`borrowing` + `sending` not allowed?

[vns]

I've been playing with some ways to work together with sending and ownership, and stumbled across case I'm not sure how to treat:

class NonSendable {
}

func foo(bar: borrowing sending NonSendable) {  // error: 'sending' cannot be used together with 'borrowing'
}

I went over to proposal to check notes on why, and the beginning of section makes total sense to me:

When a call passes an argument to a sending parameter, the caller cannot use the argument value again after the callee returns. By default sending on a function parameter implies that the callee consumes the parameter. [emphasis mine]

But then it also states that this can be opt-in by pairing with explicit ownership parameters, so that using borrowing with sending is a valid pair, yet the compiler doesn't allow this. Is that an issue in the proposal text or the compiler?

[Jumhyn (Frederick Kellison-Linn)]

Ah, if the proposal hasn’t been updated, that’s an error. This proposal was accepted with modifications:

@beccadax

A few reviewers also brought up the combination of the borrowing and sending modifiers. As proposed, this combination would have served a niche use case for ABI-stable retroactive adopters of sending, but some reviewers argued that it would be a good spelling for a future direction that allowed the callee to "borrow" a region for the duration of the call while promising to keep it intact. To avoid prematurely precluding this design, the Language Steering Group has chosen to ban the combination of borrowing and sending; when the standard library adopts sending, it will instead use a temporary compiler-internal facility to preserve ABI compatibility.