[1 of 3] Compiling SH_Overlap7_B   (.hs -> .o)
[2 of 3] Compiling SH_Overlap7_A   (.hs -> .o)
[3 of 3] Compiling SH_Overlap7     (.hs -> .o)

SH_Overlap7.hs:1:16: warning: [-Wunsafe]
    ‘SH_Overlap7’ has been inferred as unsafe!
    Reason:
        SH_Overlap7.hs:14:8: warning:
            • Unsafe overlapping instances for C [Int]
                arising from a use of ‘f’
              The matching instance is:
                instance [overlap ok] [safe] C [Int]
                  -- Defined at SH_Overlap7_A.hs:12:3
              It is compiled in a Safe module and as such can only
              overlap instances from the same module, however it
              overlaps the following instances from different modules:
                instance C [a] -- Defined at SH_Overlap7.hs:10:10
            • In the expression: f ([1, 2, 3, 4] :: [Int])
              In an equation for ‘test’: test = f ([1, 2, 3, 4] :: [Int])

<no location info>: error: 
Failing due to -Werror.