Lint against .to_string() on String

src/main.rs

@@ -21,6 +21,8 @@
 #![allow(clippy::mutable_key_type)]
 // .to_owned() is more explicit on string references.
 #![warn(clippy::str_to_string)]
+// .to_string() on a String is clearer as .clone().
+#![warn(clippy::string_to_string)]
 // Debugging features shouldn't be in checked-in code.
 #![warn(clippy::todo)]
 #![warn(clippy::dbg_macro)]

src/parse/syntax.rs

@@ -414,7 +414,6 @@ fn set_content_id(nodes: &[&Syntax], existing: &mut DftHashMap<ContentKey, u32>)
                         .map(|l| l.trim_start())
                         .collect::<Vec<_>>()
                         .join("\n")
-                        .to_string()
                 } else {
                     content.clone()
                 };