[GHC] #8883: FlexibleContexts checking should happen also on inferred signature

[GHC]

#8883: FlexibleContexts checking should happen also on inferred signature
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        Reporter:  Blaisorblade      |            Owner:  jstolarek
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.6.3
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by jstolarek):

 Before I push my patches let me remark that this is a breaking change.
 There were files in the main source code as well as boot libraries that
 required enabling either `FlexibleContexts` or `TypeFamilies` extensions
 (or both). Error messages are informative so it's easy to fix the code,
 but when we release GHC 7.10 some user libraries will need to adjust to
 this change.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8883#comment:12>
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