// lifetime_elision.bux — C.1: elided lifetimes for common &[Checked] APIs
// No 'a annotations needed when there is a single input reference.
import Std::Io::{PrintLine, PrintInt};
import Std::Test::{Test_AssertEqInt, Test_Pass};

// Elided: param and return share one lifetime automatically
@[Checked]
func Identity(p: &int) -> &int {
    return p;
}

// Explicit lifetime for documentation / multi-ref (same lifetime both sides)
@[Checked]
func IdentityNamed<'a>(p: &'a int) -> &'a int {
return p;
}

// Via intermediate let binding — lifetime is propagated
@[Checked]
func ViaLet(p: &int) -> &int {
    let r: &int = p;
    return r;
}

// self-style first param: elision prefers the first input for the return
@[Checked]
func FirstOf(self: &int, _other: int) -> &int {
    return self;
}

@[Checked]
func Main() -> int {
    var x: int = 10;
    var y: int = 20;

    let a: &int = Identity(&x);
    Test_AssertEqInt(*a, 10);

    let b: &int = IdentityNamed(&y);
    Test_AssertEqInt(*b, 20);

    let c: &int = ViaLet(&x);
    Test_AssertEqInt(*c, 10);

    let d: &int = FirstOf(&y, 0);
    Test_AssertEqInt(*d, 20);

    Test_Pass("lifetime_elision");
    PrintLine("lifetime_elision: ok");
    return 0;
}