signal: add track_caller to public APIs

tokio/src/signal/unix.rs

@@ -384,6 +384,12 @@ pub struct Signal {
 /// * If the previous initialization of this specific signal failed.
 /// * If the signal is one of
 ///   [`signal_hook::FORBIDDEN`](fn@signal_hook_registry::register#panics)
+///
+/// # Panics
+///
+/// This function panics if there is no current reactor set, or if the `rt`
+/// feature flag is not enabled.
+#[track_caller]
 pub fn signal(kind: SignalKind) -> io::Result<Signal> {
     let rx = signal_with_handle(kind, &Handle::current())?;
 

tokio/src/signal/unix/driver.rs

@@ -182,6 +182,7 @@ cfg_rt! {
         /// # Panics
         ///
         /// This function panics if there is no current signal driver set.
+        #[track_caller]
         pub(super) fn current() -> Self {
             crate::runtime::context::signal_handle().expect(
                 "there is no signal driver running, must be called from the context of Tokio runtime",
@@ -197,6 +198,7 @@ cfg_not_rt! {
         /// # Panics
         ///
         /// This function panics if there is no current signal driver set.
+        #[track_caller]
         pub(super) fn current() -> Self {
             panic!(
                 "there is no signal driver running, must be called from the context of Tokio runtime or with\

tokio/tests/signal_panic.rs

@@ -0,0 +1,29 @@
+#![warn(rust_2018_idioms)]
+#![cfg(feature = "full")]
+#![cfg(unix)]
+
+use std::error::Error;
+use tokio::runtime::Builder;
+use tokio::signal::unix::{signal, SignalKind};
+
+mod support {
+    pub mod panic;
+}
+use support::panic::test_panic;
+
+#[test]
+fn signal_panic_caller() -> Result<(), Box<dyn Error>> {
+    let panic_location_file = test_panic(|| {
+        let rt = Builder::new_current_thread().build().unwrap();
+
+        rt.block_on(async {
+            let kind = SignalKind::from_raw(-1);
+            let _ = signal(kind);
+        });
+    });
+
+    // The panic location should be in this file
+    assert_eq!(&panic_location_file.unwrap(), file!());
+
+    Ok(())
+}