#15512: Rewrite rules should be able to produce custom compiler errors -------------------------------------+------------------------------------- Reporter: ChaiTRex | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: 8.6.1 Component: Compiler | Version: 8.4.3 Resolution: | Keywords: 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 simonpj): You could rewrite {{{ forall x. length (cycle x) = error "length of cycle error" }}} but it would still be a run-time error, not a compile-time error. It's not clear how to achieve the latter. e.g. {{{ let v = length (cycle x) in if ... then ...v... else True }}} then `v` might never be evaluated. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15512#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler