rust_dag.rs

#![allow(dead_code)]

struct A {
    data: i32,
}

struct B {
    data: i32,
}

struct Composite {
    a: A,
    b: B,
}

fn take_individually(a: &mut A, b: &mut B) {
    a.data = 3;
    b.data = 3;
}

fn create() {
    let mut c = Composite {
        a: A { data: 0 },
        b: B { data: 0 },
    };
    // rustc smart enough to recognize these are disjoint object trees!
    take_individually(&mut c.a, &mut c.b);
}

fn passed_in(c: &mut Composite) {
    // rustc smart enough to recognize these are disjoint object trees!
    take_individually(&mut c.a, &mut c.b);
}

struct X {
    data: i32,
}

struct Nested {
    x: X,
}

fn take_individually2(n: &mut Nested, x: &mut X) {
    n.x.data = 3;
    assert!(x.data == 3);
}

fn create_nested() {
    let mut n = Nested { x: X { data: 0 } };

    // rustc detects these are not disjoint object trees and won't let you borrow twice!
//    take_individually2(&mut n, &mut n.x)
}

fn main() {}