#9211: Untouchable type variable (regression from 7.6) -------------------------------------+------------------------------------ Reporter: simonpj | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by simonpj): This looks right to me, and 7.4 looks wrong. There really is an equality `(f ~ g)` in the context, and so it's in general unsafe to fix `b` to `Bool`. That's what the !OutsideIn paper is all about. In this case the equality is trivial but presumably it's not trivial in your real example. For a trivial equality like this, perhaps GHC is over-conservative, but lifting that would require yet more special-case pleading. And I'm not sure it'd fix your real example anyway. In short, I don't know how to help. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9211#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler