The Validatable typeclass.

Note: It is not inteded to be used for testing of internal integrity of types, i.e. it does not check if a Text has a valid internal representation. For testing internal integrity please use the package (validity)[https:/stackage.orgpackage/validity]. The typeclass is split up into three parts:

• checkChain: A list of checks that will be performed in that order. This has to be provided to give an instance. For the reason why it is given as a list and the checks are not combined via '(<>)', see the point for isValid.
• defaulCheck: A check performing all checks of checkChain

defaultCheck = fold checkChain

• isValid: A function determining whether a value is valid. This functions stops checking after the first of the checks from checkChain fails .This function is the reason why we need the checkChain, as a Check constructed by '(<>)' goes through all operands, so `passed $ runCheck (shortCheck <> longCheck) unvalidatedInput` evalutes the argument with longCheck even if shortCheck failed. But if we define

instance Validatable e m T where
  checkChain = CheckChain [ shortCheck, longCheck ]

then `isValid unvalidatedInput` stops after shortCheck failed.

Helper for deriving Validatable

Intended for use with `-XDerivingVia` like

data X = X Int
    deriving (Validatable Void Identity) via (TrivialCheck X)
-- or with `-XStandaloneDeriving`
data Y = Y String
deriving via (TrivialCheck Y) instance (Validatable Void Identity Y)