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Edit documentation for for_loop_over_fallibles lint

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Maybe Waffle 2022-08-14 21:42:29 +04:00
parent 75ae20a42f
commit b9b2059e84
1 changed files with 21 additions and 23 deletions
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44
compiler/rustc_lint/src/for_loop_over_fallibles.rs
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@ -10,43 +10,41 @@ use rustc_span::{sym, Span};
use rustc_trait_selection::traits::TraitEngineExt;
declare_lint! {
/// ### What it does
///
/// Checks for `for` loops over `Option` or `Result` values.
///
/// ### Why is this bad?
/// Readability. This is more clearly expressed as an `if
/// let`.
/// ### Explanation
///
/// Both `Option` and `Result` implement `IntoIterator` trait, which allows using them in a `for` loop.
/// `for` loop over `Option` or `Result` will iterate either 0 (if the value is `None`/`Err(_)`)
/// or 1 time (if the value is `Some(_)`/`Ok(_)`). This is not very useful and is more clearly expressed
/// via `if let`.
///
/// `for` loop can also be accidentally written with the intention to call a function multiple times,
/// while the function returns `Some(_)`, in these cases `while let` loop should be used instead.
///
/// The "intended" use of `IntoIterator` implementations for `Option` and `Result` is passing them to
/// generic code that expects something implementing `IntoIterator`. For example using `.chain(option)`
/// to optionally add a value to an iterator.
///
/// ### Example
///
/// ```rust
/// # let opt = Some(1);
/// # let res: Result<i32, std::io::Error> = Ok(1);
/// for x in opt {
/// // ..
/// }
///
/// for x in &res {
/// // ..
/// }
///
/// for x in res.iter() {
/// // ..
/// }
/// # let recv = || Some(1);
/// for x in opt { /* ... */}
/// for x in res { /* ... */ }
/// for x in recv() { /* ... */ }
/// ```
///
/// Use instead:
/// ```rust
/// # let opt = Some(1);
/// # let res: Result<i32, std::io::Error> = Ok(1);
/// if let Some(x) = opt {
/// // ..
/// }
///
/// if let Ok(x) = res {
/// // ..
/// }
/// # let recv = || Some(1);
/// if let Some(x) = opt { /* ... */}
/// if let Ok(x) = res { /* ... */ }
/// while let Some(x) = recv() { /* ... */ }
/// ```
pub FOR_LOOP_OVER_FALLIBLES,
Warn,