anchor.diff:        }
         builder.state.breakCollectors.forEach(interceptJump);
         builder.state.continueCollectors.forEach(interceptJump);
  +      interceptJump(builder.state.returnCollector);
       }
   
       void leaveTry(IrBuilder builder) {
  
positive.code:   /// the environment.
    final Map<Local, ClosureLocation> boxedVariables = {};
  
    IrBuilderSharedState(this.program, this.constants, this.currentElement);
  }
  
  class ThisParameterLocal implements Local {
  
negative.code:     return _continuationEnvironment;
    }
  
    void addJump(IrBuilder builder,
        [ir.Primitive value, SourceInformation sourceInformation]) {
      assert(_continuation == null);
      _buildTryExit(builder);
      ir.InvokeContinuation invoke = new ir.InvokeContinuation.uninitialized(
  