Rollup of 3 pull requests

compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs

@@ -97,7 +97,7 @@ pub(crate) mod Enzyme_AD {
     use rustc_session::filesearch;
 
     use super::{CConcreteType, CTypeTreeRef, Context};
-    use crate::llvm::{EnzymeTypeTree, LLVMRustVersionMajor};
+    use crate::llvm::{self, EnzymeTypeTree};
 
     type EnzymeSetCLBoolFn = unsafe extern "C" fn(*mut c_void, u8);
     type EnzymeSetCLStringFn = unsafe extern "C" fn(*mut c_void, *const c_char);
@@ -434,7 +434,7 @@ pub(crate) mod Enzyme_AD {
         }
 
         fn get_enzyme_path(sysroot: &Sysroot) -> Result<String, EnzymeLibraryError> {
-            let llvm_version_major = unsafe { LLVMRustVersionMajor() };
+            let llvm_version_major = llvm::LLVMRustVersionMajor();
 
             let path_buf = sysroot
                 .all_paths()

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -894,7 +894,11 @@ unsafe extern "C" {
         SLen: c_uint,
     ) -> MetadataKindId;
 
-    pub(crate) fn LLVMGetVersion(major: &mut c_uint, minor: &mut c_uint, patch: &mut c_uint);
+    /// Gets the actual version of LLVM that we are linked to at runtime.
+    ///
+    /// # Safety
+    /// Can be called without initializing LLVM.
+    pub(crate) safe fn LLVMGetVersion(major: &mut c_uint, minor: &mut c_uint, patch: &mut c_uint);
 
     pub(crate) fn LLVMDisposeTargetMachine(T: ptr::NonNull<TargetMachine>);
 
@@ -2176,9 +2180,9 @@ unsafe extern "C" {
     /// Returns the LLVM major version that the compiler was built with.
     ///
     /// Note that this is hard-coded as `LLVM_VERSION_MAJOR` when `RustWrapper.cpp` is built. This
-    /// could be different than what the runtime LLVM library reports in `LLVMGetVersion`, so we
+    /// could be different than what the runtime LLVM library reports in [`LLVMGetVersion`], so we
     /// assert their equality in `configure_llvm`.
-    pub(crate) fn LLVMRustVersionMajor() -> u32;
+    pub(crate) safe fn LLVMRustVersionMajor() -> u32;
 
     /// Add LLVM module flags.
     ///

compiler/rustc_codegen_llvm/src/llvm/offload_ffi.rs

@@ -14,7 +14,7 @@ use rustc_fs_util::path_to_c_string;
 use rustc_session::config::host_tuple;
 use rustc_session::filesearch;
 
-use crate::llvm::LLVMRustVersionMajor;
+use crate::llvm;
 
 pub(crate) struct RustOffloadWrapper {
     LLVMRustBundleImages: LLVMRustBundleImagesFn,
@@ -119,7 +119,7 @@ impl RustOffloadWrapper {
     fn get_offload_and_lld_paths(
         sysroot: &rustc_session::config::Sysroot,
     ) -> Result<(PathBuf, Option<PathBuf>), RustOffloadLibraryError> {
-        let llvm_version_major = unsafe { LLVMRustVersionMajor() };
+        let llvm_version_major = llvm::LLVMRustVersionMajor();
         let mut searched = Vec::new();
 
         for root in sysroot.all_paths() {

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -459,15 +459,13 @@ pub(crate) fn print_version() {
     println!("LLVM version: {major}.{minor}.{patch}");
 }
 
