"await x as any" - Node PartiallyEmittedExpression did not pass test 'isLeftHandSideExpression' assert triggered

[goldenice]

🔎 Search Terms

"PartiallyEmittedExpression", "isLeftHandSideExpression", "NODE_ENV" "NODE_ENV=development"

🕗 Version & Regression Information

This is the behavior in every version I tried (4.0, 5.0, and 5.8.3), and I reviewed the FAQ to see if anything related was in there

⏯ Playground Link

No response

💻 Code

async function test() {
	const test = (await null as any)!;
};

Executing this code in the Playground will be fine, but the bug can be triggered by running tsc with env var NODE_ENV=development turned on.

🙁 Actual behavior

Executing this code in the Playground will be fine, but running this with tsc on the command line with env flag NODE_ENV=development will fail with the following error:

Error: Debug Failure. False expression: Unexpected node.
Verbose Debug Information: Node PartiallyEmittedExpression did not pass test 'isLeftHandSideExpression'.

We did not realize NODE_ENV=development would affect TypeScript, and start throwing errors on code that normally compiles perfectly fine.

🙂 Expected behavior

Either NODE_ENV=development should not affect TypeScript at all, or at least TypeScript shouldn't crash when hitting some debug path? If this behavior is expected then putting an item in the FAQ about ensuring NODE_ENV is not set to development might be sensible.

Additional information about the issue

No response

[RyanCavanaugh]

Copilot: Ignore everything about NODE_ENV and environment variables, instead fix the problem that triggered the assert in the first place