Include the child tag name into 'InvalidChildElement' error.

This makes the error much more useful. Including the actual name of
a tag that caused problem makes it possible to figure out what's wrong
with the gpx file without having to go through the library code
finding out what did it expect.

PR: #7

src/errors.rs

@@ -5,9 +5,9 @@ error_chain!{
     errors {
         /// InvalidChildElement signifies when an element has a child that isn't
         /// valid per the GPX spec.
-        InvalidChildElement(parent: &'static str) {
+        InvalidChildElement(child: String, parent: &'static str) {
             description("invalid child element")
-            display("invalid child element in {}", String::from(*parent))
+            display("invalid child element '{}' in {}", child, String::from(*parent))
         }
 
         /// InvalidElementLacksAttribute signifies when an element is missing a

src/parser/email.rs

@@ -40,7 +40,10 @@ pub fn consume<R: Read>(reader: &mut Peekable<Events<R>>) -> Result<String> {
 
                         email = Some(format!("{id}@{domain}", id = id, domain = domain));
                     }
-                    _ => Err(Error::from(ErrorKind::InvalidChildElement("email")))?,
+                    child => Err(Error::from(ErrorKind::InvalidChildElement(
+                        String::from(child),
+                        "email",
+                    )))?,
                 }
             }
 
@@ -117,7 +120,7 @@ mod tests {
         let err = consume!("<email id=\"id\" domain=\"domain\"><child /></email>").unwrap_err();
 
         assert_eq!(err.description(), "invalid child element");
-        assert_eq!(err.to_string(), "invalid child element in email");
+        assert_eq!(err.to_string(), "invalid child element 'child' in email");
     }
 
     #[test]

src/parser/gpx.rs

@@ -37,7 +37,10 @@ pub fn consume<R: Read>(reader: &mut Peekable<Events<R>>) -> Result<Gpx> {
                             "trk" => Ok(ParseEvent::StartTrack),
                             "wpt" => Ok(ParseEvent::StartWaypoint),
                             "gpx" => Ok(ParseEvent::Ignore),
-                            _ => Err(Error::from(ErrorKind::InvalidChildElement("gpx")))?,
+                            child => Err(Error::from(ErrorKind::InvalidChildElement(
+                                String::from(child),
+                                "gpx",
+                            )))?,
                         }
                     }
 

src/parser/link.rs

@@ -35,7 +35,10 @@ pub fn consume<R: Read>(reader: &mut Peekable<Events<R>>) -> Result<Link> {
 
                         link.href = attr.value;
                     }
-                    _ => Err(Error::from(ErrorKind::InvalidChildElement("link")))?,
+                    child => Err(Error::from(ErrorKind::InvalidChildElement(
+                        String::from(child),
+                        "link",
+                    )))?,
                 }
             }
 

src/parser/metadata.rs

@@ -43,7 +43,10 @@ pub fn consume<R: Read>(reader: &mut Peekable<Events<R>>) -> Result<Metadata> {
                             "keywords" => Ok(ParseEvent::StartKeywords),
                             "time" => Ok(ParseEvent::StartTime),
                             "link" => Ok(ParseEvent::StartLink),
-                            _ => Err(Error::from(ErrorKind::InvalidChildElement("metadata")))?,
+                            child => Err(Error::from(ErrorKind::InvalidChildElement(
+                                String::from(child),
+                                "metadata",
+                            )))?,
                         }
                     }
 

src/parser/person.rs

@@ -37,7 +37,10 @@ pub fn consume<R: Read>(reader: &mut Peekable<Events<R>>) -> Result<Person> {
                             "link" => Ok(ParseEvent::StartLink),
                             "person" => Ok(ParseEvent::Ignore),
                             "author" => Ok(ParseEvent::Ignore),
-                            _ => Err(Error::from(ErrorKind::InvalidChildElement("person"))),
+                            child => Err(Error::from(ErrorKind::InvalidChildElement(
+                                String::from(child),
+                                "person",
+                            ))),
                         }
                     }
 

src/parser/track.rs

@@ -25,7 +25,10 @@ pub fn consume<R: Read>(reader: &mut Peekable<Events<R>>) -> Result<Track> {
                 "src" => track.source = Some(string::consume(reader)?),
                 "type" => track._type = Some(string::consume(reader)?),
                 "trkseg" => track.segments.push(tracksegment::consume(reader)?),
-                _ => Err(Error::from(ErrorKind::InvalidChildElement("track")))?,
+                child => Err(Error::from(ErrorKind::InvalidChildElement(
+                    String::from(child),
+                    "track",
+                )))?,
             },
 
             XmlEvent::EndElement { .. } => {

src/parser/tracksegment.rs

@@ -32,7 +32,10 @@ pub fn consume<R: Read>(reader: &mut Peekable<Events<R>>) -> Result<TrackSegment
                         match name.local_name.as_ref() {
                             "trkseg" => Ok(TrackSegmentEvent::StartTrkSeg),
                             "trkpt" => Ok(TrackSegmentEvent::StartTrkPt),
-                            _ => Err(Error::from(ErrorKind::InvalidChildElement("tracksegment"))),
+                            child => Err(Error::from(ErrorKind::InvalidChildElement(
+                                String::from(child),
+                                "tracksegment",
+                            ))),
                         }
                     }
 

src/parser/waypoint.rs

@@ -123,7 +123,10 @@ pub fn consume<R: Read>(reader: &mut Peekable<Events<R>>) -> Result<Waypoint> {
 
                     // Finally the GPX 1.1 extensions
                     "extensions" => extensions::consume(reader)?,
-                    _ => Err(Error::from(ErrorKind::InvalidChildElement("waypoint")))?,
+                    child => Err(Error::from(ErrorKind::InvalidChildElement(
+                        String::from(child),
+                        "waypoint",
+                    )))?,
                 }
             }