Reproduction link or steps
Rolldown REPL
What is expected?
The new RegExp is not dead code eliminated.
Rollup/ES REPL (for comparison)
Input
export function supportsUnicodeRegExp() {
try {
new RegExp('\\p{Ll}', 'u'); // constructor throws on engines without \p{} support
return true;
} catch {
return false;
}
}
Output:
function supportsUnicodeRegExp() {
try {
new RegExp('\\p{Ll}', 'u'); // constructor throws on engines without \p{} support
return true;
} catch {
return false;
}
}
export { supportsUnicodeRegExp };
What is actually happening?
The new RegExp code is being dead code eliminated
Input
export function supportsUnicodeRegExp() {
try {
new RegExp('\\p{Ll}', 'u'); // constructor throws on engines without \p{} support
return true;
} catch {
return false;
}
}
Output
//#region index.ts
function supportsUnicodeRegExp() {
try {
return true; // <-- defaults to true, causing runtime errors in legacy engines
} catch {
return false;
}
}
//#endregion
export { supportsUnicodeRegExp };
System Info
System:
OS: macOS 26.5
CPU: (10) arm64 Apple M1 Max
Memory: 84.97 MB / 32.00 GB
Shell: 5.9 - /bin/zsh
Binaries:
Node: 22.17.0 - ~/.volta/tools/image/node/22.17.0/bin/node
Yarn: 1.22.19 - ~/.volta/bin/yarn
npm: 10.9.2 - ~/.volta/tools/image/node/22.17.0/bin/npm
pnpm: 11.1.2 - ~/.volta/tools/image/pnpm/11.1.2/bin/pnpm
Watchman: 2026.04.27.00 - /opt/homebrew/bin/watchman
Browsers:
Chrome: 150.0.7871.115
Chrome Canary: 152.0.7949.0
Firefox: 152.0.4
Safari: 26.5
npmPackages:
rolldown: 1.0.3 => 1.0.3Any additional comments?
This issue is primarily affecting applications compiled with Rolldown (via Vite v8) when running on older connected devices, such as 2018/2019 Samsung Tizen (Chromium v56/63 respectively).
In this specific case, the relevant code is part of a 3rd party library (Datadog v6), which we are currently patching in order to prevent the DCE.
Reproduction link or steps
Rolldown REPL
What is expected?
The
new RegExpis not dead code eliminated.Rollup/ES REPL (for comparison)
Input
Output:
What is actually happening?
The
new RegExpcode is being dead code eliminatedInput
Output
System Info
System: OS: macOS 26.5 CPU: (10) arm64 Apple M1 Max Memory: 84.97 MB / 32.00 GB Shell: 5.9 - /bin/zsh Binaries: Node: 22.17.0 - ~/.volta/tools/image/node/22.17.0/bin/node Yarn: 1.22.19 - ~/.volta/bin/yarn npm: 10.9.2 - ~/.volta/tools/image/node/22.17.0/bin/npm pnpm: 11.1.2 - ~/.volta/tools/image/pnpm/11.1.2/bin/pnpm Watchman: 2026.04.27.00 - /opt/homebrew/bin/watchman Browsers: Chrome: 150.0.7871.115 Chrome Canary: 152.0.7949.0 Firefox: 152.0.4 Safari: 26.5 npmPackages: rolldown: 1.0.3 => 1.0.3Any additional comments?
This issue is primarily affecting applications compiled with Rolldown (via Vite v8) when running on older connected devices, such as 2018/2019 Samsung Tizen (Chromium v56/63 respectively).
In this specific case, the relevant code is part of a 3rd party library (Datadog v6), which we are currently patching in order to prevent the DCE.