[GHC] #13183: Template Haskell needlessly pretty-prints empty instance contexts

[GHC]

#13183: Template Haskell needlessly pretty-prints empty instance contexts
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        Reporter:  RyanGlScott       |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Template Haskell  |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by RyanGlScott):

 Ah, I see that 499e43824bda967546ebf95ee33ec1f84a114a7c introduced a
 function called `pprHsContextAlways` which, as the name suggests,
 //always// prints out the context for an `HsQualTy`, even if it's empty.

 Is the solution here not to use `pprHsContextAlways` when printing out
 Template Haskell-spliced code? Or perhaps we should avoid constructing an
 `HsQualTy` in `hsSyn/Convert` when
 [http://git.haskell.org/ghc.git/blob/65cc7620517abec9b3e0d9bfe644accd5f649fe5:/compiler/hsSyn/Convert.hs#l257
 converting] a Template Haskell `InstanceD` into a `ClsInstDecl`?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13183#comment:2>
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