DecreasesTo1.dfy(19,9): Error: assertion might not hold
 Asserted expression: 0 decreases to 1
DecreasesTo1.dfy(23,9): Error: assertion might not hold
 Asserted expression: x - 1 decreases to x
DecreasesTo1.dfy(27,9): Error: assertion might not hold
 Asserted expression: x, y - 1 decreases to x, y
DecreasesTo1.dfy(39,34): Error: decreases clause might not decrease
 Asserted expression: n + m decreases to n + m + 1
DecreasesTo1.dfy(49,20): Error: decreases clause might not decrease
 Asserted expression: old(n + m) decreases to n + m + 1
DecreasesTo1.dfy(57,2): Error: decreases expression might not decrease
 Asserted expression: old@LoopEntry(prev_x') decreases to x'
   with the label `LoopEntry` applied to the loop
   and with the following declarations at the beginning of the loop body:
     var prev_x': int := x';
     var prev_y': int := y';
DecreasesTo1.dfy(69,9): Error: assertion might not hold
 Asserted expression: 0 nonincreases to 1
DecreasesTo1.dfy(73,9): Error: assertion might not hold
 Asserted expression: i decreases to b
DecreasesTo1.dfy(77,9): Error: assertion might not hold
 Asserted expression: 0 decreases to false

Dafny program verifier finished with 2 verified, 9 errors
