#8022: Outdated documentation for the -fwarn-lazy-unlifted-bindings warning -------------------------------------+------------------------------------ Reporter: asr | Owner: thoughtpolice Type: bug | Status: new Priority: highest | Milestone: 7.8.1 Component: Documentation | 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: -------------------------------------+------------------------------------ Changes (by simonpj): * owner: => thoughtpolice * priority: normal => highest * milestone: => 7.8.1 Comment: OK. `-fwarn-lazy-unlifted-bindings` is on by default ([http://www.haskell.org/ghc/docs/latest/html/users_guide/options- sanity.html documentation here]), with a message saying {{{ Foo.hs:6:11: Warning: Pattern bindings containing unlifted types should use an outermost bang pattern: }}} I propose: * To make `-fwarn-lazy-unlifted-bindings` into a no-op (that says "I do nothing"), and remove it altogether in 7.10. * To remove `-fwarn-lazy-unlifted-bindings` from the "on by default set" * To make lazy unlifted bindings an outright error. So GHC would reject {{{ f x = let I# y = x in ....blah.... }}} (Currently this elicits the warning, because y has type Int# in a lazy- looking binding.) * Fix the documentation to match. It would be possible (and easy to implement) to have a new language extension that allows such bindings, treating them as strict, which is what happens now. But given the long-standing warning and the easy fix, I'm disinclined to add this extra faff and documentation stuff. Any objections? Let's do this for 7.8. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8022#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler