[GHC] #11624: Cannot declare hs-boot declaration if there is already a value in scope

[GHC]

#11624: Cannot declare hs-boot declaration if there is already a value in scope
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        Reporter:  ezyang            |                Owner:  ezyang
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.1
       Component:  Compiler (Type    |              Version:  8.0.1-rc2
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by hvr):

 * priority:  normal => highest


Comment:

 This seems to be the same problem that causes regression in
 hackage:enumerator-0.4.20 with GHC HEAD/8.0:

 {{{
 [ 4 of 10] Compiling Data.Enumerator.Compatibility (
 lib/Data/Enumerator/Compatibility.hs, /tmp/enumerator-0.4.20/dist-
 newstyle/build/enumerator-0.4.20/build/Data/Enumerator/Compatibility.o )

 lib/Data/Enumerator/Compatibility.hs:55:8: error:
     • Can't find interface-file declaration for variable EL.head
         Probable cause: bug in .hi-boot file, or inconsistent .hi file
         Use -ddump-if-trace to get an idea of which file caused the error
     • In the expression: EL.head
       In an equation for ‘head’: head = EL.head

 ...and several more...
 }}}

 I'm increasing priority as this is a regression relative to 7.10 and
 there's at least on package on Hackage suffering from it.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11624#comment:1>
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