[GHC] #11243: Use Type Synonyms to Compress Errors

[GHC]

#11243: Use Type Synonyms to Compress Errors
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        Reporter:  crockeea          |                Owner:
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Compiler          |              Version:  7.10.2
      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:                    |
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Comment (by goldfire):

 Just to clarify what may be an auxiliary issue: GHC has made a (arbitrary)
 decision that vanilla type synonyms (`type Foo = ...`) should not be
 expanded, while type families should be expanded. The idea is that type
 families do computation and it might be useful to see the results of
 computation. This decision could be revisited or usefully controlled by a
 flag.

 Also, we're a bit hamstrung when it comes to expanding constraint
 synonyms, which tend to get expanded quite eagerly. But it's hard to do
 better. Is this what you're seeing?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11243#comment:6>
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