[GHC] #15659: Wacky error message when RULE mentions out-of-scope variable

[GHC]

#15659: Wacky error message when RULE mentions out-of-scope variable
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        Reporter:  RyanGlScott       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:  newcomer
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 Simon Peyton Jones <simonpj@…>):

 In [changeset:"cad5d0b69bc039b635a6eb0e5c9ed47d7c5a38ed/ghc" cad5d0b/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="cad5d0b69bc039b635a6eb0e5c9ed47d7c5a38ed"
 Buglet in reporting out of scope errors in rules

 Most out of scope errors get reported by the type checker these
 days, but not all.  Example, the function on the LHS of a RULE.

 Trace #15659 pointed out that this less-heavily-used code path
 produce a "wacky" error message.  Indeed so.  Easily fixed.
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15659#comment:1>
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