git-issue-897.dfy(10,17): Warning: Could not find a trigger for this quantifier. Without a trigger, the quantifier may cause brittle verification. To silence this warning, add an explicit trigger using the {:trigger} attribute. For more information, see the section quantifier instantiation rules in the reference manual.
git-issue-897.dfy(11,19): Error: assertion might not hold
git-issue-897.dfy(16,30): Error: possible violation of postcondition of forall statement

Dafny program verifier finished with 0 verified, 2 errors
