setTimeout incorrect typings browser

[GoGoris]

TypeScript Version: 3.4.5

Search Terms: setTimeout

Code

const timeout: number = setTimeout(() => console.log('anything'), 300);

Expected behavior:

It compiles correctly

Actual behavior:

Type 'Timeout' is not assignable to type 'number'.

1 const timeout: number = setTimeout(() => console.log('anything'), 300);
        ~~~~~~~


Found 1 error.

Playground Link:

Not reproducable in playground

Related Issues:

Possibly #19635, but this issue seems to be outdated because now the declaration of setTimeout looks like:

type TimerHandler = string | Function;
setTimeout(handler: TimerHandler, timeout?: number, ...arguments: any[]): number;

https://stackoverflow.com/q/45802988

[nmain]

Somewhere in your dependency tree is a package that works in both Node and the browser. When used in Node, it probably supports some Node types like Buffer, and so it brings in @types/node to express that relationship, which causes Node globals to become available, and Node has a setTimeout with a different definition than the browser one.

As a workaround, you can use window.setTimeout which will only have the browser definition.

I think the best solution to this is to move forward with #31894 and then change typings of all packages that optionally use Node to support them, but that's a ways off.

[AviVahl]

I find using ReturnType<typeof setTimeout> instead of number a bit cleaner workaround.