[clang] [clang] Add clang::preferred_type attribute for bitfields (PR #69104)

[Vlad Serebrennikov via cfe-commits]

================
@@ -5910,6 +5910,28 @@ static void handleBuiltinAliasAttr(Sema &S, Decl *D,
   D->addAttr(::new (S.Context) BuiltinAliasAttr(S.Context, AL, Ident));
 }
 
+static void handleDebugInfoTypeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  if (!AL.hasParsedType()) {
+    S.Diag(AL.getLoc(), diag::err_attribute_wrong_number_arguments) << AL << 1;
+    return;
+  }
+
+  TypeSourceInfo *ParmTSI = nullptr;
+  QualType type = S.GetTypeFromParser(AL.getTypeArg(), &ParmTSI);
+  assert(ParmTSI && "no type source info for attribute argument");
+
+  if (type->isEnumeralType()) {
+    QualType BitfieldType = llvm::cast<FieldDecl>(D)->getType();
+    QualType EnumUnderlyingType = type->getAs<EnumType>()->getDecl()->getIntegerType();
+    if (EnumUnderlyingType != BitfieldType) {
+      S.Diag(AL.getLoc(), diag::warn_attribute_underlying_type_mismatch) << EnumUnderlyingType << type << BitfieldType;
----------------
Endilll wrote:

> We have getTypeArg() (which is a pretty bad code smell because this only allows one type argument for an attribute -- it would probably be a reasonable idea to refactor this so it works through getArg() at some point.

I think it comes from `let Args = [TypeArgument<"Type", 1>];`, but yeah, it's a confusing naming. I'm open for suggestions.

https://github.com/llvm/llvm-project/pull/69104