Auto merge of rust-lang#120924 - xFrednet:rfc-2383-stabilization-party, r=Urgau,blyxyas

Let's `#[expect]` some lints: Stabilize `lint_reasons` (RFC 2383)

Let's give this another try! The [previous stabilization attempt](rust-lang#99063) was stalled by some unresolved questions. These have been discussed in a [lang team](rust-lang/lang-team#191) meeting. The last open question, regarding the semantics of the `#[expect]` attribute was decided on in rust-lang#115980

I've just updated the [stabilization report](rust-lang#54503 (comment)) with the discussed questions and decisions. Luckily, the decision is inline with the current implementation.

This hopefully covers everything. Let's hope that the CI will be green like the spring.

fixes rust-lang#115980
fixes rust-lang#54503

---

r? `@wesleywiser`

Tacking Issue: rust-lang#54503
Stabilization Report: rust-lang#54503 (comment)
Documentation Update: rust-lang/reference#1237

<!--
For Clippy:

changelog: [`allow_attributes`]: Is now available on stable, since the `lint_reasons` feature was stabilized
changelog: [`allow_attributes_without_reason`]: Is now available on stable, since the `lint_reasons` feature was stabilized
-->

---

Roses are red,
Violets are blue,
Let's expect lints,
With reason clues

Author: bors

Diff for: CHANGELOG.md

@@ -1943,7 +1943,7 @@ Released 2022-05-19
   [#8218](https://github.com/rust-lang/rust-clippy/pull/8218)
 * [`needless_match`]
   [#8471](https://github.com/rust-lang/rust-clippy/pull/8471)
-* [`allow_attributes_without_reason`] (Requires `#![feature(lint_reasons)]`)
+* [`allow_attributes_without_reason`]
   [#8504](https://github.com/rust-lang/rust-clippy/pull/8504)
 * [`print_in_format_impl`]
   [#8253](https://github.com/rust-lang/rust-clippy/pull/8253)

Diff for: book/src/lint_configuration.md

@@ -669,6 +669,8 @@ The minimum rust version that the project supports. Defaults to the `rust-versio
 
 ---
 **Affected lints:**
+* [`allow_attributes`](https://rust-lang.github.io/rust-clippy/master/index.html#allow_attributes)
+* [`allow_attributes_without_reason`](https://rust-lang.github.io/rust-clippy/master/index.html#allow_attributes_without_reason)
 * [`almost_complete_range`](https://rust-lang.github.io/rust-clippy/master/index.html#almost_complete_range)
 * [`approx_constant`](https://rust-lang.github.io/rust-clippy/master/index.html#approx_constant)
 * [`assigning_clones`](https://rust-lang.github.io/rust-clippy/master/index.html#assigning_clones)

Diff for: clippy_config/src/conf.rs

@@ -265,7 +265,7 @@ define_Conf! {
     ///
     /// Suppress lints whenever the suggested change would cause breakage for other crates.
     (avoid_breaking_exported_api: bool = true),
-    /// Lint: MANUAL_SPLIT_ONCE, MANUAL_STR_REPEAT, CLONED_INSTEAD_OF_COPIED, REDUNDANT_FIELD_NAMES, OPTION_MAP_UNWRAP_OR, REDUNDANT_STATIC_LIFETIMES, FILTER_MAP_NEXT, CHECKED_CONVERSIONS, MANUAL_RANGE_CONTAINS, USE_SELF, MEM_REPLACE_WITH_DEFAULT, MANUAL_NON_EXHAUSTIVE, OPTION_AS_REF_DEREF, MAP_UNWRAP_OR, MATCH_LIKE_MATCHES_MACRO, MANUAL_STRIP, MISSING_CONST_FOR_FN, UNNESTED_OR_PATTERNS, FROM_OVER_INTO, PTR_AS_PTR, IF_THEN_SOME_ELSE_NONE, APPROX_CONSTANT, DEPRECATED_CFG_ATTR, INDEX_REFUTABLE_SLICE, MAP_CLONE, BORROW_AS_PTR, MANUAL_BITS, ERR_EXPECT, CAST_ABS_TO_UNSIGNED, UNINLINED_FORMAT_ARGS, MANUAL_CLAMP, MANUAL_LET_ELSE, UNCHECKED_DURATION_SUBTRACTION, COLLAPSIBLE_STR_REPLACE, SEEK_FROM_CURRENT, SEEK_REWIND, UNNECESSARY_LAZY_EVALUATIONS, TRANSMUTE_PTR_TO_REF, ALMOST_COMPLETE_RANGE, NEEDLESS_BORROW, DERIVABLE_IMPLS, MANUAL_IS_ASCII_CHECK, MANUAL_REM_EUCLID, MANUAL_RETAIN, TYPE_REPETITION_IN_BOUNDS, TUPLE_ARRAY_CONVERSIONS, MANUAL_TRY_FOLD, MANUAL_HASH_ONE, ITER_KV_MAP, MANUAL_C_STR_LITERALS, ASSIGNING_CLONES, LEGACY_NUMERIC_CONSTANTS.
+    /// Lint: MANUAL_SPLIT_ONCE, MANUAL_STR_REPEAT, CLONED_INSTEAD_OF_COPIED, REDUNDANT_FIELD_NAMES, OPTION_MAP_UNWRAP_OR, REDUNDANT_STATIC_LIFETIMES, FILTER_MAP_NEXT, CHECKED_CONVERSIONS, MANUAL_RANGE_CONTAINS, USE_SELF, MEM_REPLACE_WITH_DEFAULT, MANUAL_NON_EXHAUSTIVE, OPTION_AS_REF_DEREF, MAP_UNWRAP_OR, MATCH_LIKE_MATCHES_MACRO, MANUAL_STRIP, MISSING_CONST_FOR_FN, UNNESTED_OR_PATTERNS, FROM_OVER_INTO, PTR_AS_PTR, IF_THEN_SOME_ELSE_NONE, APPROX_CONSTANT, DEPRECATED_CFG_ATTR, INDEX_REFUTABLE_SLICE, MAP_CLONE, BORROW_AS_PTR, MANUAL_BITS, ERR_EXPECT, CAST_ABS_TO_UNSIGNED, UNINLINED_FORMAT_ARGS, MANUAL_CLAMP, MANUAL_LET_ELSE, UNCHECKED_DURATION_SUBTRACTION, COLLAPSIBLE_STR_REPLACE, SEEK_FROM_CURRENT, SEEK_REWIND, UNNECESSARY_LAZY_EVALUATIONS, TRANSMUTE_PTR_TO_REF, ALMOST_COMPLETE_RANGE, NEEDLESS_BORROW, DERIVABLE_IMPLS, MANUAL_IS_ASCII_CHECK, MANUAL_REM_EUCLID, MANUAL_RETAIN, TYPE_REPETITION_IN_BOUNDS, TUPLE_ARRAY_CONVERSIONS, MANUAL_TRY_FOLD, MANUAL_HASH_ONE, ITER_KV_MAP, MANUAL_C_STR_LITERALS, ASSIGNING_CLONES, LEGACY_NUMERIC_CONSTANTS, ALLOW_ATTRIBUTES, ALLOW_ATTRIBUTES_WITHOUT_REASON.
     ///
     /// The minimum rust version that the project supports. Defaults to the `rust-version` field in `Cargo.toml`
     #[default_text = ""]

Diff for: clippy_config/src/msrvs.rs

@@ -17,6 +17,7 @@ macro_rules! msrv_aliases {
 
 // names may refer to stabilized feature flags or library items
 msrv_aliases! {
+    1,81,0  { LINT_REASONS_STABILIZATION }
     1,77,0 { C_STR_LITERALS }
     1,76,0 { PTR_FROM_REF }
     1,71,0 { TUPLE_ARRAY_CONVERSIONS, BUILD_HASHER_HASH_ONE }

Diff for: clippy_lints/src/allow_attributes.rs

@@ -0,0 +1,26 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::is_from_proc_macro;
+use rustc_ast::{AttrStyle, Attribute};
+use rustc_errors::Applicability;
+use rustc_lint::{LateContext, LintContext};
+use rustc_middle::lint::in_external_macro;
+use super::ALLOW_ATTRIBUTES;
+
+// Separate each crate's features.
+pub fn check<'cx>(cx: &LateContext<'cx>, attr: &'cx Attribute) {
+    if !in_external_macro(cx.sess(), attr.span)
+        && let AttrStyle::Outer = attr.style
+        && let Some(ident) = attr.ident()
+        && !is_from_proc_macro(cx, &attr)
+    {
+        span_lint_and_sugg(
+            cx,
+            ALLOW_ATTRIBUTES,
+            ident.span,
+            "#[allow] attribute found",
+            "replace it with",
+            "expect".into(),
+            Applicability::MachineApplicable,
+        );
+    }
+}

Diff for: clippy_lints/src/attrs/allow_attributes.rs

@@ -8,11 +8,6 @@ use rustc_span::sym;
 use rustc_span::symbol::Symbol;
 
 pub(super) fn check<'cx>(cx: &LateContext<'cx>, name: Symbol, items: &[NestedMetaItem], attr: &'cx Attribute) {
-    // Check for the feature
-    if !cx.tcx.features().lint_reasons {
-        return;
-    }
-
     // Check if the reason is present
     if let Some(item) = items.last().and_then(NestedMetaItem::meta_item)
         && let MetaItemKind::NameValue(_) = &item.kind

