Related to https://bugzilla.yoctoproject.org/show_bug.cgi?id=15129, it is possible to define a function in class or recipe files with specific variants for target, native, etc. in such a way that a cryptic failure may be observed if there is no "default" version. For example, if:

foo_rm_bar:class-target () {
        ...
}

foo_rm_bar:class-native () {
        ...
}

then the following should also be present to handle other cases:

foo_rm_bar () {
        :
}

otherwise failures may occur that misleadingly suggest issues with the packages themselves. If functions are incompletely defined this way, bitbake should be able to warn the user.