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]'
+tcfail001.hs:9: Function type expected, but found the type `[takz]'
In an equation for function `op': `op PrelBase.[] = PrelBase.[]'