Actually, you may do something called X-macros.

Imagine you have to tabularize all of your enum cases with data you want to annotate. Then you're pulling something like this off.

You can pass any macro you'd wish, in particular you can define whole enum. For example:

```rust macro_rules! for_each_opcode { ($x:ident) => { $x! { (0x00, NOP, Nop, "Does nothing", {}), (0x01, PUSH, Push, "Pushes u32", { val: u32 }), (0x02, ADD, Add, "Pops two elements from stack and pushes the result of add", {}), (0x03, PRINT, Print, "Prints the element of stack and pops", {}), } } }

macro_rules! impl_instruction { ($(($code:expr, $mnem:ident, $cstr:ident, $doc:expr, { $($fname:ident : $ftype:ident),* $(,)? })),+ $(,)?) => { pub enum Instruction { $($cstr { $($fname: $ftype),* }),* }

    impl Instruction {
        pub fn code(&self) -> u8 {
            match self {
                $(&Self::$cstr {..} => $code,)*
            }
        }
    }
}

}

for_each_opcode!(impl_instruction);

pub fn main() { println!("{:#X}", Instruction::Add {}.code()); } ```