Fix a subset of issues identified by cargo clippy.

src/decoder/stream.rs

@@ -958,7 +958,7 @@ impl StreamingDecoder {
             _ => Ok(Decoded::PartialChunk(type_str)),
         };
 
-        let parse_result = parse_result.map_err(|e| {
+        parse_result.map_err(|e| {
             self.state = None;
             match e {
                 // `parse_chunk` is invoked after gathering **all** bytes of a chunk, so
@@ -972,9 +972,7 @@ impl StreamingDecoder {
                 }
                 e => e,
             }
-        });
-
-        parse_result
+        })
     }
 
     fn parse_fctl(&mut self) -> Result<Decoded, DecodingError> {

src/decoder/transform.rs

@@ -30,18 +30,18 @@ pub fn create_transform_fn(
     match color_type {
         ColorType::Indexed if expand => {
             if info.palette.is_none() {
-                return Err(DecodingError::Format(
+                Err(DecodingError::Format(
                     FormatErrorInner::PaletteRequired.into(),
-                ));
+                ))
             } else if let BitDepth::Sixteen = info.bit_depth {
                 // This should have been caught earlier but let's check again. Can't hurt.
-                return Err(DecodingError::Format(
+                Err(DecodingError::Format(
                     FormatErrorInner::InvalidColorBitDepth {
                         color_type: ColorType::Indexed,
                         bit_depth: BitDepth::Sixteen,
                     }
                     .into(),
-                ));
+                ))
             } else {
                 Ok(if trns {
                     palette::create_expansion_into_rgba8(info)

src/decoder/transform/palette.rs

@@ -70,7 +70,7 @@ fn create_rgba_palette(info: &Info) -> [[u8; 4]; 256] {
             palette_iter = &palette_iter[3..];
             rgba_iter = &mut rgba_iter[1..];
         }
-        if palette_iter.len() > 0 {
+        if !palette_iter.is_empty() {
             rgba_iter[0][0..3].copy_from_slice(&palette_iter[0..3]);
         }
     }
@@ -99,7 +99,7 @@ fn expand_8bit_into_rgb8(mut input: &[u8], mut output: &mut [u8], rgba_palette:
         input = &input[1..];
         output = &mut output[3..];
     }
-    if output.len() > 0 {
+    if !output.is_empty() {
         let rgba = &rgba_palette[input[0] as usize];
         output[0..3].copy_from_slice(&rgba[0..3]);
     }

src/encoder.rs

@@ -317,7 +317,6 @@ impl<'a, W: Write> Encoder<'a, W> {
     /// based on heuristics which minimize the file size for compression rather
     /// than use a single filter for the entire image. The default method is
     /// [`AdaptiveFilterType::NonAdaptive`].
-
     pub fn set_adaptive_filter(&mut self, adaptive_filter: AdaptiveFilterType) {
         self.options.adaptive_filter = adaptive_filter;
     }