#14845: TypeInType, index GADT by constraint witness -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.5 Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #13895 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): Hmph. You're right. You could always just add a `NB: Constrained data constructors cannot be promoted` or `Have you tried promoting a constrained data constructor?`. I don't think people will often trip over this. The other place to check is in the `AGlobal (AConLike (RealDataCon dc))` case in `TcHsType.tcTyVar`. I don't suppose it would be hard to check if the datacon had constraints. The only access seems to be in the fourth component of a `dataConFullSig`, but the comments there refer to a `dataConDictTheta` (now extinct) that could be revived to return this nugget. That might be a better route. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14845#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler