`go` coroutine design

[bvssvni]

Dyon uses the go keyword to create a concurrent coroutine, similar to Go, but with the difference that Dyon uses the return value.

Example:

fn foo() -> str {
    sleep(1.0)
    return "done"
}

fn main() {
    foo_thread := go foo()
    sleep(0.5)
    val := join(thread: foo_thread)
    if is_err(val) {
        // An error happened when running the thread
        println(unwrap_err(val))
    } else {
        // Prints `done`
        println(unwrap(val))
    }
}

To provide thread safety:

1. Arguments are evaluated on the same stack
2. Arguments are deep cloned over to the new run-time's stack
3. Creating a fake AST call using expression references to the deep cloned arguments
4. The thread evaluates the fake AST call on a new thread
5. The remaining value on the new stack is the result
6. The new result is deep cloned

Rules:

• go foo() requires -> on the function foo
• go foo(a, b) must have no lifetimes on arguments of foo, because the evaluated arguments are ordered by the call and do not necessarily have the same order in the lifetime check