Markus: This is a bug in darcs, nothing to do with either scons or
Yhc. I've sent this to the darcs people as well.

Darcs People: A Yhc user has the issue below.

Thanks

Neil

> Unfortunately 'scons depends' doesn't solve the problem. I've attached
> the output from 'scons depends', 'scons' and 'darcs --exact-version'
> (done in a clean checkout), but the error seems to be this:
> ------------8<------------------
> darcs get --partial --repo-name=depends/filepath
> http://www.cs.york.ac.uk/fp/darcs/filepath
> darcs: bug in darcs!
> Impossible case at PatchRead.lhs:56 compiled 18:36:18 Dec  8 2006
> Please report this to bugs@darcs.net,
> If possible include the output of 'darcs --exact-version'.
> ------------>8------------------
> Is this a problem with the repository or darcs? Should I submit a darcs
> bug report?
>
> greetings, Markus
>
>
> cyphers-computer:~/Projects/yhc cypher$ scons depends
> scons: Reading SConscript files ...
> Building version 0.7.0-20061211043856-custom.
> Checking for architecture... (cached) x86
> Checking for operating system... (cached) darwin
> Checking for C header file gmp.h... yes
> Checking for mpz_t integ; mpz_init (integ) in C library gmp... yes
> Checking for libgmp version... 4.2.1
> darcs get --partial --repo-name=depends/cpphs http://www.cs.york.ac.uk/fp/darcs/cpphs
> Copying patch 37 of 37... done!
> Applying patch 36 of 36... done.
> Finished getting.
> darcs get --partial --repo-name=depends/filepath http://www.cs.york.ac.uk/fp/darcs/filepath
> darcs: bug in darcs!
> Impossible case at PatchRead.lhs:56 compiled 18:36:18 Dec  8 2006
> Please report this to bugs@darcs.net,
> If possible include the output of 'darcs --exact-version'.
> svn co http://svn.python.org/projects/python/trunk/Modules/_ctypes/ depends/ctypes
> A    depends/ctypes/libffi_arm_wince
> A    depends/ctypes/libffi_arm_wince/fficonfig.h
> A    depends/ctypes/libffi_arm_wince/ffitarget.h
> A    depends/ctypes/libffi_arm_wince/ffi_common.h
> A    depends/ctypes/libffi_arm_wince/sysv.asm
> A    depends/ctypes/libffi_arm_wince/ffi.c
> A    depends/ctypes/libffi_arm_wince/debug.c
> A    depends/ctypes/libffi_arm_wince/prep_cif.c
> A    depends/ctypes/libffi_arm_wince/ffi.h
> A    depends/ctypes/callbacks.c
> A    depends/ctypes/callproc.c
> A    depends/ctypes/stgdict.c
> A    depends/ctypes/ctypes_dlfcn.h
> A    depends/ctypes/libffi_msvc
> A    depends/ctypes/libffi_msvc/fficonfig.h
> A    depends/ctypes/libffi_msvc/ffitarget.h
> A    depends/ctypes/libffi_msvc/LICENSE
> A    depends/ctypes/libffi_msvc/ffi_common.h
> A    depends/ctypes/libffi_msvc/README.ctypes
> A    depends/ctypes/libffi_msvc/win32.S
> A    depends/ctypes/libffi_msvc/win32.c
> A    depends/ctypes/libffi_msvc/ffi.c
> A    depends/ctypes/libffi_msvc/types.c
> A    depends/ctypes/libffi_msvc/win64.asm
> A    depends/ctypes/libffi_msvc/prep_cif.c
> A    depends/ctypes/libffi_msvc/ffi.h
> A    depends/ctypes/libffi_msvc/README
> A    depends/ctypes/darwin
> A    depends/ctypes/darwin/dlfcn_simple.c
> A    depends/ctypes/darwin/LICENSE
> A    depends/ctypes/darwin/README.ctypes
> A    depends/ctypes/darwin/dlfcn.h
> A    depends/ctypes/darwin/README
> A    depends/ctypes/malloc_closure.c
> A    depends/ctypes/_ctypes_test.c
> A    depends/ctypes/_ctypes.c
> A    depends/ctypes/cfield.c
> A    depends/ctypes/_ctypes_test.h
> A    depends/ctypes/libffi
> A    depends/ctypes/libffi/configure
> A    depends/ctypes/libffi/LICENSE
> A    depends/ctypes/libffi/configure.ac
> A    depends/ctypes/libffi/include
> A    depends/ctypes/libffi/include/ffi.h.in
> A    depends/ctypes/libffi/include/ffi_common.h
> A    depends/ctypes/libffi/fficonfig.h.in
> A    depends/ctypes/libffi/fficonfig.py.in
> A    depends/ctypes/libffi/src
> A    depends/ctypes/libffi/src/powerpc
> A    depends/ctypes/libffi/src/powerpc/ppc_closure.S
> A    depends/ctypes/libffi/src/powerpc/darwin_closure.S
> A    depends/ctypes/libffi/src/powerpc/ffitarget.h
