anchor.diff:  
     KernelToLocalsMap get localsMap => _currentFrame.localsMap;
   
  +  Map<ir.VariableDeclaration, HInstruction> get letBindings =>
  +      _currentFrame.letBindings;
  +
     JCommonElements get _commonElements => _elementMap.commonElements;
   
     KernelToTypeInferenceMap get _typeInferenceMap =>
  
positive.code:       this.member,
        this.asyncMarker,
        this.localsMap,
        this.typeInferenceMap,
        this.sourceInformationBuilder,
        this.staticTypeProvider);
  
negative.code:   TypeBuilder typeBuilder;
  
    final NativeEmitter nativeEmitter;
  
    /// True if we are visiting the expression of a throw statement; we assume
    /// this is a slow path.
  