function ReturnStatement( node, state, clbk ) {
	state.hasReturn = true;
	walk.base.ReturnStatement( node, state, clbk ); // eslint-disable-line new-cap
}
Callback invoked upon encountering a `ReturnStatement` AST node.

@private
@param {Node} node - AST node
@param {Object} state - state
@param {Function} clbk - callback