#2600: Bind type variables in RULES -------------------------------------+------------------------------------- Reporter: simonpj | Owner: simonpj Type: feature request | Status: closed Priority: lowest | Milestone: 8.8.1 Component: Compiler | Version: 6.8.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | rename/should_compile/T2600 Blocked By: | Blocking: Related Tickets: #2110 | Differential Rev(s): Phab:D4894 Wiki Page: | -------------------------------------+------------------------------------- Comment (by mayac): It's worth mentioning that this has not been ''completely'' addressed. The following is now accepted: {{{ {-# RULES "myrule" forall t a. forall f x. from (tmap f (to x :: t a)) = map f (from (to x :: t a)) #-} }}} but, as per #10595, it does not behave as one would expect – the rules `"Class op tmap"` and `"Class op to"` may fire first. See that ticket for the appropriate workaround. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/2600#comment:27 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler