map + pow to successor + mul

What it does

Use successor instead of map of pow to calculate pow, etc.

Lint Name

map_pow_to_successor

Category

perf

Advantage

• better perf, origin: $O(n * \log(n))$ , if use exponentiating by squaring. Now: $O(n)$

Drawbacks

Longer code.

Example

fn foo(y: u32) -> Vec<u32> {
    (0..).map(|i| y.pow(i)).take(5).collect()
}
fn main() {
    println!("{:?}", foo(7));
}

Could be written as:

use std::iter::successors;
fn foo(y: u32) -> Vec<u32> {
    successors(Some(1), |x| Some(y * x)).take(5).collect()
}
fn main() {
    println!("{:?}", foo(7));
}

Start with the issue's Rust examples and the proposed lint name, map_pow_to_successor; the payload does not identify an implementation file, test, or entry point. Done means adding this performance lint so the shown map of pow pattern is recognized and the successor-based alternative is covered by tests.