Missing coverage: Function.prototype.toString revision behavior on a Proxied function

[ajklein]

We just got a report in v8 about non-compliance with a new bit of logic in the Function.prototype.toString revision proposal. In particular, step 3 of the algorithm says:

If Type(func) is Object and IsCallable(func) is true, then return an implementation-dependent String source code representation of func. The representation must have the syntax of a NativeFunction.

This is a change in behavior from the current spec, which throws a TypeError in this case. This doesn't seem to be covered by any test262 test.

@michaelficarra @erights to verify that I'm reading the proposal correctly.

[ljharb]

I agree that you're reading the proposal correctly; however I'm surprised at this change, and it seems like it's an unintentional change in the proposal.

[michaelficarra]

This was an intentional change in response to tc39/Function-prototype-toString-revision#3. I recall talking about it in committee, but I think it was only in side conversations.

edit: /cc @claudepache