From cd5de49eaa522ee10c0e8a6b36a067791270dca2 Mon Sep 17 00:00:00 2001
From: Trevor Gross <tmgross@umich.edu>
Date: Tue, 24 Jun 2025 04:33:58 -0400
Subject: [PATCH] mbe: Use `TokenTree` as the fallback for invalid fragment
 specifiers

`tt` should match more, so use this for both missing and invalid
fragment specifiers.

Also remove one unneeded instance of `String`.
---
 compiler/rustc_expand/src/errors.rs     | 2 +-
 compiler/rustc_expand/src/mbe/quoted.rs | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/compiler/rustc_expand/src/errors.rs b/compiler/rustc_expand/src/errors.rs
index ec0af67c0463..b697f2049bd8 100644
--- a/compiler/rustc_expand/src/errors.rs
+++ b/compiler/rustc_expand/src/errors.rs
@@ -444,7 +444,7 @@ pub(crate) struct InvalidFragmentSpecifier {
     #[primary_span]
     pub span: Span,
     pub fragment: Ident,
-    pub help: String,
+    pub help: &'static str,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_expand/src/mbe/quoted.rs b/compiler/rustc_expand/src/mbe/quoted.rs
index 871b3e5e4de8..2daa4e715584 100644
--- a/compiler/rustc_expand/src/mbe/quoted.rs
+++ b/compiler/rustc_expand/src/mbe/quoted.rs
@@ -117,9 +117,9 @@ pub(super) fn parse(
                 sess.dcx().emit_err(errors::InvalidFragmentSpecifier {
                     span,
                     fragment,
-                    help: VALID_FRAGMENT_NAMES_MSG.into(),
+                    help: VALID_FRAGMENT_NAMES_MSG,
                 });
-                NonterminalKind::Ident
+                NonterminalKind::TT
             });
             result.push(TokenTree::MetaVarDecl { span, name: ident, kind });
         } else {