tcfail019.hs:20: No instance for: `B [tal6]'
    arising from an instance declaration at tcfail019.hs:20
    When checking methods of an instance declaration
 
tcfail019.hs:20: No instance for: `C [tal6]'
    arising from an instance declaration at tcfail019.hs:20
    When checking methods of an instance declaration
 
tcfail019.hs:20: No instance for: `B [tal6]'
    arising from an instance declaration at tcfail019.hs:20
    When checking superclass constraints of an instance declaration
 
tcfail019.hs:20: No instance for: `C [tal6]'
    arising from an instance declaration at tcfail019.hs:20
    When checking superclass constraints of an instance declaration


Compilation had errors