[GHC] #15052: DeriveAnyClass instances may skip TypeError constraints

[GHC]

#15052: DeriveAnyClass instances may skip TypeError constraints
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        Reporter:  jcpetruzza        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.2
      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 RyanGlScott):

 Right—that's because what you've written isn't equivalent to what
 `deriving C` will give you. `deriving C` gives you:

 {{{#!hs
 instance TypeError ('Text "BOOM") => C T
 }}}

 So I'm quite unclear on what the "bug" is here.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15052#comment:3>
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