#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: | Unknown/Multiple Type of failure: GHC rejects | Test Case: indexed- valid program | types/should_compile/T11581 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by simonpj): * testcase: => indexed-types/should_compile/T11581 Comment:
In short, I think the undecidability checker should only include the indexed arguments to a type family when calculating the size of a type family application, and not any additional parametric arguments. But it doesn't work that way currently.
Good point. And easily actioned. Thanks. That still leaves the `TypeError` special case, which I have not done anything about yet. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11581#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler