anchor.diff:    js_ast.Fun _emitNativeFunctionBody(Procedure node) {
       var name = _annotationName(node, isJSAnnotation) ?? node.name.text;
       if (node.isGetter) {
  -      var returnValue = js('this.#', [name]);
  -      if (_isNullCheckableNative(node)) {
  -        // Add a potential null-check on native getter if type is non-nullable.
  -        returnValue = runtimeCall('checkNativeNonNull(#)', [returnValue]);
  -      }
  -      return js_ast.Fun([], js.block('{ return #; }', [returnValue]));
  +      return js_ast.Fun([], js.block('{ return this.#; }', [name]));
       } else if (node.isSetter) {
         var params = _emitParameters(node.function);
         return js_ast.Fun(
             params, js.block('{ this.# = #; }', [name, params.last]));
       } else {
  -      var returnValue = js('this.#.apply(this, args)', [name]);
  -      if (_isNullCheckableNative(node)) {
  -        // Add a potential null-check on return value if type is non-nullable.
  -        returnValue = runtimeCall('checkNativeNonNull(#)', [returnValue]);
  -      }
  -      return js.fun('function (...args) { return #; }', [returnValue]);
  +      return js.fun(
  +          'function (...args) { return this.#.apply(this, args); }', name);
       }
     }
   
  
positive.code: 
    @override
    js_ast.Expression visitPropertyGet(PropertyGet node) {
      return _emitPropertyGet(
          node.receiver, node.interfaceTarget, node.name.text);
    }
  
    @override
  
negative.code:   }
  
    /// Return whether [member] returns a native object whose type needs to be
    /// checked.
    bool _isCheckableNative(Member member) =>
        member != null &&
        member.isExternal &&
        _extensionTypes.isNativeClass(member.enclosingClass) &&
  