From c29405dfe1a24419ce4ce10500b5e8d05c581bee Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Fri, 19 Apr 2013 15:01:46 -0700
Subject: 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.
---
 test/files/run/macro-typecheck-macrosdisabled2.check | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'test/files/run/macro-typecheck-macrosdisabled2.check')

diff --git a/test/files/run/macro-typecheck-macrosdisabled2.check b/test/files/run/macro-typecheck-macrosdisabled2.check
index 75fd693722..347dfec1dc 100644
--- a/test/files/run/macro-typecheck-macrosdisabled2.check
+++ b/test/files/run/macro-typecheck-macrosdisabled2.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];
         $u.Apply.apply($u.Select.apply($u.build.Ident($m.staticModule("scala.Array")), $u.TermName.apply("apply")), scala.collection.immutable.List.apply[$u.Literal]($u.Literal.apply($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];
         $u.TypeRef.apply($u.ThisType.apply($m.staticPackage("scala").asModule.moduleClass), $m.staticClass("scala.Array"), scala.collection.immutable.List.apply[$u.Type]($m.staticClass("scala.Int").asType.toTypeConstructor))
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