Issue #13671 has been updated by Eregon (Benoit Daloze). @duerst Could you take a look at this? It's not fixed yet in 3.2.0. ---------------------------------------- Bug #13671: Regexp with lookbehind and case-insensitivity raises RegexpError only on strings with certain characters https://bugs.ruby-lang.org/issues/13671#change-101088 * Author: dschweisguth (Dave Schweisguth) * Status: Assigned * Priority: Normal * Assignee: duerst (Martin Dürst) * ruby -v: 2.4.1 * Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN ---------------------------------------- Here is a test program: ~~~ ruby def test(description) begin yield puts "#{description} is OK" rescue RegexpError puts "#{description} raises RegexpError" end end test("ass, case-insensitive, special") { /(?<!ass)/i =~ '✨' } test("bss, case-insensitive, special") { /(?<!bss)/i =~ '✨' } test("as, case-insensitive, special") { /(?<!as)/i =~ '✨' } test("ss, case-insensitive, special") { /(?<!ss)/i =~ '✨' } test("ass, case-sensitive, special") { /(?<!ass)/ =~ '✨' } test("ass, case-insensitive, regular") { /(?<!ass)/i =~ 'x' } ~~~ Running the test program with Ruby 2.4.1 (macOS) gives ~~~ ass, case-insensitive, special raises RegexpError bss, case-insensitive, special raises RegexpError as, case-insensitive, special is OK ss, case-insensitive, special is OK ass, case-sensitive, special is OK ass, case-insensitive, regular is OK ~~~ The RegexpError is "invalid pattern in look-behind: /(?<!ass)/i (RegexpError)" Side note: in the real code in which I found this error I was able to work around the error by using (?i) after the lookbehind instead of //i. Running the test program with Ruby 2.3.4 does not report any RegexpErrors. I think this is a regression, although I might be wrong and it might be saving me from an incorrect result with certain strings. ---Files-------------------------------- test.rb (531 Bytes) -- https://bugs.ruby-lang.org/