Made "mode" into a value class.

This is an obvious place to apply value class goodness and
collect some safety/sanity in typing modes. It does show off
a challenge in introducing value classes without disruption:
there's no way to deprecate the old signature of 'typed',
'adapt', etc. because they erase the same.

  class Bippy(val x: Int) extends AnyVal
  class A {
    @deprecated("Use a bippy") def f(x: Int): Int = 5
    def f(x: Bippy): Int = x.x
  }

  ./a.scala:5: error: double definition:
  method f:(x: Bippy)Int and
  method f:(x: Int)Int at line 4
  have same type after erasure: (x: Int)Int

An Int => Mode implicit handles most uses, but nothing can
be done to avoid breaking anything which e.g. extends Typer
and overrides typed.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/compiler/scala/tools/nsc/package.scala b/src/compiler/scala/tools/nsc/package.scala
index 00a9f3b39c..5e8d4f7885 100644
--- a/src/compiler/scala/tools/nsc/package.scala
+++ b/src/compiler/scala/tools/nsc/package.scala
@@ -6,6 +6,15 @@
 package scala.tools
 
 package object nsc {
+  type Mode = scala.reflect.internal.Mode
+  val Mode = scala.reflect.internal.Mode
+
+  def EXPRmode = Mode.EXPRmode
+  def BYVALmode = Mode.BYVALmode
+  def POLYmode = Mode.POLYmode
+  def TAPPmode = Mode.TAPPmode
+  def FUNmode = Mode.FUNmode
+
   type Phase = scala.reflect.internal.Phase
   val NoPhase = scala.reflect.internal.NoPhase