Rollup of 14 pull requests

compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs

@@ -370,6 +370,7 @@ impl<S: Stage> NoArgsAttributeParser<S> for NoMangleParser {
 pub(crate) struct UsedParser {
     first_compiler: Option<Span>,
     first_linker: Option<Span>,
+    first_default: Option<Span>,
 }
 
 // A custom `AttributeParser` is used rather than a Simple attribute parser because
@@ -382,7 +383,7 @@ impl<S: Stage> AttributeParser<S> for UsedParser {
         template!(Word, List: &["compiler", "linker"]),
         |group: &mut Self, cx, args| {
             let used_by = match args {
-                ArgParser::NoArgs => UsedBy::Linker,
+                ArgParser::NoArgs => UsedBy::Default,
                 ArgParser::List(list) => {
                     let Some(l) = list.single() else {
                         cx.expected_single_argument(list.span);
@@ -423,12 +424,29 @@ impl<S: Stage> AttributeParser<S> for UsedParser {
                 ArgParser::NameValue(_) => return,
             };
 
+            let attr_span = cx.attr_span;
+
+            // `#[used]` is interpreted as `#[used(linker)]` (though depending on target OS the
+            // circumstances are more complicated). While we're checking `used_by`, also report
+            // these cross-`UsedBy` duplicates to warn.
             let target = match used_by {
                 UsedBy::Compiler => &mut group.first_compiler,
-                UsedBy::Linker => &mut group.first_linker,
+                UsedBy::Linker => {
+                    if let Some(prev) = group.first_default {
+                        cx.warn_unused_duplicate(prev, attr_span);
+                        return;
+                    }
+                    &mut group.first_linker
+                }
+                UsedBy::Default => {
+                    if let Some(prev) = group.first_linker {
+                        cx.warn_unused_duplicate(prev, attr_span);
+                        return;
+                    }
+                    &mut group.first_default
+                }
             };
 
-            let attr_span = cx.attr_span;
             if let Some(prev) = *target {
                 cx.warn_unused_duplicate(prev, attr_span);
             } else {
@@ -440,11 +458,13 @@ impl<S: Stage> AttributeParser<S> for UsedParser {
         AllowedTargets::AllowList(&[Allow(Target::Static), Warn(Target::MacroCall)]);
 
     fn finalize(self, _cx: &FinalizeContext<'_, '_, S>) -> Option<AttributeKind> {
-        // Ratcheting behaviour, if both `linker` and `compiler` are specified, use `linker`
-        Some(match (self.first_compiler, self.first_linker) {
-            (_, Some(span)) => AttributeKind::Used { used_by: UsedBy::Linker, span },
-            (Some(span), _) => AttributeKind::Used { used_by: UsedBy::Compiler, span },
-            (None, None) => return None,
+        // If a specific form of `used` is specified, it takes precedence over generic `#[used]`.
+        // If both `linker` and `compiler` are specified, use `linker`.
+        Some(match (self.first_compiler, self.first_linker, self.first_default) {
+            (_, Some(span), _) => AttributeKind::Used { used_by: UsedBy::Linker, span },
+            (Some(span), _, _) => AttributeKind::Used { used_by: UsedBy::Compiler, span },
+            (_, _, Some(span)) => AttributeKind::Used { used_by: UsedBy::Default, span },
+            (None, None, None) => return None,
         })
     }
 }

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -263,6 +263,19 @@ fn process_builtin_attrs(
                 AttributeKind::Used { used_by, .. } => match used_by {
                     UsedBy::Compiler => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_COMPILER,
                     UsedBy::Linker => codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER,
+                    UsedBy::Default => {
+                        let used_form = if tcx.sess.target.os == "illumos" {
+                            // illumos' `ld` doesn't support a section header that would represent
+                            // `#[used(linker)]`, see
+                            // https://github.com/rust-lang/rust/issues/146169. For that target,
+                            // downgrade as if `#[used(compiler)]` was requested and hope for the
+                            // best.
+                            CodegenFnAttrFlags::USED_COMPILER
+                        } else {
+                            CodegenFnAttrFlags::USED_LINKER
+                        };
+                        codegen_fn_attrs.flags |= used_form;
+                    }
                 },
                 AttributeKind::FfiConst(_) => {
                     codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -146,12 +146,13 @@ impl Deprecation {
 }
 
 /// There are three valid forms of the attribute:
-/// `#[used]`, which is semantically equivalent to `#[used(linker)]` except that the latter is currently unstable.
+/// `#[used]`, which is equivalent to `#[used(linker)]` on targets that support it, but `#[used(compiler)]` if not.
 /// `#[used(compiler)]`
 /// `#[used(linker)]`
 #[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
 #[derive(HashStable_Generic, PrintAttribute)]
 pub enum UsedBy {
+    Default,
     Compiler,
     Linker,
 }

compiler/rustc_middle/src/ty/context.rs

@@ -207,8 +207,9 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         from_entry(entry)
     }
 