+/// Returns the version of LLVM that we are actually linked to at runtime.
 pub(crate) fn get_version() -> (u32, u32, u32) {
-    // Can be called without initializing LLVM
-    unsafe {
-        let mut llvm_major = 0;
-        let mut llvm_minor = 0;
-        let mut llvm_patch = 0;
-        llvm::LLVMGetVersion(&mut llvm_major, &mut llvm_minor, &mut llvm_patch);
-        (llvm_major, llvm_minor, llvm_patch)
-    }
+    let mut llvm_major = 0;
+    let mut llvm_minor = 0;
+    let mut llvm_patch = 0;
+    llvm::LLVMGetVersion(&mut llvm_major, &mut llvm_minor, &mut llvm_patch);
+    (llvm_major, llvm_minor, llvm_patch)
 }
 
 pub(crate) fn print_passes() {

compiler/rustc_lint/src/levels.rs

@@ -969,14 +969,18 @@ where
                 let mut lint = Diag::new(dcx, level, msg!("unknown lint: `{$name}`"))
                     .with_arg("name", lint_id.lint.name_lower())
                     .with_note(msg!("the `{$name}` lint is unstable"));
-                rustc_session::diagnostics::add_feature_diagnostics_for_issue(
-                    &mut lint,
-                    sess,
-                    feature,
-                    GateIssue::Language,
-                    lint_from_cli,
-                    None,
-                );
+                // `staged_api` is only intended for the standard library, so don't
+                // suggest enabling it just to use this lint.
+                if feature != sym::staged_api {
+                    rustc_session::diagnostics::add_feature_diagnostics_for_issue(
+                        &mut lint,
+                        sess,
+                        feature,
+                        GateIssue::Language,
+                        lint_from_cli,
+                        None,
+                    );
+                }
                 lint
             }
         }

compiler/rustc_lint_defs/src/builtin.rs

@@ -54,6 +54,7 @@ pub mod hardwired {
             HIDDEN_GLOB_REEXPORTS,
             ILL_FORMED_ATTRIBUTE_INPUT,
             INCOMPLETE_INCLUDE,
+            INEFFECTIVE_UNSTABLE_REEXPORTS,
             INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
             INLINE_NO_SANITIZE,
             INVALID_DOC_ATTRIBUTES,
@@ -2816,6 +2817,38 @@ declare_lint! {
     "detects deprecation attributes with no effect",
 }
 
+declare_lint! {
+    /// The `ineffective_unstable_reexports` lint detects `#[unstable]`
+    /// attributes on re-exports where the attribute does not make the
+    /// re-exported path unstable.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    /// #![feature(staged_api)]
+    /// #![stable(feature = "test", since = "1.0.0")]
+    ///
+    /// #[stable(feature = "test", since = "1.0.0")]
+    /// pub struct S;
+    ///
+    /// #[unstable(feature = "reexport", issue = "none")]
+    /// pub use self::S as T;
+    ///
+    /// fn main() {}
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// `#[unstable]` on a re-export does not make a stable path unstable
+    /// re-exports inside unstable modules are already on an unstable path
+    pub INEFFECTIVE_UNSTABLE_REEXPORTS,
+    Deny,
+    "detects ineffective `#[unstable]` attributes on re-exports",
+    @feature_gate = staged_api;
+}
+
 declare_lint! {
     /// The `ineffective_unstable_trait_impl` lint detects `#[unstable]` attributes which are not used.
     ///

compiler/rustc_passes/src/diagnostics.rs

@@ -950,6 +950,10 @@ pub(crate) struct UnnecessaryPartialStableFeature {
 #[note("see issue #55436 <https://github.com/rust-lang/rust/issues/55436> for more information")]
 pub(crate) struct IneffectiveUnstableImpl;
 
+#[derive(Diagnostic)]
+#[diag("`#[unstable]` does not make this re-exported path unstable")]
+pub(crate) struct IneffectiveUnstableReexport;
+
 // FIXME(jdonszelmann): move back to rustc_attr
 #[derive(Diagnostic)]
 #[diag(

compiler/rustc_passes/src/stability.rs

@@ -17,7 +17,8 @@ use rustc_hir::{
     UsePath, VERSION_PLACEHOLDER, Variant, find_attr,
 };
 use rustc_lint_defs::builtin::{
-    DEPRECATED, DUPLICATE_FEATURES, INEFFECTIVE_UNSTABLE_TRAIT_IMPL, STABLE_FEATURES,
+    DEPRECATED, DUPLICATE_FEATURES, INEFFECTIVE_UNSTABLE_REEXPORTS,
+    INEFFECTIVE_UNSTABLE_TRAIT_IMPL, STABLE_FEATURES,
 };
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::lib_features::{FeatureStability, LibFeatures};
@@ -522,7 +523,9 @@ impl<'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'tcx> {
 /// Cross-references the feature names of unstable APIs with enabled
 /// features and possibly prints errors.
 fn check_mod_unstable_api_usage(tcx: TyCtxt<'_>, mod_id: LocalModId) {
-    tcx.hir_visit_item_likes_in_module(mod_id, &mut Checker { tcx });
+    let mut checker = Checker { tcx, mod_id, unstable_reexports: FxIndexMap::default() };
+    tcx.hir_visit_item_likes_in_module(mod_id, &mut checker);
+    checker.emit_ineffective_unstable_reexports();
 
     let is_staged_api =
         tcx.sess.opts.unstable_opts.force_unstable_if_unmarked || tcx.features().staged_api();
@@ -552,8 +555,155 @@ pub(crate) fn provide(providers: &mut Providers) {
     };
 }
 
+struct UnstableReexport {
+    hir_id: HirId,
+    span: Span,
+    has_target: bool,
+    all_targets_stable: bool,
+}
+
 struct Checker<'tcx> {
     tcx: TyCtxt<'tcx>,
+    mod_id: LocalModId,
+    unstable_reexports: FxIndexMap<Span, UnstableReexport>,
+}
+
+impl<'tcx> Checker<'tcx> {
+    fn unstable_reexport_span(&self, item: &'tcx hir::Item<'tcx>) -> Option<Span> {
+        let attrs = self.tcx.hir_attrs(item.hir_id());
+        let (stability, span) =
+            find_attr!(attrs, Stability { stability, span } => (*stability, *span))?;
+
+        stability.level.is_unstable().then_some(span)
+    }
+
+    fn classify_reexport_targets<Id>(
+        &self,
+        targets: impl IntoIterator<Item = Res<Id>>,
+    ) -> (bool, bool) {
+        let mut has_target = false;
+        let mut all_targets_stable = true;
+
+        for res in targets {
+            match res {
+                Res::Def(_, def_id) => {
+                    has_target = true;
+
+                    match self.tcx.lookup_stability(def_id) {
+                        Some(stability) if stability.level.is_unstable() => {
+                            all_targets_stable = false;
+                        }
+                        Some(_) => {}
+
+                        None => {
+                            // Items from crates without staged API metadata are
+                            // effectively stable. Unmarked items in staged API
+                            // crates are diagnosed by the existing stability checks.
+                            if self.tcx.lookup_stability(def_id.krate.as_def_id()).is_some() {
+                                all_targets_stable = false;
+                            }
+                        }
+                    }
+                }
+
+                // Primitives are stable and have no DefId.
+                Res::PrimTy(_) => {
+                    has_target = true;
+                }
+
+                // Do not lint if the target cannot be classified.
+                _ => {
+                    all_targets_stable = false;
+                }
+            }
+        }
+
+        (has_target, all_targets_stable)
+    }
+
+    fn record_unstable_reexport(
+        &mut self,
+        item: &'tcx hir::Item<'tcx>,
+        attr_span: Span,
+        span: Span,
+        has_target: bool,
+        all_targets_stable: bool,
+    ) {
+        let entry = self.unstable_reexports.entry(attr_span).or_insert(UnstableReexport {
+            hir_id: item.hir_id(),
+            span,
+            has_target: false,
+            all_targets_stable: true,
+        });
+
+        entry.has_target |= has_target;
+        entry.all_targets_stable &= all_targets_stable;
+    }
+
+    fn check_single_unstable_reexport(
+        &mut self,
+        item: &'tcx hir::Item<'tcx>,
+        path: &'tcx UsePath<'tcx>,
+    ) {
+        let Some(attr_span) = self.unstable_reexport_span(item) else {
+            return;
+        };
+
+        let (has_target, all_targets_stable) =
+            self.classify_reexport_targets(path.res.present_items());
+
+        self.record_unstable_reexport(item, attr_span, path.span, has_target, all_targets_stable);
+    }
+
+    fn check_glob_unstable_reexport(
+        &mut self,
+        item: &'tcx hir::Item<'tcx>,
+        path: &'tcx UsePath<'tcx>,
+    ) {
+        let Some(attr_span) = self.unstable_reexport_span(item) else {
+            return;
+        };
+
+        let glob_def_id = item.owner_id.def_id.to_def_id();
+
+        let targets = self
+            .tcx
+            .module_children_local(self.mod_id.to_local_def_id())
+            .iter()
+            .filter(|child| {
+                child.reexport_chain.iter().any(|reexport| reexport.id() == Some(glob_def_id))
+            })
+            .map(|child| child.res);
+
+        let (has_target, all_targets_stable) = self.classify_reexport_targets(targets);
+
+        self.record_unstable_reexport(item, attr_span, path.span, has_target, all_targets_stable);
+    }
+
+    fn containing_module_is_unstable(&self) -> bool {
+        self.tcx
+            .lookup_stability(self.mod_id.to_local_def_id())
+            .is_some_and(|stability| stability.level.is_unstable())
+    }
+
+    fn emit_ineffective_unstable_reexports(&self) {
+        // an unstable module already makes its re-exports unstable
+        // keep the explicit annotation without linting it as ineffective
+        if self.unstable_reexports.is_empty() || self.containing_module_is_unstable() {
+            return;
+        }
+
+        for reexport in self.unstable_reexports.values() {
+            if reexport.has_target && reexport.all_targets_stable {
+                self.tcx.emit_node_span_lint(
+                    INEFFECTIVE_UNSTABLE_REEXPORTS,
+                    reexport.hir_id,
+                    reexport.span,
+                    diagnostics::IneffectiveUnstableReexport,
+                );
+            }
+        }
+    }
 }
 
 impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
@@ -582,6 +732,20 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
                 self.tcx.check_stability(def_id, Some(item.hir_id()), item.span, None);
             }
 
+            hir::ItemKind::Use(path, hir::UseKind::Single(_))
+                if self.tcx.features().staged_api()
+                    && self.tcx.local_visibility(item.owner_id.def_id).is_public() =>
+            {
+                self.check_single_unstable_reexport(item, path);
+            }
+
+            hir::ItemKind::Use(path, hir::UseKind::Glob)
+                if self.tcx.features().staged_api()
+                    && self.tcx.local_visibility(item.owner_id.def_id).is_public() =>
+            {
+                self.check_glob_unstable_reexport(item, path);
+            }
+
             // For implementations of traits, check the stability of each item
             // individually as it's possible to have a stable trait with unstable
             // items.

library/core/src/lib.rs

@@ -230,6 +230,11 @@ pub mod offload;
 #[unstable(feature = "contracts", issue = "128044")]
 pub mod contracts;
 
+#[allow(clippy::useless_attribute)]
+#[expect(
+    ineffective_unstable_reexports,
+    reason = "accepted as stable after accidental stabilization in 1.96, see #154645"
+)]
 #[unstable(feature = "derive_macro_global_path", issue = "154645")]
 pub use crate::macros::builtin::derive;
 #[stable(feature = "cfg_select", since = "1.95.0")]

library/core/src/ops/mod.rs

@@ -156,7 +156,7 @@ mod unsize;
 pub use self::arith::{Add, Div, Mul, Neg, Rem, Sub};
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
 pub use self::arith::{AddAssign, DivAssign, MulAssign, RemAssign, SubAssign};
-#[unstable(feature = "async_fn_traits", issue = "none")]
+#[stable(feature = "async_closure", since = "1.85.0")]
 pub use self::async_function::{AsyncFn, AsyncFnMut, AsyncFnOnce};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::bit::{BitAnd, BitOr, BitXor, Not, Shl, Shr};