code: function validateRegExp(pattern, flags, node) {
              if (typeof pattern === "string") {
                  if (hasPattern(pattern, REGEXP_NAMED_GROUP)) {
                      report(node, "regexpNamedCaptureGroups")
                  }
                  if (hasPattern(pattern, REGEXP_LOOKBEHIND)) {
                      report(node, "regexpLookbehind")
                  }
                  if (hasPattern(pattern, REGEXP_UNICODE_PROPERTY)) {
                      report(node, "regexpUnicodeProperties")
                  }
              }
              if (typeof flags === "string") {
                  if (flags.indexOf("y") !== -1) {
                      report(node, "regexpY")
                  }
                  if (flags.indexOf("u") !== -1) {
                      report(node, "regexpU")
                  }
                  if (flags.indexOf("s") !== -1) {
                      report(node, "regexpS")
                  }
              }
          }
docs: Validate RegExp syntax.
  @param {string} pattern A RegExp pattern to check.
  @param {string} flags A RegExp flags to check.
  @param {ASTNode} node A node to report.
  @returns {void}