Test := Rectangle {
    property<int32> foo;
    foo: 100;
    property<NonExistent> bar;
//           ^error{Unknown property type 'NonExistent'}
    property<float32> foo;
//                    ^error{Cannot override property 'foo'}
    property<string> text: "property with binding initializer";
    property<int32> x;
//                  ^error{Cannot override property 'x'}
}