Macro hopper_register_discs 

macro_rules! hopper_register_discs {
    ( $( $layout:ty ),+ $(,)? ) => { ... };
}

Discriminator registry – compile-time uniqueness enforcement.

Lists all account types for a program and asserts that no two share a discriminator. This prevents silent bugs where Vault::load() could accidentally succeed on a Pool account.

hopper_register_discs! {
    Vault,
    Pool,
    Position,
}

Fails at compile time if any two types share the same DISC value.