Fixtype of dynamic information for functions.
This is a product type introduced by fty::defprod.
This captures the information associated to a function in a dynamic environment for functions. The information consists of the inputs of the function (well captured by function parameters in the abstract syntax), the output type of the function, and the body of the function. The name of the function is outside this function information, so that we can define finite maps: see function-denv.
This function information is the same as in function definitions in the abstract syntax (see fundecl).