code: private static MethodRef getOneOfCaseMethod(OneofDescriptor descriptor) {
      TypeInfo message = messageRuntimeType(descriptor.getContainingType());
      return MethodRef.createInstanceMethod(
              message,
              new Method(
                  "get" + underscoresToCamelCase(descriptor.getName(), true) + "Case",
                  TypeInfo.create(JavaQualifiedNames.getCaseEnumClassName(descriptor)).type(),
                  NO_METHOD_ARGS))
          .asCheap();
    }
docs: Returns the {@link MethodRef} for the get*Case method for oneof fields.