perf(http): use custom type for ParseEof error instead of string error

src/http/io.rs

@@ -72,7 +72,8 @@ impl<T: AsyncRead + AsyncWrite> Buffered<T> {
             match self.read_from_io() {
                 Ok(0) => {
                     trace!("parse eof");
-                    return Err(io::Error::new(io::ErrorKind::UnexpectedEof, "parse eof").into());
+                    //TODO: With Rust 1.14, this can be Error::from(ErrorKind)
+                    return Err(io::Error::new(io::ErrorKind::UnexpectedEof, ParseEof).into());
                 }
                 Ok(_) => {},
                 Err(e) => match e.kind() {
@@ -316,6 +317,21 @@ impl WriteBuf {
     }
 }
 
+#[derive(Debug)]
+struct ParseEof;
+
+impl fmt::Display for ParseEof {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.write_str("parse eof")
+    }
+}
+
+impl ::std::error::Error for ParseEof {
+    fn description(&self) -> &str {
+        "parse eof"
+    }
+}
+
 #[cfg(test)]
 use std::io::Read;