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type X;
const nil: X;
var l: X;
var x: int;
procedure Allocate() returns ({:linear "tid"} xls: X);
ensures xls != nil;
procedure {:entrypoint} {:yields} main()
{
var {:linear "tid"} tid: X;
var val: int;
while (*)
{
call tid := Allocate();
havoc val;
async call foo(tid, val);
}
}
procedure {:yields} {:stable} foo({:linear "tid"} tid': X, val: int)
requires tid' != nil;
{
var {:linear "tid"} tid: X;
tid := tid';
assume l == nil;
l := tid;
call tid := Yield(tid);
x := val;
call tid := Yield(tid);
assert x == val;
call tid := Yield(tid);
l := nil;
}
procedure {:yields} Yield({:linear "tid"} tid': X) returns ({:linear "tid"} tid: X)
requires tid' != nil;
ensures tid == tid';
ensures old(l) == tid ==> old(l) == l && old(x) == x;
{
tid := tid';
yield;
assert tid != nil;
assert (old(l) == tid ==> old(l) == l && old(x) == x);
}
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