Macro xcm_primitives::parameter_type_with_key

macro_rules! parameter_type_with_key {
    (
		pub $name:ident: |$k:ident: $key:ty| -> $value:ty $body:block;
	) => { ... };
}

Create new implementations of the GetByKey trait.

The implementation is typically used like a map or set.

Example:

use primitives::CurrencyId;
parameter_type_with_key! {
    pub Rates: |currency_id: CurrencyId| -> u32 {
        match currency_id {
            CurrencyId::DOT => 1,
            CurrencyId::KSM => 2,
            _ => 3,
        }
    }
}