The consistency of a delegate's stake with respect to its delegators' balances is a critical property for Tenderbake, as it must enforce the stake balances invariants: tzip!172 (comment 677243929) The fact that the consistency of a delegate's stake with respect to its delegators' balances is enforced at multiple locations makes code maintenance and reviews more cumbersome. These locations include crediting a contract, spending from a contract, freezing fees, punishing a delegate, etc.; as well as the delegation management which is performed by Delegate_storage.set.

Design
With the transfer function of the Token module, it becomes possible to locate stake movements inside the token module so that the associated invariants are enforced in a single module.

Tasks

• Move references to Stake_storage.add_stake and Stake_storage.remove_stake related to transfers and delegations in the Token module
• Remove redundant representations: (1) remove Token.DelegateBalance constructor as it becomes redundant with the constructor Token.Contract, and (2) unify the types Receipt.balance and Token.[source | container | sink]
• Reduce the number of calls to add_stake and remove_stake depending on the nature of transfers (e.g. no stake updating needed when the source and the sink share the same delegate)