> A    depends/ctypes/libffi/src/powerpc/aix.S
> A    depends/ctypes/libffi/src/powerpc/darwin.S
> A    depends/ctypes/libffi/src/powerpc/ffi.c
> A    depends/ctypes/libffi/src/powerpc/sysv.S
> A    depends/ctypes/libffi/src/powerpc/asm.h
> A    depends/ctypes/libffi/src/powerpc/linux64_closure.S
> A    depends/ctypes/libffi/src/powerpc/ffi_darwin.c
> A    depends/ctypes/libffi/src/powerpc/linux64.S
> A    depends/ctypes/libffi/src/powerpc/aix_closure.S
> A    depends/ctypes/libffi/src/arm
> A    depends/ctypes/libffi/src/arm/ffitarget.h
> A    depends/ctypes/libffi/src/arm/ffi.c
> A    depends/ctypes/libffi/src/arm/sysv.S
> A    depends/ctypes/libffi/src/m32r
> A    depends/ctypes/libffi/src/m32r/ffitarget.h
> A    depends/ctypes/libffi/src/m32r/ffi.c
> A    depends/ctypes/libffi/src/m32r/sysv.S
> A    depends/ctypes/libffi/src/sh64
> A    depends/ctypes/libffi/src/sh64/ffitarget.h
> A    depends/ctypes/libffi/src/sh64/ffi.c
> A    depends/ctypes/libffi/src/sh64/sysv.S
> A    depends/ctypes/libffi/src/darwin
> A    depends/ctypes/libffi/src/darwin/ffitarget.h
> A    depends/ctypes/libffi/src/m68k
> A    depends/ctypes/libffi/src/m68k/ffitarget.h
> A    depends/ctypes/libffi/src/m68k/ffi.c
> A    depends/ctypes/libffi/src/m68k/sysv.S
> A    depends/ctypes/libffi/src/alpha
> A    depends/ctypes/libffi/src/alpha/ffitarget.h
> A    depends/ctypes/libffi/src/alpha/ffi.c
> A    depends/ctypes/libffi/src/alpha/osf.S
> A    depends/ctypes/libffi/src/x86
> A    depends/ctypes/libffi/src/x86/ffi64.c
> A    depends/ctypes/libffi/src/x86/ffitarget.h
> A    depends/ctypes/libffi/src/x86/win32.S
> A    depends/ctypes/libffi/src/x86/darwin.S
> A    depends/ctypes/libffi/src/x86/ffi.c
> A    depends/ctypes/libffi/src/x86/sysv.S
> A    depends/ctypes/libffi/src/x86/ffi_darwin.c
> A    depends/ctypes/libffi/src/x86/unix64.S
> A    depends/ctypes/libffi/src/frv
> A    depends/ctypes/libffi/src/frv/eabi.S
> A    depends/ctypes/libffi/src/frv/ffitarget.h
> A    depends/ctypes/libffi/src/frv/ffi.c
> A    depends/ctypes/libffi/src/s390
> A    depends/ctypes/libffi/src/s390/ffitarget.h
> A    depends/ctypes/libffi/src/s390/ffi.c
> A    depends/ctypes/libffi/src/s390/sysv.S
> A    depends/ctypes/libffi/src/pa
> A    depends/ctypes/libffi/src/pa/linux.S
> A    depends/ctypes/libffi/src/pa/ffitarget.h
> A    depends/ctypes/libffi/src/pa/ffi.c
> A    depends/ctypes/libffi/src/cris
> A    depends/ctypes/libffi/src/cris/ffitarget.h
> A    depends/ctypes/libffi/src/cris/ffi.c
> A    depends/ctypes/libffi/src/cris/sysv.S
> A    depends/ctypes/libffi/src/ia64
> A    depends/ctypes/libffi/src/ia64/ffitarget.h
> A    depends/ctypes/libffi/src/ia64/unix.S
> A    depends/ctypes/libffi/src/ia64/ffi.c
> A    depends/ctypes/libffi/src/ia64/ia64_flags.h
> A    depends/ctypes/libffi/src/sparc
> A    depends/ctypes/libffi/src/sparc/v9.S
> A    depends/ctypes/libffi/src/sparc/ffitarget.h
> A    depends/ctypes/libffi/src/sparc/ffi.c
> A    depends/ctypes/libffi/src/sparc/v8.S
> A    depends/ctypes/libffi/src/prep_cif.c
> A    depends/ctypes/libffi/src/mips
> A    depends/ctypes/libffi/src/mips/ffitarget.h
> A    depends/ctypes/libffi/src/mips/n32.S
> A    depends/ctypes/libffi/src/mips/o32.S
> A    depends/ctypes/libffi/src/mips/ffi.c
> A    depends/ctypes/libffi/src/sh
> A    depends/ctypes/libffi/src/sh/ffitarget.h
> A    depends/ctypes/libffi/src/sh/ffi.c
> A    depends/ctypes/libffi/src/sh/sysv.S
> A    depends/ctypes/libffi/config.guess
> A    depends/ctypes/libffi/README
> A    depends/ctypes/libffi/aclocal.m4
> A    depends/ctypes/libffi/config.sub
> A    depends/ctypes/libffi/install-sh
> A    depends/ctypes/ctypes.h
> Checked out revision 52997.
> scons: done reading SConscript files.
> scons: Building targets ...
> scons: Nothing to be done for `depends'.
> scons: done building targets.
> cyphers-computer:~/Projects/yhc cypher$ scons
> scons: Reading SConscript files ...
> Building version 0.7.0-20061211043856-custom.
> Checking for architecture... (cached) x86
