[GHC] #15156: Show instances for types exported from the ghc package

[GHC]

#15156: Show instances for types exported from the ghc package
-------------------------------------+-------------------------------------
        Reporter:  sjakobi           |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by sjakobi):

 Replying to [comment:1 alexbiehl]:
 > While 'show' would be nice for now you can use 'ppr' and
 'showSDocUnsafe' from 'Outputable'.

 Thanks for the tip, Alex!

 I had come accross `showSDocUnsafe` before, but was scared off by its
 documentation:

 {{{
 -- showSDocUnsafe is unsafe, because `unsafeGlobalDynFlags` might not be
 -- initialised yet.
 }}}

 I felt like I had no reason to assume that `unsafeGlobalDynFlags` was
 initialised. The
 function might be less scary if there was a comment explaining under what
 circumstances `unsafeGlobalDynFlags` ''is'' initialised.

 For my immediate needs, I made do with a few orphan instances.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15156#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler