trait bound MaxEncodedLen is not satisfied/not implemented for `RewardInfo<T>` or `<T as pallet::Config>::RelayChainAccountId`

Question

My code for this crowdloan rewards pallet

  #[pallet::config]
  pub trait Config: frame_system::Config {
    type Event: From<Event<Self>> + IsType<<Self as frame_system::Config>::Event>;
    type RelayChainAccountId: Parameter
      + Into<AccountId32>
      + From<AccountId32>
      + TypeInfo
      + Ord;
    type VestingBlockNumber: AtLeast32BitUnsigned + Parameter + Default + Into<BalanceOf<Self>>;
    type VestingBlockProvider: BlockNumberProvider<BlockNumber = Self::VestingBlockNumber>;
      ...
  }


  #[pallet::storage]
  #[pallet::getter(fn accounts_payable)]
  pub type AccountsPayable<T: Config> =
    StorageMap<_, Blake2_128Concat, T::AccountId, RewardInfo<T>>;

  #[pallet::storage]
  #[pallet::getter(fn claimed_relay_chain_ids)]
  pub type ClaimedRelayChainIds<T: Config> =
    StorageMap<_, Blake2_128Concat, T::RelayChainAccountId, ()>;

  #[pallet::storage]
  #[pallet::getter(fn unassociated_contributions)]
  pub type UnassociatedContributions<T: Config> =
    StorageMap<_, Blake2_128Concat, T::RelayChainAccountId, RewardInfo<T>>;

  #[pallet::storage]
  #[pallet::storage_prefix = "InitRelayBlock"]
  #[pallet::getter(fn init_vesting_block)]
  type InitVestingBlock<T: Config> = StorageValue<_, T::VestingBlockNumber, ValueQuery>;

  #[pallet::storage]
  #[pallet::storage_prefix = "EndRelayBlock"]
  #[pallet::getter(fn end_vesting_block)]
  type EndVestingBlock<T: Config> = StorageValue<_, T::VestingBlockNumber, ValueQuery>;


pub type BalanceOf<T> =
  <<T as Config>::RewardCurrency as Currency<<T as frame_system::Config>::AccountId>>::Balance;

#[derive(Clone, PartialEq, Eq, Encode, Decode, Default, TypeInfo)]
#[scale_info(skip_type_params(T))]
#[cfg_attr(feature = "std", derive(Debug))]
//#[codec(mel_bound())] //not working
//#[pallet::without_storage_info] // not working
pub struct RewardInfo<T: Config> {
  pub total_reward: BalanceOf<T>,
  pub claimed_reward: BalanceOf<T>,
  pub contributed_relay_addresses: Vec<T::RelayChainAccountId>,
}

Then I got error messages:

error[E0277]: the trait bound `RewardInfo<T>: parity_scale_codec::MaxEncodedLen` is not satisfied
  --> pallets/crowdloan-rewards/src/lib.rs:36:12
   |
36 |     #[pallet::pallet]
   |               ^^^^^^ the trait `parity_scale_codec::MaxEncodedLen` is not implemented for `RewardInfo<T>`
   |
   = note: required because of the requirements on the impl of `StorageInfoTrait` for `frame_support::pallet_prelude::StorageMap<_GeneratedPrefixForStorageAccountsPayable<T>, frame_support::Blake2_128Concat, <T as frame_system::Config>::AccountId, RewardInfo<T>>`

error[E0277]: the trait bound `<T as pallet::Config>::RelayChainAccountId: parity_scale_codec::MaxEncodedLen` is not satisfied
  --> pallets/crowdloan-rewards/src/lib.rs:36:12
   |
36 |     #[pallet::pallet]
   |               ^^^^^^ the trait `parity_scale_codec::MaxEncodedLen` is not implemented for `<T as pallet::Config>::RelayChainAccountId`
   |

   = note: required because of the requirements on the impl of `StorageInfoTrait` for `frame_support::pallet_prelude::StorageMap<_GeneratedPrefixForStorageClaimedRelayChainIds<T>, frame_support::Blake2_128Concat, <T as pallet::Config>::RelayChainAccountId, ()>`

error[E0277]: the trait bound `<T as pallet::Config>::VestingBlockNumber: parity_scale_codec::MaxEncodedLen` is not satisfied
  --> pallets/crowdloan-rewards/src/lib.rs:36:12
   |
36 |     #[pallet::pallet]
   |               ^^^^^^ the trait `parity_scale_codec::MaxEncodedLen` is not implemented for `<T as pallet::Config>::VestingBlockNumber`
   |
   = note: required because of the requirements on the impl of `StorageInfoTrait` for `frame_support::pallet_prelude::StorageValue<_GeneratedPrefixForStorageInitVestingBlock<T>, <T as pallet::Config>::VestingBlockNumber, frame_support::pallet_prelude::ValueQuery>`

It seems those three errors are related to the MaxEncodedLen...

I am using polkadot-v0.9.17 substrate. Please advise. Thanks

Answer 1

pub contributed_relay_addresses: Vec<T::RelayChainAccountId>,

• If you replace the Vec with a BoundedVec it won't complain.

You would want something like this instead:

pub contributed_relay_addresses: BoundedVec<T::RelayChainAccountId, ConstU32<100>>,

See How to use bounded vector for storage

You can read more about bounded vec here: When to use `BoundedVec` vs. `WeakBoundedVec` vs. `Vec`?