Add Error::unknown_field_error

src/de/mod.rs

@@ -12,7 +12,9 @@ pub trait Error {
 
     fn end_of_stream_error() -> Self;
 
-    fn missing_field_error(&'static str) -> Self;
+    fn unknown_field_error(field: &str) -> Self;
+
+    fn missing_field_error(field: &'static str) -> Self;
 }
 
 ///////////////////////////////////////////////////////////////////////////////

src/de/value.rs

@@ -18,12 +18,14 @@ use de;
 pub enum Error {
     SyntaxError,
     EndOfStreamError,
+    UnknownFieldError(String),
     MissingFieldError(&'static str),
 }
 
 impl de::Error for Error {
     fn syntax_error() -> Self { Error::SyntaxError }
     fn end_of_stream_error() -> Self { Error::EndOfStreamError }
+    fn unknown_field_error(field: &str) -> Self { Error::UnknownFieldError(field.to_string()) }
     fn missing_field_error(field: &'static str) -> Self { Error::MissingFieldError(field) }
 }