// Whole-program inferred error sets (ERR step E1.4b). A bare `-> !` function's
// error set is INFERRED: the union of the tags it raises directly plus the
// sets of the failable functions it `try`s, converged across the whole call
// graph by a fix-point pass. Here `leaf` raises {Foo}; `mid` try-propagates
// leaf AND raises Bar, so `mid` converges to {Foo, Bar}; the named caller
// `run :: -> !A` then type-checks because mid's converged set is a subset of
// A. The rejection (a converged tag NOT in the caller's set) lives in
// `examples/224-inferred-widening-reject.sx`.

#import "modules/std.sx";

A :: error { Foo, Bar }

leaf :: (n: i32) -> ! {
    if n < 0 { raise error.Foo; }
    return;
}

// Inferred set converges to {Foo, Bar}: {Foo} absorbed from `try leaf` plus
// the directly-raised Bar.
mid :: (n: i32) -> ! {
    try leaf(n);
    if n == 100 { raise error.Bar; }
    return;
}

// Named caller: mid's converged {Foo, Bar} is a subset of A -> widening OK.
run :: (n: i32) -> !A {
    try mid(n);
    return;
}

main :: () -> i32 {
    e := run(-1);                          // leaf raises Foo -> propagates out
    r : i32 = 0;
    if e == error.Foo { r = r + 7; }       // true  -> +7
    if e == error.Bar { r = r + 1; }        // false (Foo escaped, not Bar)
    print("inferred result: {}\n", r);      // -> 7
    return r;
}