unnecessary call to max function

[FelixMaetzler]

What it does

In todays AdventOfCode i caught myself using the below example.
The max() call of an unsigned number with 0 is unnecessary.
It would be nice if clippy would say something about that.

the maximum between 0 and an unsigned number is always the number.

Please let me know if i did anything wrong.
Have a nice day.

Advantage

• Remove of unnecessary function call
• Reduction of Code Complexity

Drawbacks

No response

Example

let x: usize = 5;
let y: usize = 8;
let ret = 0.max(x.saturating_sub(y));

Could be written as:

let x: usize = 5;
let y: usize = 8;
let ret = x.saturating_sub(y);

[kavania2002]

I would like to contribute in this issue if you don't mind.
Though I'll take some time as I'm new to this community but I am highly interested.

[FelixMaetzler]

Yeah feel free to do so.
I’m new to this community and “public” GitHub too.
I would love to see with what you come up with.

[FelixMaetzler]

I pushed the wrong button and I don’t know how to fix it.
Sorry

[kavania2002]

@rustbot claim

[kavania2002]

@FelixMaetzler so you meant to say that when you run the lint on

let x: usize = 5;
let y: usize = 8;
let ret = x.saturating_sub(y);

it changes to

let x: usize = 5;
let y: usize = 8;
let ret = 0.max(x.saturating_sub(y));

Am I going in the right direction?

[kavania2002]

Or do you mean that when someone runs cargo clippy on

let x: usize = 5;
let y: usize = 8;
let ret = 0.max(x.saturating_sub(y));

should give an error/warning?

[y21]

It should probably warn on 0.max(<anything>) yes. One can just use the argument directly. 0.max(x + y) is the same as x + y for unsigned integer types

[FelixMaetzler]

Or do you mean that when someone runs cargo clippy on

let x: usize = 5;
let y: usize = 8;
let ret = 0.max(x.saturating_sub(y));

should give an error/warning?

yes exactly that.

like @y21 said, you could generalize that to 0.max(<anything>) can be replaced by <anything> if <anything> evaluates (or is) an unsigned integer.
the part with the saturating_sub() was just my specific case, where i discovered that you don't need the max() method.

In my opinion this should give a similar/same cargo clippy output like following:

let b = 12 + 0;
dbg!(b);

[kavania2002]

Gotcha!