Auto merge of #132626 - workingjubilee:rollup-hbmtbzk, r=workingjubilee

Rollup of 11 pull requests

Successful merges:

 - #131153 (Improve duplicate derive Copy/Clone diagnostics)
 - #132025 (fix suggestion for diagnostic error E0027)
 - #132303 (More tests for non-exhaustive C-like enums in FFI)
 - #132492 (remove support for extern-block const intrinsics)
 - #132587 (Revert "Avoid nested replacement ranges" from #129346.)
 - #132596 ([rustdoc] Fix `--show-coverage` when JSON output format is used)
 - #132598 (Clippy: Move some attribute lints to be early pass (post expansion))
 - #132601 (Update books)
 - #132606 (Improve example of `impl Pattern for &[char]`)
 - #132608 (document `type_implements_trait`)
 - #132609 (docs: fix grammar in doc comment at unix/process.rs)

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

Author: bors

compiler/rustc_attr/src/builtin.rs

@@ -273,8 +273,7 @@ pub fn find_stability(
 /// Collects stability info from `rustc_const_stable`/`rustc_const_unstable`/`rustc_promotable`
 /// attributes in `attrs`. Returns `None` if no stability attributes are found.
 ///
-/// `is_const_fn` indicates whether this is a function marked as `const`. It will always
-/// be false for intrinsics in an `extern` block!
+/// `is_const_fn` indicates whether this is a function marked as `const`.
 pub fn find_const_stability(
     sess: &Session,
     attrs: &[Attribute],
@@ -330,7 +329,7 @@ pub fn find_const_stability(
         }
     }
 
-    // Merge promotable and not_exposed_on_stable into stability info
+    // Merge promotable and const_stable_indirect into stability info
     if promotable {
         match &mut const_stab {
             Some((stab, _)) => stab.promotable = promotable,
@@ -352,10 +351,7 @@ pub fn find_const_stability(
                     })
                 }
             }
-            _ => {
-                // We ignore the `#[rustc_const_stable_indirect]` here, it should be picked up by
-                // the `default_const_unstable` logic.
-            }
+            _ => {}
         }
     }
     // Make sure if `const_stable_indirect` is present, that is recorded. Also make sure all `const

compiler/rustc_borrowck/src/diagnostics/move_errors.rs

@@ -10,6 +10,7 @@ use rustc_middle::ty::{self, Ty};
 use rustc_mir_dataflow::move_paths::{LookupResult, MovePathIndex};
 use rustc_span::{BytePos, ExpnKind, MacroKind, Span};
 use rustc_trait_selection::error_reporting::traits::FindExprBySpan;
+use rustc_trait_selection::infer::InferCtxtExt;
 use tracing::debug;
 
 use crate::MirBorrowckCtxt;
@@ -267,6 +268,15 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 kind,
                 self.is_upvar_field_projection(original_path.as_ref())
             );
+            if self.has_ambiguous_copy(original_path.ty(self.body, self.infcx.tcx).ty) {
+                // If the type may implement Copy, skip the error.
+                // It's an error with the Copy implementation (e.g. duplicate Copy) rather than borrow check
+                self.dcx().span_delayed_bug(
+                    span,
+                    "Type may implement copy, but there is no other error.",
+                );
+                return;
+            }
             (
                 match kind {
                     &IllegalMoveOriginKind::BorrowedContent { target_place } => self
@@ -291,6 +301,13 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         self.buffer_error(err);
     }
 
+    fn has_ambiguous_copy(&mut self, ty: Ty<'tcx>) -> bool {
+        let Some(copy_trait_def) = self.infcx.tcx.lang_items().copy_trait() else { return false };
+        // This is only going to be ambiguous if there are incoherent impls, because otherwise
+        // ambiguity should never happen in MIR.
+        self.infcx.type_implements_trait(copy_trait_def, [ty], self.param_env).may_apply()
+    }
+
     fn report_cannot_move_from_static(&mut self, place: Place<'tcx>, span: Span) -> Diag<'infcx> {
         let description = if place.projection.len() == 1 {
             format!("static item {}", self.describe_any_place(place.as_ref()))

compiler/rustc_const_eval/messages.ftl

@@ -399,7 +399,7 @@ const_eval_uninhabited_enum_variant_written =
 const_eval_unmarked_const_fn_exposed = `{$def_path}` cannot be (indirectly) exposed to stable
     .help = either mark the callee as `#[rustc_const_stable_indirect]`, or the caller as `#[rustc_const_unstable]`
 const_eval_unmarked_intrinsic_exposed = intrinsic `{$def_path}` cannot be (indirectly) exposed to stable
-    .help = mark the caller as `#[rustc_const_unstable]`, or mark the intrinsic `#[rustc_const_stable_indirect]` (but this requires team approval)
+    .help = mark the caller as `#[rustc_const_unstable]`, or mark the intrinsic `#[rustc_const_stable_intrinsic]` (but this requires team approval)
 
 const_eval_unreachable = entering unreachable code
 const_eval_unreachable_unwind =

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -736,16 +736,25 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
                 // Intrinsics are language primitives, not regular calls, so treat them separately.
                 if let Some(intrinsic) = tcx.intrinsic(callee) {
+                    // We use `intrinsic.const_stable` to determine if this can be safely exposed to
+                    // stable code, rather than `const_stable_indirect`. This is to make
+                    // `#[rustc_const_stable_indirect]` an attribute that is always safe to add.
+                    // We also ask is_safe_to_expose_on_stable_const_fn; this determines whether the intrinsic
+                    // fallback body is safe to expose on stable.
+                    let is_const_stable = intrinsic.const_stable
+                        || (!intrinsic.must_be_overridden
+                            && tcx.is_const_fn(callee)
+                            && is_safe_to_expose_on_stable_const_fn(tcx, callee));
                     match tcx.lookup_const_stability(callee) {
                         None => {
                             // Non-const intrinsic.
                             self.check_op(ops::IntrinsicNonConst { name: intrinsic.name });
                         }
-                        Some(ConstStability { feature: None, const_stable_indirect, .. }) => {
+                        Some(ConstStability { feature: None, .. }) => {
                             // Intrinsic does not need a separate feature gate (we rely on the
                             // regular stability checker). However, we have to worry about recursive
                             // const stability.
-                            if !const_stable_indirect && self.enforce_recursive_const_stability() {
+                            if !is_const_stable && self.enforce_recursive_const_stability() {
                                 self.dcx().emit_err(errors::UnmarkedIntrinsicExposed {
                                     span: self.span,
                                     def_path: self.tcx.def_path_str(callee),
@@ -755,17 +764,19 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                         Some(ConstStability {
                             feature: Some(feature),
                             level: StabilityLevel::Unstable { .. },
-                            const_stable_indirect,
                             ..
                         }) => {
                             self.check_op(ops::IntrinsicUnstable {
                                 name: intrinsic.name,
                                 feature,
-                                const_stable_indirect,
+                                const_stable: is_const_stable,
                             });
                         }
                         Some(ConstStability { level: StabilityLevel::Stable { .. }, .. }) => {
-                            // All good.
+                            // All good. Note that a `#[rustc_const_stable]` intrinsic (meaning it
+                            // can be *directly* invoked from stable const code) does not always
+                            // have the `#[rustc_const_stable_intrinsic]` attribute (which controls
+                            // exposing an intrinsic indirectly); we accept this call anyway.
                         }
                     }
                     // This completes the checks for intrinsics.

compiler/rustc_const_eval/src/check_consts/ops.rs

@@ -354,14 +354,14 @@ impl<'tcx> NonConstOp<'tcx> for IntrinsicNonConst {
 pub(crate) struct IntrinsicUnstable {
     pub name: Symbol,
     pub feature: Symbol,
-    pub const_stable_indirect: bool,
+    pub const_stable: bool,
 }
 
 impl<'tcx> NonConstOp<'tcx> for IntrinsicUnstable {
     fn status_in_item(&self, _ccx: &ConstCx<'_, 'tcx>) -> Status {
         Status::Unstable {
             gate: self.feature,
-            safe_to_expose_on_stable: self.const_stable_indirect,
+            safe_to_expose_on_stable: self.const_stable,
             // We do *not* want to suggest to mark the intrinsic as `const_stable_indirect`,
             // that's not a trivial change!
             is_function_call: false,

compiler/rustc_const_eval/src/const_eval/fn_queries.rs

@@ -25,15 +25,9 @@ fn constness(tcx: TyCtxt<'_>, def_id: LocalDefId) -> hir::Constness {
             hir::Constness::Const
         }
         hir::Node::Item(hir::Item { kind: hir::ItemKind::Impl(impl_), .. }) => impl_.constness,
-        hir::Node::ForeignItem(hir::ForeignItem { kind: hir::ForeignItemKind::Fn(..), .. }) => {
-            // Intrinsics use `rustc_const_{un,}stable` attributes to indicate constness. All other
-            // foreign items cannot be evaluated at compile-time.
-            let is_const = if tcx.intrinsic(def_id).is_some() {
-                tcx.lookup_const_stability(def_id).is_some()
-            } else {
-                false
-            };
-            if is_const { hir::Constness::Const } else { hir::Constness::NotConst }
+        hir::Node::ForeignItem(_) => {
+            // Foreign items cannot be evaluated at compile-time.
+            hir::Constness::NotConst
         }
         hir::Node::Expr(e) if let hir::ExprKind::Closure(c) = e.kind => c.constness,
         _ => {

compiler/rustc_feature/src/builtin_attrs.rs

@@ -837,6 +837,10 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         rustc_const_stable_indirect, Normal,
         template!(Word), WarnFollowing, EncodeCrossCrate::No, IMPL_DETAIL,
     ),
+    rustc_attr!(
+        rustc_const_stable_intrinsic, Normal,
+        template!(Word), WarnFollowing, EncodeCrossCrate::No, IMPL_DETAIL,
+    ),
     gated!(
         rustc_allow_const_fn_unstable, Normal,
         template!(Word, List: "feat1, feat2, ..."), DuplicatesOk, EncodeCrossCrate::No,

compiler/rustc_hir_typeck/src/pat.rs

@@ -2071,6 +2071,25 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 s = pluralize!(len),
                 them = if len == 1 { "it" } else { "them" },
             ),
+            format!(
+                "{}{}{}{}",
+                prefix,
+                unmentioned_fields
+                    .iter()
+                    .map(|(_, name)| {
+                        let field_name = name.to_string();
+                        format!("{field_name}: _")
+                    })
+                    .collect::<Vec<_>>()
+                    .join(", "),
+                if have_inaccessible_fields { ", .." } else { "" },
+                postfix,
+            ),
+            Applicability::MachineApplicable,
+        );
+        err.span_suggestion(
+            sp,
+            "or always ignore missing fields here",
             format!("{prefix}..{postfix}"),
             Applicability::MachineApplicable,
         );

compiler/rustc_middle/src/ty/intrinsic.rs

@@ -9,6 +9,8 @@ pub struct IntrinsicDef {
     pub name: Symbol,
     /// Whether the intrinsic has no meaningful body and all backends need to shim all calls to it.
     pub must_be_overridden: bool,
+    /// Whether the intrinsic can be invoked from stable const fn
+    pub const_stable: bool,
 }
 
 impl TyCtxt<'_> {

compiler/rustc_middle/src/ty/util.rs

@@ -1789,6 +1789,7 @@ pub fn intrinsic_raw(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::Intrinsi
         Some(ty::IntrinsicDef {
             name: tcx.item_name(def_id.into()),
             must_be_overridden: tcx.has_attr(def_id, sym::rustc_intrinsic_must_be_overridden),
+            const_stable: tcx.has_attr(def_id, sym::rustc_const_stable_intrinsic),
         })
     } else {
         None