Cabal Bug

[Dominic Steinitz]

When I try to build using 

./Setup build

I get the following error:

Compiling Codec.Encryption.DESAux ( ./Codec/Encryption/DESAux.hs, 
dist/build/./Codec/Encryption/DESAux.o )

./Codec/Encryption/DESAux.hs:19:0:
    Illegal instance declaration for `Num [Bool]'
        (The instance type must be of form (T a b c)
         where T is not a synonym, and a,b,c are distinct type variables)
    In the instance declaration for `Num [Bool]'

./Codec/Encryption/DESAux.hs:21:0:
    Illegal instance declaration for `Bits [Bool]'
        (The instance type must be of form (T a b c)
         where T is not a synonym, and a,b,c are distinct type variables)
    In the instance declaration for `Bits [Bool]'

 So I added

Ghc-options:     -fglasgow-exts

to the cabal file. Now this module compiles but I still get the same error on 
a different module and I know -fglasgow-exts allows this to compile when I do 
it by hand.

./Codec/ASN1/TLV.hs:140:0:
    Illegal instance declaration for `Binary (State ([Octet], Offset))'
        (The instance type must be of form (T a b c)
         where T is not a synonym, and a,b,c are distinct type variables)
    In the instance declaration for `Binary (State ([Octet], Offset))'

In fact, this seems to be the second time this module has been compiled and 
the first it completed successfully.

Compiling Codec.ASN1.TLV   ( ./Codec/ASN1/TLV.hs, 
dist/build/./Codec/ASN1/TLV.o )
Compiling Codec.ASN1.X509  ( ./Codec/ASN1/X509.hs, 
dist/build/./Codec/ASN1/X509.o )

Why is cabal recompiling sources and why am I getting errors on the second 
compilation?

The sources and the cabal file are available via:

darcs get http://www.haskell.org/Codec

Dominic.