Improve error message for failed deriving
The following does not work:
type family F a :: *
data D a = D (F a)
deriving (Show)
The natural way of adding an instance does work (with enough extensions turned on):
instance (Show (F a)) => Show (D a) where
show (D x) = "D " ++ show x
It would be nice if the deriving mechanism could derive this code.
Trac metadata
Trac field | Value |
---|---|
Version | 6.10.1 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |