Macro for creating auto-enumerated constants in Golang's iota-like way

main.rs

macro_rules! iota_consts {
    (
        $iota:ident: $($tt:tt)*
    ) => {
        iota_consts!(
            $iota(0, $iota): $($tt)*
        );
    };

    (
        $iota:ident($iota_value:expr, $prev_expr:expr):

        $(#[$attr:meta])*
        $vis:vis
        const $name:ident : $ty:ty;

        $($tt:tt)*
    ) => {
        $(#[$attr])*
        $vis
        const $name: $ty = {
            #[allow(dead_code, non_upper_case_globals)]
            const $iota: $ty = $iota_value;
            $prev_expr
        };
        iota_consts!(
            $iota($iota_value + 1, $prev_expr):
            $($tt)*
        );
    };

    (
        $iota:ident($iota_value:expr, $prev_expr:expr):

        $(#[$attr:meta])*
        $vis:vis
        static $name:ident : $ty:ty;

        $($tt:tt)*
    ) => {
        $(#[$attr])*
        $vis
        static $name: $ty = {
            #[allow(dead_code, non_upper_case_globals)]
            const $iota: $ty = $iota_value;
            $prev_expr
        };
        iota_consts!(
            $iota($iota_value + 1, $prev_expr):
            $($tt)*
        );
    };

    (
        $iota:ident($iota_value:expr, $prev_expr:expr):

        $(#[$attr:meta])*
        $vis:vis
        static mut $name:ident : $ty:ty;

        $($tt:tt)*
    ) => {
        $(#[$attr])*
        $vis
        static mut $name: $ty = {
            #[allow(dead_code, non_upper_case_globals)]
            const $iota: $ty = $iota_value;
            $prev_expr
        };
        iota_consts!(
            $iota($iota_value + 1, $prev_expr):
            $($tt)*
        );
    };

    (
        $iota:ident($iota_value:expr, $prev_expr:expr):

        $(#[$attr:meta])*
        $vis:vis
        const $name:ident : $ty:ty = $const_value:expr;

        $($tt:tt)*
    ) => {
        $(#[$attr])*
        $vis
        const $name: $ty = {
            #[allow(dead_code, non_upper_case_globals)]
            const $iota: $ty = $iota_value;
            $const_value
        };
        iota_consts!(
            $iota($iota_value + 1, $const_value):
            $($tt)*
        );
    };

    (
        $iota:ident($iota_value:expr, $prev_expr:expr):

        $(#[$attr:meta])*
        $vis:vis
        static $name:ident : $ty:ty = $const_value:expr;

        $($tt:tt)*
    ) => {
        $(#[$attr])*
        $vis
        static $name: $ty = {
            #[allow(dead_code, non_upper_case_globals)]
            const $iota: $ty = $iota_value;
            $const_value
        };
        iota_consts!(
            $iota($iota_value + 1, $const_value):
            $($tt)*
        );
    };

    (
        $iota:ident($iota_value:expr, $prev_expr:expr):

        $(#[$attr:meta])*
        $vis:vis
        static mut $name:ident : $ty:ty = $const_value:expr;

        $($tt:tt)*
    ) => {
        $(#[$attr])*
        $vis
        static mut $name: $ty = {
            #[allow(dead_code, non_upper_case_globals)]
            const $iota: $ty = $iota_value;
            $const_value
        };
        iota_consts!(
            $iota($iota_value + 1, $const_value):
            $($tt)*
        );
    };

    (
        $iota:ident($iota_value:expr, $prev_expr:expr):

        _;

        $($tt:tt)*
    ) => {
        iota_consts!(
            $iota($iota_value + 1, $prev_expr):
            $($tt)*
        );
    };

    (
        $iota:ident($iota_value:expr, $prev_expr:expr):
    ) => {};
}

iota_consts!(iota:
    const FOO: u32 = 1 << iota;    // iota = 0, FOO = 1
    static BAR: i32;               // iota = 1, BAR = 2
    _;                             // iota = 2
    #[allow(dead_code)]
    static mut BAZ: i8 = iota + 2; // iota = 3, BAZ = 5
    const QUX: i16;                // iota = 4, QUX = 6
);

macro_rules! print_consts {
    ($($name:ident),*) => {
        $(println!("{} = {}", stringify!($name), $name);)*
    };
}

fn main() {
    print_consts! {
        FOO,
        BAR,
        /* BAZ */
        QUX
    };
}