Auto merge of rust-lang#133234 - jhpratt:rollup-42dmg4p, r=jhpratt

Rollup of 5 pull requests

Successful merges:

 - rust-lang#132732 (Use attributes for `dangling_pointers_from_temporaries` lint)
 - rust-lang#133108 (lints_that_dont_need_to_run: never skip future-compat-reported lints)
 - rust-lang#133190 (CI: use free runner in dist-aarch64-msvc)
 - rust-lang#133196 (Make rustc --explain compatible with BusyBox less)
 - rust-lang#133216 (Implement `~const Fn` trait goal in the new solver)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

Diff for: compiler/rustc_driver_impl/src/lib.rs

@@ -577,7 +577,7 @@ fn show_md_content_with_pager(content: &str, color: ColorConfig) {
     let mut cmd = Command::new(&pager_name);
     // FIXME: find if other pagers accept color options
     let mut print_formatted = if pager_name == "less" {
-        cmd.arg("-r");
+        cmd.arg("-R");
         true
     } else {
         ["bat", "catbat", "delta"].iter().any(|v| *v == pager_name)

Diff for: compiler/rustc_feature/src/builtin_attrs.rs

@@ -879,6 +879,11 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         lang, Normal, template!(NameValueStr: "name"), DuplicatesOk, EncodeCrossCrate::No, lang_items,
         "lang items are subject to change",
     ),
+    rustc_attr!(
+        rustc_as_ptr, Normal, template!(Word), ErrorFollowing,
+        EncodeCrossCrate::Yes,
+        "#[rustc_as_ptr] is used to mark functions returning pointers to their inner allocations."
+    ),
     rustc_attr!(
         rustc_pass_by_value, Normal, template!(Word), ErrorFollowing,
         EncodeCrossCrate::Yes,

Diff for: compiler/rustc_lint/src/dangling.rs

@@ -43,13 +43,10 @@ declare_lint! {
 }
 
 /// FIXME: false negatives (i.e. the lint is not emitted when it should be)
-/// 1. Method calls that are not checked for:
-///    - [`temporary_unsafe_cell.get()`][`core::cell::UnsafeCell::get()`]
-///    - [`temporary_sync_unsafe_cell.get()`][`core::cell::SyncUnsafeCell::get()`]
-/// 2. Ways to get a temporary that are not recognized:
+/// 1. Ways to get a temporary that are not recognized:
 ///    - `owning_temporary.field`
 ///    - `owning_temporary[index]`
-/// 3. No checks for ref-to-ptr conversions:
+/// 2. No checks for ref-to-ptr conversions:
 ///    - `&raw [mut] temporary`
 ///    - `&temporary as *(const|mut) _`
 ///    - `ptr::from_ref(&temporary)` and friends
@@ -133,10 +130,11 @@ impl DanglingPointerSearcher<'_, '_> {
 
 fn lint_expr(cx: &LateContext<'_>, expr: &Expr<'_>) {
     if let ExprKind::MethodCall(method, receiver, _args, _span) = expr.kind
-        && matches!(method.ident.name, sym::as_ptr | sym::as_mut_ptr)
+        && let Some(fn_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
+        && cx.tcx.has_attr(fn_id, sym::rustc_as_ptr)
         && is_temporary_rvalue(receiver)
         && let ty = cx.typeck_results().expr_ty(receiver)
-        && is_interesting(cx.tcx, ty)
+        && owns_allocation(cx.tcx, ty)
     {
         // FIXME: use `emit_node_lint` when `#[primary_span]` is added.
         cx.tcx.emit_node_span_lint(
@@ -199,24 +197,25 @@ fn is_temporary_rvalue(expr: &Expr<'_>) -> bool {
     }
 }
 
-// Array, Vec, String, CString, MaybeUninit, Cell, Box<[_]>, Box<str>, Box<CStr>,
-// or any of the above in arbitrary many nested Box'es.
-fn is_interesting(tcx: TyCtxt<'_>, ty: Ty<'_>) -> bool {
+// Array, Vec, String, CString, MaybeUninit, Cell, Box<[_]>, Box<str>, Box<CStr>, UnsafeCell,
+// SyncUnsafeCell, or any of the above in arbitrary many nested Box'es.
+fn owns_allocation(tcx: TyCtxt<'_>, ty: Ty<'_>) -> bool {
     if ty.is_array() {
         true
     } else if let Some(inner) = ty.boxed_ty() {
         inner.is_slice()
             || inner.is_str()
             || inner.ty_adt_def().is_some_and(|def| tcx.is_lang_item(def.did(), LangItem::CStr))
-            || is_interesting(tcx, inner)
+            || owns_allocation(tcx, inner)
     } else if let Some(def) = ty.ty_adt_def() {
-        for lang_item in [LangItem::String, LangItem::MaybeUninit] {
+        for lang_item in [LangItem::String, LangItem::MaybeUninit, LangItem::UnsafeCell] {
             if tcx.is_lang_item(def.did(), lang_item) {
                 return true;
             }
         }
-        tcx.get_diagnostic_name(def.did())
-            .is_some_and(|name| matches!(name, sym::cstring_type | sym::Vec | sym::Cell))
+        tcx.get_diagnostic_name(def.did()).is_some_and(|name| {
+            matches!(name, sym::cstring_type | sym::Vec | sym::Cell | sym::SyncUnsafeCell)
+        })
     } else {
         false
     }

Diff for: compiler/rustc_lint/src/levels.rs

@@ -123,17 +123,19 @@ fn lints_that_dont_need_to_run(tcx: TyCtxt<'_>, (): ()) -> FxIndexSet<LintId> {
     let dont_need_to_run: FxIndexSet<LintId> = store
         .get_lints()
         .into_iter()
+        .filter(|lint| {
+            // Lints that show up in future-compat reports must always be run.
+            let has_future_breakage =
+                lint.future_incompatible.is_some_and(|fut| fut.reason.has_future_breakage());
+            !has_future_breakage && !lint.eval_always
+        })
         .filter_map(|lint| {
-            if !lint.eval_always {
-                let lint_level = map.lint_level_id_at_node(tcx, LintId::of(lint), CRATE_HIR_ID);
-                if matches!(lint_level, (Level::Allow, ..))
-                    || (matches!(lint_level, (.., LintLevelSource::Default)))
-                        && lint.default_level(tcx.sess.edition()) == Level::Allow
-                {
-                    Some(LintId::of(lint))
-                } else {
-                    None
-                }
+            let lint_level = map.lint_level_id_at_node(tcx, LintId::of(lint), CRATE_HIR_ID);
+            if matches!(lint_level, (Level::Allow, ..))
+                || (matches!(lint_level, (.., LintLevelSource::Default)))
+                    && lint.default_level(tcx.sess.edition()) == Level::Allow
+            {
+                Some(LintId::of(lint))
             } else {
                 None
             }

Diff for: compiler/rustc_lint_defs/src/lib.rs

@@ -466,6 +466,20 @@ impl FutureIncompatibilityReason {
             | FutureIncompatibilityReason::Custom(_) => None,
         }
     }
+
+    pub fn has_future_breakage(self) -> bool {
+        match self {
+            FutureIncompatibilityReason::FutureReleaseErrorReportInDeps => true,
+
+            FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps
+            | FutureIncompatibilityReason::FutureReleaseSemanticsChange
+            | FutureIncompatibilityReason::EditionError(_)
+            | FutureIncompatibilityReason::EditionSemanticsChange(_)
+            | FutureIncompatibilityReason::EditionAndFutureReleaseError(_)
+            | FutureIncompatibilityReason::EditionAndFutureReleaseSemanticsChange(_)
+            | FutureIncompatibilityReason::Custom(_) => false,
+        }
+    }
 }
 
 impl FutureIncompatibleInfo {

Diff for: compiler/rustc_middle/src/lint.rs

@@ -290,12 +290,7 @@ pub fn lint_level(
         let has_future_breakage = future_incompatible.map_or(
             // Default allow lints trigger too often for testing.
             sess.opts.unstable_opts.future_incompat_test && lint.default_level != Level::Allow,
-            |incompat| {
-                matches!(
-                    incompat.reason,
-                    FutureIncompatibilityReason::FutureReleaseErrorReportInDeps
-                )
-            },
+            |incompat| incompat.reason.has_future_breakage(),
         );
 
         // Convert lint level to error level.

Diff for: compiler/rustc_middle/src/ty/context.rs

@@ -376,7 +376,11 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         self.explicit_implied_predicates_of(def_id).map_bound(|preds| preds.into_iter().copied())
     }
 
-    fn is_const_impl(self, def_id: DefId) -> bool {
+    fn impl_is_const(self, def_id: DefId) -> bool {
+        self.is_conditionally_const(def_id)
+    }
+
+    fn fn_is_const(self, def_id: DefId) -> bool {
         self.is_conditionally_const(def_id)
     }
 

Diff for: compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs

@@ -633,6 +633,76 @@ fn coroutine_closure_to_ambiguous_coroutine<I: Interner>(
     )
 }
 
+/// This duplicates `extract_tupled_inputs_and_output_from_callable` but needs
+/// to return different information (namely, the def id and args) so that we can
+/// create const conditions.
+///
+/// Doing so on all calls to `extract_tupled_inputs_and_output_from_callable`
+/// would be wasteful.
+pub(in crate::solve) fn extract_fn_def_from_const_callable<I: Interner>(
+    cx: I,
+    self_ty: I::Ty,
+) -> Result<(ty::Binder<I, (I::FnInputTys, I::Ty)>, I::DefId, I::GenericArgs), NoSolution> {
+    match self_ty.kind() {
+        ty::FnDef(def_id, args) => {
+            let sig = cx.fn_sig(def_id);
+            if sig.skip_binder().is_fn_trait_compatible()
+                && !cx.has_target_features(def_id)
+                && cx.fn_is_const(def_id)
+            {
+                Ok((
+                    sig.instantiate(cx, args).map_bound(|sig| (sig.inputs(), sig.output())),
+                    def_id,
+                    args,
+                ))
+            } else {
+                return Err(NoSolution);
+            }
+        }
+        // `FnPtr`s are not const for now.
+        ty::FnPtr(..) => {
+            return Err(NoSolution);
+        }
+        // `Closure`s are not const for now.
+        ty::Closure(..) => {
+            return Err(NoSolution);
+        }
+        // `CoroutineClosure`s are not const for now.
+        ty::CoroutineClosure(..) => {
+            return Err(NoSolution);
+        }
+
+        ty::Bool
+        | ty::Char
+        | ty::Int(_)
+        | ty::Uint(_)
+        | ty::Float(_)
+        | ty::Adt(_, _)
+        | ty::Foreign(_)
+        | ty::Str
+        | ty::Array(_, _)
+        | ty::Slice(_)
+        | ty::RawPtr(_, _)
+        | ty::Ref(_, _, _)
+        | ty::Dynamic(_, _, _)
+        | ty::Coroutine(_, _)
+        | ty::CoroutineWitness(..)
+        | ty::Never
+        | ty::Tuple(_)
+        | ty::Pat(_, _)
+        | ty::Alias(_, _)
+        | ty::Param(_)
+        | ty::Placeholder(..)
+        | ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
+        | ty::Error(_) => return Err(NoSolution),
+
+        ty::Bound(..)
+        | ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
+            panic!("unexpected type `{self_ty:?}`")
+        }
+    }
+}
+
 /// Assemble a list of predicates that would be present on a theoretical
 /// user impl for an object type. These predicates must be checked any time
 /// we assemble a built-in object candidate for an object type, since they

Diff for: compiler/rustc_next_trait_solver/src/solve/effect_goals.rs

@@ -3,15 +3,15 @@
 
 use rustc_type_ir::fast_reject::DeepRejectCtxt;
 use rustc_type_ir::inherent::*;
+use rustc_type_ir::lang_items::TraitSolverLangItem;
 use rustc_type_ir::{self as ty, Interner, elaborate};
 use tracing::instrument;
 
-use super::assembly::Candidate;
+use super::assembly::{Candidate, structural_traits};
 use crate::delegate::SolverDelegate;
-use crate::solve::assembly::{self};
 use crate::solve::{
     BuiltinImplSource, CandidateSource, Certainty, EvalCtxt, Goal, GoalSource, NoSolution,
-    QueryResult,
+    QueryResult, assembly,
 };
 
 impl<D, I> assembly::GoalKind<D> for ty::HostEffectPredicate<I>
@@ -142,7 +142,7 @@ where
             ty::ImplPolarity::Positive => {}
         };
 
-        if !cx.is_const_impl(impl_def_id) {
+        if !cx.impl_is_const(impl_def_id) {
             return Err(NoSolution);
         }
 
@@ -207,7 +207,7 @@ where
         _ecx: &mut EvalCtxt<'_, D>,
         _goal: Goal<I, Self>,
     ) -> Result<Candidate<I>, NoSolution> {
-        todo!("Copy/Clone is not yet const")
+        Err(NoSolution)
     }
 
     fn consider_builtin_pointer_like_candidate(
@@ -225,11 +225,48 @@ where
     }
 
     fn consider_builtin_fn_trait_candidates(
-        _ecx: &mut EvalCtxt<'_, D>,
-        _goal: Goal<I, Self>,
+        ecx: &mut EvalCtxt<'_, D>,
+        goal: Goal<I, Self>,
         _kind: rustc_type_ir::ClosureKind,
     ) -> Result<Candidate<I>, NoSolution> {
-        todo!("Fn* are not yet const")
+        let cx = ecx.cx();
+
+        let self_ty = goal.predicate.self_ty();
+        let (inputs_and_output, def_id, args) =
+            structural_traits::extract_fn_def_from_const_callable(cx, self_ty)?;
+
+        // A built-in `Fn` impl only holds if the output is sized.
+        // (FIXME: technically we only need to check this if the type is a fn ptr...)
+        let output_is_sized_pred = inputs_and_output.map_bound(|(_, output)| {
+            ty::TraitRef::new(cx, cx.require_lang_item(TraitSolverLangItem::Sized), [output])
+        });
+        let requirements = cx
+            .const_conditions(def_id)
+            .iter_instantiated(cx, args)
+            .map(|trait_ref| {
+                (
+                    GoalSource::ImplWhereBound,
+                    goal.with(cx, trait_ref.to_host_effect_clause(cx, goal.predicate.constness)),
+                )
+            })
+            .chain([(GoalSource::ImplWhereBound, goal.with(cx, output_is_sized_pred))]);
+
+        let pred = inputs_and_output
+            .map_bound(|(inputs, _)| {
+                ty::TraitRef::new(cx, goal.predicate.def_id(), [
+                    goal.predicate.self_ty(),
+                    Ty::new_tup(cx, inputs.as_slice()),
+                ])
+            })
+            .to_host_effect_clause(cx, goal.predicate.constness);
+
+        Self::probe_and_consider_implied_clause(
+            ecx,
+            CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
+            goal,
+            pred,
+            requirements,
+        )
     }
 
     fn consider_builtin_async_fn_trait_candidates(
@@ -314,7 +351,7 @@ where
         _ecx: &mut EvalCtxt<'_, D>,
         _goal: Goal<I, Self>,
     ) -> Result<Candidate<I>, NoSolution> {
-        unreachable!("Destruct is not const")
+        Err(NoSolution)
     }
 
     fn consider_builtin_transmute_candidate(

Diff for: compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs

@@ -394,6 +394,9 @@ where
                     return ecx.forced_ambiguity(MaybeCause::Ambiguity);
                 }
             };
+
+        // A built-in `Fn` impl only holds if the output is sized.
+        // (FIXME: technically we only need to check this if the type is a fn ptr...)
         let output_is_sized_pred = tupled_inputs_and_output.map_bound(|(_, output)| {
             ty::TraitRef::new(cx, cx.require_lang_item(TraitSolverLangItem::Sized), [output])
         });
@@ -408,8 +411,6 @@ where
             })
             .upcast(cx);
 
-        // A built-in `Fn` impl only holds if the output is sized.
-        // (FIXME: technically we only need to check this if the type is a fn ptr...)
         Self::probe_and_consider_implied_clause(
             ecx,
             CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
@@ -438,6 +439,9 @@ where
                 goal_kind,
                 env_region,
             )?;
+
+        // A built-in `AsyncFn` impl only holds if the output is sized.
+        // (FIXME: technically we only need to check this if the type is a fn ptr...)
         let output_is_sized_pred = tupled_inputs_and_output_and_coroutine.map_bound(
             |AsyncCallableRelevantTypes { output_coroutine_ty: output_ty, .. }| {
                 ty::TraitRef::new(cx, cx.require_lang_item(TraitSolverLangItem::Sized), [output_ty])
@@ -494,8 +498,6 @@ where
             )
             .upcast(cx);
 
-        // A built-in `AsyncFn` impl only holds if the output is sized.
-        // (FIXME: technically we only need to check this if the type is a fn ptr...)
         Self::probe_and_consider_implied_clause(
             ecx,
             CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),