[GHC] #8207: Pretty Printer for textual version of Language (name) in DynFlags

[GHC]

#8207: Pretty Printer for textual version of  Language (name) in DynFlags
-------------------------------------+-------------------------------------
        Reporter:  Fuuzetsu          |                Owner:  seraphime
            Type:  feature request   |               Status:  closed
        Priority:  low               |            Milestone:  8.0.1
       Component:  GHC API           |              Version:  7.7
      Resolution:  fixed             |             Keywords:  newcomer
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 bgamari):

 * status:  new => closed
 * resolution:   => fixed
 * milestone:   => 8.0.1


@@ -7,1 +7,1 @@
- {{{
+ {{{#!hs

New description:

 I feel that the GHC API could benefit from a Show instance for Language in
 DynFlags.hs.

 Currently, if we want to display the language being used we have to do
 something like

 {{{#!hs
           foo inf = case hmi_language inf of
             Nothing -> Nothing
             Just Haskell98 -> Just "Haskell98"
             Just Haskell2010 -> Just "Haskell2010"
 }}}

 This is pretty much just the Show instance (over Maybe) and Haskell can
 derive it for us automatically: we just need to change `deriving Enum` to
 `deriving (Enum, Show)`. The above solution is not the most robust ever as
 if this data type is ever changed, this starts to form an incomplete
 pattern. If we have a catch all `_`, GHC complains about overlapping
 patterns. Easily solved with `show <$> hmi_language inf`.

--

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8207#comment:5>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler