#11646: Make pattern synonym export type mismatch a warning -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1-rc2 checker) | Keywords: Resolution: | PatternSynonyms Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | PatternSynonyms/AssociatingSynonyms| -------------------------------------+------------------------------------- Comment (by simonpj): So to be concrete, you want to allow this: {{{ module M( Maybe( Nothing, Just, P ) ) where pattern P x = [x, True] }}} So now an importing module can import `Maybe(..)` and will get two data constructors for `Maybe` and one for lists. I agree that there is nothing unsound about this, just a bit unexpected. I'd be perfectly OK with issuing a warning rather than an error. But doing anything at all requires ''some'' work from someone. And it may well be that someone then pops up to say "it really really should be an error". So a compelling use-case or two, and evidence of interest from other users would help. Does anyone else have an opinion. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11646#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler