19:18
<kriskowal>
I think that being able to completely virtualize that prototype attachment (i.e. have a hook for it) is neither needed nor desiderabile, but I'm happy to discuss it further :)
For the record, Nicolò convinced me of this last time we met. By introducing some opaque token for a cohort of disjoint prototypes, we can have the Module, Evaluators, and/or Compartment constructors designate which cohort of shared structs prototypes will be used in their lexical scope. I had already convinced myself that the mechanism for looking up the prototype was already lexical, so this mechanism would work fine for isolation.