- -- * In the case of data family instances, any overlap is fundamentally a
- -- conflict (as these instances imply injective type mappings).
- -- * In the case of type family instances, overlap is admitted as long as
- -- the right-hand sides of the overlapping rules coincide under the
- -- overlap substitution. We require that they are syntactically equal;
- -- anything else would be difficult to test for at this stage.
- conflicting tycon1 ((famInst2, _), subst)
- | isAlgTyCon tycon1 = True
- | otherwise = not (rhs1 `tcEqType` rhs2)
- where
- tycon2 = famInstTyCon famInst2
- rhs1 = substTy subst $ synTyConType tycon1
- rhs2 = substTy subst $ synTyConType tycon2