This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
if (context !== context.Consumer) {
        if (!hasWarnedAboutUsingContextAsConsumer) {
          hasWarnedAboutUsingContextAsConsumer = true;
          console.error(
            'Rendering <Context> directly is not supported and will be removed in ' +
              'a future major release. Did you mean to render <Context.Consumer> instead?',
          );
        }