Is "should never run" more appropriate than "should never be able to run"?

Question

There seems to be some errors in this post. I am trying to fix some.

It may be a pain to see compile errors, but trust me, getting error here is good for you. You did something stupid you tried to compare string with int and decide which one is equal. This does not make any sense to the computer most of the time (nor does it make sense to human), so you should never be able to run program like this. Computer says “No!” and you have to cope with that.

Consider this part "should never be able to run program like this".

Per Oxford dictionary "able to" means "competent to", "capable of".

I guess this expression "You could be able to run program like this but you shout never do" is more appropriate and clear than the original one, is it?

Answer 1

The phrase 'you should never be able to run...' in this context is using 'should' in the sense of what is allowed. (The particular phrase 'computer says no' is a reference to a catch-phrase in a television comedy sketch programme in the UK. But that is irrelevant to answering your question.)

The writer is saying that it is good, though irritating, when your computer program issues an error if you ask it to add 3 oranges to 4 lemons. If your computer tried to run such a request without complaining then the result , '7 oranges' say, would be meaningless and you might then go on to make horrible mistakes in your further work.

Answer 2

You should never run your car’s engine without enough engine oil - this makes sense, doing so would damage the car, don’t do it.

Now say you have a more advanced car where an attempt to start the engine without enough engine oil will fail, by design. You can try, but the engine won’t start. In this case: You shouldn’t be able to start the engine.