#13985: GHC 8.0 regression: ‘k’ is not in scope during type checking, but it passed the renamer -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.0.1 checker) | Resolution: | Keywords: TypeFamilies Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: #13738 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): I was hoping to nab this in a drive-by fix, but that didn't happen. The solution here, I think, is to put the kind variables in the implicit part of the `dfid_pats` field. (This is rather like what happens with ordinary data declarations.) Then, they'll be in scope during type-checking and we can discover that they're "floating". There's an interesting invariant that data instance declarations violate: every `Name` invented by the renamer must be bound precisely once. Indeed the "not in scope during type checking" error says the invariant is not upheld. It makes me want a linear type system, but we can't always get what we want. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13985#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler