#15687: Type synonym unused binds no warning? -------------------------------------+------------------------------------- Reporter: AntC | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.6.1 (Parser) | Resolution: | Keywords: Operating System: Windows | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by AntC):
Note that this behavior is not new.
Indeed. Probably been there forever: there's nothing in the Report requiring all type vars to appear on rhs. I can't see there would ever be any sense in it, though; unlike unused vars in other places, for which there's `-fwarn-unused-binds`.
we don't warn about ...
There's sense to not using all the arguments at term level. Never the less it's sufficiently unusual for GHC to recognise a special form. You can (I usually do) write {{{#!hs const x _ = x const x _y = x }}} (Yes I could use `_a` for `Silly`, but I can still see no sense to it.) In some contexs, using `_` avoids getting a warning. (I'm thinking this for `type` could be a small tweak/enhancement for somebody starting GHC development: steal the logic from checking bidirectional patterns.) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15687#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler