType.apply($u.Constant.apply(2))