3 No instance for: `B [a]'
4 arising from an instance declaration, at tcfail019.hs:19
5 Available context: (B [a], C [a])
6 From the superclasses of the instance declaration
9 No instance for: `C [a]'
10 arising from an instance declaration, at tcfail019.hs:19
11 Available context: (B [a], C [a])
12 From the superclasses of the instance declaration
15 Compilation had errors