Before, when the type was determined, it was assumed that the method can be resolved. But off course tis is not true, as methods may be defined later in the file.
Two solutions for that. One could (and should) define all methods and only then start to compile. Thus having the type safety.
Or (as now) make a dynamic call and let it fail at runtime.
Since Builtin generates risc, just like mom instructions, it was a design mistake to put builtin into risc in the first place. Now that borders are coming more into focus, it make much more sense to have the builtin in mom.
In fact the instructions should be moved out and a seperate invocation mechanism used , so functions can be parsed, not generated (wip)