[GHC] #15520: Invalid warning Defined but not used

[GHC]

#15520: Invalid warning Defined but not used
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        Reporter:  rik               |                Owner:  (none)
            Type:  bug               |               Status:  infoneeded
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      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):

 Do you export `x`? I can get the warning you claim with this program,
 which does //not// export `x`, for instance:

 {{{#!hs
 {-# LANGUAGE OverloadedStrings #-}
 {-# OPTIONS -Wunused-top-binds #-}
 module Foo (U) where

 import Data.Text (Text)

 data U = Text :+++ Text

 x :: U
 x = "ss" :+++ "ss"
 }}}

 However, this is correct behavior, since `x` is not used anywhere (and
 therefore `:+++` is transitively not used), so I'm still not sure what the
 bug is.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15520#comment:3>
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