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

[Owen Pan via cfe-commits]

https://github.com/owenca created https://github.com/llvm/llvm-project/pull/126340

Fixes #125012.

>From a0e44456a4fa1f5ef1168ac0e399b7113252bf96 Mon Sep 17 00:00:00 2001
From: Owen Pan <owenpiano at gmail.com>
Date: Fri, 7 Feb 2025 19:53:17 -0800
Subject: [PATCH] [clang-format] Handle C-style cast of member function pointer
 type

Fixes #125012.
---
 clang/lib/Format/TokenAnnotator.cpp           | 7 +++++--
 clang/unittests/Format/TokenAnnotatorTest.cpp | 6 ++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index 94fd7ba9c0e79e3..b3540f39e6f69fc 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -477,8 +477,9 @@ 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))
@@ -486,8 +487,10 @@ class AnnotatingParser {
       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) ||
diff --git a/clang/unittests/Format/TokenAnnotatorTest.cpp b/clang/unittests/Format/TokenAnnotatorTest.cpp
index 1b09c4570345622..54d8ff0571ca686 100644
--- a/clang/unittests/Format/TokenAnnotatorTest.cpp
+++ b/clang/unittests/Format/TokenAnnotatorTest.cpp
@@ -874,6 +874,12 @@ 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);