tracing: fix warnings with log/log-always features (#753)

This commit fixes up a few new Clippy lints and rustc warnings that
occur with the `log`/`log-always` features enabled.

Signed-off-by: Eliza Weisman <[email protected]>

Author: hawkw

tracing/src/macros.rs

@@ -2034,11 +2034,11 @@ macro_rules! fieldset {
 #[macro_export]
 macro_rules! level_to_log {
     ($level:expr) => {
-        match $level {
-            &$crate::Level::ERROR => $crate::log::Level::Error,
-            &$crate::Level::WARN => $crate::log::Level::Warn,
-            &$crate::Level::INFO => $crate::log::Level::Info,
-            &$crate::Level::DEBUG => $crate::log::Level::Debug,
+        match *$level {
+            $crate::Level::ERROR => $crate::log::Level::Error,
+            $crate::Level::WARN => $crate::log::Level::Warn,
+            $crate::Level::INFO => $crate::log::Level::Info,
+            $crate::Level::DEBUG => $crate::log::Level::Debug,
             _ => $crate::log::Level::Trace,
         }
     };
@@ -2327,7 +2327,7 @@ macro_rules! __tracing_log {
 #[macro_export]
 macro_rules! if_log_enabled {
     ($e:expr;) => {
-        $crate::if_log_enabled! {{ $e }}
+        $crate::if_log_enabled! { $e }
     };
     ($if_log:block) => {
         $crate::if_log_enabled! { $if_log else {} }
@@ -2342,7 +2342,7 @@ macro_rules! if_log_enabled {
 #[macro_export]
 macro_rules! if_log_enabled {
     ($e:expr;) => {
-        $crate::if_log_enabled! {{ $e }}
+        $crate::if_log_enabled! { $e }
     };
     ($if_log:block) => {
         $crate::if_log_enabled! { $if_log else {} }
@@ -2361,12 +2361,13 @@ macro_rules! if_log_enabled {
 #[macro_export]
 macro_rules! if_log_enabled {
     ($e:expr;) => {
-        $crate::if_log_enabled! {{ $e }}
+        $crate::if_log_enabled! { $e }
     };
     ($if_log:block) => {
         $crate::if_log_enabled! { $if_log else {} }
     };
     ($if_log:block else $else_block:block) => {
+        #[allow(unused_braces)]
         $if_log
     };
 }

tracing/src/span.rs

@@ -366,7 +366,7 @@ pub struct Entered<'a> {
 
 /// `log` target for span lifecycle (creation/enter/exit/close) records.
 #[cfg(feature = "log")]
-const LIFECYCLE_LOG_TARGET: &'static str = "tracing::span";
+const LIFECYCLE_LOG_TARGET: &str = "tracing::span";
 
 // ===== impl Span =====