Re: [GHC] #7901: Bad error message when using UnicodeSyntax ∀ without ExplicitForall

[GHC]

#7901: Bad error message when using UnicodeSyntax ∀ without ExplicitForall
-------------------------------------------------+-------------------------
        Reporter:  exbb2                         |            Owner:  ajp
            Type:  bug                           |           Status:  patch
        Priority:  normal                        |        Milestone:
       Component:  Compiler                      |          Version:  7.6.2
      Resolution:                                |         Keywords:
Operating System:  Unknown/Multiple              |     Architecture:
 Type of failure:  Incorrect warning at          |  Unknown/Multiple
  compile-time                                   |       Difficulty:
       Test Case:                                |  Unknown
        Blocking:                                |       Blocked By:
                                                 |  Related Tickets:
-------------------------------------------------+-------------------------

Comment (by Austin Seipp <aseipp@…>):

 In [changeset:96adf0e99b1a6595ee40ef9c05263a4fe73eb7c5/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="96adf0e99b1a6595ee40ef9c05263a4fe73eb7c5"
 Improve error when using forall with UnicodeSyntax

 Fixes Trac #7901.

 '∀' is neither upper nor lowercase, unlike the 'f' in 'forall', so when
 explicit forall is not enabled, it creates a parse error before reaching
 the '.', which is where we give a nice message for ascii 'forall'.
 Therefore, we make '∀' into a token as long as UnicodeSyntax is enabled,
 which is safe because its caselessness means it can never be mistaken
 for a symbol, and check extensions in the parser when the 'forall' rule
 is used.

 Authored-by: Paul Cavallaro <ptc at fb.com>
 Authored-by: Anders Papitto <anderspapitto at gmail.com>
 Signed-off-by: Austin Seipp <aseipp at pobox.com>
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7901#comment:6>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler