GHC chooses an instance between two overlapping, but cannot resolve a clause within the similar closed type family
We hoped that closed type families could replace overlapping instances. It is not currently the case: GHC can resolve overlapping instances but cannot resolve the similar closed type family.
I'm attaching a minimized example of program where it can be observed. This is reproducible on ghc-7.8.3 and HEAD.
Trac metadata
Trac field | Value |
---|---|
Version | 7.8.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
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Blocking | |
CC | |
Operating system | |
Architecture |