type RequestInfo should include URL

[aslilac]

Currently RequestInfo is Request | string, but should (minimally) be Request | URL | string.

fetch(new URL('/some_api', 'https://example.com')) is valid, and works as you'd expect.

Technically it should be Request | { toString(): string } | string according to MDN, but I'm not sure if there are intricacies around that.

[Paril]

I think the intricacy for the latter is that it's not very type-safe and more error-prone, since everything will toString to something, but it's often not what you expect it to be unless it's a primitive. They use the same thing for dataset/css style values, as well as other writeables, even if the spec allows and/or encourages it (for instance writing to window.location can be done with a string, and is most commonly done as such, but currently it's only writeable with a URL)

[aslilac]

Yeah, it feels like { toString(): string } falls into the same pit as {} in that almost anything could be cast to it.

[orta]

Agree, I think we probably don't want this

[orta]

Related: #1003

[dnalborczyk]

Agree, I think we probably don't want this

Actually I would think we do want this.

https://developer.mozilla.org/en-US/docs/Web/API/fetch#parameters

A string or any other object with a stringifier — including a URL object — that provides the URL of the resource you want to fetch.

[dnalborczyk]

speaking of which, this is pretty much the same problem, but has been added:

#331
#332

[dnalborczyk]

as well as: #600

fetch falls pretty much into the same category.

similar: microsoft/TypeScript#43066