Demonstrating an unfortunate interaction between `#[track_caller]` and const-evaluation.

const_track_caller.rs

#![allow(dead_code)]
use std::panic::Location;

#[track_caller]
fn runtime_line() -> &'static u32 {
    Box::leak(Box::new(core::panic::Location::caller().line()))
}

#[track_caller]
fn inline_const_line() -> &'static u32 {
    const { &core::panic::Location::caller().line() }
}

#[track_caller]
fn decl_const_line() -> &'static u32 {
    const LINE: u32 = Location::caller().line();
    &LINE
}

#[test]
fn runtime() {
    let line = runtime_line();
    assert_eq!(*line, line!() - 1);
}

#[test]
fn inline_const() {
    let line = inline_const_line();
    assert_eq!(*line, line!() - 1);
}

#[test]
fn decl_const() {
    let line = decl_const_line();
    assert_eq!(*line, line!() - 1);
}