[NFC] Supress GCC "Bitfield too small to hold all values of enum" warning.

[tianqing]

Summary

974c8b7e2fd introduced a warning for GCC:

llvm-project/clang/include/clang/Sema/Overload.h:835:48: warning: ‘clang::OverloadCandidate::RewriteKind’ is too small to hold all values of ‘enum clang::OverloadCandidateRewriteKind’

OverloadCandidateRewriteKind RewriteKind : 2;

[rsmith]

Thanks, this seems fine to me. (It's unfortunate that the combination of MSVC's behavior and GCC's non-disableable warning forces this upon us, but so be it.)

[xbolva00]

Can you please land it? These warnings are quite annoying.

clang/include/clang/Sema/Overload.h

struct OverloadCandidate {
     /// non-static member function when the call doesn't have an
     /// object argument.
     bool IgnoreObjectArgument : 1;
 
     /// True if the candidate was found using ADL.
     CallExpr::ADLCallKind IsADLCandidate : 1;
 
     /// Whether this is a rewritten candidate, and if so, of what kind?
-    OverloadCandidateRewriteKind RewriteKind : 2;
+    unsigned RewriteKind : 2;
 
     /// FailureKind - The reason why this candidate is not viable.
     /// Actually an OverloadFailureKind.
     unsigned char FailureKind;
 
     /// The number of call arguments that were explicitly provided,
     /// to be used while performing partial ordering of function templates.
     unsigned ExplicitCallArguments;
 
     union {
       DeductionFailureInfo DeductionFailure;
 
       /// FinalConversion - For a conversion function (where Function is
       /// a CXXConversionDecl), the standard conversion that occurs
       /// after the call to the overload candidate to convert the result
       /// of calling the conversion function to the required type.
       StandardConversionSequence FinalConversion;
     };
 
+    /// Get RewriteKind value in OverloadCandidateRewriteKind type (This
+    /// function is to workaround the spurious GCC bitfield enum warning)
+    OverloadCandidateRewriteKind getRewriteKind() const {
+      return static_cast<OverloadCandidateRewriteKind>(RewriteKind);
+    }
+
     /// hasAmbiguousConversion - Returns whether this overload
     /// candidate requires an ambiguous conversion or not.
     bool hasAmbiguousConversion() const {
       for (auto &C : Conversions) {
         if (!C.isInitialized()) return false;
         if (C.isAmbiguous()) return true;
       }
       return false;

clang/lib/Sema/SemaOverload.cpp

if (isa<CXXMethodDecl>(Fn) && !isa<CXXConstructorDecl>(Fn)) {
     if (I == 0)
       isObjectArgument = true;
     else
       I--;
   }
 
   std::string FnDesc;
   std::pair<OverloadCandidateKind, OverloadCandidateSelect> FnKindPair =
-      ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn, Cand->RewriteKind,
+      ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn, Cand->getRewriteKind(),
                                 FnDesc);
 
   Expr *FromExpr = Conv.Bad.FromExpr;
   QualType FromTy = Conv.Bad.getFromType();
   QualType ToTy = Conv.Bad.getToType();
 
   if (FromTy == S.Context.OverloadTy) {
     assert(FromExpr && "overload set argument came from implicit argument?");
static void DiagnoseBadTarget(Sema &S, OverloadCandidate *Cand) {
   FunctionDecl *Caller = cast<FunctionDecl>(S.CurContext);
   FunctionDecl *Callee = Cand->Function;
 
   Sema::CUDAFunctionTarget CallerTarget = S.IdentifyCUDATarget(Caller),
                            CalleeTarget = S.IdentifyCUDATarget(Callee);
 
   std::string FnDesc;
   std::pair<OverloadCandidateKind, OverloadCandidateSelect> FnKindPair =
-      ClassifyOverloadCandidate(S, Cand->FoundDecl, Callee, Cand->RewriteKind,
-                                FnDesc);
+      ClassifyOverloadCandidate(S, Cand->FoundDecl, Callee,
+                                Cand->getRewriteKind(), FnDesc);
 
   S.Diag(Callee->getLocation(), diag::note_ovl_candidate_bad_target)
       << (unsigned)FnKindPair.first << (unsigned)ocs_non_template
       << FnDesc /* Ignored */
       << CalleeTarget << CallerTarget;
 
   // This could be an implicit constructor for which we could not infer the
   // target due to a collsion. Diagnose that case.
static void NoteFunctionCandidate(Sema &S, OverloadCandidate *Cand,
                                   LangAS CtorDestAS = LangAS::Default) {
   FunctionDecl *Fn = Cand->Function;
 
   // Note deleted candidates, but only if they're viable.
   if (Cand->Viable) {
     if (Fn->isDeleted()) {
       std::string FnDesc;
       std::pair<OverloadCandidateKind, OverloadCandidateSelect> FnKindPair =
-          ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn, Cand->RewriteKind,
-                                    FnDesc);
+          ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn,
+                                    Cand->getRewriteKind(), FnDesc);
 
       S.Diag(Fn->getLocation(), diag::note_ovl_candidate_deleted)
           << (unsigned)FnKindPair.first << (unsigned)FnKindPair.second << FnDesc
           << (Fn->isDeleted() ? (Fn->isDeletedAsWritten() ? 1 : 2) : 0);
       MaybeEmitInheritedConstructorNote(S, Cand->FoundDecl);
       return;
     }
 
     // We don't really have anything else to say about viable candidates.
-    S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->RewriteKind);
+    S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->getRewriteKind());
     return;
   }
 
   switch (Cand->FailureKind) {
   case ovl_fail_too_many_arguments:
   case ovl_fail_too_few_arguments:
     return DiagnoseArityMismatch(S, Cand, NumArgs);
 
S.Diag(Fn->getLocation(),
         << QualsForPrinting;
     MaybeEmitInheritedConstructorNote(S, Cand->FoundDecl);
     return;
   }
 
   case ovl_fail_trivial_conversion:
   case ovl_fail_bad_final_conversion:
   case ovl_fail_final_conversion_not_exact:
-    return S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->RewriteKind);
+    return S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->getRewriteKind());
 
   case ovl_fail_bad_conversion: {
     unsigned I = (Cand->IgnoreObjectArgument ? 1 : 0);
     for (unsigned N = Cand->Conversions.size(); I != N; ++I)
       if (Cand->Conversions[I].isBad())
         return DiagnoseBadConversion(S, Cand, I, TakingCandidateAddress);
 
     // FIXME: this currently happens when we're called from SemaInit
     // when user-conversion overload fails.  Figure out how to handle
     // those conditions and diagnose them well.
-    return S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->RewriteKind);
+    return S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->getRewriteKind());
   }
 
   case ovl_fail_bad_target:
     return DiagnoseBadTarget(S, Cand);
 
   case ovl_fail_enable_if:
     return DiagnoseFailedEnableIfAttr(S, Cand);