-    fn evaluation_is_concurrent(&self) -> bool {
-        self.sess.threads() > 1
+    fn assert_evaluation_is_concurrent(&self) {
+        // Turns out, the assumption for this function isn't perfect.
+        // See trait-system-refactor-initiative#234.
     }
 
     fn expand_abstract_consts<T: TypeFoldable<TyCtxt<'tcx>>>(self, t: T) -> T {

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -467,7 +467,8 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                             span,
                             leaf_trait_predicate,
                         );
-                        self.note_version_mismatch(&mut err, leaf_trait_predicate);
+                        self.note_trait_version_mismatch(&mut err, leaf_trait_predicate);
+                        self.note_adt_version_mismatch(&mut err, leaf_trait_predicate);
                         self.suggest_remove_await(&obligation, &mut err);
                         self.suggest_derive(&obligation, &mut err, leaf_trait_predicate);
 
@@ -2424,7 +2425,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
     /// If the `Self` type of the unsatisfied trait `trait_ref` implements a trait
     /// with the same path as `trait_ref`, a help message about
     /// a probable version mismatch is added to `err`
-    fn note_version_mismatch(
+    fn note_trait_version_mismatch(
         &self,
         err: &mut Diag<'_>,
         trait_pred: ty::PolyTraitPredicate<'tcx>,
@@ -2464,15 +2465,87 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 impl_spans,
                 format!("trait impl{} with same name found", pluralize!(trait_impls.len())),
             );
-            let trait_crate = self.tcx.crate_name(trait_with_same_path.krate);
-            let crate_msg =
-                format!("perhaps two different versions of crate `{trait_crate}` are being used?");
-            err.note(crate_msg);
+            self.note_two_crate_versions(trait_with_same_path, err);
             suggested = true;
         }
         suggested
     }
 
+    fn note_two_crate_versions(&self, did: DefId, err: &mut Diag<'_>) {
+        let crate_name = self.tcx.crate_name(did.krate);
+        let crate_msg =
+            format!("perhaps two different versions of crate `{crate_name}` are being used?");
+        err.note(crate_msg);
+    }
+
+    fn note_adt_version_mismatch(
+        &self,
+        err: &mut Diag<'_>,
+        trait_pred: ty::PolyTraitPredicate<'tcx>,
+    ) {
+        let ty::Adt(impl_self_def, _) = trait_pred.self_ty().skip_binder().peel_refs().kind()
+        else {
+            return;
+        };
+
+        let impl_self_did = impl_self_def.did();
+
+        // We only want to warn about different versions of a dependency.
+        // If no dependency is involved, bail.
+        if impl_self_did.krate == LOCAL_CRATE {
+            return;
+        }
+
+        let impl_self_path = self.comparable_path(impl_self_did);
+        let impl_self_crate_name = self.tcx.crate_name(impl_self_did.krate);
+        let similar_items: UnordSet<_> = self
+            .tcx
+            .visible_parent_map(())
+            .items()
+            .filter_map(|(&item, _)| {
+                // If we found ourselves, ignore.
+                if impl_self_did == item {
+                    return None;
+                }
+                // We only want to warn about different versions of a dependency.
+                // Ignore items from our own crate.
+                if item.krate == LOCAL_CRATE {
+                    return None;
+                }
+                // We want to warn about different versions of a dependency.
+                // So make sure the crate names are the same.
+                if impl_self_crate_name != self.tcx.crate_name(item.krate) {
+                    return None;
+                }
+                // Filter out e.g. constructors that often have the same path
+                // str as the relevant ADT.
+                if !self.tcx.def_kind(item).is_adt() {
+                    return None;
+                }
+                let path = self.comparable_path(item);
+                // We don't know if our item or the one we found is the re-exported one.
+                // Check both cases.
+                let is_similar = path.ends_with(&impl_self_path) || impl_self_path.ends_with(&path);
+                is_similar.then_some((item, path))
+            })
+            .collect();
+
+        let mut similar_items =
+            similar_items.into_items().into_sorted_stable_ord_by_key(|(_, path)| path);
+        similar_items.dedup();
+
+        for (similar_item, _) in similar_items {
+            err.span_help(self.tcx.def_span(similar_item), "item with same name found");
+            self.note_two_crate_versions(similar_item, err);
+        }
+    }
+
+    /// Add a `::` prefix when comparing paths so that paths with just one item
+    /// like "Foo" does not equal the end of "OtherFoo".
+    fn comparable_path(&self, did: DefId) -> String {
+        format!("::{}", self.tcx.def_path_str(did))
+    }
+
     /// Creates a `PredicateObligation` with `new_self_ty` replacing the existing type in the
     /// `trait_ref`.
     ///

compiler/rustc_type_ir/src/interner.rs

@@ -183,7 +183,9 @@ pub trait Interner:
         from_entry: impl FnOnce(&CanonicalParamEnvCacheEntry<Self>) -> R,
     ) -> R;
 
-    fn evaluation_is_concurrent(&self) -> bool;
+    /// Useful for testing. If a cache entry is replaced, this should
+    /// (in theory) only happen when concurrent.
+    fn assert_evaluation_is_concurrent(&self);
 
     fn expand_abstract_consts<T: TypeFoldable<Self>>(self, t: T) -> T;
 
@@ -567,7 +569,7 @@ impl<I: Interner> search_graph::Cx for I {
     fn with_global_cache<R>(self, f: impl FnOnce(&mut search_graph::GlobalCache<Self>) -> R) -> R {
         I::with_global_cache(self, f)
     }
-    fn evaluation_is_concurrent(&self) -> bool {
-        self.evaluation_is_concurrent()
+    fn assert_evaluation_is_concurrent(&self) {
+        self.assert_evaluation_is_concurrent()
     }
 }

compiler/rustc_type_ir/src/search_graph/global_cache.rs

@@ -56,13 +56,13 @@ impl<X: Cx> GlobalCache<X> {
             let with_overflow = WithOverflow { nested_goals, result };
             let prev = entry.with_overflow.insert(required_depth, with_overflow);
             if let Some(prev) = &prev {
-                assert!(cx.evaluation_is_concurrent());
+                cx.assert_evaluation_is_concurrent();
                 assert_eq!(cx.get_tracked(&prev.result), evaluation_result.result);
             }
         } else {
             let prev = entry.success.replace(Success { required_depth, nested_goals, result });
             if let Some(prev) = &prev {
-                assert!(cx.evaluation_is_concurrent());
+                cx.assert_evaluation_is_concurrent();
                 assert_eq!(cx.get_tracked(&prev.result), evaluation_result.result);
             }
         }

compiler/rustc_type_ir/src/search_graph/mod.rs

@@ -53,7 +53,7 @@ pub trait Cx: Copy {
 
     fn with_global_cache<R>(self, f: impl FnOnce(&mut GlobalCache<Self>) -> R) -> R;
 
-    fn evaluation_is_concurrent(&self) -> bool;
+    fn assert_evaluation_is_concurrent(&self);
 }
 
 pub trait Delegate: Sized {

library/alloc/src/lib.rs

@@ -96,6 +96,7 @@
 #![feature(bstr)]
 #![feature(bstr_internals)]
 #![feature(cast_maybe_uninit)]
+#![feature(cell_get_cloned)]
 #![feature(char_internals)]
 #![feature(char_max_len)]
 #![feature(clone_to_uninit)]

library/alloc/src/rc.rs

@@ -242,7 +242,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use core::any::Any;
-use core::cell::Cell;
+use core::cell::{Cell, CloneFromCell};
 #[cfg(not(no_global_oom_handling))]
 use core::clone::CloneToUninit;
 use core::clone::UseCloned;
@@ -340,6 +340,10 @@ impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Rc<U, A>> for
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Rc<U>> for Rc<T> {}
 
+// SAFETY: `Rc::clone` doesn't access any `Cell`s which could contain the `Rc` being cloned.
+#[unstable(feature = "cell_get_cloned", issue = "145329")]
+unsafe impl<T: ?Sized> CloneFromCell for Rc<T> {}
+
 impl<T: ?Sized> Rc<T> {
     #[inline]
     unsafe fn from_inner(ptr: NonNull<RcInner<T>>) -> Self {
@@ -3013,6 +3017,10 @@ impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Weak<U, A>> f
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Weak<U>> for Weak<T> {}
 
+// SAFETY: `Weak::clone` doesn't access any `Cell`s which could contain the `Weak` being cloned.
+#[unstable(feature = "cell_get_cloned", issue = "145329")]
+unsafe impl<T: ?Sized> CloneFromCell for Weak<T> {}
+
 impl<T> Weak<T> {
     /// Constructs a new `Weak<T>`, without allocating any memory.
     /// Calling [`upgrade`] on the return value always gives [`None`].

library/alloc/src/sync.rs

@@ -9,6 +9,7 @@
 //! `#[cfg(target_has_atomic = "ptr")]`.
 
 use core::any::Any;
+use core::cell::CloneFromCell;
 #[cfg(not(no_global_oom_handling))]
 use core::clone::CloneToUninit;
 use core::clone::UseCloned;
@@ -281,6 +282,10 @@ impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Arc<U, A>> fo
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Arc<U>> for Arc<T> {}
 
+// SAFETY: `Arc::clone` doesn't access any `Cell`s which could contain the `Arc` being cloned.
+#[unstable(feature = "cell_get_cloned", issue = "145329")]
+unsafe impl<T: ?Sized> CloneFromCell for Arc<T> {}
+
 impl<T: ?Sized> Arc<T> {
     unsafe fn from_inner(ptr: NonNull<ArcInner<T>>) -> Self {
         unsafe { Self::from_inner_in(ptr, Global) }
@@ -356,6 +361,10 @@ impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Weak<U, A>> f
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Weak<U>> for Weak<T> {}
 
+// SAFETY: `Weak::clone` doesn't access any `Cell`s which could contain the `Weak` being cloned.
+#[unstable(feature = "cell_get_cloned", issue = "145329")]
+unsafe impl<T: ?Sized> CloneFromCell for Weak<T> {}
+
 #[stable(feature = "arc_weak", since = "1.4.0")]
 impl<T: ?Sized, A: Allocator> fmt::Debug for Weak<T, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {