True, even I were not sure which should mean which. ;)

> When I manually trigger the code in typeobject.c:5827, I get a segfault;
I'm surprised no test triggered that.

I think this triggered one of Victor's guards, added to catch such sort of errors. In this case the function both raises an exception and returns a result. If not catch such sort of error, it can cause unexpected errors or very strange results during executing unrelated code, so crashing as early as possible is lesser evil.