#10018: Cannot define custom fixity for infix data constructors in GHCi -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.12.1 Component: GHCi | Version: 7.10.1-rc2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | ghci/scripts/T10018 Related Tickets: #9830, #2947, | Blocking: #4929 | Differential Revisions: Phab:D1028 -------------------------------------+------------------------------------- Comment (by RyanGlScott): Replying to [comment:5 thomie]:
I'm not sure why it partially worked when you added `deriving Show` in comment:2, but I have a patch up for review in Phab:D1028 that enables custom fixity declarations for infix data constructors.
I'm guessing that the fixity info that derived `Read`/`Show` instances see must be distinct from the fixity info that's used when parenthesizing expressions (I'm not a GHC developer, this is just my speculation). I added #9830 since it addresses a similar issue, so maybe there's a clue in simonpj's fix for it. In any case, it looks like your patch will fix this discrepancy, so all is good. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10018#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler