error: implement Display

Useful for printing out error messages to users.

src/error.rs

@@ -1,5 +1,6 @@
 //! Error handling.
 
+use std::fmt::Display;
 use std::io;
 use std::result;
 
@@ -22,3 +23,38 @@ impl From<io::Error> for Error {
         Error::IOError(e)
     }
 }
+
+impl Display for Error {
+    fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Error::IOError(e) => e.fmt(fmt),
+            Error::LZMAError(e) => e.fmt(fmt),
+            Error::XZError(e) => e.fmt(fmt),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::Error;
+
+    #[test]
+    fn test_display() {
+        assert_eq!(
+            Error::IOError(std::io::Error::new(
+                std::io::ErrorKind::Other,
+                "this is an error"
+            ))
+            .to_string(),
+            "this is an error"
+        );
+        assert_eq!(
+            Error::LZMAError("this is an error".to_string()).to_string(),
+            "this is an error"
+        );
+        assert_eq!(
+            Error::XZError("this is an error".to_string()).to_string(),
+            "this is an error"
+        );
+    }
+}