Closed as not planned
Description
openedon May 14, 2024
What it does
Check for trivial functions marked pub that aren't marked #[inline] (or #[inline(always)] or #[inline(never)]).
Related issue:
Advantage
Adding #[inline] to trivial methods can have a huge effect on performance when the methods are called cross-crate and LTO is not enabled.
The Rust compilers sometimes auto-inlines some of these methods, but not reliably so (at least not yet).
Drawbacks
Defining what makes for a "trivial" function will not be easy. Suggestion is to only trigger the lint if the function restricts itself to:
- constructs/destruct an object
- gets/sets fields
- does at most one function call
- gets arguments and returns a value
Example
pub struct Foo {
name: String,
age: Option<i32>,
}
impl Foo {
pub fn new(name: String) -> Self {
Self { name, age: None }
}
pub fn with_age(mut self, age: i32) -> Self {
self.age = Some(age);
self
}
pub fn name(&self) -> &str {
self.name.as_str()
}
}
impl AsRef<str> for Foo {
fn as_ref(&self) -> &str {
self.as_str()
}
}Could be written as:
pub struct Foo {
name: String,
age: Option<i32>,
}
impl Foo {
#[inline]
pub fn new(name: String) -> Self {
Self { name, age: None }
}
#[inline]
pub fn with_age(mut self, age: i32) -> Self {
self.age = Some(age);
self
}
#[inline]
pub fn name(&self) -> &str {
self.name.as_str()
}
}
impl AsRef<str> for Foo {
#[inline]
fn as_ref(&self) -> &str {
self.as_str()
}
}A lot of people don't realize that #[inline] is also important when implementing simple trait functions like these, so that's why I'm calling it out explicitly.
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