Let's assume an ebuild has the following RDEPEND: || ( foo:0= bar:0= ) After installing the package against bar, portage writes the following to vdb: || ( foo:0 bar:0/1= ) So, it expands the used provider to trigger slot-op rebuilds and removes the slot operator from the other to prevent them. However, if there's at least one := in || (), I think we can clearly guess that switching providers at run-time is not safe (we can't guarantee matching binary ABI). Right now, if I do: emerge -1v foo and the two are mutually exclusive, emerge just wants to replace bar with any version of foo without rebuilding. If we instead stored: || ( foo:notinst= bar:0/1= ) emerge notices you can't replace one with the other and fails with conflict. If I tip it: emerge -1v foo otherpkg it plans rebuild of otherpkg and everything works as expected :). Sadly, I can't get the same behavior via large --backtrack. Note that instead of 'notinst' we ought to probably use something alike '-notinst' -> reserved value that doesn't match valid slot names.
Oh, and this also breaks my @changed-deps magic. If we at least stored foo:0= (instead of plain foo:0) it would fix it, and this doesn't change emerge behavior at all.
