use std::panic::Location;

/// ```
///      |1        |11       |21       |31       |41
///    +-|---------|---------|---------|---------|--------
/// 15 | #[track_caller]
/// 16 | fn new_location() -> &'static Location<'static> {
/// 17 |     Location::caller()
///    |     ------------------| the value of this expression depends on the caller,
///    |                       | since the function is marked #[track_caller]
/// 18 | }
/// ```
#[track_caller]
fn new_location() -> &'static Location<'static> {
    Location::caller()
}

/// ```
///      |1  |5    |11       |21       |31       |41       |51
///    +-|---|-----|---------|---------|---------|---------|---
/// 29 | fn constant_location() -> &'static Location<'static> {
/// 30 |     new_location()
///    |     ^ any invocation of constant_location() points here,
///    |       no matter the location it is called from
/// 31 | }
/// ```
fn constant_location() -> &'static Location<'static> {
    new_location()
}

fn main() {
    //      |1  |5    |11       |21       |31       |41       |51
    //    +-|---|-----|---------|---------|---------|---------|---
    // 29 | fn constant_location() -> &'static Location<'static> {
    // 30 |     new_location()
    //    |     ^ `let constant` points here
    // 31 | }
    let constant = constant_location();
    assert_eq!(constant.file(), file!());
    assert_eq!((constant.line(), constant.column()), (30, 5));

    let constant_2 = constant_location();
    assert_eq!(
        (constant.file(), constant.line(), constant.column()),
        (constant_2.file(), constant_2.line(), constant_2.column())
    );

    //      |1        |11  |16  |21       |31
    //    +-|---------|----|----|---------|------
    // 55 |     let here = new_location();
    //    |                ^ `let here` points here, as `new_location()` is the callsite
    // 56 |     assert_eq!(here.file(), file!());
    let here = new_location();
    assert_eq!(here.file(), file!());
    assert_eq!((here.line(), here.column()), (55, 16));

    //      |1        |11       |21       ||32      |41       |51
    //    +-|---------|---------|---------||--------|---------|------
    // 64 |     let yet_another_location = new_location();
    //    |                                ^ `let yet_another_location` points here
    // 65 |     assert_eq!(here.file(), yet_another_location.file());
    let yet_another_location = new_location();
    assert_eq!(here.file(), yet_another_location.file());
    assert_ne!(
        (here.line(), here.column()),
        (yet_another_location.line(), yet_another_location.column())
    );
}