[clang] [clang-format] Correctly annotate token-pasted function decl names (PR #142337)

[Owen Pan via cfe-commits]

https://github.com/owenca created https://github.com/llvm/llvm-project/pull/142337

Fix #142178

>From d088a50da78e67ee182074af594dd4f230d98357 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Sun, 1 Jun 2025 23:56:32 -0700
Subject: [PATCH] [clang-format] Correctly annotate token-pasted function decl
 names

Fix #142178
---
 clang/lib/Format/TokenAnnotator.cpp           | 2 ++
 clang/unittests/Format/TokenAnnotatorTest.cpp | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index da1b6dd5254b8..da279d07b5918 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -3848,6 +3848,8 @@ static bool isFunctionDeclarationName(const LangOptions &LangOpts,
   } else {
     if (Current.isNot(TT_StartOfName) || Current.NestingLevel != 0)
       return false;
+    while (Next && Next->startsSequence(tok::hashhash, tok::identifier))
+      Next = Next->Next->Next;
     for (; Next; Next = Next->Next) {
       if (Next->is(TT_TemplateOpener) && Next->MatchingParen) {
         Next = Next->MatchingParen;
diff --git a/clang/unittests/Format/TokenAnnotatorTest.cpp b/clang/unittests/Format/TokenAnnotatorTest.cpp
index 1a5ed4b9040c2..9637085c70502 100644
--- a/clang/unittests/Format/TokenAnnotatorTest.cpp
+++ b/clang/unittests/Format/TokenAnnotatorTest.cpp
@@ -2257,6 +2257,13 @@ TEST_F(TokenAnnotatorTest, UnderstandsFunctionDeclarationNames) {
   EXPECT_TOKEN(Tokens[1], tok::identifier, TT_FunctionDeclarationName);
   EXPECT_TOKEN(Tokens[2], tok::l_paren, TT_FunctionDeclarationLParen);
 
+  Tokens = annotate("#define FUNC(foo, bar) \\\n"
+                    "  auto foo##bar() -> Type {}");
+  ASSERT_EQ(Tokens.size(), 19u) << Tokens;
+  EXPECT_TOKEN(Tokens[9], tok::identifier, TT_FunctionDeclarationName);
+  EXPECT_TOKEN(Tokens[12], tok::l_paren, TT_FunctionDeclarationLParen);
+  EXPECT_TOKEN(Tokens[14], tok::arrow, TT_TrailingReturnArrow);
+
   Tokens = annotate("int iso_time(time_t);");
   ASSERT_EQ(Tokens.size(), 7u) << Tokens;
   EXPECT_TOKEN(Tokens[1], tok::identifier, TT_FunctionDeclarationName);