#13415: Instance declarations don't recognize named wildcards -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: patch Priority: normal | Milestone: 8.4.1 Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Poor/confusing | Unknown/Multiple error message | Test Case: Blocked By: | Blocking: Related Tickets: #13324 | Differential Rev(s): Phab:D3332 Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): What would you like it to say? You get the exact same message from {{{ instance x => Show (Maybe a) }}} namely {{{ Foo.hs:4:10: error: * Illegal constraint: x (Use ConstraintKinds to permit this) * In the context: x While checking an instance declaration In the instance declaration for `Show (Maybe a)' | 4 | instance x => Show (Maybe a) | ^^^^^^^^^^^^^^^^^^^ }}} In any case, making instance declarations have `LHsSIgWcType` sounds as if instnace are ''allowed''' to have wildcards, but they aren't, so that feels like the wrong solution. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13415#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler