#9161: Pattern synonyms interact badly with data kinds -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: cactus Type: bug | Status: new Priority: lowest | Milestone: Component: Compiler (Type | Version: 7.8.2 checker) | Keywords: renamer, pattern Resolution: | synonyms, data kinds Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: Compile-time | Difficulty: Unknown crash | Blocked By: Test Case: | Related Tickets: Blocking: | -------------------------------------+------------------------------------- Comment (by simonpj): Basically yes. I suggest one of two things: * Add pattern synonyms as `AGlobal (AConLike (PatSynCon (panic "...")))`. Apart from the panic, this is exactly how ''imported'' pattern synonyms will appear, and `TcHsType.tcTyVar` will call `wrongThingErr` on it. It would make sense for ''local'' pattern synonmys to behave the same way. The panic won't be looked at because `TcEnv.wrongThingErr` doesn't look at the payload. * Short cut: don't extend the environment. Instead, in the "no in scope during type checking" error, test for `DataName` and instead complain about using a pattern synonym in a type. Better: do this only in the context of `tcTyVar`, by replicating a certain amount of the `tcLookup` code. This is bit of a hack; I'd rather not do it. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9161#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler