git-issue-555.dfy(17,11): Error: assertion might not hold

Dafny program verifier finished with 2 verified, 1 error

Dafny program verifier did not attempt verification
[Program halted] git-issue-555.dfy(22,2): expectation violation

Dafny program verifier did not attempt verification
[Program halted] git-issue-555.dfy(22,2): expectation violation

Dafny program verifier did not attempt verification
[Program halted] git-issue-555.dfy(22,2): expectation violation

Dafny program verifier did not attempt verification
[Program halted] git-issue-555.dfy(22,2): expectation violation
