Auto merge of rust-lang#8797 - xFrednet:0000-expect-a-playground, r=flip1995

Replace `#[allow]` with `#[expect]` in Clippy

Hey `@rust-lang/clippy,` `@Alexendoo,` `@dswij,` I'm currently working on the expect attribute as defined in [Rust RFC 2383](https://rust-lang.github.io/rfcs/2383-lint-reasons.html). With that, an `#[allow]` attribute can be replaced with a `#[expect]` attribute that suppresses the lint, but also emits a warning, if the lint isn't emitted in the expected scope.

With this PR I would like to test the attribute on a project scale and Clippy obviously came to mind. This PR replaces (almost) all `#[allow]` attributes in `clippy_utils` and `clippy_lints` with the `#[expect]` attribute. I was also able to remove some allows since, the related FPs have been fixed 🎉.

My question is now, are there any concerns regarding this? It's still okay to add normal `#[allow]` attributes, I see the need to nit-pick about that in new PRs, unless it's actually a FP. Also, I would not recommend using `#[expect]` in tests, as changes to a lint could the trigger the expect attribute in other files.

Additionally, I've noticed that Clippy has a bunch of `#[allow(clippy::too_many_lines)]` attributes. Should we maybe allow the lint all together or increase the threshold setting? To me, it seems like we mostly just ignore it in our code. 😅 🙃

---

changelog: none

r? `@flip1995` (I've requested you for now, since you're also helping with reviewing the expect implementation. You are welcome to delegate this PR, even if it should be a simple review 🙃 )

Author: bors

clippy_lints/src/booleans.rs

@@ -137,7 +137,7 @@ impl<'a, 'tcx, 'v> Hir2Qmm<'a, 'tcx, 'v> {
         }
         for (n, expr) in self.terminals.iter().enumerate() {
             if eq_expr_value(self.cx, e, expr) {
-                #[allow(clippy::cast_possible_truncation)]
+                #[expect(clippy::cast_possible_truncation)]
                 return Ok(Bool::Term(n as u8));
             }
 
@@ -149,15 +149,15 @@ impl<'a, 'tcx, 'v> Hir2Qmm<'a, 'tcx, 'v> {
                 if eq_expr_value(self.cx, e_lhs, expr_lhs);
                 if eq_expr_value(self.cx, e_rhs, expr_rhs);
                 then {
-                    #[allow(clippy::cast_possible_truncation)]
+                    #[expect(clippy::cast_possible_truncation)]
                     return Ok(Bool::Not(Box::new(Bool::Term(n as u8))));
                 }
             }
         }
         let n = self.terminals.len();
         self.terminals.push(e);
         if n < 32 {
-            #[allow(clippy::cast_possible_truncation)]
+            #[expect(clippy::cast_possible_truncation)]
             Ok(Bool::Term(n as u8))
         } else {
             Err("too many literals".to_owned())

clippy_lints/src/cognitive_complexity.rs

@@ -48,7 +48,7 @@ impl CognitiveComplexity {
 impl_lint_pass!(CognitiveComplexity => [COGNITIVE_COMPLEXITY]);
 
 impl CognitiveComplexity {
-    #[allow(clippy::cast_possible_truncation)]
+    #[expect(clippy::cast_possible_truncation)]
     fn check<'tcx>(
         &mut self,
         cx: &LateContext<'tcx>,
@@ -70,7 +70,7 @@ impl CognitiveComplexity {
         let ret_adjust = if is_type_diagnostic_item(cx, ret_ty, sym::Result) {
             returns
         } else {
-            #[allow(clippy::integer_division)]
+            #[expect(clippy::integer_division)]
             (returns / 2)
         };
 

clippy_lints/src/default.rs

@@ -110,7 +110,7 @@ impl<'tcx> LateLintPass<'tcx> for Default {
         }
     }
 
-    #[allow(clippy::too_many_lines)]
+    #[expect(clippy::too_many_lines)]
     fn check_block(&mut self, cx: &LateContext<'tcx>, block: &Block<'tcx>) {
         // start from the `let mut _ = _::default();` and look at all the following
         // statements, see if they re-assign the fields of the binding

clippy_lints/src/default_numeric_fallback.rs

@@ -116,7 +116,6 @@ impl<'a, 'tcx> NumericFallbackVisitor<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> Visitor<'tcx> for NumericFallbackVisitor<'a, 'tcx> {
-    #[allow(clippy::too_many_lines)]
     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
         match &expr.kind {
             ExprKind::Call(func, args) => {

clippy_lints/src/dereference.rs

@@ -168,7 +168,7 @@ struct RefPat {
 }
 
 impl<'tcx> LateLintPass<'tcx> for Dereferencing {
-    #[allow(clippy::too_many_lines)]
+    #[expect(clippy::too_many_lines)]
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         // Skip path expressions from deref calls. e.g. `Deref::deref(e)`
         if Some(expr.hir_id) == self.skip_expr.take() {
@@ -580,7 +580,7 @@ fn find_adjustments<'tcx>(
     }
 }
 
-#[allow(clippy::needless_pass_by_value)]
+#[expect(clippy::needless_pass_by_value)]
 fn report(cx: &LateContext<'_>, expr: &Expr<'_>, state: State, data: StateData) {
     match state {
         State::DerefMethod {

clippy_lints/src/doc.rs

@@ -198,7 +198,7 @@ declare_clippy_lint! {
     "presence of `fn main() {` in code examples"
 }
 
-#[allow(clippy::module_name_repetitions)]
+#[expect(clippy::module_name_repetitions)]
 #[derive(Clone)]
 pub struct DocMarkdown {
     valid_idents: FxHashSet<String>,
@@ -373,7 +373,7 @@ fn lint_for_missing_headers<'tcx>(
 /// `rustc_ast::parse::lexer::comments::strip_doc_comment_decoration` because we
 /// need to keep track of
 /// the spans but this function is inspired from the later.
-#[allow(clippy::cast_possible_truncation)]
+#[expect(clippy::cast_possible_truncation)]
 #[must_use]
 pub fn strip_doc_comment_decoration(doc: &str, comment_kind: CommentKind, span: Span) -> (String, Vec<(usize, Span)>) {
     // one-line comments lose their prefix
@@ -428,7 +428,7 @@ fn check_attrs<'a>(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, attrs
     /// We don't want the parser to choke on intra doc links. Since we don't
     /// actually care about rendering them, just pretend that all broken links are
     /// point to a fake address.
-    #[allow(clippy::unnecessary_wraps)] // we're following a type signature
+    #[expect(clippy::unnecessary_wraps)] // we're following a type signature
     fn fake_broken_link_callback<'a>(_: BrokenLink<'_>) -> Option<(CowStr<'a>, CowStr<'a>)> {
         Some(("fake".into(), "fake".into()))
     }

clippy_lints/src/double_comparison.rs

@@ -40,7 +40,7 @@ declare_clippy_lint! {
 declare_lint_pass!(DoubleComparisons => [DOUBLE_COMPARISONS]);
 
 impl<'tcx> DoubleComparisons {
-    #[allow(clippy::similar_names)]
+    #[expect(clippy::similar_names)]
     fn check_binop(cx: &LateContext<'tcx>, op: BinOpKind, lhs: &'tcx Expr<'_>, rhs: &'tcx Expr<'_>, span: Span) {
         let (lkind, llhs, lrhs, rkind, rlhs, rrhs) = match (&lhs.kind, &rhs.kind) {
             (ExprKind::Binary(lb, llhs, lrhs), ExprKind::Binary(rb, rlhs, rrhs)) => {

clippy_lints/src/entry.rs

@@ -63,7 +63,7 @@ declare_clippy_lint! {
 declare_lint_pass!(HashMapPass => [MAP_ENTRY]);
 
 impl<'tcx> LateLintPass<'tcx> for HashMapPass {
-    #[allow(clippy::too_many_lines)]
+    #[expect(clippy::too_many_lines)]
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         let (cond_expr, then_expr, else_expr) = match higher::If::hir(expr) {
             Some(higher::If { cond, then, r#else }) => (cond, then, r#else),
@@ -319,7 +319,7 @@ struct Insertion<'tcx> {
 ///   `or_insert_with`.
 /// * Determine if there's any sub-expression that can't be placed in a closure.
 /// * Determine if there's only a single insert statement. `or_insert` can be used in this case.
-#[allow(clippy::struct_excessive_bools)]
+#[expect(clippy::struct_excessive_bools)]
 struct InsertSearcher<'cx, 'tcx> {
     cx: &'cx LateContext<'tcx>,
     /// The map expression used in the contains call.

clippy_lints/src/enum_clike.rs

@@ -37,7 +37,7 @@ declare_clippy_lint! {
 declare_lint_pass!(UnportableVariant => [ENUM_CLIKE_UNPORTABLE_VARIANT]);
 
 impl<'tcx> LateLintPass<'tcx> for UnportableVariant {
-    #[allow(clippy::cast_possible_truncation, clippy::cast_possible_wrap, clippy::cast_sign_loss)]
+    #[expect(clippy::cast_possible_wrap)]
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
         if cx.tcx.data_layout.pointer_size.bits() != 64 {
             return;

clippy_lints/src/enum_variants.rs

@@ -240,7 +240,7 @@ impl LateLintPass<'_> for EnumVariantNames {
         assert!(last.is_some());
     }
 
-    #[allow(clippy::similar_names)]
+    #[expect(clippy::similar_names)]
     fn check_item(&mut self, cx: &LateContext<'_>, item: &Item<'_>) {
         let item_name = item.ident.name.as_str();
         let item_camel = to_camel_case(item_name);