slint/sixtyfps_compiler/tests/basic/self_assign.60

SuperSimple := Rectangle {
    TouchArea {
        clicked => { root.x += 1; }
    }
    TouchArea {
        clicked => { x += 1; }
    }
    TouchArea {
        clicked => { 12 += 1; }
//                   ^error{Self assignement need to be done on a property}
    }
    TouchArea {
        clicked => { x += "string"; }
//                       ^error{Cannot convert string to float32}
    }
}