Re: [GHC] #11581: TypeError requires UndecidableInstances unnecessarily

#11581: TypeError requires UndecidableInstances unnecessarily -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: feature request | Status: new Priority: low | Milestone: Component: Compiler (Type | Version: 8.0.1-rc2 checker) | Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: GHC rejects | Unknown/Multiple valid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones ): In [changeset:"a008eadfaa4816be349b4fefde9b9b9edc1ca359/ghc" a008eadf/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="a008eadfaa4816be349b4fefde9b9b9edc1ca359" Take type-function arity into account ...when computing the size of a call on the RHS of a type instance declaration. This came up in Trac #11581. The change is in TcType.tcTyFamInsts which now trims the type arguments in a call. See the comments with that function definition. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11581#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler