[clang] [clang] Refactor `IdentifierInfo::ObjcOrBuiltinID` (PR #71709)

[Chuanqi Xu via cfe-commits]

================
@@ -86,19 +87,26 @@ enum { IdentifierInfoAlignment = 8 };
 static constexpr int ObjCOrBuiltinIDBits = 16;
 
 /// The "layout" of ObjCOrBuiltinID is:
-///  - The first value (0) represents "not a special identifier".
-///  - The next (NUM_OBJC_KEYWORDS - 1) values represent ObjCKeywordKinds (not
-///    including objc_not_keyword).
-///  - The next (NUM_INTERESTING_IDENTIFIERS - 1) values represent
-///    InterestingIdentifierKinds (not including not_interesting).
-///  - The rest of the values represent builtin IDs (not including NotBuiltin).
-static constexpr int FirstObjCKeywordID = 1;
-static constexpr int LastObjCKeywordID =
-    FirstObjCKeywordID + tok::NUM_OBJC_KEYWORDS - 2;
-static constexpr int FirstInterestingIdentifierID = LastObjCKeywordID + 1;
-static constexpr int LastInterestingIdentifierID =
-    FirstInterestingIdentifierID + tok::NUM_INTERESTING_IDENTIFIERS - 2;
-static constexpr int FirstBuiltinID = LastInterestingIdentifierID + 1;
+///  - ObjCKeywordKind enumerators
+///  - InterestingIdentifierKind enumerators
+///  - Builtin::ID enumerators
+///  - NonSpecialIdentifier
+enum class ObjCKeywordOrInterestingOrBuiltin {
+#define OBJC_AT_KEYWORD(X) objc_##X,
+#include "clang/Basic/TokenKinds.def"
+  NUM_OBJC_KEYWORDS,
----------------
ChuanqiXu9 wrote:

It looks like we have `tok::NUM_OBJC_KEYWORDS` and `ObjCKeywordOrInterestingOrBuiltin::NUM_OBJC_KEYWORDS` now. And it smells not good to have them with the same name.

https://github.com/llvm/llvm-project/pull/71709