Canonical references can not be used to model symbolic references.
Relax this restriction by adding another member to the payload, named
"symbolic". Its key-value/name-target pairs then translate directly to
canonical symbolic references.
Care is taken to not allow circular references, and that there always
is a rule that could generate the target of a symbolic reference
(or a chain of symbolic references). Still, a symbolic reference may
dangle (for example when its target reference cannot be computed
because of divergence), but at least it can be prevented that a
symref *always* dangles, because there is no rule that would produce
its target.
Co-authored-by: Fintan Halpenny <fintan.halpenny@gmail.com>
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