> Checking for operating system... (cached) darwin
> Checking for C header file gmp.h... (cached) yes
> Checking for mpz_t integ; mpz_init (integ) in C library gmp... (cached) yes
> Checking for libgmp version... (cached)
> Checking for Python version 2.3 or later... (cached) Found version 2.4.3 final (0).
> Checking for Scons binary... (cached) "/opt/local/bin/scons"
> Checking for Scons version... (cached) Found version 0.96.92.D002.
> Checking for Darcs binary... (cached) "/opt/local/bin/darcs"
> Checking for Darcs version... (cached) Found version 1.0.8 (release).
> Checking for Subversion binary... (cached) "/opt/local/bin/svn"
> Checking for Subversion version... (cached) Found version 1.4.2.
> Checking for GHC binary... (cached) "/opt/local/bin/ghc"
> Checking for GHC version 6.4.1 or later... (cached) Found version 6.6.
> Checking whether byte ordering is bigendian... no
> Checking size of char... 1
> Checking size of short... 2
> Checking size of int... 4
> Checking size of long... 4
> Checking size of long long... 8
> Checking size of float... 4
> Checking size of double... 8
> Checking size of void*... 4
> Checking for pthread_create() in C library pthread... no
>
> Generating config.h with the following settings:
>
>     WORDS_BIGENDIAN      False
>     HAVE_LIBPTHREAD      False
>     SIZEOF_LONG_LONG     8
>     SIZEOF_LONG          4
>     WIN32                0
>     SIZEOF_VOIDP         4
>     SIZEOF_CHAR          1
>     SIZEOF_DOUBLE        8
>     SIZEOF_FLOAT         4
>     SIZEOF_INT           4
>     HAVE_GCC_LABELS      1
>     SIZEOF_SHORT         2
>
> Bootstrapping...
> build/SConscript.depends -> depends/SConscript
> build/SConscript.cpphs -> depends/cpphs/SConscript
> build/SConscript.filepath -> depends/filepath/SConscript
> build/SConscript.ctypes -> depends/ctypes/SConscript
> build/SConscript.libffi -> depends/ctypes/libffi/SConscript
> build/ffih/fficonfig.h -> depends/ctypes/libffi/fficonfig.h
> build/ffih/ffi.h -> depends/ctypes/libffi/include/ffi.h
> build/ffih/cfield.c -> depends/ctypes/libffi/src/cfield.c
> bootstrap/packages/yhc-base/1.0/Prelude.hi -> src/packages/yhc-base-1.0/Prelude.hi
> bootstrap/packages/yhc-base/1.0/PreludeBuiltin.hi -> src/packages/yhc-base-1.0/PreludeBuiltin.hi
> bootstrap/packages/yhc-base/1.0/YHC/Internal.hi -> src/packages/yhc-base-1.0/YHC/Internal.hi
> bootstrap/packages/yhc-base/1.0/Data/Ratio.hi -> src/packages/yhc-base-1.0/Data/Ratio.hi
> Done.
> scons: done reading SConscript files.
> scons: Building targets ...
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs/CppIfdef.hs.
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs/SymTab.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs/SymTab.hs -o depends/cpphs/Language/Preprocessor/Cpphs/SymTab.o
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs/Position.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs/Position.hs -o depends/cpphs/Language/Preprocessor/Cpphs/Position.o
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs/HashDefine.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs/HashDefine.hs -o depends/cpphs/Language/Preprocessor/Cpphs/HashDefine.o
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs/Tokenise.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs/Tokenise.hs -o depends/cpphs/Language/Preprocessor/Cpphs/Tokenise.o
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs/ReadFirst.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs/ReadFirst.hs -o depends/cpphs/Language/Preprocessor/Cpphs/ReadFirst.o
> Getting dependencies for depends/cpphs/Text/ParserCombinators/HuttonMeijer.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Text/ParserCombinators/HuttonMeijer.hs -o depends/cpphs/Text/ParserCombinators/HuttonMeijer.o
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs/CppIfdef.hs -o depends/cpphs/Language/Preprocessor/Cpphs/CppIfdef.o
