#8501: Improve error message when using rec/mdo keyword without RecursiveDo extention. -------------------------------------+------------------------------------- Reporter: shelarcy | Owner: Type: feature | Status: new request | Milestone: Priority: normal | Version: 7.6.3 Component: Compiler | Keywords: (Parser) | Architecture: Unknown/Multiple Resolution: | Difficulty: Unknown Operating System: | Blocked By: Unknown/Multiple | Related Tickets: #3968 Type of failure: | None/Unknown | Test Case: | Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- Description changed by thomie: Old description:

GHC shows unhelpful error message when using rec keyword and/or mdo keyword without RecursiveDo extention.

{{{ module NoRecursiveDo where

foo = do rec str <- return "foo" putStrLn str }}}

{{{ $ ghc -c NoRecursiveDo.hs

NoRecursiveDo1.hs:4:5: Parse error in pattern: rec

}}}

{{{ module NoRecursiveDo2 where

bar = mdo str <- return "bar" putStrLn str }}}

{{{ $ ghc -c NoRecursiveDo2.hs

NoRecursiveDo2.hs:4:9: parse error on input `<-'

}}}

{{{ module NoRecursiveDo3 where

baz = mdo putStrLn "baz" }}}

{{{ $ ghc -c NoRecursiveDo3.hs

NoRecursiveDo3.hs:3:7: Not in scope: `mdo' Perhaps you meant `mod' (imported from Prelude)

}}}

I think that GHC should suggest to use RecursiveDo extention when using mdo/rec keyword.

New description: GHC shows unhelpful error message when using rec keyword and/or mdo keyword without RecursiveDo extention. {{{ module NoRecursiveDo where foo = do rec str <- return "foo" putStrLn str }}} {{{ $ ghc -c NoRecursiveDo.hs NoRecursiveDo1.hs:4:5: Parse error in pattern: rec Possibly caused by a missing 'do'? }}} {{{ module NoRecursiveDo2 where bar = mdo str <- return "bar" putStrLn str }}} {{{ $ ghc -c NoRecursiveDo2.hs NoRecursiveDo2.hs:4:9: parse error on input `<-' }}} {{{ module NoRecursiveDo3 where baz = mdo putStrLn "baz" }}} {{{ $ ghc -c NoRecursiveDo3.hs NoRecursiveDo3.hs:3:7: Not in scope: `mdo' Perhaps you meant `mod' (imported from Prelude) }}} I think that GHC should suggest to use RecursiveDo extention when using mdo/rec keyword. -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8501#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8501: Improve error message when using rec/mdo keyword without RecursiveDo extention. -------------------------------------+------------------------------------- Reporter: shelarcy | Owner: ruperthorlick Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Parser) | Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #3968 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by ruperthorlick): * owner: (none) => ruperthorlick * version: 7.6.3 => 8.1 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8501#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler

#8501: Improve error message when using rec/mdo keyword without RecursiveDo extention. -------------------------------------+------------------------------------- Reporter: shelarcy | Owner: ruperthorlick Type: feature request | Status: patch Priority: normal | Milestone: Component: Compiler | Version: 8.1 (Parser) | Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: | parser/should_fail/T8501a Blocked By: | Blocking: Related Tickets: #3968 | Differential Rev(s): Phab:D3271 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"5856c564dff79a5c2b6a92b1c6c350798b538da3/ghc" 5856c564/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="5856c564dff79a5c2b6a92b1c6c350798b538da3" Fixed error messages for RecursiveDo (#8501) Changes in a few different places to catch several different types of error related to RecursiveDo Signed-off-by: Rupert Horlick Test Plan: Three test cases, with further tests in comments Reviewers: austin, bgamari Reviewed By: bgamari Subscribers: thomie Differential Revision: https://phabricator.haskell.org/D3271 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8501#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler