CoPrefix.dfy(63,56): Error: decreases clause might not decrease
CoPrefix.dfy(76,55): Error: cannot prove termination; try supplying a decreases clause
CoPrefix.dfy(114,0): Error: a postcondition could not be proved on this return path
CoPrefix.dfy(113,10): Related location: this is the postcondition that could not be proved
CoPrefix.dfy(101,16): Related location: this proposition could not be proved
CoPrefix.dfy(142,24): Error: assertion might not hold
CoPrefix.dfy(117,22): Related location: this proposition could not be proved
CoPrefix.dfy(151,0): Error: a postcondition could not be proved on this return path
CoPrefix.dfy(150,10): Related location: this is the postcondition that could not be proved
CoPrefix.dfy(164,2): Error: a postcondition could not be proved on this return path
CoPrefix.dfy(163,14): Related location: this is the postcondition that could not be proved
CoPrefix.dfy(169,2): Error: a postcondition could not be proved on this return path
CoPrefix.dfy(168,14): Related location: this is the postcondition that could not be proved
CoPrefix.dfy(176,10): Error: cannot prove termination; try supplying a decreases clause
CoPrefix.dfy(205,6): Error: the calculation step between the previous line and this line could not be proved
CoPrefix.dfy(207,6): Error: the calculation step between the previous line and this line could not be proved
CoPrefix.dfy(220,12): Error: ORDINAL subtraction might underflow a limit ordinal (that is, RHS might be too large)

Dafny program verifier finished with 13 verified, 11 errors
