#12007: Panic when loading file with nested pattern synonyms into ghci -------------------------------------+------------------------------------- Reporter: MikeIzbicki | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: | Keywords: | PatternSynonyms 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 wanted a break from dissertation-writing so I took a look. The problem is surely in the byte-code generator, which is opaque to me. The nub of the problem seems to be here: {{{#!hs -- introduce a let binding for a ticked case expression. This rule -- *should* only fire when the expression was not already let-bound -- (the code gen for let bindings should take care of that). Todo: we -- call exprFreeVars on a deAnnotated expression, this may not be the -- best way to calculate the free vars but it seemed like the least -- intrusive thing to do schemeE d s p exp@(AnnTick (Breakpoint _id _fvs) _rhs) = if isUnliftedType ty then do ... else do id <- newId ty ... where exp' = deAnnotate' exp ty = exprType exp' }}} The problem is that `ty :: TYPE rep` for a skolem `rep`. So we've created an abomination: a runtime variable (the `id`) whose type is representation polymorphic. Indeed, even the `isUnliftedType` query is bogus, because there is no way to know whether or not `ty` is unlifted at this point. How we've gotten here or what this code is doing, I don't know. But this is definitely the source of the problem! I'm afraid I won't have a chance to dig deeper here, but hopefully these bread crumbs can be picked up by the next traveler. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12007#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler