-- "Golubev I. N." <gin(a)mo.msk.ru> spake thusly:
>> But when I try to do that with a new session, it just whines
>> "Command attempted to use minibuffer while in minibuffer", as it
>> should.
>
> One can also start input in minibuffer, switch to other window (e. g.,
> with default binding of C-x o) and call write-file or so.
>
> See doc on enable-recursive-minibuffers and
> enable-recursive-minibuffers.
>
> write-file always sets name of written buffer. Buffer listing code
> detects minibuffers and such by space at the beginning of buffer
> names. I can not see a bug in behavior that you describe.
Possibly true, except that I don't have recursive minibuffers enabled, and it was a fairly confusing situation to deal with (which presumably is why recursive minibuffers are disabled by default).
The minibuffer was selected in the upper frame and was the only frame showing. I kept getting the 'Cannot switch buffers in minibuffer window' error when trying to switch to another buffer, and ended up having to split the buffers, select the other one (which was now showing a file), and then doing C-X 0 to close the minibuffer 'frame'.
If I ever manage to figure out how I did it (your proposed steps won't work, because they'll write-file on whatever buffer is selected, not the minibuffer), I'll post the information.