Corecursion.dfy(17,12): Error: cannot prove termination; try supplying a decreases clause (note that only functions without side effects can be called co-recursively)
Execution trace:
    (0,0): anon0
    (0,0): anon4_Else
Corecursion.dfy(23,12): Error: cannot prove termination; try supplying a decreases clause (note that only functions without any ensures clause can be called co-recursively)
Execution trace:
    (0,0): anon0
    (0,0): anon4_Else
Corecursion.dfy(58,4): Error: cannot prove termination; try supplying a decreases clause
Execution trace:
    (0,0): anon0
    (0,0): anon4_Else
Corecursion.dfy(71,15): Error: cannot prove termination; try supplying a decreases clause (note that calls cannot be co-recursive in this context)
Execution trace:
    (0,0): anon0
    (0,0): anon7_Else
Corecursion.dfy(93,14): Error: cannot prove termination; try supplying a decreases clause (note that a call can be co-recursive only if all intra-cluster calls are in non-destructive contexts)
Execution trace:
    (0,0): anon0
    (0,0): anon7_Else
    (0,0): anon8_Then
Corecursion.dfy(103,14): Error: cannot prove termination; try supplying a decreases clause (note that a call can be co-recursive only if all intra-cluster calls are in non-destructive contexts)
Execution trace:
    (0,0): anon0
    (0,0): anon7_Else
    (0,0): anon8_Then
Corecursion.dfy(148,12): Error: failure to decrease termination measure (note that a call can be co-recursive only if all intra-cluster calls are in non-destructive contexts)
Execution trace:
    (0,0): anon0
    (0,0): anon4_Else
Corecursion.dfy(161,12): Error: failure to decrease termination measure (note that a call can be co-recursive only if all intra-cluster calls are in non-destructive contexts)
Execution trace:
    (0,0): anon0
    (0,0): anon4_Else

Dafny program verifier finished with 20 verified, 8 errors