ModuleError design choice

Question

I'm curious to the design decisions for the ModuleError:

ModuleError {
    index: u8,
    error: [u8; 4],
    _,
}

This allows to describe an error within a range of 256 pallets and u32::max error index within that pallet. Why is there such a big difference?

Answer 1

In the early days, index and error used to be u8 ;)

However, there is support for nested errors and thus, it was increased to 4 bytes for the error type.