Rollup merge of rust-lang#97005 - est31:master, r=petrochenkov

Two small improvements of rustc_expand

I found them while doing rust-lang#96150

r? ``@petrochenkov``

compiler/rustc_expand/src/mbe/macro_parser.rs

@@ -76,6 +76,7 @@ crate use ParseResult::*;
 use crate::mbe::{KleeneOp, TokenTree};
 
 use rustc_ast::token::{self, DocComment, Nonterminal, NonterminalKind, Token};
+use rustc_lint_defs::pluralize;
 use rustc_parse::parser::{NtOrTt, Parser};
 use rustc_span::symbol::MacroRulesNormalizedIdent;
 use rustc_span::Span;
@@ -668,8 +669,7 @@ impl TtParser {
                 self.macro_name,
                 match self.next_mps.len() {
                     0 => format!("built-in NTs {}.", nts),
-                    1 => format!("built-in NTs {} or 1 other option.", nts),
-                    n => format!("built-in NTs {} or {} other options.", nts, n),
+                    n => format!("built-in NTs {} or {n} other option{s}.", nts, s = pluralize!(n)),
                 }
             ),
         )

compiler/rustc_expand/src/mbe/macro_rules.rs

@@ -175,7 +175,7 @@ impl TTMacroExpander for MacroRulesMacroExpander {
         if !self.valid {
             return DummyResult::any(sp);
         }
-        generic_extension(
+        expand_macro(
             cx,
             sp,
             self.span,
@@ -202,8 +202,9 @@ fn trace_macros_note(cx_expansions: &mut FxHashMap<Span, Vec<String>>, sp: Span,
     cx_expansions.entry(sp).or_default().push(message);
 }
 
-/// Given `lhses` and `rhses`, this is the new macro we create
-fn generic_extension<'cx, 'tt>(
+/// Expands the rules based macro defined by `lhses` and `rhses` for a given
+/// input `arg`.
+fn expand_macro<'cx, 'tt>(
     cx: &'cx mut ExtCtxt<'_>,
     sp: Span,
     def_span: Span,