[clang-format] Annotate ::operator and Foo::operator correctly (#164048)

This effectively reverts commit b5f6689
and fixes #111011 more narrowly.

Fixes #160513

Author: owenca

clang/lib/Format/TokenAnnotator.cpp

@@ -3794,18 +3794,12 @@ static bool isFunctionDeclarationName(const LangOptions &LangOpts,
   if (Current.is(TT_FunctionDeclarationName))
     return true;
 
-  if (!Current.Tok.getIdentifierInfo())
+  if (Current.isNoneOf(tok::identifier, tok::kw_operator))
     return false;
 
   const auto *Prev = Current.getPreviousNonComment();
   assert(Prev);
 
-  if (Prev->is(tok::coloncolon))
-    Prev = Prev->Previous;
-
-  if (!Prev)
-    return false;
-
   const auto &Previous = *Prev;
 
   if (const auto *PrevPrev = Previous.getPreviousNonComment();
@@ -3854,6 +3848,8 @@ static bool isFunctionDeclarationName(const LangOptions &LangOpts,
 
   // Find parentheses of parameter list.
   if (Current.is(tok::kw_operator)) {
+    if (Line.startsWith(tok::kw_friend))
+      return true;
     if (Previous.Tok.getIdentifierInfo() &&
         Previous.isNoneOf(tok::kw_return, tok::kw_co_return)) {
       return true;

clang/unittests/Format/TokenAnnotatorTest.cpp

@@ -1129,6 +1129,11 @@ TEST_F(TokenAnnotatorTest, UnderstandsOverloadedOperators) {
   ASSERT_EQ(Tokens.size(), 7u) << Tokens;
   // Not TT_FunctionDeclarationName.
   EXPECT_TOKEN(Tokens[3], tok::kw_operator, TT_Unknown);
+
+  Tokens = annotate("SomeAPI::operator()();");
+  ASSERT_EQ(Tokens.size(), 9u) << Tokens;
+  // Not TT_FunctionDeclarationName.
+  EXPECT_TOKEN(Tokens[2], tok::kw_operator, TT_Unknown);
 }
 
 TEST_F(TokenAnnotatorTest, OverloadedOperatorInTemplate) {