src/v8/test/mjsunit/es6/unicode-regexp-backrefs.js

// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Back reference does not end in the middle of a surrogate pair.
function replace(string) {
  return string.replace(/L/g, "\ud800")
               .replace(/l/g, "\ud801")
               .replace(/T/g, "\udc00")
               .replace(/\./g, "[^]");
}

function test(expectation, regexp_source, subject) {
  if (expectation !== null) expectation = expectation.map(replace);
  subject = replace(subject);
  regexp_source = replace(regexp_source);
  assertEquals(expectation, new RegExp(regexp_source, "u").exec(subject));
}

// Back reference does not end in the middle of a surrogate pair.
test(null, "(L)\\1", "LLT");
test(["LLTLl", "L", "l"], "(L).*\\1(.)", "LLTLl");
test(null, "(aL).*\\1", "aLaLT");
test(["aLaLTaLl", "aL", "l"], "(aL).*\\1(.)", "aLaLTaLl");

var s = "TabcLxLTabcLxTabcLTyTabcLz";
test([s, "TabcL", "z"], "([^x]+).*\\1(.)", s);

// Back reference does not start in the middle of a surrogate pair.
test(["TLTabTc", "T", "c"], "(T).*\\1(.)", "TLTabTc");

// Lookbehinds.
test(null, "(?<=\\1(T)x)", "LTTx");
test(["", "b", "T"], "(?<=(.)\\2.*(T)x)", "bTaLTTx");
test(null, "(?<=\\1.*(L)x)", "LTLx");
test(["", "b", "L"], "(?<=(.)\\2.*(L)x)", "bLaLTLx");


test(null, "([^x]+)x*\\1", "LxLT");
test(null, "([^x]+)x*\\1", "TxLT");
test(null, "([^x]+)x*\\1", "LTxL");
test(null, "([^x]+)x*\\1", "LTxT");
test(null, "([^x]+)x*\\1", "xLxLT");
test(null, "([^x]+)x*\\1", "xTxLT");
test(null, "([^x]+)x*\\1", "xLTxL");
test(null, "([^x]+)x*\\1", "xLTxT");
test(null, "([^x]+)x*\\1", "xxxLxxLTxx");
test(null, "([^x]+)x*\\1", "xxxTxxLTxx");
test(null, "([^x]+)x*\\1", "xxxLTxxLxx");
test(null, "([^x]+)x*\\1", "xxxLTxxTxx");
test(["LTTxxLTT", "LTT"], "([^x]+)x*\\1", "xxxLTTxxLTTxx");