Fixup Rust 1.52 cargo clippy suggestions

Author: bluk

src/de.rs

@@ -66,7 +66,7 @@ where
     /// An error is returned if there are unconsumed bytes in the readable source.
     pub fn end(&mut self) -> Result<()> {
         match self.read.peek() {
-            Some(r) => r.and_then(|_| Err(Error::TrailingData)),
+            Some(r) => r.and(Err(Error::TrailingData)),
             None => Ok(()),
         }
     }

src/ser.rs

@@ -372,10 +372,7 @@ where
     where
         T: ?Sized + Serialize,
     {
-        let key = self
-            .current_key
-            .take()
-            .ok_or_else(|| Error::ValueWithoutKey)?;
+        let key = self.current_key.take().ok_or(Error::ValueWithoutKey)?;
         let buf: Vec<u8> = Vec::new();
         let mut ser = Serializer::new(buf);
         value.serialize(&mut ser)?;

src/value.rs

@@ -138,20 +138,14 @@ impl Value {
 
     pub fn as_u64(&self) -> Option<u64> {
         match self {
-            Value::Int(n) => match n {
-                Number::Unsigned(n) => Some(*n),
-                _ => None,
-            },
+            Value::Int(Number::Unsigned(n)) => Some(*n),
             _ => None,
         }
     }
 
     pub fn as_i64(&self) -> Option<i64> {
         match self {
-            Value::Int(n) => match n {
-                Number::Signed(n) => Some(*n),
-                _ => None,
-            },
+            Value::Int(Number::Signed(n)) => Some(*n),
             _ => None,
         }
     }

src/value/ser.rs

@@ -276,10 +276,7 @@ impl ser::SerializeMap for SerializeDict {
     where
         T: ?Sized + Serialize,
     {
-        let key = self
-            .current_key
-            .take()
-            .ok_or_else(|| Error::ValueWithoutKey)?;
+        let key = self.current_key.take().ok_or(Error::ValueWithoutKey)?;
         let value = to_value(value)?;
         self.dict.insert(key, value);
         Ok(())