Derive Generic1 instances for types of kind (k -> *) -> * that include applications of the parameter
The Generic1
class is polykinded. The DeriveGeneric
extension can derive Generic1
instances for types of kind k -> *
parameterized over a parameter with a kind other than k ~ *
, but only if they don't apply the parameter to other types.
It currently cannot derive an instance for
newtype Fix f = In (f (Fix f))
deriving (Generic1)
or for
data Child f = Child {
ordinal :: Int,
nickname :: f String
}
deriving (Generic1)
It's possible to represent these types generically, either with composition that can include occurrences of the parameter or with new types that represent applications of the parameter.
Trac metadata
Trac field | Value |
---|---|
Version | |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | low |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |