#9207: Detect obvious cases of infinite recursion. -------------------------------------+------------------------------------- Reporter: mrugiero | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.4 Resolution: | Keywords: infinite | recursion Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by bebarker): * status: closed => new * version: 7.8.2 => 8.4.4 * resolution: invalid => Comment: I respectfully disagree with Fuuzetsu's suggestion that there are no obvious cases, here is an example that came up for me recently. I'm somewhat new to Haskell but am also fairly familiar with writing recursive functions in other languages. Probably, this was difficult for me to spot because I wrote it: {{{#!haskell loadImage :: MonadIO m => FilePath -> m HicoImage loadImage fpath = liftIO $ loadImage fpath where loadImg :: FilePath -> IO HicoImage loadImg fp = Image <$> SDL.Image.load fp }}} Now, there are several issues with this function stylistically that probably would have prevented this, such as not really needing the `where` clause and choosing bad naming conventions (`loadImage` and `loadImg`). The good news is for folks who know more about GHC than myself, I think, is this snippet I found in [https://www.reddit.com/r/haskell/comments/6hng6n/which_haskell_features_prev... another discussion] regarding detecting "syntactic cycles" with GHC. To quote: Core differentiates between a single [https://downloads.haskell.org/~ghc/8.4.4/docs/html/libraries/ghc-8.4.4/CoreS... NonRec] binding at a time vs. a [https://downloads.haskell.org/~ghc/8.4.4/docs/html/libraries/ghc-8.4.4/CoreS... Rec] binding group. The part of GHC which does the conversion from a single, recursive group to these let nestings is called the Occurence Analyzer. It's basically a strongly connected component analysis, once you have figured out all edges. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9207#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler