anchor.diff:    var _x;
     var _y;
   
  -  C(this.x, y)
  +  C(this._x, y)
       : _y = y,
         super();
   
  
positive.code: }
  
  foo1() {}
  
  int get x => 42;
  set x(value) { }
  
negative.code:       "    // Discard this one.\n"
        "  }");
    expectSource(cm.constructors[const Symbol("C")],
        "C(this._x, y)\n"
        "    : _y = y,\n"
        "      super();");
    expectSource(cm.constructors[const Symbol("C.other")],
  