#14813: EmptyCase thinks pattern match involving type family is not exhaustive, when it actually is -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.8.1 Component: Compiler | Version: 8.2.2 Resolution: | Keywords: | PatternMatchWarnings Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple error/warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): * A `CHoleCan` ''is'' a `Ct`! (`CHoleCan` is a data constructor of `Ct`.) * How exactly do I build a CHoleCan? Currently they are born in one place, in `TcExpr.tcUnboundId`: {{{ tcUnboundId rn_expr unbound res_ty = do { ty <- newOpenFlexiTyVarTy -- Allow Int# etc (Trac #12531) ; let occ = unboundVarOcc unbound ; name <- newSysName occ ; let ev = mkLocalId name ty ; loc <- getCtLocM HoleOrigin Nothing ; let can = CHoleCan { cc_ev = CtWanted { ctev_pred = ty , ctev_dest = EvVarDest ev , ctev_nosh = WDeriv , ctev_loc = loc} , cc_hole = ExprHole unbound } ... }}} Perhaps you can copy that? * Also, where exactly should I be calling tcNormalise? Call it in `pmTopNormaliseType`. (It might need to become monadic to access the ambient constraints. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14813#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler