@foo({class C; ()}) trait A
You can see the problem by calling `companionSymbolOf` during Namers:
~/code/scala git diff
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tool
index cac6bd2..89a2f2f 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -258,11 +258,15 @@ trait Namers extends MethodSynthesis {
             returnContext = context.make(tree)
           case _ =>
         }
+        if (tree.symbol != null && tree.symbol != NoSymbol)
+          companionSymbolOf(tree.symbol, this.context)
+
         returnContext
       }
       tree.symbol match {
         case NoSymbol => try dispatch() catch typeErrorHandler(tree, this.context)
-        case sym      => enterExistingSym(sym)
+        case sym      =>
+          enterExistingSym(sym)
       }
     }

@@ -1703,7 +1707,7 @@ trait Namers extends MethodSynthesis {
     // SI-7264 Force the info of owners from previous compilation runs.
     //         Doing this generally would trigger cycles; that's what we also
     //         use the lower-level scan through the current Context as a fall back.
-    if (!currentRun.compiles(owner)) owner.initialize
+    if (!owner.ownerChain.exists(_.isLocalDummy) && !currentRun.compiles(owner)) owner.init
     original.companionSymbol orElse {