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 xIt 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 |
Edited by guest