#15869: Discrepancy between seemingly equivalent type synonym and type family -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.6.2 checker) | Resolution: | Keywords: TypeFamilies 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 goldfire): Lots of bugs here! 1. I would expect `Apply1` to be rejected without an explicit `forall` in the equation, giving the polytype of `f`. 2. The error message for `Apply2` shouldn't say that it expects for arguments to `f`. The rest of the error message is perhaps confusing, but it's not unreasonable. 3. The version of `Apply2` with the explicit `forall` in the equation should be accepted. 4. In the `g` and `h` with `KindOf1`: Their types should be `forall a -> a -> Type`, not what GHC is reporting. 5. Ditto for `h` in the `KindOf2` case. Note that the inferred nature (as opposed to specified) of `a` is a non- bug: when you don't write a type signature, you don't get specified variables. But of course these should be required, not invisible or specified. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15869#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler