[clang-format] Handle C-style cast of member function pointer type (#126340)

Fixes #125012.

(cherry picked from commit 8d373ce)

Author: owenca

clang/lib/Format/TokenAnnotator.cpp

@@ -477,17 +477,20 @@ class AnnotatingParser {
     FormatToken *PossibleObjCForInToken = nullptr;
     while (CurrentToken) {
       const auto &Prev = *CurrentToken->Previous;
+      const auto *PrevPrev = Prev.Previous;
       if (Prev.is(TT_PointerOrReference) &&
-          Prev.Previous->isOneOf(tok::l_paren, tok::coloncolon)) {
+          PrevPrev->isOneOf(tok::l_paren, tok::coloncolon)) {
         ProbablyFunctionType = true;
       }
       if (CurrentToken->is(tok::comma))
         MightBeFunctionType = false;
       if (Prev.is(TT_BinaryOperator))
         Contexts.back().IsExpression = true;
       if (CurrentToken->is(tok::r_paren)) {
-        if (Prev.is(TT_PointerOrReference) && Prev.Previous == &OpeningParen)
+        if (Prev.is(TT_PointerOrReference) &&
+            (PrevPrev == &OpeningParen || PrevPrev->is(tok::coloncolon))) {
           MightBeFunctionType = true;
+        }
         if (OpeningParen.isNot(TT_CppCastLParen) && MightBeFunctionType &&
             ProbablyFunctionType && CurrentToken->Next &&
             (CurrentToken->Next->is(tok::l_paren) ||

clang/unittests/Format/TokenAnnotatorTest.cpp

@@ -845,6 +845,12 @@ TEST_F(TokenAnnotatorTest, UnderstandsCasts) {
   EXPECT_TOKEN(Tokens[14], tok::r_paren, TT_CastRParen);
   EXPECT_TOKEN(Tokens[15], tok::amp, TT_UnaryOperator);
 
+  Tokens = annotate("return (Foo (Bar::*)())&Bar::foo;");
+  ASSERT_EQ(Tokens.size(), 17u) << Tokens;
+  EXPECT_TOKEN(Tokens[3], tok::l_paren, TT_FunctionTypeLParen);
+  EXPECT_TOKEN(Tokens[10], tok::r_paren, TT_CastRParen);
+  EXPECT_TOKEN(Tokens[11], tok::amp, TT_UnaryOperator);
+
   auto Style = getLLVMStyle();
   Style.TypeNames.push_back("Foo");
   Tokens = annotate("#define FOO(bar) foo((Foo)&bar)", Style);