Can't derive a fixed-size arrays.

[KokaKiwi]

When compiling this:

#[deriving(Eq)]
struct Toto {
    data: [u8, ..20],
}

fn main() {
}

rustc output an error:

$ rustc main.rs
main.rs:4:5: 4:21 error: mismatched types: expected `&&[u8]` but found `&[u8, .. 20]` (expected &-ptr but found vector)
main.rs:4     data: [u8, ..20],
              ^~~~~~~~~~~~~~~~
note: in expansion of #[deriving]
main.rs:2:1: 3:7 note: expansion site
main.rs:4:5: 4:21 error: mismatched types: expected `&&[u8]` but found `&[u8, .. 20]` (expected &-ptr but found vector)
main.rs:4     data: [u8, ..20],
              ^~~~~~~~~~~~~~~~
note: in expansion of #[deriving]
main.rs:2:1: 3:7 note: expansion site
error: aborting due to 2 previous errors

It seems to me that there is no reason to not allow this, so I reported it.

My rustc version:

$ rustc --version
rustc 0.11-pre-nightly (abdacec 2014-05-04 23:16:40 -0700)
host: x86_64-unknown-linux-gnu

[sfackler]

This should be covered by #7622.