3 Duplicate or overlapping instance declarations
4 for `A B' at tcfail023.hs:14 and tcfail023.hs:11
7 Couldn't match the type `Bool' against `B'
10 In an equation for function `op': op C = True
11 In the definition for method `op'
14 Couldn't match the type `Bool' against `B'
17 In an equation for function `op': op C = True
18 In the definition for method `op'
21 Compilation had errors