[clang-format] Exclude kw_decltype in RemoveParentheses

[owenpan]

Summary

From https://en.cppreference.com/w/cpp/language/decltype:
Note that if the name of an object is parenthesized, it is treated as an ordinary lvalue expression, thus decltype(x) and decltype((x)) are often different types.

Fixes https://github.com/llvm/llvm-project/issues/64786.

clang/lib/Format/UnwrappedLineParser.cpp

case tok::r_paren:
           Style.RemoveParentheses > FormatStyle::RPS_Leave) {
         const auto *Prev = LeftParen->Previous;
         const auto *Next = Tokens->peekNextToken();
         const bool DoubleParens =
             Prev && Prev->is(tok::l_paren) && Next && Next->is(tok::r_paren);
         const auto *PrevPrev = Prev ? Prev->getPreviousNonComment() : nullptr;
         const bool Blacklisted =
             PrevPrev &&
-            (PrevPrev->is(tok::kw___attribute) ||
+            (PrevPrev->isOneOf(tok::kw___attribute, tok::kw_decltype) ||
              (SeenEqual &&
               (PrevPrev->isOneOf(tok::kw_if, tok::kw_while) ||
                PrevPrev->endsSequence(tok::kw_constexpr, tok::kw_if))));
         const bool ReturnParens =
             Style.RemoveParentheses == FormatStyle::RPS_ReturnStatement &&
             Prev && Prev->isOneOf(tok::kw_return, tok::kw_co_return) && Next &&
             Next->is(tok::semi);
         if ((DoubleParens && !Blacklisted) || ReturnParens) {

clang/unittests/Format/FormatTest.cpp

 }
 
 TEST_F(FormatTest, RemoveParentheses) {
   FormatStyle Style = getLLVMStyle();
   EXPECT_EQ(Style.RemoveParentheses, FormatStyle::RPS_Leave);
 
   Style.RemoveParentheses = FormatStyle::RPS_MultipleParentheses;
   verifyFormat("int x __attribute__((aligned(16))) = 0;", Style);
+  verifyFormat("decltype((foo->bar)) baz;", Style);
   verifyFormat("class __declspec(dllimport) X {};",
                "class __declspec((dllimport)) X {};", Style);
   verifyFormat("int x = (({ 0; }));", "int x = ((({ 0; })));", Style);
   verifyFormat("while (a)\n"
                "  b;",
                "while (((a)))\n"
                "  b;",
                Style);