struct FooBuilder;
struct Foo;

impl FooBuilder {
    fn new() -> Self { FooBuilder }
    fn build(self) -> Foo { Foo }
    fn set_x(&mut self, _: u8) -> &mut Self {
        self
    }
    fn set_y(&mut self, _: u8) -> &mut Self {
        self
    }
    fn set_f(&mut self) -> &mut Self { self }

    fn with<T>(mut self, f: T) -> Self where T: FnOnce(&mut Self) -> &mut Self {
        f(&mut self);
        self
    }
    fn with1<T, Q>(mut self, f: T, v: Q) -> Self where T: FnOnce(&mut Self, Q) -> &mut Self {
        f(&mut self, v);
        self
    }
}

fn main() {
    let _ = FooBuilder::new()
        .with(FooBuilder::set_f)
        .with1(FooBuilder::set_x, 5)
        .with(|s| {s.set_y(3); s})
        .build();
}