Simplify fmt::Debug representations

The Debug renderings of the Watch and Signal types are quite verbose, dumping
the state of the internal watch (which isn't really useful to) callers.

This change minimizes the Debug output to just the type names and bumps
the package version in anticipation of the next release.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "drain"
-version = "0.1.1"
+version = "0.1.2"
 authors = ["Linkerd Developers <[email protected]>"]
 license = "Apache-2.0"
 edition = "2018"

src/lib.rs

@@ -31,7 +31,6 @@ pub fn channel() -> (Signal, Watch) {
 enum Never {}
 
 /// Send a drain command to all watchers.
-#[derive(Debug)]
 pub struct Signal {
     drained_rx: mpsc::Receiver<Never>,
     signal_tx: watch::Sender<()>,
@@ -41,14 +40,14 @@ pub struct Signal {
 ///
 /// All `Watch` instances must be dropped for a `Signal::signal` call to
 /// complete.
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct Watch {
     drained_tx: mpsc::Sender<Never>,
     signal_rx: watch::Receiver<()>,
 }
 
 #[must_use = "ReleaseShutdown should be dropped explicitly to release the runtime"]
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct ReleaseShutdown(mpsc::Sender<Never>);
 
 // === impl Signal ===
@@ -74,6 +73,12 @@ impl Signal {
     }
 }
 
+impl std::fmt::Debug for Signal {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Signal").finish_non_exhaustive()
+    }
+}
+
 // === impl Watch ===
 
 impl Watch {
@@ -117,6 +122,12 @@ impl Watch {
     }
 }
 
+impl std::fmt::Debug for Watch {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Watch").finish_non_exhaustive()
+    }
+}
+
 impl ReleaseShutdown {
     /// Releases shutdown after `future` completes.
     pub async fn release_after<F: Future>(self, future: F) -> F::Output {
@@ -125,6 +136,11 @@ impl ReleaseShutdown {
         res
     }
 }
+impl std::fmt::Debug for ReleaseShutdown {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("ReleaseShutdown").finish_non_exhaustive())
+    }
+}
 
 #[cfg(test)]
 mod tests {