Cfg.Deriving.Assert

This module provides type level assertions so that we can constrain the instances user's can create, and give them good error messages

Since: 0.0.2.0

Documentation

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

A type level helper for creating custom error messages based on a predicate

Since: 0.0.2.0

Instances

(TypeError msg :: ()) ~ '() => Assert 'False msg

Defined in Cfg.Deriving.Assert

Assert 'True msg

Defined in Cfg.Deriving.Assert

type family IsTopLevelRecord (f :: k -> Type) :: Bool where ...

A type level predicate that helps us identify top level product types

Since: 0.0.2.0

Equations

IsTopLevelRecord (V1 :: k -> Type) = 'False

IsTopLevelRecord (U1 :: k -> Type) = 'False

IsTopLevelRecord (K1 i c :: k -> Type) = 'False

IsTopLevelRecord (M1 D c f :: k -> Type) = IsTopLevelRecord f

IsTopLevelRecord (M1 C c f :: k -> Type) = IsTopLevelRecord f

IsTopLevelRecord (M1 S c f :: k -> Type) = 'True

IsTopLevelRecord (f :*: g :: k -> Type) = IsTopLevelRecord f

IsTopLevelRecord (f :+: g :: k -> Type) = 'False

type AssertTopLevelRecord (constraint :: Type -> Constraint) a = Assert (IsTopLevelRecord (Rep a)) (((('Text "\128683 Cannot derive " ':<>: 'ShowType constraint) ':<>: 'Text " instance for ") ':<>: 'ShowType a) ':$$: (('Text "\128161 " ':<>: 'ShowType constraint) ':<>: 'Text " must be derived on a top level record type with named fields."))

A custom error message for non-top-level records

Since: 0.0.2.0