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/presentation/callcc-interpreter.check b/test/files/presentation/callcc-interpreter.check
index af0154fe60..804b365101 100644
--- a/test/files/presentation/callcc-interpreter.check
+++ b/test/files/presentation/callcc-interpreter.check
@@ -69,13 +69,13 @@ retrieved 63 members
 askType at CallccInterpreter.scala(14,21)
 ================================================================================
 [response] askTypeAt at (14,21)
-def unitM[A >: Nothing <: Any](a: A): callccInterpreter.M[A] = callccInterpreter.this.M.apply[A](((c: A => callccInterpreter.Answer) => c.apply(a)))
+def unitM[A](a: A): callccInterpreter.M[A] = callccInterpreter.this.M.apply[A](((c: A => callccInterpreter.Answer) => c.apply(a)))
 ================================================================================
 
 askType at CallccInterpreter.scala(16,12)
 ================================================================================
 [response] askTypeAt at (16,12)
-def id[A >: Nothing <: Any]: A => A = ((x: A) => x)
+def id[A]: A => A = ((x: A) => x)
 ================================================================================
 
 askType at CallccInterpreter.scala(17,25)