Add test for incorrectly nested elements with transparent

instant-xml/tests/transparent.rs

@@ -1,4 +1,6 @@
-use instant_xml::{from_str, to_string, FromXml, ToXml};
+use similar_asserts::assert_eq;
+
+use instant_xml::{from_str, to_string, Error, FromXml, ToXml};
 
 #[derive(Debug, Eq, FromXml, PartialEq, ToXml)]
 struct Wrapper {
@@ -36,4 +38,10 @@ fn inline() {
     let xml = r#"<Wrapper><Foo><i>42</i></Foo><Bar><s>hello</s></Bar></Wrapper>"#;
     assert_eq!(xml, to_string(&v).unwrap());
     assert_eq!(v, from_str(xml).unwrap());
+
+    assert_eq!(
+        from_str::<Wrapper>("<Wrapper><Foo><i>42</i><Bar><s>hello</s></Bar></Foo></Wrapper>")
+            .unwrap_err(),
+        Error::MissingValue("Inline::bar")
+    );
 }