tcfail001.hs:9:warning:
    Duplicated class assertion `A a' in context: `(A a, A a)'
 
tcfail001.hs:9: Couldn't match the type
		    `PrelBase.[]' against `GHC.-> [takw]'
    Expected: `[takv]'
    Inferred: `[takw] -> [takx]'
    In an equation for function `op': `op PrelBase.[] = PrelBase.[]'


Compilation had errors