use sort_unstable to sort primitive types

It's not important to retain original order if we have &[1, 1, 2, 3] for example.

clippy::stable_sort_primitive

compiler/rustc_ast/src/util/lev_distance.rs

@@ -103,6 +103,7 @@ fn find_match_by_sorted_words<'a>(iter_names: Vec<&'a Symbol>, lookup: &str) ->
 
 fn sort_by_words(name: &str) -> String {
     let mut split_words: Vec<&str> = name.split('_').collect();
-    split_words.sort();
+    // We are sorting primitive &strs and can use unstable sort here
+    split_words.sort_unstable();
     split_words.join("_")
 }