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

#69104 introduce a diagnostic that checked underlying type of an enum against type of bit-field that is annotated with `[[clang::preferred_type]]`. When I tried to introduce this annotation in #70349, it turned out to be too chatty, despite effort to avoid that.

Author: Endilll

clang/include/clang/Basic/DiagnosticGroups.td

@@ -54,7 +54,6 @@ def BitFieldConstantConversion : DiagGroup<"bitfield-constant-conversion",
                                            [SingleBitBitFieldConstantConversion]>;
 def BitFieldEnumConversion : DiagGroup<"bitfield-enum-conversion">;
 def BitFieldWidth : DiagGroup<"bitfield-width">;
-def BitFieldType : DiagGroup<"bitfield-type">;
 def CompoundTokenSplitByMacro : DiagGroup<"compound-token-split-by-macro">;
 def CompoundTokenSplitBySpace : DiagGroup<"compound-token-split-by-space">;
 def CompoundTokenSplit : DiagGroup<"compound-token-split",

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -3167,9 +3167,6 @@ def err_invalid_branch_protection_spec : Error<
   "invalid or misplaced branch protection specification '%0'">;
 def warn_unsupported_branch_protection_spec : Warning<
   "unsupported branch protection specification '%0'">, InGroup<BranchProtection>;
-def warn_attribute_underlying_type_mismatch : Warning<
-  "underlying type %0 of enumeration %1 doesn't match bit-field type %2">,
-  InGroup<BitFieldType>;
 
 def warn_unsupported_target_attribute
     : Warning<"%select{unsupported|duplicate|unknown}0%select{| CPU|"

clang/lib/Sema/SemaDeclAttr.cpp

@@ -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)) {
-      S.Diag(ParmTSI->getTypeLoc().getBeginLoc(),
-             diag::warn_attribute_underlying_type_mismatch)
-          << EnumUnderlyingType << QT << BitfieldType;
-      return;
-    }
-  }
-
   D->addAttr(::new (S.Context) PreferredTypeAttr(S.Context, AL, ParmTSI));
 }