allow simple enum variants as hash map keys

Author: Oliver Schneider

src/json.rs

@@ -538,7 +538,6 @@ impl<'a> ::Encoder for Encoder<'a> {
     fn emit_enum<F>(&mut self, _name: &str, f: F) -> EncodeResult where
         F: FnOnce(&mut Encoder<'a>) -> EncodeResult,
     {
-        if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
         f(self)
     }
 
@@ -552,10 +551,10 @@ impl<'a> ::Encoder for Encoder<'a> {
         // enums are encoded as strings or objects
         // Bunny => "Bunny"
         // Kangaroo(34,"William") => {"variant": "Kangaroo", "fields": [34,"William"]}
-        if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
         if cnt == 0 {
             escape_str(self.writer, name)
         } else {
+            if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
             try!(write!(self.writer, "{{\"variant\":"));
             try!(escape_str(self.writer, name));
             try!(write!(self.writer, ",\"fields\":["));
@@ -787,7 +786,6 @@ impl<'a> ::Encoder for PrettyEncoder<'a> {
     fn emit_enum<F>(&mut self, _name: &str, f: F) -> EncodeResult where
         F: FnOnce(&mut PrettyEncoder<'a>) -> EncodeResult,
     {
-        if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
         f(self)
     }
 
@@ -799,10 +797,10 @@ impl<'a> ::Encoder for PrettyEncoder<'a> {
                             -> EncodeResult where
         F: FnOnce(&mut PrettyEncoder<'a>) -> EncodeResult,
     {
-        if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
         if cnt == 0 {
             escape_str(self.writer, name)
         } else {
+            if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
             try!(write!(self.writer, "{{\n"));
             self.curr_indent += self.indent;
             try!(spaces(self.writer, self.curr_indent));
@@ -3564,12 +3562,8 @@ mod tests {
         }
         let mut map = HashMap::new();
         map.insert(Enum::Foo, 0);
-        let result = json::encode(&map);
-        match result.unwrap_err() {
-            EncoderError::BadHashmapKey => (),
-            _ => panic!("expected bad hash map key")
-        }
-        //assert_eq!(&enc[], r#"{"Foo": 0}"#);
+        let result = json::encode(&map).unwrap();
+        assert_eq!(&result[], r#"{"Foo":0}"#);
     }
 
     #[test]