SnapshotableTrees.dfy(68,24): Error BP5002: A precondition for this call might not hold.
SnapshotableTrees.dfy(648,16): Related location: This is the precondition that might not hold.
Execution trace:
    (0,0): anon0
    (0,0): anon3_Then

Dafny program verifier finished with 65 verified, 1 error
Compiled assembly into SnapshotableTrees.exe