[GHC] #10708: Rejection of constant functions defined using conditional pattern matching

[GHC]

#10708: Rejection of constant functions defined using conditional pattern matching
-------------------------------------+-------------------------------------
        Reporter:  HubertGaravel     |                   Owner:
            Type:  bug               |                  Status:  closed
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.1
      Resolution:  invalid           |                Keywords:
Operating System:  Linux             |            Architecture:  x86
 Type of failure:  GHC rejects       |               Test Case:
  valid program                      |
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by simonpj):

 well of course you ''can'' define `d3` like that.  But the question posed
 by the ticket is: is it valid Haskell to write `d3` as in the description.
 Looking at the
 [https://www.haskell.org/onlinereport/haskell2010/haskellch4.html language
 spec] section 4.4.3, it seems that a 'funlhs' must have at least one
 argument. So this must be a 'pat' lhs, which can only have one set of
 guarded rhss.  So yes, I think it's invalid.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10708#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler