> Hopefully in future Rust will adopt something like Go’s automatic initialisation of all values to zero, or at least have this as an option (or document it better, if it already is an option).

First, thanks for the feedback!

Unfortunately, I don't think this feature will be added to Rust, though. IMO it causes bugs, as accidentally failing to initialize a variable yields a garbage value at runtime. There's no reason that 0 is any more likely to be a valid integer value than 1, or 42, or 0xdeadbeef, and the compiler shouldn't try to guess. And the feature wouldn't work in Rust anyhow due to the lack of null pointers.

However, having an explicit zero value is convenient, and this is what the Zero trait is for. With Rust traits you can overload on the return value, like Haskell, so you can write:

    let (emptyr: Room, emptyt: Tile, emptyl: Lev) = Zero::zero();
    let mut ls = [ emptyl, ..100 ];

assuming that your types derive Zero (which you can do with #[deriving(Zero)]). In the future it should be:

    let (emptyr, emptyt, emptyl) = zero();
    let mut ls = [ emptyl, ..100 ];

This could be done by either writing a zero() wrapper in the prelude or allowing static methods to be imported, both of which are probably good ideas.