"Btw I use Rust".
I don't get your analogy.
How do you know someone uses "X"? Don't worry, they'll tell you.
The desk sergeant asks, "Can you describe the mugger?"
"Not really, he grabbed me from behind. I know he's a man, bigger than me, and he's vegan."
"How on earth do you know he's vegan?"
"He bloody told me!"