SI-5954 Implementation restriction preventing companions in package objs

Companion objects (and thus also case classes) in package objects caused
an assert about an overloaded symbol when everything was compiled twice.
It's a hairy problem that doesn't fit in 2.10.1. So this fix adds an
implementation restriction. It also has a test to make sure the error
messages are clean and reasonably friendly, and does not catch other
things defined in package objects. The test includes a
commented out test in case somebody thinks they've solved the underlying
problem.

A handful of tests were falling afoul of the new implementation
restriction. I verified that they do in fact fail on second compile so
they aren't false casualties. But they do test real things we'd like
to work once the re-compile issue is fixed. So I added a -X flag to
disable the implementation restriction and made all the tests
accidentally clobbered by the restriction use that flag.

2 files changed, 3 insertions, 0 deletions

diff --git a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
index 81368df7a6..ec3501d5bc 100644
--- a/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
+++ b/src/reflect/scala/reflect/internal/settings/MutableSettings.scala
@@ -47,4 +47,6 @@ abstract class MutableSettings extends AbsSettings {
   def XoldPatmat: BooleanSetting
   def XnoPatmatAnalysis: BooleanSetting
   def XfullLubs: BooleanSetting
+  def companionsInPkgObjs: BooleanSetting
+  
 }
diff --git a/src/reflect/scala/reflect/runtime/Settings.scala b/src/reflect/scala/reflect/runtime/Settings.scala
index 0e0cf3fc40..2d5b76f094 100644
--- a/src/reflect/scala/reflect/runtime/Settings.scala
+++ b/src/reflect/scala/reflect/runtime/Settings.scala
@@ -43,6 +43,7 @@ private[reflect] class Settings extends MutableSettings {
   val printtypes        = new BooleanSetting(false)
   val uniqid            = new BooleanSetting(false)
   val verbose           = new BooleanSetting(false)
+  val companionsInPkgObjs = new BooleanSetting(false)
 
   val Yrecursion        = new IntSetting(0)
   val maxClassfileName  = new IntSetting(255)