judge is_dir first.

src/main.rs

@@ -5,7 +5,10 @@ use std::process::Command;
 use std::env;
 
 fn process_compressed_files(path: &Path) -> io::Result<()> {
-    if path.is_dir() {
+    if !path.is_dir() {
+        return Err(io::Error::new(io::ErrorKind::Other, "Not a directory"));
+    }
+
     println!("Processing directory: {}", path.display());
     for entry in fs::read_dir(path)? {
         let entry_path = entry?.path();
@@ -35,7 +38,6 @@ fn process_compressed_files(path: &Path) -> io::Result<()> {
             }
         }
     }
-    }
 
     Ok(())
 }