Implement Halt

compiler/src/l3/CPSOptimizer.scala

@@ -118,6 +118,9 @@ abstract class CPSOptimizer[T <: CPSTreeModule { type Name = Symbol }]
         LetC(nonInlinedConts, newBody)
       }
 
+    case Halt(a) =>
+      Halt(s.aSubst.getOrElse(a, a))
+
   }
 
   // (Non-shrinking) inlining