id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
2057	inconsistent .hi file error gets ignored	duncan		"{{{
[20 of 20] Compiling Main             ( ./Main.hs, dist/build/cabal/cabal-tmp/Main.o )
The interface for `main:Hackage.Config'
Declaration for savedConfigToConfigFlags
Unfolding of Hackage.Config.savedConfigToConfigFlags:
  Can't find interface-file declaration for variable Distribution.Simple.Setup.a401
    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
Linking dist/build/cabal/cabal ...
dist/build/cabal/cabal-tmp/Hackage/Config.o: In function `sfsu_info':
(.text+0x70cc): undefined reference to `Cabalzm1zi3zi3_DistributionziSimpleziSetup_a401_closure'
dist/build/cabal/cabal-tmp/Hackage/Config.o: In function `rf7U_closure':
(.data+0xf28): undefined reference to `Cabalzm1zi3zi3_DistributionziSimpleziSetup_a401_closure'
collect2: ld returned 1 exit status
}}}

Now, the inconsistent .hi file was entirely my fault. However note that `ghc --make` did not stop at the error! It continued and tried to link.

This is bad because sometimes linker errors are very long and a user might loose the real source of the error.

The error gets raised in `iface/TcIface.lhs` by `importDecl`. The uses of that function look like they are translating the error into failure in other monads ok. It's not immediately obvious at what point in the propagation of this error it gets ignored and linking continues irrespective.

It should not be too hard to reproduce I hope. Generating inconsistent .hi files is fairly easy to do. In this case I just built cabal-install against an existing Cabal. Then rebuilt and re-registered a slightly changed Cabal lib. Then did another build of cabal-install without cleaning first."	bug	new	normal	_|_	Compiler	6.8.2			nicolas.pouillard@…	Unknown/Multiple	Unknown/Multiple		Unknown