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs/MacroPass.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs/MacroPass.hs -o depends/cpphs/Language/Preprocessor/Cpphs/MacroPass.o
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs/Options.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs/Options.hs -o depends/cpphs/Language/Preprocessor/Cpphs/Options.o
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs/RunCpphs.hs.
> Getting dependencies for depends/cpphs/Language/Preprocessor/Unlit.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Unlit.hs -o depends/cpphs/Language/Preprocessor/Unlit.o
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs/RunCpphs.hs -o depends/cpphs/Language/Preprocessor/Cpphs/RunCpphs.o
> Getting dependencies for depends/cpphs/Language/Preprocessor/Cpphs.hs.
> ghc -i./src/compiler98 -i./src/libraries/general -i./src/libraries/core -idepends/cpphs -idepends/filepath -i./src/interactive -package mtl -fwarn-missing-signatures -c depends/cpphs/Language/Preprocessor/Cpphs.hs -o depends/cpphs/Language/Preprocessor/Cpphs.o
> gcc -o depends/ctypes/libffi/src/cfield.o -c -DX86 -Wall -DVERSION=\"0.7.0-20061211043856-custom\" -Idepends/ctypes/libffi/include -Idepends/ctypes/libffi/src/x86 -Idepends/ctypes/libffi -I. -I/usr/local/include -I/opt/local/include -I/Library/Frameworks/GMP.Framework/Headers -Idepends/ctypes/libffi/include -Idepends/ctypes/libffi/src/x86 depends/ctypes/libffi/src/cfield.c
> gcc -o depends/ctypes/libffi/src/prep_cif.o -c -DX86 -Wall -DVERSION=\"0.7.0-20061211043856-custom\" -Idepends/ctypes/libffi/include -Idepends/ctypes/libffi/src/x86 -Idepends/ctypes/libffi -I. -I/usr/local/include -I/opt/local/include -I/Library/Frameworks/GMP.Framework/Headers -Idepends/ctypes/libffi/include -Idepends/ctypes/libffi/src/x86 depends/ctypes/libffi/src/prep_cif.c
> gcc -Idepends/ctypes/libffi/include -Idepends/ctypes/libffi/src/x86 -Idepends/ctypes/libffi -I. -I/usr/local/include -I/opt/local/include -I/Library/Frameworks/GMP.Framework/Headers -Idepends/ctypes/libffi/include -Idepends/ctypes/libffi/src/x86 -c -o depends/ctypes/libffi/src/x86/darwin.o depends/ctypes/libffi/src/x86/darwin.S
> gcc -o depends/ctypes/libffi/src/x86/ffi_darwin.o -c -DX86 -Wall -DVERSION=\"0.7.0-20061211043856-custom\" -Idepends/ctypes/libffi/include -Idepends/ctypes/libffi/src/x86 -Idepends/ctypes/libffi -I. -I/usr/local/include -I/opt/local/include -I/Library/Frameworks/GMP.Framework/Headers -Idepends/ctypes/libffi/include -Idepends/ctypes/libffi/src/x86 depends/ctypes/libffi/src/x86/ffi_darwin.c
> depends/ctypes/libffi/src/x86/ffi_darwin.c: In function 'ffi_prep_args':
> depends/ctypes/libffi/src/x86/ffi_darwin.c:127: warning: implicit declaration of function 'bcopy'
> depends/ctypes/libffi/src/x86/ffi_darwin.c:127: warning: incompatible implicit declaration of built-in function 'bcopy'
> depends/ctypes/libffi/src/x86/ffi_darwin.c: In function 'ffi_prep_args_raw':
> depends/ctypes/libffi/src/x86/ffi_darwin.c:519: warning: incompatible implicit declaration of built-in function 'bcopy'
> Getting dependencies for depends/filepath/System/FilePath/Version_0_09.hs.
> An error ocurred running `ghc -M -optdep-f -optdepdepends/filepath/System/FilePath/.Version_0_09.hs.dep -fwarn-missing-signatures -i./src/compiler98:./src/libraries/general:./src/libraries/core:depends/cpphs:depends/filepath:./src/interactive depends/filepath/System/FilePath/Version_0_09.hs`:
> >
> ><no location info>:
> >    can't find file: depends/filepath/System/FilePath/Version_0_09.hs
> >
> Dependencies will not be calculated.
> scons: *** Source `depends/filepath/System/FilePath/Version_0_09.hs' not found, needed by target `depends/filepath/System/FilePath/Version_0_09.o'.  Stop.
> scons: building terminated because of errors.
> cyphers-computer:~/Projects/yhc cypher$ darcs --exact-version
> darcs compiled on Dec  8 2006, at 18:38:21
> # configured Fri Jun 16 14:55:21 EDT 2006
> ./configure --no-create --no-recursion
>
> Context:
>
> [TAG 1.0.8
> Tommy Pettersson <ptp@lysator.liu.se>**20060616160213]
>
>

On Mon, Dec 11, 2006 at 14:01:47 +0000, Neil Mitchell wrote:
> darcs get --partial --repo-name=depends/filepath http://www.cs.york.ac.uk/fp/darcs/filepath
>
> darcs: bug in darcs!
> Impossible case at PatchRead.lhs:56 compiled 18:36:18 Dec  8 2006
> Please report this to bugs@darcs.net,
> If possible include the output of 'darcs --exact-version'.

I was able to reproduce this on Windows, but not on MacOS X.  Both with
1.0.9rc2.

That this only happens under Windows should be a pretty big (and
perhaps worrisome) clue.

darcs get --partial http://www.cs.york.ac.uk/fp/darcs/filepath

On Sun, Dec 24, 2006 at 02:27:55PM +0000, Eric Kow wrote:
> On Mon, Dec 11, 2006 at 14:01:47 +0000, Neil Mitchell wrote:
> > darcs get --partial --repo-name=depends/filepath http://www.cs.york.ac.uk/fp/darcs/filepath
> >
> > darcs: bug in darcs!
> > Impossible case at PatchRead.lhs:56 compiled 18:36:18 Dec  8 2006
> > Please report this to bugs@darcs.net,
> > If possible include the output of 'darcs --exact-version'.
> 
> I was able to reproduce this on Windows, but not on MacOS X.  Both with
> 1.0.9rc2.
> 
> That this only happens under Windows should be a pretty big (and
> perhaps worrisome) clue.

Hmmmm.  Does sound like a big clue, but seems like one that'll be hard to
track down.  :( (But well worth-while...)

> darcs get --partial http://www.cs.york.ac.uk/fp/darcs/filepath

I just tested this now with 1.0.9 and 2.0.0pre2 on Ubuntu Gutsy Linux:

darcs get --partial http://www.cs.york.ac.uk/fp/darcs/filepath

Neither version of darcs triggered the issue, possibly because the referenced
repo  changed, or because it takes some environmental issue on the client to
trigger it. 

This bug how has 5 registered duplicates in the system, so would be great to
make progress on. 

Maybe one of the five duplicates contains a test case which consistently
triggers the issue?

   Mark

I'm upgrading this to "urgent" because it has so many duplicates in the system,
and is a bug that can be a "blocker" for projects in some cases.

I've just pushed a patch that eliminates this impossible case, which is caused
by lazy parsing of patches.  I'm not sure quite how it was triggered, but
parsing strictly will almost always give us better error messages (when patches
fail to be read), and may be faster, and rarely uses noticeably more memory.

David

David, 

The bug tracker has been tracking two variations of this. One of them is
triggered by "get", and the other by "record". Does your update to eliminate
this impossible case also cover the "record" case?

An example would be http://bugs.darcs.net/issue415 
issue488 is a dupe of it.