#14710: GHC 8.4.1-alpha allows the use of kind polymorphism without PolyKinds -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Compiler (Type | Version: 8.4.1-alpha1 checker) | Resolution: | Keywords: PolyKinds Operating System: Unknown/Multiple | Architecture: Type of failure: GHC accepts | Unknown/Multiple invalid program | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): You'll need to make a few changes to fix this: - `TcHsType.tcLHsKindSig` should really call `checkValidType`. This was an oversight from likely long ago. - The `tc_infer_hs_type` case that deals with `HsKindSig` should, in turn, use `tcLHsKindSig`. - `checkValidType` will need to know whether it's checking a kind. If it is, and if `-XPolyKinds` isn't on (which is implied by `-XTypeInType`, so you don't need a separate `-XTypeInType` check), then complain about variables. Alternatively, you could conceivably catch this in the renamer. `RnTypes.rnHsTyKi` knows when it's renaming a kind (vs. a type). In the `HsTyVar` case, you could bleat with `-XNoPolyKinds` and spotting a variable whose name is in the type variable namespace (as opposed to a tycon, recalling tat `HsTyVar` includes both). -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14710#comment:7 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler