#9757: Warn about derivable instances -------------------------------------+------------------------------------- Reporter: dfeuer | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.9 Component: Compiler | Keywords: Resolution: | Architecture: Unknown/Multiple Operating System: | Difficulty: Unknown Unknown/Multiple | Blocked By: Type of failure: | Related Tickets: None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by rwbarton): Thinking more about about this ticket and #9756, I think the purpose of compiler warnings should be to warn about code that is probably bad, not code that is probably fine that could be written in a (potentially) better way. (After all, we don't warn about excess parentheses in code either.) That is the domain of hlint, as Richard notes. Now #9756 is possibly an exception, if GHC is in a unique position to decide whether the replacement of `coerce` will type check, but I think the principle is a good one. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9757#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler