chore: fix warnings on nightly (#558)

Signed-off-by: David Barsky <[email protected]>

Author: davidbarsky

tracing-attributes/src/lib.rs

@@ -58,6 +58,8 @@
     unused_parens,
     while_true
 )]
+// TODO: once `tracing` bumps its MSRV to 1.42, remove this allow.
+#![allow(unused)]
 extern crate proc_macro;
 
 use std::collections::HashSet;

tracing-subscriber/src/filter/env/mod.rs

@@ -413,13 +413,6 @@ impl fmt::Display for FromEnvError {
 }
 
 impl Error for FromEnvError {
-    fn description(&self) -> &str {
-        match self.kind {
-            ErrorKind::Parse(ref p) => p.description(),
-            ErrorKind::Env(ref e) => e.description(),
-        }
-    }
-
     fn source(&self) -> Option<&(dyn Error + 'static)> {
         match self.kind {
             ErrorKind::Parse(ref p) => Some(p),

tracing-subscriber/src/reload.rs

@@ -228,15 +228,12 @@ impl Error {
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        error::Error::description(self).fmt(f)
-    }
-}
-
-impl error::Error for Error {
-    fn description(&self) -> &str {
-        match self.kind {
+        let msg = match self.kind {
             ErrorKind::SubscriberGone => "subscriber no longer exists",
             ErrorKind::Poisoned => "lock poisoned",
-        }
+        };
+        f.pad(msg)
     }
 }
+
+impl error::Error for Error {}