#16175: wrong wording (and possibly wrong location) in parse error message for "do $ bar" -------------------------------------+------------------------------------- Reporter: j.waldmann | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 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: -------------------------------------+------------------------------------- Not a bug, as GHC correctly rejects an invalid program. Still - {{{ Prelude> foo x = do $ bar ; return () <interactive>:1:20: error: Parse error: module header, import declaration or top-level declaration expected. }}} Of the three suggestions, only "top-level declaration" can actually happen here (as this also happens deep inside a module). For reference, * ghc-7.10 : "parse error on input ‘=’" * ghc-8.0 : "naked expression at top level" * ghc-8.2 and later: as above I think the wording was introduced with https://ghc.haskell.org/trac/ghc/ticket/12146 Anyway one could also think that the actual error happened earlier, since after removing "return ()" as suggested by the error message, we get {{{ Prelude> foo x = do $ bar <interactive>:1:9: error: Empty 'do' block }}} so GHC could also use this as the original error message? By putting "; return ()" at the end, the 'do' block does not become non-empty? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16175 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler