What it does

Arguments that are used only in recursion to itself.
Since it is used, the warning unused_variables does not come out, but it is useless.

Lint Name

only_used_in_recursion

Category

perf

Advantage

• Lowers the complexity of the function.
• Better performance when the useless argument have some operation (like below example)

Drawbacks

No response

Example

fn f(a: usize, b: usize) -> usize { if a == 0 { 1 } else { f(a - 1, b + 1) } } fn main() { print!("{}", f(1, 1)); }

Could be written as:

fn f(a: usize) -> usize { if a == 0 { 1 } else { f(a - 1) } } fn main() { print!("{}", f(1)); }