#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): Phab:D4769 Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
Can you remember whether that situation involved raw VarSets, or FVs?
The old code for `tyCoFVsOfType` looked like {{{ fvs_of_type (AppTy fun arg) a b c = (fvs_of_type fun `unionFV` fvs_of_type arg) a b c }}} I believe that if you eta reduce this to {{{ fvs_of_type (AppTy fun arg) = (fvs_of_type fun `unionFV` fvs_of_type arg) }}} it runs a lot slower. That should not happen, but I recall that it did. I don't understand what you mean about "avoiding hitting the underlying `IntSet` entirely". -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14880#comment:60 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler