Question about Raw Origin in Frame System Pallet

Question

Inside mod pallet {}, there is code for RawOrigin, which is

pub enum RawOrigin<AccountId> {
    Root,
    Signed(AccountId),
    None,
}

I don't know how we can use this AccountId type explicitly, I mean shouldn't the code look like this?

pub enum RawOrigin<T:config::AccounId> {
    Root,
    Signed(T:config::AccountId),
    None,
}

Answer 1

You should review how generics work in Rust.

By defining RawOrigin as pub enum RawOrigin<AccountId>, we allow this enum object to work for any generic AccountId type.

What you seem to want actually is defined in the frame_system pallet elsewhere:

/// Exposed trait-generic origin type.
#[pallet::origin]
pub type Origin<T> = RawOrigin<<T as Config>::AccountId>;

Here you can see we take this RawOrigin type, and directly use the AccountId definition from Config as you wanted.

However, doing it this way takes advantage of the #[pallet::origin] macro, which allows pallets to register new origins in the Substrate runtime, rather than making some hard coded assumptions about this kind of thing.

So this is a very intended abstraction, and part of the overall modular design of Substrate.