Needless call of to_vec() on temporary Vec

[Kixunil]

What it does

When to_vec() is called on temporary Vec<_> the lint should warn that to_vec() is not needed and causes extra allocation. (Suggesting removing it.)

Categories

• Kind: performance

What is the advantage of the recommended code over the original code

• One less allocation
• More concise code (the returned value is already a Vec<_>)

Drawbacks

None.

Example

(playground)

fn create_vec() -> Vec<u8> {
    vec![1, 2, 42]
}

fn main() {
    println!("{:?}", create_vec().to_vec());
}

Could be written as:

fn create_vec() -> Vec<u8> {
    vec![1, 2, 42]
}

fn main() {
    println!("{:?}", create_vec());
}

[camsteffen]

This can be an enhancement of redundant_clone. And it should share logic with implicit_clone.

[tyilo]

This can be an enhancement of redundant_clone. And it should share logic with implicit_clone.

As redundant_clone has been moved to the nursery, would it make sense to create a new lint for this?
I don't see how this could trigger false positives.