vecbuilder.rs

pub struct VecBuilder<'a, T: 'a> {
    inner: *mut Vec<T>,
    _marker: std::marker::PhantomData<&'a mut Vec<T>>,
}

impl<'a, T> VecBuilder<'a, T> {
    pub fn new(v: &'a mut Vec<T>) -> Self {
        VecBuilder {
            inner: v,
            _marker: Default::default(),
        }
    }

    pub fn push(&self, val: T) {
        let vec: &mut Vec<T> = unsafe { &mut *self.inner };
        vec.push(val);
    }
}

#[cfg(test)]
mod tests {
    use VecBuilder;

    #[test]
    fn it_works() {
        let mut v = Vec::new();

        {
            let builder = VecBuilder::new(&mut v);

            let a = || {
                builder.push(0);
            };

            let b = || {
                builder.push(1);
            };

            a();
            b();
            a();
            b();
        }

        assert_eq!(&v, &[0, 1, 0, 1]);
    }
}