Fixtype of dynamic information about variables and constants.
This is a product type introduced by fty::defprod.
This captures the information associated to a variable or constant name in a dynamic environment. The information consists of the value stored in the variable or constant, and a flag indicating whether it is a variable or a constant.
Note that Leo has no undefined or null value: when a variable comes into existence, it immediately has a value. Thus, it is appropriate for this variable information to always have a value.
This fixtype is the dynamic counterpart of var/const-sinfo.