Modulegeneric-data-1.1.0.2Haskell2010

Generic.Data.Internal.Error

Error messages.

Warning

This is an internal module: it is not subject to any versioning policy, breaking changes can happen at any time.

If something here seems useful, please report it or create a pull request to export it from an external module.

1 type
1 class

Packagegeneric-data-1.1.0.2
Exports3
LanguageHaskell2010
LicenceMIT
SourceError.hs

familytype family HasSum (f :: Type -> Type) :: Bool where

Equations

HasSum V1 = 'False
HasSum U1 = 'False
HasSum (K1 i c) = 'False
HasSum (M1 i c f) = HasSum f
HasSum (f :*: g) = HasSum f || HasSum g
HasSum (f :+: g) = 'True

classclass Assert (pred :: Bool) (msg :: ErrorMessage)

Instances2Assert

Assert 'True msgDefined in generic-data-1.1.0.2 · Generic.Data.Internal.Error
TypeError msg ~ '() => Assert 'False msgDefined in generic-data-1.1.0.2 · Generic.Data.Internal.Error

type

type AssertNoSum (constraint :: Type -> Constraint) a = Assert (Not (HasSum (Rep a))) (((('Text "Cannot derive " ':<>: 'ShowType constraint) ':<>: 'Text " instance for ") ':<>: 'ShowType a) ':<>: 'Text " due to sum type")

Example3 expressions

>>> :set -XDeriveGeneric -XDerivingVia>>> import Generic.Data (Generically(..))>>> :{  data AB = A | B    deriving stock Generic    deriving Semigroup via Generically AB:}...    • Cannot derive Semigroup instance for AB due to sum type    • When deriving the instance for (Semigroup AB)