Misc fixes to the runtime for MSVC compatability with it's public headers

Author: hughbe

include/swift/Runtime/Metadata.h

@@ -1993,7 +1993,7 @@ struct TargetValueMetadata : public TargetMetadata<Runtime> {
       return nullptr;
 
     auto asWords = reinterpret_cast<
-      ConstTargetMetadataPointer<Runtime, TargetMetadata> const *>(this);
+      ConstTargetMetadataPointer<Runtime, swift::TargetMetadata> const *>(this);
     return (asWords + Description->GenericParams.Offset);
   }
 

stdlib/public/runtime/MetadataImpl.h

@@ -881,6 +881,7 @@ struct NonFixedBufferValueWitnesses : BufferValueWitnessesBase<Impl> {
 
   static OpaqueValue *projectBuffer(ValueBuffer *buffer, const Metadata *self) {
     auto vwtable = self->getValueWitnesses();
+    (void)vwtable;
     if (!IsKnownAllocated && vwtable->isValueInline()) {
       return reinterpret_cast<OpaqueValue*>(buffer);
     } else {
@@ -900,6 +901,7 @@ struct NonFixedBufferValueWitnesses : BufferValueWitnessesBase<Impl> {
                                                        ValueBuffer *src,
                                                        const Metadata *self) {
     auto vwtable = self->getValueWitnesses();
+    (void)vwtable;
     if (!IsKnownAllocated && !vwtable->isValueInline()) {
       return Impl::initializeWithTake(reinterpret_cast<OpaqueValue*>(dest),
                                       reinterpret_cast<OpaqueValue*>(src),

stdlib/public/runtime/Reflection.mm

@@ -233,6 +233,8 @@ AnyReturn swift_MagicMirrorData_objcValue(HeapObject *owner,
     case MetadataKind::ErrorObject:
       return "(ErrorType Object)";
   }
+
+  swift_runtime_unreachable("Unhandled MetadataKind in switch.");
 }
 
 SWIFT_CC(swift) SWIFT_RUNTIME_STDLIB_INTERFACE