#8269: Suggest LANGUAGE pragmas instead of -XFoo -------------------------------------+------------------------------------ Reporter: nomeata | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by monoidal): We already have #3647. Close as duplicate? (My preference is that {-# LANGUAGE ... #-} makes the error too long, I would prefer merely "Use MultiParamTypeClasses pragma" or the status quo) No matter what we decide, it might be a good idea to have something like this: {{{ needPragma :: Flag -> SDoc needPragma x = "Use" <+> ptext (sLit (show flag)) <+> "to allow this" }}} and use it in error messages. That could be changed more easily and the error message would be more consistent. Currently we have different wordings {{{ Too many parameters for class ‛A’ (Use -XMultiParamTypeClasses to allow multi-parameter classes) Empty list of alterantives in case expression Use -XEmptyCase to allow this Multi-way if-expressions need -XMultiWayIf turned on ‛A’ has no constructors (-XEmptyDataDecls permits this) }}} that would make it consistent. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8269#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler