Rollup of 12 pull requests

compiler/rustc_builtin_macros/src/deriving/bounds.rs

@@ -23,6 +23,7 @@ pub(crate) fn expand_deriving_copy(
         methods: Vec::new(),
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
 
     trait_def.expand(cx, mitem, item, push);
@@ -46,6 +47,7 @@ pub(crate) fn expand_deriving_const_param_ty(
         methods: Vec::new(),
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
 
     trait_def.expand(cx, mitem, item, push);
@@ -60,6 +62,7 @@ pub(crate) fn expand_deriving_const_param_ty(
         methods: Vec::new(),
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
 
     trait_def.expand(cx, mitem, item, push);
@@ -83,6 +86,7 @@ pub(crate) fn expand_deriving_unsized_const_param_ty(
         methods: Vec::new(),
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
 
     trait_def.expand(cx, mitem, item, push);

compiler/rustc_builtin_macros/src/deriving/clone.rs

@@ -87,6 +87,7 @@ pub(crate) fn expand_deriving_clone(
         }],
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
 
     trait_def.expand_ext(cx, mitem, item, push, is_simple)

compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs

@@ -43,6 +43,7 @@ pub(crate) fn expand_deriving_eq(
         }],
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
     trait_def.expand_ext(cx, mitem, item, push, true)
 }

compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs

@@ -34,6 +34,7 @@ pub(crate) fn expand_deriving_ord(
         }],
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
 
     trait_def.expand(cx, mitem, item, push)

compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs

@@ -30,6 +30,7 @@ pub(crate) fn expand_deriving_partial_eq(
         methods: Vec::new(),
         associated_types: Vec::new(),
         is_const: false,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
     structural_trait_def.expand(cx, mitem, item, push);
 
@@ -58,6 +59,7 @@ pub(crate) fn expand_deriving_partial_eq(
         methods,
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
     trait_def.expand(cx, mitem, item, push)
 }

compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs

@@ -64,6 +64,7 @@ pub(crate) fn expand_deriving_partial_ord(
         methods: vec![partial_cmp_def],
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
     trait_def.expand(cx, mitem, item, push)
 }

compiler/rustc_builtin_macros/src/deriving/debug.rs

@@ -41,6 +41,7 @@ pub(crate) fn expand_deriving_debug(
         }],
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
     trait_def.expand(cx, mitem, item, push)
 }

compiler/rustc_builtin_macros/src/deriving/default.rs

@@ -51,6 +51,7 @@ pub(crate) fn expand_deriving_default(
         }],
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
     trait_def.expand(cx, mitem, item, push)
 }

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -181,9 +181,11 @@ use std::{iter, vec};
 pub(crate) use StaticFields::*;
 pub(crate) use SubstructureFields::*;
 use rustc_ast::ptr::P;
+use rustc_ast::token::{IdentIsRaw, LitKind, Token, TokenKind};
+use rustc_ast::tokenstream::{DelimSpan, Spacing, TokenTree};
 use rustc_ast::{
-    self as ast, AnonConst, BindingMode, ByRef, EnumDef, Expr, GenericArg, GenericParamKind,
-    Generics, Mutability, PatKind, VariantData,
+    self as ast, AnonConst, AttrArgs, BindingMode, ByRef, DelimArgs, EnumDef, Expr, GenericArg,
+    GenericParamKind, Generics, Mutability, PatKind, Safety, VariantData,
 };
 use rustc_attr_data_structures::{AttributeKind, ReprPacked};
 use rustc_attr_parsing::AttributeParser;
@@ -222,6 +224,8 @@ pub(crate) struct TraitDef<'a> {
     pub associated_types: Vec<(Ident, Ty)>,
 
     pub is_const: bool,
+
+    pub is_staged_api_crate: bool,
 }
 
 pub(crate) struct MethodDef<'a> {
@@ -784,8 +788,45 @@ impl<'a> TraitDef<'a> {
         // Create the type of `self`.
         let path = cx.path_all(self.span, false, vec![type_ident], self_params);
         let self_type = cx.ty_path(path);
+        let rustc_const_unstable =
+            cx.path_ident(self.span, Ident::new(sym::rustc_const_unstable, self.span));
+
+        let mut attrs = thin_vec![cx.attr_word(sym::automatically_derived, self.span),];
+
+        // Only add `rustc_const_unstable` attributes if `derive_const` is used within libcore/libstd,
+        // Other crates don't need stability attributes, so adding them is not useful, but libcore needs them
+        // on all const trait impls.
+        if self.is_const && self.is_staged_api_crate {
+            attrs.push(
+                cx.attr_nested(
+                    rustc_ast::AttrItem {
+                        unsafety: Safety::Default,
+                        path: rustc_const_unstable,
+                        args: AttrArgs::Delimited(DelimArgs {
+                            dspan: DelimSpan::from_single(self.span),
+                            delim: rustc_ast::token::Delimiter::Parenthesis,
+                            tokens: [
+                                TokenKind::Ident(sym::feature, IdentIsRaw::No),
+                                TokenKind::Eq,
+                                TokenKind::lit(LitKind::Str, sym::derive_const, None),
+                                TokenKind::Comma,
+                                TokenKind::Ident(sym::issue, IdentIsRaw::No),
+                                TokenKind::Eq,
+                                TokenKind::lit(LitKind::Str, sym::derive_const_issue, None),
+                            ]
+                            .into_iter()
+                            .map(|kind| {
+                                TokenTree::Token(Token { kind, span: self.span }, Spacing::Alone)
+                            })
+                            .collect(),
+                        }),
+                        tokens: None,
+                    },
+                    self.span,
+                ),
+            )
+        }
 
-        let attrs = thin_vec![cx.attr_word(sym::automatically_derived, self.span),];
         let opt_trait_ref = Some(trait_ref);
 
         cx.item(

compiler/rustc_builtin_macros/src/deriving/hash.rs

@@ -41,6 +41,7 @@ pub(crate) fn expand_deriving_hash(
         }],
         associated_types: Vec::new(),
         is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
     };
 
     hash_trait_def.expand(cx, mitem, item, push);

compiler/rustc_expand/src/build.rs

@@ -3,8 +3,8 @@ use rustc_ast::token::Delimiter;
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::util::literal;
 use rustc_ast::{
-    self as ast, AnonConst, AttrVec, BlockCheckMode, Expr, LocalKind, MatchKind, PatKind, UnOp,
-    attr, token, tokenstream,
+    self as ast, AnonConst, AttrItem, AttrVec, BlockCheckMode, Expr, LocalKind, MatchKind, PatKind,
+    UnOp, attr, token, tokenstream,
 };
 use rustc_span::source_map::Spanned;
 use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw, sym};
@@ -766,4 +766,10 @@ impl<'a> ExtCtxt<'a> {
             span,
         )
     }
+
+    // Builds an attribute fully manually.
+    pub fn attr_nested(&self, inner: AttrItem, span: Span) -> ast::Attribute {
+        let g = &self.sess.psess.attr_id_generator;
+        attr::mk_attr_from_item(g, inner, None, ast::AttrStyle::Outer, span)
+    }
 }

compiler/rustc_hir_analysis/messages.ftl

@@ -158,7 +158,7 @@ hir_analysis_dispatch_from_dyn_zst = the trait `DispatchFromDyn` may only be imp
 hir_analysis_drop_impl_negative = negative `Drop` impls are not supported
 
 hir_analysis_drop_impl_on_wrong_item =
-    the `Drop` trait may only be implemented for local structs, enums, and unions
+    the `{$trait_}` trait may only be implemented for local structs, enums, and unions
     .label = must be a struct, enum, or union in the current crate
 
 hir_analysis_drop_impl_reservation = reservation `Drop` impls are not supported

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -37,6 +37,7 @@ pub(super) fn check_trait<'tcx>(
     let lang_items = tcx.lang_items();
     let checker = Checker { tcx, trait_def_id, impl_def_id, impl_header };
     checker.check(lang_items.drop_trait(), visit_implementation_of_drop)?;
+    checker.check(lang_items.async_drop_trait(), visit_implementation_of_drop)?;
     checker.check(lang_items.copy_trait(), visit_implementation_of_copy)?;
     checker.check(lang_items.const_param_ty_trait(), |checker| {
         visit_implementation_of_const_param_ty(checker, LangItem::ConstParamTy)
@@ -83,7 +84,10 @@ fn visit_implementation_of_drop(checker: &Checker<'_>) -> Result<(), ErrorGuaran
 
     let impl_ = tcx.hir_expect_item(impl_did).expect_impl();
 
-    Err(tcx.dcx().emit_err(errors::DropImplOnWrongItem { span: impl_.self_ty.span }))
+    Err(tcx.dcx().emit_err(errors::DropImplOnWrongItem {
+        span: impl_.self_ty.span,
+        trait_: tcx.item_name(checker.impl_header.trait_ref.skip_binder().def_id),
+    }))
 }
 
 fn visit_implementation_of_copy(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> {

compiler/rustc_hir_analysis/src/errors.rs

@@ -205,6 +205,7 @@ pub(crate) struct DropImplOnWrongItem {
     #[primary_span]
     #[label]
     pub span: Span,
+    pub trait_: Symbol,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1650,7 +1650,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 }
             }
 
-            let sources = candidates.iter().map(|p| self.candidate_source(p, self_ty)).collect();
+            let sources =
+                applicable_candidates.iter().map(|p| self.candidate_source(p.0, self_ty)).collect();
             return Some(Err(MethodError::Ambiguity(sources)));
         }
 

compiler/rustc_mir_transform/src/inline/cycle.rs

@@ -64,15 +64,15 @@ fn process<'tcx>(
     typing_env: ty::TypingEnv<'tcx>,
     caller: ty::Instance<'tcx>,
     target: LocalDefId,
-    seen: &mut FxHashSet<ty::Instance<'tcx>>,
+    seen: &mut FxHashMap<ty::Instance<'tcx>, bool>,
     involved: &mut FxHashSet<LocalDefId>,
     recursion_limiter: &mut FxHashMap<DefId, usize>,
     recursion_limit: Limit,
 ) -> bool {
     trace!(%caller);
-    let mut cycle_found = false;
+    let mut reaches_root = false;
 
-    for &(callee, args) in tcx.mir_inliner_callees(caller.def) {
+    for &(callee_def_id, args) in tcx.mir_inliner_callees(caller.def) {
         let Ok(args) = caller.try_instantiate_mir_and_normalize_erasing_regions(
             tcx,
             typing_env,
@@ -81,14 +81,17 @@ fn process<'tcx>(
             trace!(?caller, ?typing_env, ?args, "cannot normalize, skipping");
             continue;
         };
-        let Ok(Some(callee)) = ty::Instance::try_resolve(tcx, typing_env, callee, args) else {
-            trace!(?callee, "cannot resolve, skipping");
+        let Ok(Some(callee)) = ty::Instance::try_resolve(tcx, typing_env, callee_def_id, args)
+        else {
+            trace!(?callee_def_id, "cannot resolve, skipping");
             continue;
         };
 
         // Found a path.
         if callee.def_id() == target.to_def_id() {
-            cycle_found = true;
+            reaches_root = true;
+            seen.insert(callee, true);
+            continue;
         }
 
         if tcx.is_constructor(callee.def_id()) {
@@ -101,10 +104,17 @@ fn process<'tcx>(
             continue;
         }
 
-        if seen.insert(callee) {
+        let callee_reaches_root = if let Some(&c) = seen.get(&callee) {
+            // Even if we have seen this callee before, and thus don't need
+            // to recurse into it, we still need to propagate whether it reaches
+            // the root so that we can mark all the involved callers, in case we
+            // end up reaching that same recursive callee through some *other* cycle.
+            c
+        } else {
+            seen.insert(callee, false);
             let recursion = recursion_limiter.entry(callee.def_id()).or_default();
             trace!(?callee, recursion = *recursion);
-            let found_recursion = if recursion_limit.value_within_limit(*recursion) {
+            let callee_reaches_root = if recursion_limit.value_within_limit(*recursion) {
                 *recursion += 1;
                 ensure_sufficient_stack(|| {
                     process(
@@ -122,17 +132,19 @@ fn process<'tcx>(
                 // Pessimistically assume that there could be recursion.
                 true
             };
-            if found_recursion {
-                if let Some(callee) = callee.def_id().as_local() {
-                    // Calling `optimized_mir` of a non-local definition cannot cycle.
-                    involved.insert(callee);
-                }
-                cycle_found = true;
+            seen.insert(callee, callee_reaches_root);
+            callee_reaches_root
+        };
+        if callee_reaches_root {
+            if let Some(callee_def_id) = callee.def_id().as_local() {
+                // Calling `optimized_mir` of a non-local definition cannot cycle.
+                involved.insert(callee_def_id);
             }
+            reaches_root = true;
         }
     }
 
-    cycle_found
+    reaches_root
 }
 
 #[instrument(level = "debug", skip(tcx), ret)]
@@ -166,7 +178,7 @@ pub(crate) fn mir_callgraph_cyclic<'tcx>(
         typing_env,
         root_instance,
         root,
-        &mut FxHashSet::default(),
+        &mut FxHashMap::default(),
         &mut involved,
         &mut FxHashMap::default(),
         recursion_limit,