allow duplicate deriving / standalone deriving
I would like to avoid conditional compilation. Currently I need to write:
#if MIN_VERSION_Cabal(1,18,0)
-- cabal 1.18 has these instances
#else
deriving instance Typeable Flag
#endifWould it be sane to have the deriving instance do nothing if the imported instance that clashes was also derived?
reifyInstances together with a fixed #8100 (closed) could allow faking this feature.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.6.3 |
| Type | FeatureRequest |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |