#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): I don't feel strongly, but I'm -1 on defaulting to a warning over an error. It seems to invite the possibility that holes could make their way into released code, which sometimes has plenty of warnings. It's easy for a distribution tool to check for (and prohibit) `-fdefer-type-errors`, but it would be much harder to avoid holes under the proposed change. I also have to say that the current interface to this feature is very confusing! The flag `-fwarn-typed-holes`, on by default, causes '''errors''' to be reported, not warnings. And, the inverse, `-fno-warn- typed-holes` changes the nature of '''error''' messages, once again, as opposed to suppressing warnings, the usual behavior of `-fno-warn-...` flags. These flags are described in the "Warnings" section of [http://www.haskell.org/ghc/docs/latest/html/users_guide/flag- reference.html the flag reference], rather misleadingly. To be concrete, I propose the following: * By default, holes behave exactly as they do now. * A new flag, `-fdefer-typed-holes` turns typed-hole errors into warnings, just like `-fdefer-type-errors` (which would imply `-fdefer-typed-holes`). * Re-appropriate `-fno-warn-typed-holes` to suppress the warnings generated by `-fdefer-typed-holes`. The current behavior of `-fno-warn- typed-holes` (to turn the usage of holes into out-of-scope errors) would no longer be available. Thoughts? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9497#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler