Auto merge of rust-lang#93468 - matthiaskrgr:rollup-vxullvd, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#93256 (Make `join!` description more accurate)
 - rust-lang#93358 (Add note suggesting that predicate may be satisfied, but is not `const`)
 - rust-lang#93362 (Do not register infer var for GAT projection in RPIT)
 - rust-lang#93391 (rustdoc: remove tooltip from source link)
 - rust-lang#93414 (Move unstable is_{arch}_feature_detected! macros to std::arch)
 - rust-lang#93441 (rustdoc: load the set of in-scope traits for modules with no docstring)
 - rust-lang#93459 (fs: Don't copy d_name from struct dirent)
 - rust-lang#93463 (Rename _args -> args in format_args expansion)

Failed merges:

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

Author: bors

compiler/rustc_builtin_macros/src/format.rs

@@ -791,7 +791,7 @@ impl<'a, 'b> Context<'a, 'b> {
         // Thus in the not nicely ordered case we emit the following instead:
         //
         //     match (&$arg0, &$arg1, …) {
-        //         _args => [ArgumentV1::new(_args.$i, …), ArgumentV1::new(_args.$j, …), …]
+        //         args => [ArgumentV1::new(args.$i, …), ArgumentV1::new(args.$j, …), …]
         //     }
         //
         // for the sequence of indices $i, $j, … governed by fmt_arg_index_and_ty.
@@ -804,7 +804,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 self.ecx.expr_addr_of(expansion_span, P(e.take()))
             } else {
                 let def_site = self.ecx.with_def_site_ctxt(span);
-                let args_tuple = self.ecx.expr_ident(def_site, Ident::new(sym::_args, def_site));
+                let args_tuple = self.ecx.expr_ident(def_site, Ident::new(sym::args, def_site));
                 let member = Ident::new(sym::integer(arg_index), def_site);
                 self.ecx.expr(def_site, ast::ExprKind::Field(args_tuple, member))
             };
@@ -828,7 +828,7 @@ impl<'a, 'b> Context<'a, 'b> {
                     .map(|e| self.ecx.expr_addr_of(e.span.with_ctxt(self.macsp.ctxt()), e))
                     .collect();
 
-                let pat = self.ecx.pat_ident(self.macsp, Ident::new(sym::_args, self.macsp));
+                let pat = self.ecx.pat_ident(self.macsp, Ident::new(sym::args, self.macsp));
                 let arm = self.ecx.arm(self.macsp, pat, args_array);
                 let head = self.ecx.expr(self.macsp, ast::ExprKind::Tup(heads));
                 self.ecx.expr_match(self.macsp, head, vec![arm])

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -7,7 +7,6 @@ use crate::interpret::{
 };
 
 use rustc_errors::ErrorReported;
-use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::ErrorHandled;
@@ -216,7 +215,7 @@ pub fn eval_to_const_value_raw_provider<'tcx>(
     tcx: TyCtxt<'tcx>,
     key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>,
 ) -> ::rustc_middle::mir::interpret::EvalToConstValueResult<'tcx> {
-    assert!(key.param_env.constness() == hir::Constness::Const);
+    assert!(key.param_env.is_const());
     // see comment in eval_to_allocation_raw_provider for what we're doing here
     if key.param_env.reveal() == Reveal::All {
         let mut key = key;
@@ -251,7 +250,7 @@ pub fn eval_to_allocation_raw_provider<'tcx>(
     tcx: TyCtxt<'tcx>,
     key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>,
 ) -> ::rustc_middle::mir::interpret::EvalToAllocationRawResult<'tcx> {
-    assert!(key.param_env.constness() == hir::Constness::Const);
+    assert!(key.param_env.is_const());
     // Because the constant is computed twice (once per value of `Reveal`), we are at risk of
     // reporting the same error twice here. To resolve this, we check whether we can evaluate the
     // constant in the more restrictive `Reveal::UserFacing`, which most likely already was

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -569,13 +569,15 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
             let predicate = predicate.fold_with(&mut BottomUpFolder {
                 tcx,
                 ty_op: |ty| match ty.kind() {
-                    ty::Projection(projection_ty) => infcx.infer_projection(
-                        self.param_env,
-                        *projection_ty,
-                        traits::ObligationCause::misc(self.value_span, self.body_id),
-                        0,
-                        &mut self.obligations,
-                    ),
+                    ty::Projection(projection_ty) if !projection_ty.has_escaping_bound_vars() => {
+                        infcx.infer_projection(
+                            self.param_env,
+                            *projection_ty,
+                            traits::ObligationCause::misc(self.value_span, self.body_id),
+                            0,
+                            &mut self.obligations,
+                        )
+                    }
                     _ => ty,
                 },
                 lt_op: |lt| lt,

compiler/rustc_lint/src/traits.rs

@@ -86,15 +86,14 @@ declare_lint_pass!(
 
 impl<'tcx> LateLintPass<'tcx> for DropTraitConstraints {
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
-        use rustc_middle::ty;
         use rustc_middle::ty::PredicateKind::*;
 
         let predicates = cx.tcx.explicit_predicates_of(item.def_id);
         for &(predicate, span) in predicates.predicates {
             let Trait(trait_predicate) = predicate.kind().skip_binder() else {
                 continue
             };
-            if trait_predicate.constness == ty::BoundConstness::ConstIfConst {
+            if trait_predicate.is_const_if_const() {
                 // `~const Drop` definitely have meanings so avoid linting here.
                 continue;
             }

compiler/rustc_middle/src/ty/mod.rs

@@ -784,6 +784,11 @@ impl<'tcx> TraitPredicate<'tcx> {
     pub fn self_ty(self) -> Ty<'tcx> {
         self.trait_ref.self_ty()
     }
+
+    #[inline]
+    pub fn is_const_if_const(self) -> bool {
+        self.constness == BoundConstness::ConstIfConst
+    }
 }
 
 impl<'tcx> PolyTraitPredicate<'tcx> {
@@ -803,6 +808,11 @@ impl<'tcx> PolyTraitPredicate<'tcx> {
             p
         });
     }
+
+    #[inline]
+    pub fn is_const_if_const(self) -> bool {
+        self.skip_binder().is_const_if_const()
+    }
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, TyEncodable, TyDecodable)]
@@ -1388,6 +1398,11 @@ impl<'tcx> ParamEnv<'tcx> {
         self.packed.tag().constness
     }
 
+    #[inline]
+    pub fn is_const(self) -> bool {
+        self.packed.tag().constness == hir::Constness::Const
+    }
+
     /// Construct a trait environment with no where-clauses in scope
     /// where the values of all `impl Trait` and other hidden types
     /// are revealed. This is suitable for monomorphized, post-typeck
@@ -1503,6 +1518,7 @@ impl<'tcx> PolyTraitRef<'tcx> {
             polarity: ty::ImplPolarity::Positive,
         })
     }
+
     #[inline]
     pub fn without_const(self) -> PolyTraitPredicate<'tcx> {
         self.with_constness(BoundConstness::NotConst)

compiler/rustc_span/src/symbol.rs

@@ -272,7 +272,6 @@ symbols! {
         __H,
         __S,
         __try_var,
-        _args,
         _d,
         _e,
         _task_context,
@@ -324,6 +323,7 @@ symbols! {
         append_const_msg,
         arbitrary_enum_discriminant,
         arbitrary_self_types,
+        args,
         arith_offset,
         arm,
         arm_target_feature,

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

@@ -439,6 +439,28 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                         } else {
                             err.span_label(span, explanation);
                         }
+
+                        if trait_predicate.is_const_if_const() && obligation.param_env.is_const() {
+                            let non_const_predicate = trait_ref.without_const();
+                            let non_const_obligation = Obligation {
+                                cause: obligation.cause.clone(),
+                                param_env: obligation.param_env.without_const(),
+                                predicate: non_const_predicate.to_predicate(tcx),
+                                recursion_depth: obligation.recursion_depth,
+                            };
+                            if self.predicate_may_hold(&non_const_obligation) {
+                                err.span_note(
+                                    span,
+                                    &format!(
+                                        "the trait `{}` is implemented for `{}`, \
+                                        but that implementation is not `const`",
+                                        non_const_predicate.print_modifiers_and_trait_path(),
+                                        trait_ref.skip_binder().self_ty(),
+                                    ),
+                                );
+                            }
+                        }
+
                         if let Some((msg, span)) = type_def {
                             err.span_label(span, &msg);
                         }

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -305,7 +305,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             } else if lang_items.unsize_trait() == Some(def_id) {
                 self.assemble_candidates_for_unsizing(obligation, &mut candidates);
             } else if lang_items.drop_trait() == Some(def_id)
-                && obligation.predicate.skip_binder().constness == ty::BoundConstness::ConstIfConst
+                && obligation.predicate.is_const_if_const()
             {
                 self.assemble_const_drop_candidates(obligation, &mut candidates);
             } else {

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -72,9 +72,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // CheckPredicate(&A: Super)
         // CheckPredicate(A: ~const Super) // <- still const env, failure
         // ```
-        if obligation.param_env.constness() == Constness::Const
-            && obligation.predicate.skip_binder().constness == ty::BoundConstness::NotConst
-        {
+        if obligation.param_env.is_const() && !obligation.predicate.is_const_if_const() {
             new_obligation = TraitObligation {
                 cause: obligation.cause.clone(),
                 param_env: obligation.param_env.without_const(),

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -1173,9 +1173,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     ImplCandidate(def_id)
                         if tcx.impl_constness(def_id) == hir::Constness::Const => {}
                     // const param
-                    ParamCandidate(trait_pred)
-                        if trait_pred.skip_binder().constness
-                            == ty::BoundConstness::ConstIfConst => {}
+                    ParamCandidate(trait_pred) if trait_pred.is_const_if_const() => {}
                     // auto trait impl
                     AutoImplCandidate(..) => {}
                     // generator, this will raise error in other places