#11376: Inconsistent specified type variables among functions and datatypes/classes when using -XTypeApplications -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.1 checker) | Keywords: Resolution: | TypeApplications Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by rwbarton):
Is there a way to mention a type/kind variable but to still make it implicit?
I doubt it. You don't even have to write `forall a .` to make `a` explicit in `prox1`. {{{ rwbarton@morphism:~/zulip$ ~/ghc-newest/inplace/bin/ghc-stage2 --interactive GHCi, version 8.1.20160107: http://www.haskell.org/ghc/ :? for help Prelude> :set -XTypeInType -XTypeApplications -XScopedTypeVariables -fprint-explicit-foralls Prelude> data Prox a = Prox Prelude> prox0 :: Prox a; prox1 = Prox Prelude> :t prox0 prox0 :: forall {k} (a :: k). Prox a }}} Based on experimentation, the rule seems to be: all type variables mentioned in the type signature are explicit, from left to right as they appear in the signature. I guess `k` counts as to the left of `a` in `a :: k`, though, since it is implicitly quantified earlier. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11376#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler