[clang] [clang] Remove diagnostic that came with `[[clang::preferred_type]]` (PR #70632)

[Vlad Serebrennikov via cfe-commits]

================
@@ -5928,28 +5928,6 @@ static void handlePreferredTypeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   S.RequireCompleteType(ParmTSI->getTypeLoc().getBeginLoc(), QT,
                         diag::err_incomplete_type);
 
-  if (QT->isEnumeralType()) {
-    auto IsCorrespondingType = [&](QualType LHS, QualType RHS) {
-      assert(LHS != RHS);
-      if (LHS->isSignedIntegerType())
-        return LHS == S.getASTContext().getCorrespondingSignedType(RHS);
-      return LHS == S.getASTContext().getCorrespondingUnsignedType(RHS);
-    };
-    QualType BitfieldType =
-        cast<FieldDecl>(D)->getType()->getCanonicalTypeUnqualified();
-    QualType EnumUnderlyingType = QT->getAs<EnumType>()
-                                      ->getDecl()
-                                      ->getIntegerType()
-                                      ->getCanonicalTypeUnqualified();
-    if (EnumUnderlyingType != BitfieldType &&
-        !IsCorrespondingType(EnumUnderlyingType, BitfieldType)) {
----------------
Endilll wrote:

> Another solution would be to compare the number of bits of the greater enumerator with the number of bits in the bitfield.

I've had this idea myself, but it's defeated by likes of https://github.com/llvm/llvm-project/blob/e79f0506cf6fd32ed466fdd2ccbb68dcacbb4bf5/clang/include/clang/AST/DeclarationName.h#L174-L185
where `UncommonNameKindOffset` is an enumerator that is not there to be stored in memory.

https://github.com/llvm/llvm-project/pull/70632