#9273: TypeNats and record syntax don't compile ----------------------------------------------+---------------------------- Reporter: br1 | Owner: Type: bug | Status: closed Priority: normal | Milestone: Component: Compiler (Type checker) | Version: 7.8.2 Resolution: invalid | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects valid program | Unknown/Multiple Test Case: | Difficulty: Unknown Blocking: | Blocked By: | Related Tickets: ----------------------------------------------+---------------------------- Changes (by rwbarton): * status: new => closed * resolution: => invalid Comment: That's because record syntax additionally defines an accessor function {{{ sNatPred :: SNat (n+1) -> SNat n sNatPred (SNatS x) = x }}} which you cannot define manually using the non-record syntax `SNat` either. As the error message says, GHC does not (yet) know that `n+1` determines `n`, so it cannot type check the above definition because as far as it is concerned, `x` might have type `SNat n1` for some other `n1` with `n1+1 = n+1`. Once the Nat solver is improved, your record syntax `SNat` should compile. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9273#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler