Update message for skipped enum variant

serde_codegen/src/ser.rs

@@ -255,8 +255,11 @@ fn serialize_variant(
 
     let variant_ident = variant.ident.clone();
     let variant_name = variant.attrs.name().serialize_name();
+
+    let skipped_msg = format!("The enum variant {}::{} cannot be serialized",
+                              type_ident, variant_ident);
     let skipped_err = quote! {
-        Err(_serde::ser::Error::invalid_value("The enum variant was skipped for serialization"))
+        Err(_serde::ser::Error::invalid_value(#skipped_msg))
     };
 
     if variant.attrs.skip_serializing() {

testing/tests/test_ser.rs

@@ -402,17 +402,17 @@ fn test_enum_skipped() {
     assert_ser_tokens_error(
         &Enum::SkippedUnit,
         &[],
-        Error::InvalidValue("The enum variant was skipped for serialization".to_owned()));
+        Error::InvalidValue("The enum variant Enum::SkippedUnit cannot be serialized".to_owned()));
     assert_ser_tokens_error(
         &Enum::SkippedOne(42),
         &[],
-        Error::InvalidValue("The enum variant was skipped for serialization".to_owned()));
+        Error::InvalidValue("The enum variant Enum::SkippedOne cannot be serialized".to_owned()));
     assert_ser_tokens_error(
         &Enum::SkippedSeq(1, 2),
         &[],
-        Error::InvalidValue("The enum variant was skipped for serialization".to_owned()));
+        Error::InvalidValue("The enum variant Enum::SkippedSeq cannot be serialized".to_owned()));
     assert_ser_tokens_error(
         &Enum::SkippedMap { _a: 1, _b: 2 },
         &[],
-        Error::InvalidValue("The enum variant was skipped for serialization".to_owned()));
+        Error::InvalidValue("The enum variant Enum::SkippedMap cannot be serialized".to_owned()));
 }