#11648: assertPprPanic, called at compiler/types/TyCoRep.hs:1932 -------------------------------------+------------------------------------- Reporter: thomie | Owner: goldfire Type: bug | Status: new Priority: highest | Milestone: 8.0.1 Component: Compiler | Version: 8.1 Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by goldfire): I've been wondering if this dragon would bite. And now it has. Consider {{{ data T (a :: Proxy k) }}} Does that have a CUSK? According to the CUSK rules for datatypes, it does indeed: all of the type variables have a kind signature. But there's a problem in that we don't know `k`'s type! So this kind signature isn't complete. Instead, we should need to say, e.g., {{{ data T :: forall (k :: *). Proxy k -> * }}} Note the explicit `:: *` on `k`'s binder, which is necessary for us to have completely specify the kind. However, in looking more closely at this case, I don't actually think this is the problem. A mistake in detecting CUSKness should affect type inference and whether or not we have principal kinds, etc., but it shouldn't produce the drastic failure that we're seeing above. Somehow, it seems that `quantifyTyVars` is making a mistake. I don't have the ability to test this at the moment (I'm in an intermediate state) but should get to this later this week. I propose to fix the immediate problem (which should be straightforward) and then to delay the debate about CUSKs for another time. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11648#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler