[clang-format] Correctly annotate kw_operator in using decls (llvm#136545)

Fix llvm#136541

(cherry picked from commit 037657d)

Author: owenca

clang/lib/Format/TokenAnnotator.cpp

@@ -3961,8 +3961,10 @@ void TokenAnnotator::calculateFormattingInformation(AnnotatedLine &Line) const {
   FormatToken *AfterLastAttribute = nullptr;
   FormatToken *ClosingParen = nullptr;
 
-  for (auto *Tok = FirstNonComment ? FirstNonComment->Next : nullptr; Tok;
-       Tok = Tok->Next) {
+  for (auto *Tok = FirstNonComment && FirstNonComment->isNot(tok::kw_using)
+                       ? FirstNonComment->Next
+                       : nullptr;
+       Tok; Tok = Tok->Next) {
     if (Tok->is(TT_StartOfName))
       SeenName = true;
     if (Tok->Previous->EndsCppAttributeGroup)

clang/unittests/Format/TokenAnnotatorTest.cpp

@@ -1073,6 +1073,11 @@ TEST_F(TokenAnnotatorTest, UnderstandsOverloadedOperators) {
   ASSERT_EQ(Tokens.size(), 11u) << Tokens;
   EXPECT_TOKEN(Tokens[3], tok::identifier, TT_FunctionDeclarationName);
   EXPECT_TOKEN(Tokens[7], tok::l_paren, TT_OverloadedOperatorLParen);
+
+  Tokens = annotate("using std::operator==;");
+  ASSERT_EQ(Tokens.size(), 7u) << Tokens;
+  // Not TT_FunctionDeclarationName.
+  EXPECT_TOKEN(Tokens[3], tok::kw_operator, TT_Unknown);
 }
 
 TEST_F(TokenAnnotatorTest, OverloadedOperatorInTemplate) {