Before You File a Proposal Please Confirm You Have Done The Following...

• I have searched for related issues and found none that match my proposal.
• I have searched the current rule list and found no rules that match my proposal.
• I have read the FAQ and my problem is not listed.

My proposal is suitable for this project

• I believe my proposal would be useful to the broader TypeScript community (meaning it is not a niche proposal).

Link to the rule's documentation

https://typescript-eslint.io/rules/no-floating-promises

Description

As of #8433 -> #9263, no-floating-promises has a checkThenables option (enabled by default as of v8) that stops it from flagging anything that's not explicitly a Promise type. That means the rule won't flag something that's explicitly marked as type PromiseLike (rather than Promise) without explicitly enabling checkThenables.

Coming out of conversation with @jakebailey: PromiseLike does semantically indicate a value is intended to be used like a Promise. That's different from something that coincidentally has a .then() which can be used with await (🤯).

Proposal: should we have the rule also check for PromiseLike, in addition to Promise?

Fail

declare function createThenable(): PromiseLike<void>;

createThenable();

Pass

declare function createThenable(): { then(a: () => void, b: () => void): void }

createThenable();

Additional Info

I'm in favor of this personally, for the stated reasoning.

In terms of whether this would be a breaking change: it almost feels like a bugfix rather than a feature? PromiseLike is quite rare in real-world usage. If this is accepted, I'd also be in favor of landing it in a minor version rather than a major.

💖