A fixed string search interpolator is permanently bound to a given set of value sources,
an is totally fixed and stateless over these value sources.
The fixed interpolator is also a #StatelessValueSource and can be used as a source
for a different fixed interpolator, creating a scope chain.
Once constructed, this interpolator will always point to the same set of objects (value sources),
in such a way that if the underlying object is fixed, expressions will always
evaluate to the same result.
Th fixed interpolator can be shared among different clients and is thread safe to
the extent the underlying value sources can be accessed safely.
Since interpolation expressions cannot modify the objects, thread safety concerns
this will normally be limited to safe publication and memory model visibility of
The fixed interpolator can be a valuesource