Customizing AccountId

Question

In my runtime I'm using pub type AccountId = <<Signature as Verify>::Signer as IdentifyAccount>::AccountId;. Within my pallet I also need this type to implement From<SomeType>. I attempted to add type CustomAccountId: From<SomeType>; to my pallet's config, but encountered numerous errors. I'm not even sure if I'm on the right track. What is the proper way to achieve this?

Edit: To be more specific, I have the following type definition in my pallet, which is also used in a StorageMap

type AccountId: IsType<<Self as frame_system::Config>::AccountId> + From<H160>;

// some code...

#[pallet::storage]
pub(super) type AssetOwner<T: Config> = StorageMap<_, Blake2_128Concat, U256, <T as pallet::Config>::AccountId, OptionQuery>;

Some errors I got:

error[E0599]: the function or associated item `get` exists for struct `StorageMap<_GeneratedPrefixForStorageAssetOwner<T>, Blake2_128Concat, U256, <T as Config>::AccountId>`, but its trait bounds were not satisfied
...
error[E0277]: the trait bound `<T as pallet::Config>::AccountId: std::clone::Clone` is not satisfied
...
the trait bound `<T as pallet::Config>::AccountId: WrapperTypeEncode` is not satisfied
...
error[E0369]: binary operation `==` cannot be applied to type `&<T as pallet::Config>::AccountId`
...

These errors make me suspect that I'm not extending the AccountId type from the runtime config correctly. What is the proper way to achieve this functionality?

Answer 1

Outdated

The error message is still unclear. It appears that the error originated from the runtime instead of the pallet. When passing AccountId = YourImplementation, YourImplementation must meet all trait bounds.

You can check how other projects implement their account id here: link.

---

For example, this line #[derive(Clone)] at line 30 will satisfy the following error: ``` error[E0277]: the trait bound <T as pallet::Config>::AccountId: std::clone::Clone is not satisfied

I believe so.

---

After reviewing your source code, it appears that the IsType function removes the trait bound of frame_system::Config::AccountId. It seems there is no straightforward way to extend the associated type for this.

If you really want to do this that way, try:

type AccountId: IsType<<Self as frame_system::Config>::AccountId> + From<H160> + Parameter + Member + MaxEncodedLen;

This almost re-define a new AccountId.

Check: https://github.com/freeverseio/laos-ownership-node/pull/143.

---

There is another way, use the frame_system::Config::AccountId directly and provide a converter for it. For example:

trait Config: frame_system::Config {
    type H160ToAccountId: Convert<Self::AccountId, H160>
}

trait Convert<A, B> {
    fn convert(a: A) -> B;
}

enum H160ToAccountIdConverter {}
impl Convert<AccountId, H160> for H160ToAccountIdConverter {
    ...
}

impl your_pallet::Config for Runtime {
    type H160ToAccountId = H160ToAccountIdConverter;
}