Panic when compiling cmm file together with -outputdir

To reproduce:

$ touch test.cmm
$ ghc -c test.cmm -outputdir=build
ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.9.20140428 for x86_64-unknown-linux):
	hscCmmFile: no_mod

The panic is declared in main/HscMain.hs:hscCompileCmmFile in place of current module name, but forced in main/CodeOutput.lhs:outputForeignStubs by doesFileExist.

It works without -outputdir because in that case module name is not used to create path to stub file, see main/Finder.lhs:mkStubPaths.

Trac metadata

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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Panic when compiling cmm file together with -outputdir