[clang-tools-extra] [clang-tidy] Move `ClassifiedToken` to cpp file (PR #196820)

[David Stone via cfe-commits]

https://github.com/davidstone created https://github.com/llvm/llvm-project/pull/196820

`ClassifiedToken` is used in only the implementation of `UseTrailingReturnTypeCheck`. Move it into the unnamed namespace of the cpp file instead of it being in the header.

>From 232aa7855916ecb6d3ed175bf8711ae469675524 Mon Sep 17 00:00:00 2001
From: David Stone <davidfromonline at gmail.com>
Date: Sun, 10 May 2026 11:41:27 -0600
Subject: [PATCH] [clang-tidy] Move `ClassifiedToken` to cpp file

`ClassifiedToken` is used in only the implementation of `UseTrailingReturnTypeCheck`. Move it into the unnamed namespace of the cpp file instead of it being in the header.
---
 .../modernize/UseTrailingReturnTypeCheck.cpp           | 10 ++++++++++
 .../clang-tidy/modernize/UseTrailingReturnTypeCheck.h  |  6 ------
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
index ea43cd6c42222..8bc06afaeb33c 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.cpp
@@ -205,6 +205,16 @@ static bool isSpecifier(Token T) {
                    tok::kw_static, tok::kw_friend, tok::kw_virtual);
 }
 
+namespace {
+
+struct ClassifiedToken {
+  Token T;
+  bool IsQualifier;
+  bool IsSpecifier;
+};
+
+} // namespace
+
 static std::optional<ClassifiedToken>
 classifyToken(const FunctionDecl &F, Preprocessor &PP, Token Tok) {
   ClassifiedToken CT;
diff --git a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
index 4aa1adaf30db5..05a8952f03700 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
+++ b/clang-tools-extra/clang-tidy/modernize/UseTrailingReturnTypeCheck.h
@@ -14,12 +14,6 @@
 
 namespace clang::tidy::modernize {
 
-struct ClassifiedToken {
-  Token T;
-  bool IsQualifier;
-  bool IsSpecifier;
-};
-
 /// Rewrites function signatures to use a trailing return type.
 ///
 /// For the user-facing documentation see: