[clang] [clang-format] Improve QualifierAlignment in guessing macros (PR #145468)

[Owen Pan via cfe-commits]

https://github.com/owenca created https://github.com/llvm/llvm-project/pull/145468

Fixes #145388

>From 349d309467c1251a9206f665886bde06b96ced32 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Mon, 23 Jun 2025 23:32:31 -0700
Subject: [PATCH] [clang-format] Improve QualifierAlignment in guessing macros

Fixes #145388
---
 clang/lib/Format/QualifierAlignmentFixer.cpp  | 25 +++++++++++++------
 clang/unittests/Format/QualifierFixerTest.cpp |  7 ++++--
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/clang/lib/Format/QualifierAlignmentFixer.cpp b/clang/lib/Format/QualifierAlignmentFixer.cpp
index 8e55d339b2388..b0dda65adfba1 100644
--- a/clang/lib/Format/QualifierAlignmentFixer.cpp
+++ b/clang/lib/Format/QualifierAlignmentFixer.cpp
@@ -635,15 +635,26 @@ bool isConfiguredQualifierOrType(const FormatToken *Tok,
 // If a token is an identifier and it's upper case, it could
 // be a macro and hence we need to be able to ignore it.
 bool isPossibleMacro(const FormatToken *Tok) {
-  if (!Tok)
-    return false;
+  assert(Tok);
   if (Tok->isNot(tok::identifier))
     return false;
-  if (Tok->TokenText.upper() == Tok->TokenText.str()) {
-    // T,K,U,V likely could be template arguments
-    return Tok->TokenText.size() != 1;
-  }
-  return false;
+
+  const auto Text = Tok->TokenText;
+  assert(Text.size() > 0);
+
+  // T,K,U,V likely could be template arguments
+  if (Text.size() == 1)
+    return false;
+
+  // It's unlikely that qualified names are object-like macros.
+  const auto *Prev = Tok->getPreviousNonComment();
+  if (Prev && Prev->is(tok::coloncolon))
+    return false;
+  const auto *Next = Tok->getNextNonComment();
+  if (Next && Next->is(tok::coloncolon))
+    return false;
+
+  return Text == Text.upper();
 }
 
 } // namespace format
diff --git a/clang/unittests/Format/QualifierFixerTest.cpp b/clang/unittests/Format/QualifierFixerTest.cpp
index 3eae39f267c3e..f42f2e307f713 100644
--- a/clang/unittests/Format/QualifierFixerTest.cpp
+++ b/clang/unittests/Format/QualifierFixerTest.cpp
@@ -1122,14 +1122,17 @@ TEST_F(QualifierFixerTest, IsQualifierType) {
 }
 
 TEST_F(QualifierFixerTest, IsMacro) {
-
   auto Tokens = annotate("INT INTPR Foo int");
   ASSERT_EQ(Tokens.size(), 5u) << Tokens;
-
   EXPECT_TRUE(isPossibleMacro(Tokens[0]));
   EXPECT_TRUE(isPossibleMacro(Tokens[1]));
   EXPECT_FALSE(isPossibleMacro(Tokens[2]));
   EXPECT_FALSE(isPossibleMacro(Tokens[3]));
+
+  Tokens = annotate("FOO::BAR");
+  ASSERT_EQ(Tokens.size(), 4u) << Tokens;
+  EXPECT_FALSE(isPossibleMacro(Tokens[0]));
+  EXPECT_FALSE(isPossibleMacro(Tokens[2]));
 }
 
 TEST_F(QualifierFixerTest, OverlappingQualifier) {