src/common/ast-path.js/AstPath/getName
class AstPath:  getName() {
    const { stack } = this;
    const { length } = stack;
    if (length > 1) {
      return stack[length - 2];
    }
    // Since the name is always a string, null is a safe sentinel value to
    // return if we do not know the name of the (root) value.
    /* istanbul ignore next */
    return null;
  }