Conversely, I use this "block pattern" a lot, and sometimes it causes lifetime issues:

    let foo: &[SomeType] = {
        let mut foo = vec![];
        // ... initialize foo ...
        &foo
    };

This doesn't work: the memory is owned by the Vec, whose lifetime is tied to the block, so the slice is invalid outside of that block. To be fair, it's probably best to just make foo a Vec, and turn it into a slice where needed.