Re: [GHC] #14953: Panic when exporting duplicate record fields from separate modules

25 Mar 2018


      #14953: Panic when exporting duplicate record fields from separate modules
-------------------------------------+-------------------------------------
        Reporter:  lyxia             |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.5
      Resolution:  fixed             |             Keywords:  ORF
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Compile-time      |            Test Case:
  crash or panic                     |  overloadedrecflds/should_fail/T14953
      Blocked By:                    |             Blocking:
 Related Tickets:  #13352            |  Differential Rev(s):  Phab:D4527
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by bgamari):

 * status:  patch => closed
 * resolution:   => fixed


Old description:
...
`A.hs`
{{{
{-# LANGUAGE DuplicateRecordFields #-}
module A where
data R = R {unR :: Int}
}}}
---
`B.hs`
{{{
{-# LANGUAGE DuplicateRecordFields #-}
module B where
data R = R {unR :: Int}
}}}
---
`C.hs`
{{{
{-# LANGUAGE DuplicateRecordFields #-}
module C (module A, module B) where
import A
import B
}}}
---
Output of `ghc C.hs`:
{{{
C.hs:3:21: error:ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 8.5.20180224 for x86_64-unknown-linux):
        exportClashErr
  $sel:unR:R
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in
ghc:Outputable
        pprPanic, called at compiler/typecheck/TcRnExports.hs:740:22 in
ghc:TcRnExports
}}}
New description:

 `A.hs`

 {{{#!hs
 {-# LANGUAGE DuplicateRecordFields #-}
 module A where
 data R = R {unR :: Int}
 }}}

 ---

 `B.hs`

 {{{#!hs
 {-# LANGUAGE DuplicateRecordFields #-}
 module B where
 data R = R {unR :: Int}
 }}}

 ---

 `C.hs`

 {{{#!hs
 {-# LANGUAGE DuplicateRecordFields #-}

 module C (module A, module B) where

 import A
 import B
 }}}

 ---

 Output of `ghc C.hs`:

 {{{
 C.hs:3:21: error:ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.5.20180224 for x86_64-unknown-linux):
         exportClashErr
   $sel:unR:R
   Call stack:
       CallStack (from HasCallStack):
         callStackDoc, called at compiler/utils/Outputable.hs:1150:37 in
 ghc:Outputable
         pprPanic, called at compiler/typecheck/TcRnExports.hs:740:22 in
 ghc:TcRnExports

 }}}

--

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14953#comment:6
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