Rust: Testing if fluent interfaces are optimized away on releases

optimizing_fluent.rs

#![feature(asm)]

#[inline(never)]
fn noop() {
    unsafe {
        asm!("NOP");
    }
}

struct S { x: usize }

impl S {
    fn new() -> Self { S { x: 3 } }

    #[inline(never)]
    fn a( &mut self ) -> &mut Self {
        noop();
        self.x *= 5;
        noop();
        self
    }

    #[inline(never)]
    fn b( &mut self ) -> &mut Self {
        noop();
        self.x /= 17;
        noop();
        self
    }
}

fn main() {
    let n: u32 = "10".parse().unwrap_or( 13 );

    let mut s = S::new();
    
    for _ in 0..n {
        s.a().b().a();
    }
    
    for _ in 0..n {
        s.a();
        s.b();
        s.a();
    }
    
    println!( "{}", s.x );
}