#11554: Self quantification in GADT data declarations -------------------------------------+------------------------------------- Reporter: Rafbill | Owner: Type: bug | Status: new Priority: high | Milestone: 8.0.2 Component: Compiler (Type | Version: 8.0.1-rc2 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by alexvieth): I have a patch which will reject the example in comment:7 and give this error {{{ • Type constructor ‘A’ cannot be used here (it is defined and used in the same recursive group) • In the kind ‘A’ In the definition of data constructor ‘B’ In the data declaration for ‘A’ }}} The details: - `ATcTyThing` has a new variant `ATcTyConUnpromoted TyCon` meaning the `TyCon` can't be used as a kind. - `tcTyVar` will give a promotion error (`TyConPE`) whenever an `ATcTyConUnpromoted` is encountered and the `TcTyMode` is kind level. - When checking the constructors of a `DataDecl`, the name of the type is associated with an `ATcTyConUnpromoted`, rather than `ATcTyCon` as it is now. Think this is a sane thing to do? If so I'll upload it to phab. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11554#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler