#16203: Unhelpful names for wildcard type variables -------------------------------------+------------------------------------- Reporter: simonpj | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 Resolution: | Keywords: | PartialTypeSignatures Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): Due to #16082, we're going to pretty-print certain things less than optimally regardless of whether we choose `w` or `_`—it's just a question of which pill we find easier to swallow. I don't have a strong opinion on the matter, but it is worth noting that the choice of `_` actually causes some things to be printed out in a manner that's flat-out incorrect. For example, here is the [https://gitlab.haskell.org/ghc/ghc/blob/master/testsuite/tests/partial- sigs/should_compile/Either.stderr stderr from the Either test]: {{{ TYPE SIGNATURES barry :: forall _. _ -> (Either [Char] _, Either [Char] _) Dependent modules: [] Dependent packages: [base-4.12.0.0, ghc-prim-0.5.3, integer-gmp-1.0.2.0] }}} Notice the use of `forall _` there, which isn't valid GHC code. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16203#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler