#13621: Problems with injective type families -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: | InjectiveFamilies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): No, injectivity can't yet do this. Injectivity annotations are very much like functional dependencies, working only to do type inference. They have no representation in Core. Why not, you ask? Because I was unable to prove the soundness of doing so. But perhaps [http://cs.brynmawr.edu/~rae/papers/2017/partiality/partiality.pdf Constrained Type Families] gives us a way forward here. I have yet to attempt the injectivity proof in the context of that paper, but my hunch is that it will succeed. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13621#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler