1 files changed, 71 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/allow_attributes.rs b/src/tools/clippy/clippy_lints/src/allow_attributes.rs
new file mode 100644
index 000000000..15d46e954
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/allow_attributes.rs
@@ -0,0 +1,71 @@
+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! {
+    /// Detects uses 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,
+                );
+            }
+        }
+    }
+}