#13160: Simplify CoreFV.FVAnn -------------------------------------+------------------------------------- Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- When introducing type-in-type, Richard elaborated the free varaible finder so that it finds three things at once (in `CoreFV`): {{{ data FVAnn = FVAnn { fva_fvs :: DVarSet -- free in expression , fva_ty_fvs :: DVarSet -- free only in expression's type , fva_ty :: Type -- expression's type } }}} I think `fva_ty` is needed only to support `fva_ty_fvs`. And `fva_ty_fvs` seems to be used only to support the calls to `freeVarsOfType` in `FloatIn`. And those calls in turn are only to suppor `used_in_ty` in `FloatIn.sepBindsByDropPoint`. In conversation yesterday, Richard and I agreed that all this is unnecessary. Coercion bindings simply do not float inwards, so we do not need to take these precautions. (We should add a Note to explain why they don't float, and what problem might arise if they did.) To confirm this I set `used_in_ty` to `False` and compiled from scratch; everything is fine. So I propose that we * get rid of the `ty_fvs` argument to `sepBindsByDropPoint` * simplfy `FVAnn` to just gather free variables (ie one field only) Result: it's all simpler. Richard will do this when he gets a moment. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13160 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler