Do not create companions that will be dropped later.

Fix blocker bug reported in #1114
I dislike this fix as now phase needs to know in advance
if it will ever need a companion for the class.
On the bright side, this change makes it clear
which phases need companions

1 files changed, 5 insertions, 0 deletions

diff --git a/src/dotty/tools/dotc/core/Phases.scala b/src/dotty/tools/dotc/core/Phases.scala
index 83ac64d53..b60f437d5 100644
--- a/src/dotty/tools/dotc/core/Phases.scala
+++ b/src/dotty/tools/dotc/core/Phases.scala
@@ -4,6 +4,7 @@ package core
 import Periods._
 import Contexts._
 import dotty.tools.backend.jvm.{LabelDefs, GenBCode}
+import dotty.tools.dotc.core.Symbols.ClassSymbol
 import util.DotClass
 import DenotTransformers._
 import Denotations._
@@ -347,6 +348,10 @@ object Phases {
     override def toString = phaseName
   }
 
+  trait NeedsCompanions {
+    def isCompanionNeeded(cls: ClassSymbol)(implicit ctx: Context): Boolean
+  }
+
   /** Replace all instances of `oldPhaseClass` in `current` phases
    *  by the result of `newPhases` applied to the old phase.
    */