style: Make clippy happy

src/fmt/humantime.rs

@@ -85,7 +85,7 @@ impl fmt::Debug for Timestamp {
         /// A `Debug` wrapper for `Timestamp` that uses the `Display` implementation.
         struct TimestampValue<'a>(&'a Timestamp);
 
-        impl<'a> fmt::Debug for TimestampValue<'a> {
+        impl fmt::Debug for TimestampValue<'_> {
             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                 fmt::Display::fmt(&self.0, f)
             }

src/fmt/kv.rs

@@ -41,7 +41,7 @@ pub fn default_kv_format(formatter: &mut Formatter, fields: &dyn Source) -> io::
 
 struct DefaultVisitSource<'a>(&'a mut Formatter);
 
-impl<'a, 'kvs> VisitSource<'kvs> for DefaultVisitSource<'a> {
+impl<'kvs> VisitSource<'kvs> for DefaultVisitSource<'_> {
     fn visit_pair(&mut self, key: Key<'_>, value: Value<'kvs>) -> Result<(), Error> {
         write!(self.0, " {}={}", self.style_key(key), value)?;
         Ok(())

src/fmt/mod.rs

@@ -317,7 +317,7 @@ struct DefaultFormat<'a> {
     kv_format: &'a KvFormatFn,
 }
 
-impl<'a> DefaultFormat<'a> {
+impl DefaultFormat<'_> {
     fn write(mut self, record: &Record<'_>) -> io::Result<()> {
         self.write_timestamp()?;
         self.write_level(record)?;
@@ -454,7 +454,7 @@ impl<'a> DefaultFormat<'a> {
                     indent_count: usize,
                 }
 
-                impl<'a, 'b> Write for IndentWrapper<'a, 'b> {
+                impl Write for IndentWrapper<'_, '_> {
                     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
                         let mut first = true;
                         for chunk in buf.split(|&x| x == b'\n') {

src/logger.rs

@@ -806,7 +806,7 @@ where
     }
 }
 
-impl<'a> Default for Env<'a> {
+impl Default for Env<'_> {
     fn default() -> Self {
         Env {
             filter: Var::new(DEFAULT_FILTER_ENV),