do-not-backtrack.js (1132B)
1 // Copyright (C) 2017 the V8 project authors. All rights reserved. 2 // This code is governed by the BSD license found in the LICENSE file. 3 4 /*--- 5 esid: sec-assertion 6 description: Do not backtrack into a lookbehind. 7 info: | 8 The production Assertion :: (?<=Disjunction) evaluates as follows: 9 1. Evaluate Disjunction with -1 as its direction argument to obtain a Matcher m. 10 2. Return an internal Matcher closure that takes two arguments, a State x and a Continuation 11 c, and performs the following steps: 12 a. Let d be a Continuation that always returns its State argument as a successful MatchResult. 13 b. Call m(x, d) and let r be its result. 14 c. If r is failure, return failure. 15 d. Let y be r's State. 16 e. Let cap be y's captures List. 17 f. Let xe be x's endIndex. 18 g. Let z be the State (xe, cap). 19 h. Call c(z) and return its result. 20 features: [regexp-lookbehind] 21 ---*/ 22 23 // The lookbehind captures "abc" so that \1 does not match. We do not backtrack 24 // to capture only "bc" in the lookbehind. 25 assert.sameValue("abcdbc".match(/(?<=([abc]+)).\1/), null); 26 27 reportCompare(0, 0);