requires-weaker.dfy(15,2): Error: the method must provide an equal or more permissive precondition than in its parent trait
 Asserted expression: P(i') && Q(i') ==> P(i' + 1) ==> Q(i' + 1)
requires-weaker.dfy(15,2): Error: the method must provide an equal or more permissive precondition than in its parent trait
 Asserted expression: P(i') && Q(i') ==> Q(i' * 2)

Dafny program verifier finished with 1 verified, 2 errors
