#11451: Inconsistent warnings for unused binders in type and instance declarations -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: patch Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D1825 Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): Replying to [comment:28 RyanGlScott]:
Simon, I believe we will have precisely what you described with Phab:D1825. `-Wname-shadowing` controls unused `forall`-ed type variables, and `-Wtype-variables` controls unused type patterns separately. You can enable different combinations of them to achieve A, B, and C.
OK good. Minor suggestions: * Personally I think `-Wunused-matches` is a bit surprising as a control for `forall`'d type variables. I suggest `-Wunused-foralls`. Having one more warning flag is low overhead. * The documentation for `-Wunused-matches` is out of date. * I really like the specification that: "if a type variable bound by an explicit, user-written forall is unused, we warn". Let's use it for `-Wunused-foralls`. And mention it in the section on explicit `forall` (9.14.1). * In the documentation for `-Wunused-type-variables` I think it is helpful to speak of "type patterns", and contrast with `-Wunused-foralls` (cross- ref in manual). * No one is pushing for extending `-Wunused-type-variables` to class instances. It's a little inconsistent but I think fair enough. Maybe in the documentation for `-Wunused-type-varaibles` mention this point.
The only remaining question is if we want a single flag that implies C (my previous name suggestion was `-pedantic`). This would be pretty easy to implement if we wanted it, since it would just enable a superset of the flags implied by `-Wall`.
Separately [wiki:Design/Warnings] is debating sets of flags. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11451#comment:31 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler