Boot file problem

Here are two modules and a boot file. Compile by

ghc -c Foo.hs-boot; ghc -c Bar.hs; ghc -c Foo.hs

and observe this error message

Foo.hs:12:1:
    Type constructor `Foo' has conflicting definitions in the module
    and its hs-boot file
    Main module: data Foo = Foo {x :: {-# UNPACK #-} !Int}
    Boot file:   data Foo = Foo {x :: !Int}

But the definitions are not conflicting, they are identical.

Foo.hs-boot:

module Foo where
data Foo = Foo { x :: {-# UNPACK #-} !Int }

Foo.hs:

module Foo where
import Bar
data Foo = Foo { x :: {-# UNPACK #-} !Int }

Bar.hs:

module Bar where
import {-# SOURCE #-} Foo

Removing the unbox pragma gives the even more perplexing:

Foo.hs:3:1:
    Type constructor `Foo' has conflicting definitions in the module
    and its hs-boot file
    Main module: data Foo = Foo {x :: !Int}
    Boot file:   data Foo = Foo {x :: !Int}

Trac metadata

Trac field	Value
Version	7.8.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 5

added Tbug Trac import labels

I can reproduce this error with GHC 7.10.3 but not with HEAD. Can someone verify whether it exists on ghc-8.0 branch?

I can confirm that the error does not occur in 8.0:

rwbarton@morphism:/tmp/boot$ ls
Bar.hs  Foo.hs  Foo.hs-boot
rwbarton@morphism:/tmp/boot$ GHC=~/ghc-8.0-install/bin/ghc
rwbarton@morphism:/tmp/boot$ $GHC --version
The Glorious Glasgow Haskell Compilation System, version 8.0.0.20160123
rwbarton@morphism:/tmp/boot$ $GHC -c Foo.hs-boot; $GHC -c Bar.hs; $GHC -c Foo.hs

and (as jstolarek already mentioned) it does occur in 7.10:

rwbarton@morphism:/tmp/boot$ rm *.hi* *.o*; ls
Bar.hs  Foo.hs  Foo.hs-boot
rwbarton@morphism:/tmp/boot$ GHC=ghc-7.10.1
rwbarton@morphism:/tmp/boot$ $GHC --version
The Glorious Glasgow Haskell Compilation System, version 7.10.1
rwbarton@morphism:/tmp/boot$ $GHC -c Foo.hs-boot; $GHC -c Bar.hs; $GHC -c Foo.hs

Foo.hs:4:2:
    Type constructor ‘Foo’ has conflicting definitions in the module
    and its hs-boot file
    Main module: data Foo = Foo {x :: !Int}
    Boot file:   data Foo = Foo {x :: !Int}
    The constructors do not match:
      The strictness annotations for ‘Foo’ differ

But the message is a bit strange: it claims that the annotations differ, but then prints out the identical annotations... Something still looks wrong there.

My last comment was possibly confusing. The error with the identical declarations is from 7.10, not 8.0. I've edited it to try to make it more clear.

I can repro what looks like a similar issue on HEAD, but I don't have a good test yet. I'm experimenting building GHC with the following build flavour:

SRC_HC_OPTS        = -O -H64m
GhcStage1HcOpts    = -O
GhcStage2HcOpts    = -O2 -XStrictData -XUnboxedSums -funbox-strict-fields  -fexpose-all-unfoldings -flate-dmd-anal -fmax-simplifier-iterations=8 -funfolding-use-threshold=120 -fstatic-argument-transformation -fsimpl-tick-factor=100000
GhcLibHcOpts       = -O2 -XUnboxedSums -funbox-strict-fields  -flate-dmd-anal -fmax-simplifier-iterations=8 -funfolding-use-threshold=120 -fsimpl-tick-factor=100000
BUILD_PROF_LIBS    = NO
HADDOCK_DOCS       = NO
BUILD_SPHINX_HTML  = NO
BUILD_SPHINX_PDF   = NO
BUILD_MAN          = NO

Where the error pops up building stage2:

"inplace/bin/ghc-stage1" -hisuf hi -osuf  o -hcsuf hc -static  -O -H64m -Wall   -Iincludes -Iincludes/dist -Iincludes/dist-derivedconstants/header -Iincludes/dist-ghcconstants/header   -this-unit-i
d ghc-8.1 -hide-all-packages -i -icompiler/basicTypes -icompiler/cmm -icompiler/codeGen -icompiler/coreSyn -icompiler/deSugar -icompiler/ghci -icompiler/hsSyn -icompiler/iface -icompiler/llvmGen -i
compiler/main -icompiler/nativeGen -icompiler/parser -icompiler/prelude -icompiler/profiling -icompiler/rename -icompiler/simplCore -icompiler/simplStg -icompiler/specialise -icompiler/stgSyn -icom
piler/stranal -icompiler/typecheck -icompiler/types -icompiler/utils -icompiler/vectorise -icompiler/stage2/build -Icompiler/stage2/build -icompiler/stage2/build/./autogen -Icompiler/stage2/build/.
/autogen -Icompiler/. -Icompiler/parser -Icompiler/utils -Icompiler/../rts/dist/build -Icompiler/stage2   -optP-DGHCI -optP-include -optPcompiler/stage2/build/./autogen/cabal_macros.h -package-id a
rray-0.5.1.1 -package-id base-4.9.0.0 -package-id binary-0.8.3.0 -package-id bytestring-0.10.8.1 -package-id containers-0.5.7.1 -package-id deepseq-1.4.2.0 -package-id directory-1.2.6.2 -package-id
 filepath-1.4.1.0 -package-id ghc-boot-8.1 -package-id ghci-8.1 -package-id hoopl-3.10.2.1 -package-id hpc-0.6.0.3 -package-id process-1.4.2.0 -package-id template-haskell-2.11.0.0 -package-id time
-1.6.0.1 -package-id transformers-0.5.2.0 -package-id unix-2.7.2.0 -Wall -fno-warn-name-shadowing -this-unit-id ghc -XHaskell2010 -optc-DTHREADED_RTS -DGHCI_TABLES_NEXT_TO_CODE -DSTAGE=2 -Rghc-timi
ng -O2 -XStrictData -XUnboxedSums -funbox-strict-fields  -fexpose-all-unfoldings -flate-dmd-anal -fmax-simplifier-iterations=8 -funfolding-use-threshold=120 -fstatic-argument-transformation -fsimpl
-tick-factor=100000  -no-user-package-db -rtsopts      -Wnoncanonical-monad-instances  -odir compiler/stage2/build -hidir compiler/stage2/build -stubdir compiler/stage2/build   -dynamic-too -c comp
iler/basicTypes/ConLike.hs -o compiler/stage2/build/ConLike.o -dyno compiler/stage2/build/ConLike.dyn_o

compiler/basicTypes/ConLike.hs:50:1: error:
    Type constructor ‘ConLike’ has conflicting definitions in the module
    and its hs-boot file
    Main module: data ConLike
                   = RealDataCon {-# UNPACK #-}DataCon
                   | PatSynCon {-# UNPACK #-}PatSyn
    Boot file:   data ConLike
                   = RealDataCon !DataCon | PatSynCon !PatSyn
    The constructors do not match:
      The strictness annotations for ‘RealDataCon’ differ
      The strictness annotations for ‘PatSynCon’ differ
<<ghc: 246434928 bytes, 111 GCs, 12727312/40013680 avg/max bytes residency (7 samples), 83M in use, 0.000 INIT (0.000 elapsed), 0.130 MUT (0.135 elapsed), 0.179 GC (0.179 elapsed) :ghc>>
compiler/ghc.mk:577: recipe for target 'compiler/stage2/build/ConLike.o' failed
make[1]: *** [compiler/stage2/build/ConLike.o] Error 1

Yet I can't repro with the original test case above, even when I pass all the flags I specify in the flavor above:

$ ~/inplace/bin/ghc-stage1 -O2 -XStrictData -XUnboxedSums -funbox-strict-fields  -fexpose-all-unfoldings -flate-dmd-anal -fmax-simplifier-iterations=8 -funfolding-use-threshold=120 -fstatic-argument-transformation -fsimpl-tick-factor=100000  -c /tmp/Foo.hs-boot
...and so on for Bar.hs and Foo.hs

No error is thrown. I don't understand enough of the way ghc-stage1 is being called in the ghc build's invocation to know where to begin experimenting further with this.

Note, you have to put spaces around occurences of #. from Data.Functor.Utils for UnboxedSums to get the compile to go this far, but otherwise my ghc tree is unmodified from 14c2e8e0

FWIW freezing stage1 and adding the following to the top of compiler/basicTypes/ConLike.hs and compiler/basicTypes/ConLike.hs-boot got me past that to a successfully built (though panic-throwing stage2)

{-# LANGUAGE NoStrictData #-}

added Pnormal label