[trackoor]

After a NoSubstitutionTemplate or a TemplateTail, / is a division operator (InputElementDiv goal). I couldn't find a test where a template literal is followed by /.

Engines that got this wrong:

• Hermes: / after a template literal is lexed as the start of a regular expression meta/hermes#2294 (fixed): `4` / 2 is "non-terminated regular expression literal"
• quickjs-ng: / after a template literal inside parentheses is scanned as a regexp: (a = 8 / 2) => a is a SyntaxError quickjs-ng/quickjs#1886 (fix in Fix '/' after a template literal in the arrow function lookahead quickjs-ng/quickjs#1887) and QuickJS: (a = 8 / 2) => a and (a = this.#x / 2) => a are SyntaxErrors: the arrow lookahead scans / as a regexp bellard/quickjs#596: the arrow-function lookahead scans the / as a regexp, so (a = `8` / 2) => a is a SyntaxError

The tests also check the other direction: after a TemplateHead or TemplateMiddle, / starts a regular expression, including inside arrow parameters ((a = `${/[)]/.source}`) => a).

All three files pass (sloppy and strict) on V8 15.9.109, SpiderMonkey 160.0b5, JavaScriptCore (macOS 26.3), engine262 67a6b615, GraalJS 25.5.5, XS 17.9.3 and Boa nightly. Hermes 0.11.0 (the last CLI release, before the fix) fails all three; quickjs-ng e22ce4d and QuickJS 712e8c0 fail arrow-function/dflt-params-template-literal-division.js.

[github-actions]

3 new or modified tests were run on 7 engines.

View workflow run

Test	Engine262	GraalJS	JavaScriptCore	QuickJS	SpiderMonkey	V8	XS
language/expressions/arrow-function/dflt-params-template-literal-division.js	✅	✅	✅	❌	✅	✅	✅
language/expressions/template-literal/division-after-no-substitution-template.js	✅	✅	✅	✅	✅	✅	✅
language/expressions/template-literal/division-after-template-tail.js	✅	✅	✅	✅	✅	✅	✅