Rollup merge of #114351 - ttsugriy:sort-by-words, r=fee1-dead

[rustc_span][perf] Remove unnecessary string joins and allocs.

Comparing vectors of string parts yields the same result but avoids unnecessary `join` and potential allocation for resulting `String`. This code is cold so it's unlikely to have any measurable impact, but considering but since it's also simpler, why not? :)

compiler/rustc_span/src/edit_distance.rs

@@ -248,9 +248,9 @@ fn find_match_by_sorted_words(iter_names: &[Symbol], lookup: &str) -> Option<Sym
     })
 }
 
-fn sort_by_words(name: &str) -> String {
+fn sort_by_words(name: &str) -> Vec<&str> {
     let mut split_words: Vec<&str> = name.split('_').collect();
     // We are sorting primitive &strs and can use unstable sort here.
     split_words.sort_unstable();
-    split_words.join("_")
+    split_words
 }