Thanks for the feedback. Indeed, as I tried to explain in an older
message, that was also my understanding. The practical difficulty with
the mapping (which you can also guess from the current structure of
get_delta_difference_1, the if (kind == bk_inaccessible || kind ==
bk_ambig) check) is that ba_quiet, as used by lookup_base, doesn't just
control the error calls - like normally tf_error does - it *also*
changes the return value, error_mark_node or NULL_TREE. I'm still not
sure about the correct (and concise! see get_delta_difference_1, again)
way to handle this...