This bug was reported on StackOverflow today. Filipe Rodrigues noticed that the initializer of a zero-length array is leaked:

#[derive(PartialEq, Debug)]
struct A;

impl Drop for A {
    fn drop(&mut self) {
        println!("Dropping A");
    }
}

fn main() {
    let vec: Vec<A> = vec![];
    let a = A;
    assert_eq!(vec, [a; 0]);
}

The code above does not run drop() for a, while I'd expect that it should. According to a comment by @mcarton, this regression occurred between Rust 1.11.0 and 1.12.0, i.e. when MIR code generation was enabled by default.