Error enum

src/error.rs

@@ -2,29 +2,29 @@ use std::error::Error;
 use std::fmt;
 
 #[derive(Debug, Clone)]
-pub struct PngError {
-    description: String,
+pub enum PngError {
+    Other(Box<str>),
 }
 
 impl Error for PngError {
-    #[inline]
+    // deprecated
     fn description(&self) -> &str {
-        &self.description
+        ""
     }
 }
 
 impl fmt::Display for PngError {
     #[inline]
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", self.description)
+        match self {
+            PngError::Other(s) => f.write_str(s),
+        }
     }
 }
 
 impl PngError {
     #[inline]
     pub fn new(description: &str) -> PngError {
-        PngError {
-            description: description.to_owned(),
-        }
+        PngError::Other(description.into())
     }
 }