[GHC] #13983: Type synonym referred to as datatype in error message

[GHC]

#13983: Type synonym referred to as datatype in error message
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3747
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"6e3c901db7a624d030614113c51be5731d1ac862/ghc"
 6e3c901d/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="6e3c901db7a624d030614113c51be5731d1ac862"
 Fix #13983 by creating a TyConFlavour type, and using it

 An error message was referring to a type synonym as a datatype.
 Annoyingly, learning that the TyCon over which the error message is
 operating is actually a type synonym was previously impossible, since
 that code only had access to a TcTyCon, which doesn't retain any
 information about what sort of TyCon it is.

 To rectify this, I created a new TyConFlavour datatype, intended to
 capture roughly what sort of TyCon we're dealing with. I then performing
 the necessary plumbing to ensure all TcTyCons have a TyConFlavour, and
 propagated this information through to the relevant error message.

 Test Plan: ./validate

 Reviewers: goldfire, austin, bgamari, simonpj

 Reviewed By: simonpj

 Subscribers: simonpj, rwbarton, thomie

 GHC Trac Issues: #13983

 Differential Revision: https://phabricator.haskell.org/D3747
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13983#comment:2>
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