Do you mean a function which returns "nothing" in the sense that it does return but it has no particular value to return, like Vec::clear which gets rid of the values but preserves the capacity of the container ?
In Rust the return type of this function is the unit type, the empty tuple (). So, the variable has this type, there's no problem with this in Rust, even though some lesser languages can't handle the idea of a type this small.
Or did you mean a function which never returns, like std::process::exit ? In Rust this function's return type is ! the Never type, an empty type that you ordinarily can't name in stable Rust.
Because this type is empty, a variable of this type will evaporate, the compiler knows that we can't bring values into existence if there are no values of that type, the code paths in which this variable exists will never be executed, so no need to emit machine code.
In a language with generic programming like Rust this isn't an error, it's actually a convenience. We can write generic error handling code, and then for cases where there will never be an error our error handling code doesn't even compile, it evaporates entirely, yet for cases which can have actual errors, the error handling code is emitted.
In Rust the return type of this function is the unit type, the empty tuple (). So, the variable has this type, there's no problem with this in Rust, even though some lesser languages can't handle the idea of a type this small.
Or did you mean a function which never returns, like std::process::exit ? In Rust this function's return type is ! the Never type, an empty type that you ordinarily can't name in stable Rust.
Because this type is empty, a variable of this type will evaporate, the compiler knows that we can't bring values into existence if there are no values of that type, the code paths in which this variable exists will never be executed, so no need to emit machine code.
In a language with generic programming like Rust this isn't an error, it's actually a convenience. We can write generic error handling code, and then for cases where there will never be an error our error handling code doesn't even compile, it evaporates entirely, yet for cases which can have actual errors, the error handling code is emitted.