`.map(|x| x.into())` → `.map(Into::into)`

[fenollp]

What it does

This lint replaces the introduction of a simple closure with the named function that is being used in said closure.

Lint Name

replace_mapped_closure_with_into

Category

complexity

Advantage

• Reduces complexity of the map by introducing a common function name instead of a closure + identifier

Drawbacks

• May be less readable for newcomers.
• No performance drawback.

Example

impl IpResource {
    pub fn mac_address(&self) -> Option<MacAddr6> {
        self.mac_address.map(|x| x.into())
    }
}

Could be written as:

impl IpResource {
    pub fn mac_address(&self) -> Option<MacAddr6> {
        self.mac_address.map(Into::into)
    }
}

[Alexendoo]

There's an existing lint that covers this: redundant_closure_for_method_calls

It is in the pedantic category though so it doesn't warn by default - #4101

[samueltardieu]

Also note that, unlike in many functional languages, |x| f(x) cannot always be replaced by f (η-reduction) in Rust as f(x) might involve one or more reference and one dereference of x (such as &***x). Those dereferences/reference won't happen automatically when using only the function name, which wants the exact signature as declared.