Diff for: clippy_lints/src/attrs/allow_attributes_without_reason.rs

@@ -1,6 +1,7 @@
 //! checks for attributes
 
 mod allow_attributes_without_reason;
+mod allow_attributes;
 mod blanket_clippy_restriction_lints;
 mod deprecated_cfg_attr;
 mod deprecated_semver;
@@ -14,11 +15,11 @@ mod unnecessary_clippy_cfg;
 mod useless_attribute;
 mod utils;
 
-use clippy_config::msrvs::Msrv;
+use clippy_config::msrvs::{self, Msrv};
 use rustc_ast::{Attribute, MetaItemKind, NestedMetaItem};
 use rustc_hir::{ImplItem, Item, ItemKind, TraitItem};
 use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass};
-use rustc_session::{declare_lint_pass, impl_lint_pass};
+use rustc_session::impl_lint_pass;
 use rustc_span::sym;
 use utils::{is_lint_level, is_relevant_impl, is_relevant_item, is_relevant_trait};
 
@@ -272,23 +273,17 @@ declare_clippy_lint! {
     /// ### What it does
     /// Checks for attributes that allow lints without a reason.
     ///
-    /// (This requires the `lint_reasons` feature)
-    ///
     /// ### Why restrict this?
     /// Justifying each `allow` helps readers understand the reasoning,
     /// and may allow removing `allow` attributes if their purpose is obsolete.
     ///
     /// ### Example
     /// ```no_run
-    /// #![feature(lint_reasons)]
-    ///
     /// #![allow(clippy::some_lint)]
     /// ```
     ///
     /// Use instead:
     /// ```no_run
-    /// #![feature(lint_reasons)]
-    ///
     /// #![allow(clippy::some_lint, reason = "False positive rust-lang/rust-clippy#1002020")]
     /// ```
     #[clippy::version = "1.61.0"]
@@ -297,6 +292,41 @@ declare_clippy_lint! {
     "ensures that all `allow` and `expect` attributes have a reason"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// 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))
+    ///
+    /// 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
+    /// #[expect(unused_mut)]
+    /// fn foo() -> usize {
+    ///     let mut a = Vec::new();
+    ///     a.len()
+    /// }
+    /// ```
+    #[clippy::version = "1.70.0"]
+    pub ALLOW_ATTRIBUTES,
+    restriction,
+    "`#[allow]` will not trigger if a warning isn't found. `#[expect]` triggers if there are no warnings."
+}
+
 declare_clippy_lint! {
     /// ### What it does
     /// Checks for `#[should_panic]` attributes without specifying the expected panic message.
@@ -469,7 +499,12 @@ declare_clippy_lint! {
     "duplicated attribute"
 }
 
-declare_lint_pass!(Attributes => [
+#[derive(Clone)]
+pub struct Attributes {
+    msrv: Msrv,
+}
+
+impl_lint_pass!(Attributes => [
     ALLOW_ATTRIBUTES_WITHOUT_REASON,
     INLINE_ALWAYS,
     DEPRECATED_SEMVER,
@@ -480,6 +515,13 @@ declare_lint_pass!(Attributes => [
     DUPLICATED_ATTRIBUTES,
 ]);
 
+impl Attributes {
+    #[must_use]
+    pub fn new(msrv: Msrv) -> Self {
+        Self { msrv }
+    }
+}
+
 impl<'tcx> LateLintPass<'tcx> for Attributes {
     fn check_crate(&mut self, cx: &LateContext<'tcx>) {
         blanket_clippy_restriction_lints::check_command_line(cx);
@@ -492,8 +534,15 @@ impl<'tcx> LateLintPass<'tcx> for Attributes {
                 if is_lint_level(ident.name, attr.id) {
                     blanket_clippy_restriction_lints::check(cx, ident.name, items);
                 }
+                if matches!(ident.name, sym::allow) {
+                    if self.msrv.meets(msrvs::LINT_REASONS_STABILIZATION) {
+                        allow_attributes::check(cx, attr);
+                    }
+                }
                 if matches!(ident.name, sym::allow | sym::expect) {
-                    allow_attributes_without_reason::check(cx, ident.name, items, attr);
+                    if self.msrv.meets(msrvs::LINT_REASONS_STABILIZATION) {
+                        allow_attributes_without_reason::check(cx, ident.name, items, attr);
+                    }
                 }
                 if items.is_empty() || !attr.has_name(sym::deprecated) {
                     return;
@@ -537,6 +586,8 @@ impl<'tcx> LateLintPass<'tcx> for Attributes {
             inline_always::check(cx, item.span, item.ident.name, cx.tcx.hir().attrs(item.hir_id()));
         }
     }
+
+    extract_msrv_attr!(LateContext);
 }
 
 pub struct EarlyAttributes {

Diff for: clippy_lints/src/attrs/mod.rs

@@ -38,7 +38,6 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     #[cfg(feature = "internal")]
     crate::utils::internal_lints::unsorted_clippy_utils_paths::UNSORTED_CLIPPY_UTILS_PATHS_INFO,
     crate::absolute_paths::ABSOLUTE_PATHS_INFO,
-    crate::allow_attributes::ALLOW_ATTRIBUTES_INFO,
     crate::almost_complete_range::ALMOST_COMPLETE_RANGE_INFO,
     crate::approx_const::APPROX_CONSTANT_INFO,
     crate::arc_with_non_send_sync::ARC_WITH_NON_SEND_SYNC_INFO,
@@ -49,6 +48,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::assertions_on_result_states::ASSERTIONS_ON_RESULT_STATES_INFO,
     crate::assigning_clones::ASSIGNING_CLONES_INFO,
     crate::async_yields_async::ASYNC_YIELDS_ASYNC_INFO,
+    crate::attrs::ALLOW_ATTRIBUTES_INFO,
     crate::attrs::ALLOW_ATTRIBUTES_WITHOUT_REASON_INFO,
     crate::attrs::BLANKET_CLIPPY_RESTRICTION_LINTS_INFO,
     crate::attrs::DEPRECATED_CFG_ATTR_INFO,

Diff for: clippy_lints/src/declared_lints.rs

@@ -6,7 +6,7 @@
 #![feature(if_let_guard)]
 #![feature(iter_intersperse)]
 #![feature(let_chains)]
-#![feature(lint_reasons)]
+#![cfg_attr(bootstrap, feature(lint_reasons))]
 #![feature(never_type)]
 #![feature(rustc_private)]
 #![feature(stmt_expr_attributes)]
@@ -73,7 +73,6 @@ mod renamed_lints;
 
 // begin lints modules, do not remove this comment, it’s used in `update_lints`
 mod absolute_paths;
-mod allow_attributes;
 mod almost_complete_range;
 mod approx_const;
 mod arc_with_non_send_sync;
@@ -699,7 +698,7 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     store.register_late_pass(|_| Box::new(mut_reference::UnnecessaryMutPassed));
     store.register_late_pass(|_| Box::<significant_drop_tightening::SignificantDropTightening<'_>>::default());
     store.register_late_pass(|_| Box::new(len_zero::LenZero));
-    store.register_late_pass(|_| Box::new(attrs::Attributes));
+    store.register_late_pass(move |_| Box::new(attrs::Attributes::new(msrv())));
     store.register_late_pass(|_| Box::new(blocks_in_conditions::BlocksInConditions));
     store.register_late_pass(|_| Box::new(unicode::Unicode));
     store.register_late_pass(|_| Box::new(uninit_vec::UninitVec));
@@ -1065,7 +1064,6 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     store.register_late_pass(|_| Box::new(needless_maybe_sized::NeedlessMaybeSized));
     store.register_late_pass(|_| Box::new(redundant_async_block::RedundantAsyncBlock));
     store.register_late_pass(|_| Box::new(let_with_type_underscore::UnderscoreTyped));
-    store.register_late_pass(|_| Box::new(allow_attributes::AllowAttribute));
     store.register_late_pass(move |_| Box::new(manual_main_separator_str::ManualMainSeparatorStr::new(msrv())));
     store.register_late_pass(|_| Box::new(unnecessary_struct_initialization::UnnecessaryStruct));
     store.register_late_pass(move |_| {

Diff for: clippy_lints/src/lib.rs

@@ -5,7 +5,7 @@
 #![feature(f16)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
-#![feature(lint_reasons)]
+#![cfg_attr(bootstrap, feature(lint_reasons))]
 #![feature(never_type)]
 #![feature(rustc_private)]
 #![feature(assert_matches)]

Diff for: clippy_utils/src/lib.rs

@@ -2,7 +2,7 @@
 #![allow(rustc::untranslatable_diagnostic)]
 #![feature(rustc_private)]
 #![feature(let_chains)]
-#![feature(lint_reasons)]
+#![cfg_attr(bootstrap, feature(lint_reasons))]
 #![cfg_attr(feature = "deny-warnings", deny(warnings))]
 // warn on lints, that are included in `rust-lang/rust`s bootstrap
 #![warn(rust_2018_idioms, unused_lifetimes)]

Diff for: src/driver.rs

@@ -1,4 +1,3 @@
-#![feature(lint_reasons)]
 
 mod a;
 

Diff for: tests/ui-cargo/duplicate_mod/fail/src/main.rs

@@ -1,5 +1,5 @@
 //! Tests macro_metavars_in_unsafe with default configuration
-#![feature(decl_macro, lint_reasons)]
+#![feature(decl_macro)]
 #![warn(clippy::macro_metavars_in_unsafe)]
 #![allow(clippy::no_effect)]