// Module A authors its OWN chain: `M :: 1`, `K :: M + 1` (= 2). Both the value
// read and the array dimension must resolve `K` through A's `M`.
M :: 1;
K :: M + 1;
a_val :: () -> s64 { return K; }
a_len :: () -> s64 {
    arr : [K]u8 = ---;
    return arr.len;
}