function {:existential true} b0(x:bool, y:bool): bool;
function {:existential true} b1(x:bool, y:bool): bool;
function {:existential true} b2(x:bool, y:bool): bool;

var g: int;

procedure main()
modifies g;
ensures b0(g == 0, g == 5);
{
  g := 0;
  if(*) { g := 5; }
  call foo();
}

procedure foo()
  modifies g;
  requires b1(g == 0, g == 5);
  ensures b2(g == 0, g == 5);
{
  assume g != 5;
}