ES2025 regex syntax (duplicate named groups, pattern modifiers) is not gated by `target`

[dayongkr]

Version

Reproduced on 5.5 through 7.0.2. Present since #55600 introduced regex syntax checking.

Playground

https://www.typescriptlang.org/play/?target=9#code/PTAEHEEMBcFMBNQGMD2AnNsnQDYE9RAUAlGgAsBLAZ1ABEB5AUQGVRYN0AoVAO0ulABuAMRyQA5qAC8oYAG0AOgAcA3gBkAvgF1gAgNygDho8ZOmTIUABUmARgCsABhsAuUJgCOAV3KZqsSgBMDgEALBwcFgByKPxiMAhEJKT+sKCUpCieOIhsaOigAEae-PAo3ADk0FxlfKDwnoqRkAC2-lIyABQA-AA8eAB88vDKIeoAlAC0Q8oB6gA+07PywN19g8OjY8D6BhbMQQF21bz8zSjw5ABm5GzU0itd5M6QBUhbO2afXzJg+8F2QA

Code

// target: ES2022

// Gated correctly — this DOES error
const vFlag = /[\p{L}]/v;                                  // TS1501: requires es2024

// Not gated — these should error but don't
const dupNames = /(?<y>\d{4})-\d{2}|\d{2}\/(?<y>\d{4})/;   // ES2025
const modifiers = /(?i:abc)/;                              // ES2025

Actual behavior

Only vFlag errors. Verified at es2018, es2020, es2022, es2024 — the two ES2025 patterns pass at every target.
modifiers also passes at es2017, meaning it has no gate at all.

Both fail at module load time on Node 22 (V8 12.4):

SyntaxError: Invalid regular expression: ... Duplicate capture group name
SyntaxError: Invalid regular expression: /(?i:abc)/: Invalid group

Expected behavior

An error consistent with how other regex features are gated:

Regex feature	Introduced	Gate
Named capturing groups	ES2018	TS1503
d flag	ES2022	TS1501
v flag	ES2024	TS1501
Duplicate named groups	ES2025	none
Pattern modifiers	ES2025	none

Notes

TypeScript already parses and validates both features — TS1515 (mutual exclusivity) and TS1500/TS1509 (flag rules) fire correctly. Only the version gate is missing.

Downleveling is not a prerequisite: named capturing groups are gated without being rewritten, so the same approach applies.

Both features were Stage 3 with no assigned ES version when #55600 was merged, which likely explains the omission. Both reached Stage 4 and shipped in ES2025.

Suggested locations, next to the existing validation:

• scanGroupName — where the mutual-exclusivity error is reported
• scanPatternModifiers — currently calls checkRegularExpressionFlagAvailability for individual flags only, not for the modifier syntax itself

Impact

Mainly affects library code. Bundlers that do not rewrite regexes (rolldown/oxc) emit the pattern as-is, so Node.js < 23 fails when the module is loaded — the failure surfaces in consumers' builds rather than in the authoring package.

Related

• Provide Syntax Checking for Regular Expressions #55600
• RegExp named capture groups don't get transpiled #36132