unsafe

Does that mean an explicit unsafe will be allowed on the definition part only for iterators with language version 13?

partial IEnumerable<int> M6();
partial unsafe IEnumerable<int> M6() { yield break; }

Yes, exactly.

even when its declaration

Consider using "even when the iterator declaration" to clarify "its" here. #Closed

In C# 12 it is an error to have an iterator method marked with the unsafe modifier

Why does that follow? From the spec above it sounds like the following is valid regardless of language version:

unsafe IEnumerable F() // unsafe context
{ // safe context
    yield return 42;
}

Well, you're right, the C# 12/13 thing does not follow just from the spec but also from this:

I'm not sure, but I thought the spec is usually not conditional on langversion, the whole spec is for one specific langversion, hence I left this out of the spec itself. Anyway I will clarify this, thanks.