Runtime: Use accessor method to get TargetWitnessTable::Description

Author: slavapestov

include/swift/ABI/Metadata.h

@@ -1871,11 +1871,16 @@ using ProtocolDescriptor = TargetProtocolDescriptor<InProcess>;
 /// the layout of a witness table is dependent on the protocol being
 /// represented.
 template <typename Runtime>
-struct TargetWitnessTable {
+class TargetWitnessTable {
   /// The protocol conformance descriptor from which this witness table
   /// was generated.
   ConstTargetMetadataPointer<Runtime, TargetProtocolConformanceDescriptor>
     Description;
+
+public:
+  const TargetProtocolConformanceDescriptor<Runtime> *getDescription() const {
+    return Description;
+  }
 };
 
 using WitnessTable = TargetWitnessTable<InProcess>;

stdlib/public/runtime/AnyHashableSupport.cpp

@@ -89,7 +89,7 @@ static const Metadata *findHashableBaseTypeImpl(const Metadata *type) {
     return nullptr;
   }
   // By this point, `type` is known to conform to `Hashable`.
-  const auto *conformance = witnessTable->Description;
+  const auto *conformance = witnessTable->getDescription();
   const Metadata *baseTypeThatConformsToHashable =
     findConformingSuperclass(type, conformance);
   HashableConformances.getOrInsert(HashableConformanceKey{type},

stdlib/public/runtime/Casting.cpp

@@ -2568,7 +2568,7 @@ MetadataResponse _getBridgedObjectiveCType(
                              const Metadata *conformingType,
                              const _ObjectiveCBridgeableWitnessTable *wtable) {
   // FIXME: Can we directly reference the descriptor somehow?
-  const ProtocolConformanceDescriptor *conformance = wtable->Description;
+  const ProtocolConformanceDescriptor *conformance = wtable->getDescription();
   const ProtocolDescriptor *protocol = conformance->getProtocol();
   auto assocTypeRequirement = protocol->getRequirements().begin();
   assert(assocTypeRequirement->Flags.getKind() ==

stdlib/public/runtime/Metadata.cpp

@@ -4624,7 +4624,7 @@ swift_getAssociatedTypeWitnessSlowImpl(
                                       const ProtocolRequirement *assocType) {
 #ifndef NDEBUG
   {
-    const ProtocolConformanceDescriptor *conformance = wtable->Description;
+    const ProtocolConformanceDescriptor *conformance = wtable->getDescription();
     const ProtocolDescriptor *protocol = conformance->getProtocol();
     auto requirements = protocol->getRequirements();
     assert(assocType >= requirements.begin() &&
@@ -4669,7 +4669,7 @@ swift_getAssociatedTypeWitnessSlowImpl(
   }
 
   // Dig out the protocol.
-  const ProtocolConformanceDescriptor *conformance = wtable->Description;
+  const ProtocolConformanceDescriptor *conformance = wtable->getDescription();
   const ProtocolDescriptor *protocol = conformance->getProtocol();
 
   // Extract the mangled name itself.
@@ -4788,7 +4788,7 @@ static const WitnessTable *swift_getAssociatedConformanceWitnessSlowImpl(
                                   const ProtocolRequirement *assocConformance) {
 #ifndef NDEBUG
   {
-    const ProtocolConformanceDescriptor *conformance = wtable->Description;
+    const ProtocolConformanceDescriptor *conformance = wtable->getDescription();
     const ProtocolDescriptor *protocol = conformance->getProtocol();
     auto requirements = protocol->getRequirements();
     assert(assocConformance >= requirements.begin() &&

stdlib/public/runtime/MetadataCache.h

@@ -365,8 +365,8 @@ class MetadataCacheKey {
     if (awt == bwt)
       return 0;
 
-    auto *aDescription = awt->Description;
-    auto *bDescription = bwt->Description;
+    auto *aDescription = awt->getDescription();
+    auto *bDescription = bwt->getDescription();
     if (aDescription == bDescription)
       return 0;