Defer

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defer.fl

// Build: build/flecha build examples/defer.fl -o /tmp/flecha-defer
void report(i32 value) { stdoutln(value); }
void set_answer(&i32 value) { *value = 42; }
unsafe void write_pointer(*i32 value, i32 next) { *value = next; }

i32 main() {
    i32 captured = 10;
    defer report(captured);
    captured = 20;

    {
        defer report(1);
        defer report(2);
    } // Prints 2, then 1.

    loop i := 0; i < 2; i++ {
        defer report(i + 3);
        proceed; // Prints 3 on the first iteration, then 4.
    }

    i32 answer = 0;
    {
        defer set_answer(&answer);
        // The mutable borrow holds until this block ends.
    }
    stdoutln(answer); // 42.

    unsafe {
        defer write_pointer(&raw captured, 99);
    }
    stdoutln(captured); // 99; raw-pointer operations still require unsafe.

    string text = "snapshot";
    {
        defer stdoutln(text.view());
        text = "changed";
    } // Prints snapshot: string/view arguments are copied at registration.

    return answer; // Prints the captured 10, then exits with 42.
}