Lint for Min/Max If Statements

[mmstick]

Clippy should be able to detect instances where an if statement is being used to calculate the min or max of two or more values and recommend using the cmp::min/max functions instead. These two examples were taken from real-world code directly translated from C into Rust.

Example 1:

Unnecessary

let mut x = if a < b { a } else { b };
if x > y { x = y; }

Recommended

let x = cmp::min(cmp::min(a ,b), y);

Example 2:

Unnecessary

let mut count = (sum + stride / 2) / stride;
if count < 1 { count = 1; }
if sum == 0 { count = 0; }

Recommended

let count = if sum == 0 { 0 } else { cmp::max((sum + stride / 2) / stride, 1) };

[mcarton]

let x = cmp::min(cmp::min(a ,b), y);

could even be [a, b, y].iter().min().unwrap() which is better IMO.

[mmstick]

Although I don't know how I feel about it requring unwrap(). In what scenario would it return None?

[mcarton]

[].iter().min()

[shepmaster]

I'd disagree that the iterator version is better. It introduces the potential for failure (the unwrap) when the original one didn't have that potential. Chained min or max calls would be better.

[mcarton]

The failure case would be using .iter().min() on an empty array, it's not a problem here. Anyway, we can also suggest both and let the user choose.