SnapshotableTrees.dfy(68,23): Error BP5002: A precondition for this call might not hold.
SnapshotableTrees.dfy(648,15): Related location: This is the precondition that might not hold.
SnapshotableTrees.dfy(545,15): Related location
Execution trace:
    (0,0): anon0
    (0,0): anon3_Then
SnapshotableTrees.dfy(68,23): Error BP5002: A precondition for this call might not hold.
SnapshotableTrees.dfy(648,15): Related location: This is the precondition that might not hold.
SnapshotableTrees.dfy(548,18): Related location
Execution trace:
    (0,0): anon0
    (0,0): anon3_Then

Dafny program verifier finished with 65 verified, 2 errors
Compiled assembly into SnapshotableTrees.exe