Shared via Rust Playground

playground.rs

macro_rules! as_stmt { ($s:stmt) => ($s) }
macro_rules! as_item { ($s:item) => ($s) }

macro_rules! declare_array {
    ($storage:ident $n:ident: [$t:ty] = [$($vals:expr),*]) => {
        declare_array!(_parse $storage $n, $t, 0, [], $($vals),*);
    };
    (_parse $s:ident $n:ident, $t:ty, $size:expr, [$($accs:expr),*], $val:expr, $($vals:expr),+) => {
        declare_array!(_parse $s $n, $t, $size+1, [$($accs,)* $val], $($vals),*);
    };
    (_parse $s:ident $n:ident, $t:ty, $size:expr, [$($accs:expr),*], $val:expr) => {
        declare_array!(_output $s $n, $t, $size+1, [$($accs,)* $val]);
    };
    (_parse $s:ident $n:ident, $t:ty, $size:expr, $acc:tt, ) => {
        declare_array!(_output $s $n, $t, $size, $acc);
    };
    (_output let $n:ident, $t:ty, $size:expr, $acc:tt) => {
        as_stmt!(let $n: [$t; $size] = $acc)
    };
    (_output static $n:ident, $t:ty, $size:expr, $acc:tt) => {
        as_item!(static $n: [$t; $size] = $acc;);
    };
}

declare_array!(static ARR: [i32] = [1, 2, 3]);

fn main() {
    declare_array!(let arr: [i32] = [4, 5, 6]);
    println!("{:?}", ARR);
    println!("{:?}", arr);
}