I agree with you: no matter how good of a job the code (by construction or types or otherwise) does of “making unsafe states unrepresentable”, that in no way makes a real world complex system “safe” by itself.
Code can be structured so that valves may only be open OR closed, but nothing stops the real world from returning a sensor reading that says “the valve is <undefined>”. To remain a “safe” system, the system must deal with inconsistent states like “heisen-valves”.
I agree with you: no matter how good of a job the code (by construction or types or otherwise) does of “making unsafe states unrepresentable”, that in no way makes a real world complex system “safe” by itself.
Code can be structured so that valves may only be open OR closed, but nothing stops the real world from returning a sensor reading that says “the valve is <undefined>”. To remain a “safe” system, the system must deal with inconsistent states like “heisen-valves”.