src/tools/clippy/src/docs/return_self_not_must_use.txt

   1 ### What it does
   2 This lint warns when a method returning `Self` doesn't have the `#[must_use]` attribute.
   3
   4 ### Why is this bad?
   5 Methods returning `Self` often create new values, having the `#[must_use]` attribute
   6 prevents users from "forgetting" to use the newly created value.
   7
   8 The `#[must_use]` attribute can be added to the type itself to ensure that instances
   9 are never forgotten. Functions returning a type marked with `#[must_use]` will not be
  10 linted, as the usage is already enforced by the type attribute.
  11
  12 ### Limitations
  13 This lint is only applied on methods taking a `self` argument. It would be mostly noise
  14 if it was added on constructors for example.
  15
  16 ### Example
  17 ```
  18 pub struct Bar;
  19 impl Bar {
  20     // Missing attribute
  21     pub fn bar(&self) -> Self {
  22         Self
  23     }
  24 }
  25 ```
  26
  27 Use instead:
  28 ```
  29 // It's better to have the `#[must_use]` attribute on the method like this:
  30 pub struct Bar;
  31 impl Bar {
  32     #[must_use]
  33     pub fn bar(&self) -> Self {
  34         Self
  35     }
  36 }
  37
  38 // Or on the type definition like this:
  39 #[must_use]
  40 pub struct Bar;
  41 impl Bar {
  42     pub fn bar(&self) -> Self {
  43         Self
  44     }
  45 }
  46 ```