Produce coercion rules for derived Functor instances
I don't think we do this yet, but I think we probably can. If we derive a Functor instance, we should, whenever possible and valid, produce some sort of fmap coerce = coerce rule for that type. This is done manually for lists in GHC.Base, but I imagine it probably applies (much) more generally.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.9 |
| Type | FeatureRequest |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
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| Operating system | |
| Architecture |