modifiable.dfy(10,4): Error: assignment might update an object not in the enclosing context's modifies clause
 Asserted expression: this in {}
modifiable.dfy(33,7): Error: assignment might update an object not in the enclosing context's modifies clause
 Asserted expression: s[0] == s[1] || s[0] == s[1] as C || s[0] in {s[1]} || s[0] in {s[1] as C}
modifiable.dfy(42,6): Error: assignment might update an object field not in the enclosing context's modifies clause
 Asserted expression: c == s[1]
modifiable.dfy(50,5): Error: assignment might update an array element not in the enclosing context's modifies clause
 Asserted expression: a == b
modifiable.dfy(59,5): Error: assignment might update an array element not in the enclosing context's modifies clause
 Asserted expression: a == s[1]
modifiable.dfy(66,5): Error: assignment might update an array element not in the enclosing context's modifies clause
 Asserted expression: a in {}

Dafny program verifier finished with 4 verified, 6 errors
