a.txt

1.  If |F| corresponds to an attribute, operation or stringifier, then return
    the global environment associated with the
    [=interface=] that definition appears on.
1.  Otherwise, if |F| corresponds to an indexed or named property, then return
    the global environment associated with the interface that
    the indexed or named property getter, setter or deleter was defined on.

b.txt

1.  If |F| corresponds to an attribute, operation or stringifier, then:
    1.  return the global environment associated with the
        [=interface=] that definition appears on.
1.  Otherwise, if |F| corresponds to an indexed or named property, then:
    1.  return the global environment associated with the interface that
        the indexed or named property getter, setter or deleter was defined on.