tcfail023.hs:1:
    Duplicate or overlapping instance declarations
	for `A B' defined at tcfail023.hs:13 and defined at tcfail023.hs:10

tcfail023.hs:11:
    Couldn't match `B' against `Bool'
	Expected type: B
	Inferred type: Bool
    In the right-hand side of an equation for `op': True

tcfail023.hs:14:
    Couldn't match `B' against `Bool'
	Expected type: B
	Inferred type: Bool
    In the right-hand side of an equation for `op': True

Compilation had errors