default-boxed 0.2.0

Helper trait to help create large struct on heap directly
Documentation 
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use default_boxed::DefaultBoxed;

struct A(u8);
impl Default for A {
    fn default() -> A {
        A(1)
    }
}

struct B(u32);
impl Default for B {
    fn default() -> B {
        B(2)
    }
}

struct C(u16);
impl Default for C {
    fn default() -> C {
        C(3)
    }
}

#[derive(DefaultBoxed)]
struct Foo {
    a: A,
    b: [B; 2],
    c: C,
}

fn main() {
    // Assert that Rust does pack this struct.
    assert_eq!(std::mem::size_of::<Foo>(), 12);
    let foo = Foo::default_boxed();
    assert_eq!(foo.a.0, 1);
    assert_eq!(foo.b[0].0, 2);
    assert_eq!(foo.b[1].0, 2);
    assert_eq!(foo.c.0, 3);
}