#9497: Silent typed holes -------------------------------------+------------------------------------- Reporter: merijn | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.8.3 Component: Compiler | Keywords: typed holes, Resolution: | warnings Operating System: | Architecture: Unknown/Multiple Unknown/Multiple | Difficulty: Unknown Type of failure: | Blocked By: None/Unknown | Related Tickets: Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Comment (by goldfire): Replying to [comment:4 simonpj]:
Two issues with Richard's proposals:
* There is no way to switch off typed holes altogether, and revert to {{{ Hole.hs:1:7: Pattern syntax in expression context: _ }}} Maybe that is OK.
I think this is OK. It's conceivable that a user makes a typo in an identifier that begins with an underscore and will be very confused by the error message. But, that exact same scenario would happen today, unless the user also somehow knows to use an obscure compiler option (`-fno-warn- typed-holes`). One way to mitigate this problem is to have typed-hole error/warning messages link to a description of the feature.
* What does `-fno-warn-typed-holes` do in the absence of `-fdefer-
typed-holes`? No-op with a warning?
It suppresses typed-hole warnings, of which there would be none. This is the same behavior as other `-fno-warn-...` options, when the condition that is being suppressed doesn't happen. I'm not bothered here.
* What does `-fwarn-typed-holes` do? Perhaps just re-enable the warning after switching off all warnings with `-w`.
Yep. One issue with this bikeshed color: having options `-fdefer-type-errors` and `-fdefer-typed-holes` forced users to remember the difference between `type` and `typed`. I think the choices here make sense (`type` in the first, `typed` in the second), but it is a little annoying. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9497#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler