port error.rs to error_chain, bump version to 0.4.0

src/error.rs

@@ -7,33 +7,24 @@ use std::convert::From;
 use xml::writer::Error as WriterError;
 use xml::reader::Error as ReaderError;
 
-/// An enum representing the possible errors.
-#[derive(Debug)]
-pub enum Error {
-    /// An io::Error.
-    IoError(io::Error),
-    /// An error in the xml-rs `EventWriter`.
-    XmlWriterError(WriterError),
-    /// An error in the xml-rs `EventReader`.
-    XmlReaderError(ReaderError),
-    /// The end of the document has been reached unexpectedly.
-    EndOfDocument,
-}
+error_chain! {
+    foreign_links {
+        XmlWriterError(WriterError)
+            /// An error with writing an XML event, from xml::writer::EventWriter.
+        ;
+        XmlReaderError(ReaderError)
+            /// An error with reading an XML event, from xml::reader::EventReader.
+        ;
+        IoError(io::Error)
+            /// An I/O error, from std::io.
+        ;
+    }
 
-impl From<io::Error> for Error {
-    fn from(err: io::Error) -> Error {
-        Error::IoError(err)
-    }
-}
-
-impl From<WriterError> for Error {
-    fn from(err: WriterError) -> Error {
-        Error::XmlWriterError(err)
-    }
-}
-
-impl From<ReaderError> for Error {
-    fn from(err: ReaderError) -> Error {
-        Error::XmlReaderError(err)
+    errors {
+        /// En error which is returned when the end of the document was reached prematurely.
+        EndOfDocument {
+            description("the end of the document has been reached prematurely")
+            display("the end of the document has been reached prematurely")
+        }
     }
 }