#11371: Bogus in-scope set in substitutions -------------------------------------+------------------------------------- Reporter: simonpj | Owner: niteria Type: bug | Status: new Priority: high | Milestone: 8.2.1 Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #11360 | Differential Rev(s): phab:D1792, Wiki Page: | phab:D1801, phab:D1802 -------------------------------------+------------------------------------- Comment (by simonpj): There's a lot going on here. Concerning comment:39, here is what is happening: * `CoreSyn.applyTypeToArg` deliberately calls `piResultTy` with a possibly-bottom second argument. It'll be bottom when the type is `t1 -> t2` and the arg is some non-`Type` expression. * `piResultTy` calls `piResultTys` * When `piResultTys` finishes it calls `substTy` * Which looks at the substitution * Which is bottom because you built it strictly from its in-scope set * Which was bottom because the second arg to `piResultTy` was bottom Sigh. We could improve matters, but that is at least why you are getting the panic. So go back to being lazy. The exponential `typeKind` stuff seems more likely. Can you just count how many calls to `piResultTy` and/or `typeKind` are being made? And if large, then on what shaped types? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11371#comment:41 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler