#14880: GHC panic: updateRole -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 8.2.2 checker) | Resolution: | Keywords: TypeInType Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: #15076 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
The trouble is that MkBar has an implicit forall's variable a, whose kind mentions an explicit type variable arg.
Richard and I discussed this on Monday. Our conclusions * `Inferred` variables should always precede `Specified` ones. That is, do not top-sort * Idea: simply refrain from quantifying any inferred variables that mention specified ones. They'll get defaulted to `Any` which is probably fine. This refraining can readily be done in `candidatesQTyVarsOfType`. * Also came up: close over kinds once in `tyCoVarsOfType` instead of at every leaf. This is not just an efficiency issue: consider {{{ tyCoVarsOfType (forall a. b::a) }}} Richard is on the job -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14880#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler