[GHC] #15621: Error message involving type families points to wrong location

[GHC]

#15621: Error message involving type families points to wrong location
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler (Type    |              Version:  8.4.3
  checker)                           |
      Resolution:                    |             Keywords:  TypeFamilies
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by goldfire):

 But what about a function that mentions

 {{{#!hs
 let x = (Refl :: F Int :~: F Int) `seq`
         (Refl :: F Int :~: F Bool) `seq`
         ()
 }}}

 We'll get the error on the wrong line, won't we? The solution to #14185
 improves the status quo, but only by a lucky coincidence (that the
 problems in both tickets stem from two different functions). What's nice
 about #14185 is that it prevents the error from jumping arbitrarily far in
 a file, but I still don't think it's the real solution to the problem.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15621#comment:8>
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