diff --git a/src/adapters/ffmpeg.rs b/src/adapters/ffmpeg.rs
index b18b666..2ed3612 100644
--- a/src/adapters/ffmpeg.rs
+++ b/src/adapters/ffmpeg.rs
@@ -134,7 +134,7 @@ impl WritingFileAdapter for FFmpegAdapter {
                 return Err(format_err!("ffprobe failed: {:?}", exit));
             }
         }
-        if subtitle_streams.len() > 0 {
+        if !subtitle_streams.is_empty() {
             for probe_stream in subtitle_streams.iter() {
                 // extract subtitles
                 let mut cmd = Command::new("ffmpeg");
@@ -143,7 +143,7 @@ impl WritingFileAdapter for FFmpegAdapter {
                     .arg("-i")
                     .arg(&inp_fname)
                     .arg("-map")
-                    .arg(format!("0:{}", probe_stream.index.to_string())) // 0 for first input
+                    .arg(format!("0:{}", probe_stream.index)) // 0 for first input
                     .arg("-f")
                     .arg("webvtt")
                     .arg("-");
diff --git a/src/adapters/sqlite.rs b/src/adapters/sqlite.rs
index 826d091..dba24a4 100644
--- a/src/adapters/sqlite.rs
+++ b/src/adapters/sqlite.rs
@@ -138,7 +138,7 @@ mod test {
 
     #[tokio::test]
     async fn simple() -> Result<()> {
-        let adapter: Box<dyn FileAdapter> = Box::new(SqliteAdapter::default());
+        let adapter: Box<dyn FileAdapter> = Box::<SqliteAdapter>::default();
         let fname = test_data_dir().join("hello.sqlite3");
         let (a, d) = simple_fs_adapt_info(&fname).await?;
         let res = adapter.adapt(a, &d).await?;
diff --git a/src/preproc_cache.rs b/src/preproc_cache.rs
index f361792..d0eed0e 100644
--- a/src/preproc_cache.rs
+++ b/src/preproc_cache.rs
@@ -181,7 +181,7 @@ mod test {
     #[tokio::test]
     async fn test_read_write() -> anyhow::Result<()> {
         let path = tempfile::tempdir()?;
-        let db = open_cache_db(&path.path().join("foo.sqlite3")).await?;
+        let _db = open_cache_db(&path.path().join("foo.sqlite3")).await?;
         // db.set();
         Ok(())
     }