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use ast::AttrStyle;
use clippy_utils::diagnostics::span_lint_and_sugg;
use rustc_ast as ast;
use rustc_errors::Applicability;
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
declare_clippy_lint! {
/// Checks for usage of the `#[allow]` attribute and suggests replacing it with
/// the `#[expect]` (See [RFC 2383](https://rust-lang.github.io/rfcs/2383-lint-reasons.html))
///
/// The expect attribute is still unstable and requires the `lint_reasons`
/// on nightly. It can be enabled by adding `#![feature(lint_reasons)]` to
/// the crate root.
///
/// This lint only warns outer attributes (`#[allow]`), as inner attributes
/// (`#![allow]`) are usually used to enable or disable lints on a global scale.
///
/// ### Why is this bad?
///
/// `#[expect]` attributes suppress the lint emission, but emit a warning, if
/// the expectation is unfulfilled. This can be useful to be notified when the
/// lint is no longer triggered.
///
/// ### Example
/// ```rust,ignore
/// #[allow(unused_mut)]
/// fn foo() -> usize {
/// let mut a = Vec::new();
/// a.len()
/// }
/// ```
/// Use instead:
/// ```rust,ignore
/// #![feature(lint_reasons)]
/// #[expect(unused_mut)]
/// fn foo() -> usize {
/// let mut a = Vec::new();
/// a.len()
/// }
/// ```
#[clippy::version = "1.69.0"]
pub ALLOW_ATTRIBUTES,
restriction,
"`#[allow]` will not trigger if a warning isn't found. `#[expect]` triggers if there are no warnings."
}
declare_lint_pass!(AllowAttribute => [ALLOW_ATTRIBUTES]);
impl LateLintPass<'_> for AllowAttribute {
// Separate each crate's features.
fn check_attribute(&mut self, cx: &LateContext<'_>, attr: &ast::Attribute) {
if_chain! {
if cx.tcx.features().lint_reasons;
if let AttrStyle::Outer = attr.style;
if let Some(ident) = attr.ident();
if ident.name == rustc_span::symbol::sym::allow;
then {
span_lint_and_sugg(
cx,
ALLOW_ATTRIBUTES,
ident.span,
"#[allow] attribute found",
"replace it with",
"expect".into(),
Applicability::MachineApplicable,
);
}
}
}
}
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