Implement Error and Display for FromStrError and `parse::ParseE…

…rror`

src/lib.rs

@@ -32,6 +32,7 @@
 extern crate unicase;
 
 use std::cmp::Ordering;
+use std::error::Error;
 use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::str::FromStr;
@@ -74,6 +75,18 @@ pub struct FromStrError {
     inner: parse::ParseError,
 }
 
+impl Error for FromStrError {
+    fn description(&self) -> &str {
+        "an error occurred while parsing a MIME type"
+    }
+}
+
+impl fmt::Display for FromStrError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}: {}", self.description(), self.inner)
+    }
+}
+
 #[derive(Clone)]
 enum Source {
     Atom(u8, &'static str),

src/parse.rs

@@ -1,4 +1,6 @@
 use std::ascii::AsciiExt;
+use std::error::Error;
+use std::fmt;
 use std::iter::Enumerate;
 use std::str::Bytes;
 
@@ -15,6 +17,29 @@ pub enum ParseError {
     },
 }
 
+impl Error for ParseError {
+    fn description(&self) -> &str {
+        use self::ParseError::*;
+
+        match *self {
+            MissingSlash => "a slash (/) was missing between the type and subtype",
+            MissingEqual => "an equals sign (=) was missing between a parameter and its value",
+            MissingQuote => "a quote (\") was missing from a parameter value",
+            InvalidToken { .. } => "an invalid token was encountered",
+        }
+    }
+}
+
+impl fmt::Display for ParseError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if let ParseError::InvalidToken { pos, byte } = *self {
+            write!(f, "{}, {:X} at position {}", self.description(), byte, pos)
+        } else {
+            f.write_str(self.description())
+        }
+    }
+}
+
 pub fn parse(s: &str) -> Result<Mime, ParseError> {
     if s == "*/*" {
         return Ok(::STAR_STAR);