refactor(parse): Be consistent in naming

compiler/rustc_parse/src/lexer/mod.rs

diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index 7c969dd..6c9ecd7 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -598,9 +598,9 @@ fn validate_frontmatter(
         let s = self.str_from(start);
         let real_start = s.find("---").unwrap();
         let frontmatter_opening_pos = BytePos(real_start as u32) + start;
-        let s_new = &s[real_start..];
-        let within = s_new.trim_start_matches('-');
-        let len_opening = s_new.len() - within.len();
+        let real_s = &s[real_start..];
+        let within = real_s.trim_start_matches('-');
+        let len_opening = real_s.len() - within.len();
 
         let frontmatter_opening_end_pos = frontmatter_opening_pos + BytePos(len_opening as u32);
         if has_invalid_preceding_whitespace {