[GHC] #15043: Expand type synonym

[GHC]

#15043: Expand type synonym
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        Reporter:  domenkozar        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.2.2
  checker)                           |
      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:                    |
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Comment (by osa1):

 RyanGlScott, your analysis is correct, this is by design.

 It's impossible to provide one flag that'll make everyone happy, because
 expanding _all_ synonyms (as noted in the note quoted in comment:5) often
 results in huge types that are impossible to compare -- that's why we
 choose to expand until the difference becomes apparent.

 So perhaps we can provide another flag for expanding _all_ synonyms when
 needed (although I'm not sure if that'd result in reasonably-sized types
 in this case -- servant's types are quite complex!)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15043#comment:7>
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