Sema: remove unnecessary parameter for SwiftName handling (NFCI)

[compnerd]

Summary

This code never actually did anything in the implementation.

mergeDeclAttribute is declared as static, and referenced exactly
once in the file: from Sema::mergeDeclAttributes.

Sema::mergeDeclAttributes sets LocalAMK to AMK_None. If the
attribute is DeprecatedAttr, UnavailableAttr, or AvailabilityAttr
then the LocalAMK is updated. However, because we are dealing with a
SwiftNameDeclAttr here, LocalAMK remains AMK_None. This is then
passed to the function which will as a result pass the value of
AMK_None == AMK_Override aka false. Simply propagate the value
through and erase the dead codepath.

Thanks to Aaron Ballman for flagging the use of the availability merge
kind here leading to this simplification!

[aaron.ballman]

LGTM!

clang/include/clang/Sema/Sema.h

public:
   MinSizeAttr *mergeMinSizeAttr(Decl *D, const AttributeCommonInfo &CI);
   NoSpeculativeLoadHardeningAttr *
   mergeNoSpeculativeLoadHardeningAttr(Decl *D,
                                       const NoSpeculativeLoadHardeningAttr &AL);
   SpeculativeLoadHardeningAttr *
   mergeSpeculativeLoadHardeningAttr(Decl *D,
                                     const SpeculativeLoadHardeningAttr &AL);
   SwiftNameAttr *mergeSwiftNameAttr(Decl *D, const SwiftNameAttr &SNA,
-                                    StringRef Name, bool Override);
+                                    StringRef Name);
   OptimizeNoneAttr *mergeOptimizeNoneAttr(Decl *D,
                                           const AttributeCommonInfo &CI);
   InternalLinkageAttr *mergeInternalLinkageAttr(Decl *D, const ParsedAttr &AL);
   InternalLinkageAttr *mergeInternalLinkageAttr(Decl *D,
                                                 const InternalLinkageAttr &AL);
   CommonAttr *mergeCommonAttr(Decl *D, const ParsedAttr &AL);
   CommonAttr *mergeCommonAttr(Decl *D, const CommonAttr &AL);
   WebAssemblyImportNameAttr *mergeImportNameAttr(

clang/lib/Sema/SemaDecl.cpp

else if (S.getLangOpts().CUDA && isa<FunctionDecl>(D) &&
            (isa<CUDAHostAttr>(Attr) || isa<CUDADeviceAttr>(Attr) ||
             isa<CUDAGlobalAttr>(Attr))) {
     // CUDA target attributes are part of function signature for
     // overloading purposes and must not be merged.
     return false;
   } else if (const auto *MA = dyn_cast<MinSizeAttr>(Attr))
     NewAttr = S.mergeMinSizeAttr(D, *MA);
   else if (const auto *SNA = dyn_cast<SwiftNameAttr>(Attr))
-    NewAttr = S.mergeSwiftNameAttr(D, *SNA, SNA->getName(),
-                                   AMK == Sema::AMK_Override);
+    NewAttr = S.mergeSwiftNameAttr(D, *SNA, SNA->getName());
   else if (const auto *OA = dyn_cast<OptimizeNoneAttr>(Attr))
     NewAttr = S.mergeOptimizeNoneAttr(D, *OA);
   else if (const auto *InternalLinkageA = dyn_cast<InternalLinkageAttr>(Attr))
     NewAttr = S.mergeInternalLinkageAttr(D, *InternalLinkageA);
   else if (const auto *CommonA = dyn_cast<CommonAttr>(Attr))
     NewAttr = S.mergeCommonAttr(D, *CommonA);
   else if (isa<AlignedAttr>(Attr))
     // AlignedAttrs are handled separately, because we need to handle all

clang/lib/Sema/SemaDeclAttr.cpp

NoSpeculativeLoadHardeningAttr *Sema::mergeNoSpeculativeLoadHardeningAttr(
     Decl *D, const NoSpeculativeLoadHardeningAttr &AL) {
   if (checkAttrMutualExclusion<SpeculativeLoadHardeningAttr>(*this, D, AL))
     return nullptr;
 
   return ::new (Context) NoSpeculativeLoadHardeningAttr(Context, AL);
 }
 
 SwiftNameAttr *Sema::mergeSwiftNameAttr(Decl *D, const SwiftNameAttr &SNA,
-                                        StringRef Name, bool Override) {
+                                        StringRef Name) {
   if (const auto *PrevSNA = D->getAttr<SwiftNameAttr>()) {
-    if (Override) {
-      // FIXME: warn about incompatible override
-      return nullptr;
-    }
-
     if (PrevSNA->getName() != Name && !PrevSNA->isImplicit()) {
       Diag(PrevSNA->getLocation(), diag::err_attributes_are_not_compatible)
           << PrevSNA << &SNA;
       Diag(SNA.getLoc(), diag::note_conflicting_attribute);
     }
 
     D->dropAttr<SwiftNameAttr>();
   }