function isSimple(node) {
      return node.type === 'Identifier' || node.type === 'RestElement';
    }
Checks whether a given node is a pattern which doesn't have any side effects.
Default parameters and Destructuring parameters can have side effects.
@see eslint no-useless-constructor rule
@param {ASTNode} node - A pattern node.
@returns {boolean} `true` if the node doesn't have any side effects.