Auto merge of rust-lang#120654 - matthiaskrgr:rollup-ywlixr5, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#119481 (Clarify ambiguity in select_nth_unstable docs)
 - rust-lang#120384 (Use `<T, U>` for array/slice equality `impl`s)
 - rust-lang#120423 (update indirect structural match lints to match RFC and to show up for dependencies)
 - rust-lang#120458 (Document `&CStr` to `CString` conversion)
 - rust-lang#120558 (Stop bailing out from compilation just because there were incoherent traits)
 - rust-lang#120572 (Update libc to 0.2.153)
 - rust-lang#120641 (rustdoc: trait.impl, type.impl: sort impls to make it not depend on serialization order)

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

Author: bors

Diff for: Cargo.lock

@@ -2169,9 +2169,9 @@ checksum = "db13adb97ab515a3691f56e4dbab09283d0b86cb45abd991d8634a9d6f501760"
 
 [[package]]
 name = "libc"
-version = "0.2.150"
+version = "0.2.153"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "89d92a4743f9a61002fae18374ed11e7973f530cb3a3255fb354818118b2203c"
+checksum = "9c198f91728a82281a64e1f4f9eeb25d82cb32a5de251c6bd1b5154d63a8e7bd"
 dependencies = [
  "rustc-std-workspace-core",
 ]

Diff for: compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -20,7 +20,7 @@ use std::mem;
 use std::ops::{ControlFlow, Deref};
 
 use super::ops::{self, NonConstOp, Status};
-use super::qualifs::{self, CustomEq, HasMutInterior, NeedsDrop, NeedsNonConstDrop};
+use super::qualifs::{self, HasMutInterior, NeedsDrop, NeedsNonConstDrop};
 use super::resolver::FlowSensitiveAnalysis;
 use super::{ConstCx, Qualif};
 use crate::const_eval::is_unstable_const_fn;
@@ -149,37 +149,10 @@ impl<'mir, 'tcx> Qualifs<'mir, 'tcx> {
 
         let return_loc = ccx.body.terminator_loc(return_block);
 
-        let custom_eq = match ccx.const_kind() {
-            // We don't care whether a `const fn` returns a value that is not structurally
-            // matchable. Functions calls are opaque and always use type-based qualification, so
-            // this value should never be used.
-            hir::ConstContext::ConstFn => true,
-
-            // If we know that all values of the return type are structurally matchable, there's no
-            // need to run dataflow.
-            // Opaque types do not participate in const generics or pattern matching, so we can safely count them out.
-            _ if ccx.body.return_ty().has_opaque_types()
-                || !CustomEq::in_any_value_of_ty(ccx, ccx.body.return_ty()) =>
-            {
-                false
-            }
-
-            hir::ConstContext::Const { .. } | hir::ConstContext::Static(_) => {
-                let mut cursor = FlowSensitiveAnalysis::new(CustomEq, ccx)
-                    .into_engine(ccx.tcx, ccx.body)
-                    .iterate_to_fixpoint()
-                    .into_results_cursor(ccx.body);
-
-                cursor.seek_after_primary_effect(return_loc);
-                cursor.get().contains(RETURN_PLACE)
-            }
-        };
-
         ConstQualifs {
             needs_drop: self.needs_drop(ccx, RETURN_PLACE, return_loc),
             needs_non_const_drop: self.needs_non_const_drop(ccx, RETURN_PLACE, return_loc),
             has_mut_interior: self.has_mut_interior(ccx, RETURN_PLACE, return_loc),
-            custom_eq,
             tainted_by_errors,
         }
     }

Diff for: compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs

@@ -10,7 +10,7 @@ use rustc_middle::mir::*;
 use rustc_middle::traits::BuiltinImplSource;
 use rustc_middle::ty::{self, AdtDef, GenericArgsRef, Ty};
 use rustc_trait_selection::traits::{
-    self, ImplSource, Obligation, ObligationCause, ObligationCtxt, SelectionContext,
+    ImplSource, Obligation, ObligationCause, ObligationCtxt, SelectionContext,
 };
 
 use super::ConstCx;
@@ -24,7 +24,6 @@ pub fn in_any_value_of_ty<'tcx>(
         has_mut_interior: HasMutInterior::in_any_value_of_ty(cx, ty),
         needs_drop: NeedsDrop::in_any_value_of_ty(cx, ty),
         needs_non_const_drop: NeedsNonConstDrop::in_any_value_of_ty(cx, ty),
-        custom_eq: CustomEq::in_any_value_of_ty(cx, ty),
         tainted_by_errors,
     }
 }
@@ -213,35 +212,6 @@ impl Qualif for NeedsNonConstDrop {
     }
 }
 
-/// A constant that cannot be used as part of a pattern in a `match` expression.
-pub struct CustomEq;
-
-impl Qualif for CustomEq {
-    const ANALYSIS_NAME: &'static str = "flow_custom_eq";
-
-    fn in_qualifs(qualifs: &ConstQualifs) -> bool {
-        qualifs.custom_eq
-    }
-
-    fn in_any_value_of_ty<'tcx>(cx: &ConstCx<'_, 'tcx>, ty: Ty<'tcx>) -> bool {
-        // If *any* component of a composite data type does not implement `Structural{Partial,}Eq`,
-        // we know that at least some values of that type are not structural-match. I say "some"
-        // because that component may be part of an enum variant (e.g.,
-        // `Option::<NonStructuralMatchTy>::Some`), in which case some values of this type may be
-        // structural-match (`Option::None`).
-        traits::search_for_structural_match_violation(cx.body.span, cx.tcx, ty).is_some()
-    }
-
-    fn in_adt_inherently<'tcx>(
-        cx: &ConstCx<'_, 'tcx>,
-        def: AdtDef<'tcx>,
-        args: GenericArgsRef<'tcx>,
-    ) -> bool {
-        let ty = Ty::new_adt(cx.tcx, def, args);
-        !ty.is_structural_eq_shallow(cx.tcx)
-    }
-}
-
 // FIXME: Use `mir::visit::Visitor` for the `in_*` functions if/when it supports early return.
 
 /// Returns `true` if this `Rvalue` contains qualif `Q`.

Diff for: compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -1990,6 +1990,10 @@ pub(super) fn check_type_bounds<'tcx>(
     impl_ty: ty::AssocItem,
     impl_trait_ref: ty::TraitRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
+    // Avoid bogus "type annotations needed `Foo: Bar`" errors on `impl Bar for Foo` in case
+    // other `Foo` impls are incoherent.
+    tcx.ensure().coherent_trait(impl_trait_ref.def_id)?;
+
     let param_env = tcx.param_env(impl_ty.def_id);
     debug!(?param_env);
 

Diff for: compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1005,6 +1005,10 @@ fn check_associated_item(
     enter_wf_checking_ctxt(tcx, span, item_id, |wfcx| {
         let item = tcx.associated_item(item_id);
 
+        // Avoid bogus "type annotations needed `Foo: Bar`" errors on `impl Bar for Foo` in case
+        // other `Foo` impls are incoherent.
+        tcx.ensure().coherent_trait(tcx.local_parent(item_id))?;
+
         let self_ty = match item.container {
             ty::TraitContainer => tcx.types.self_param,
             ty::ImplContainer => tcx.type_of(item.container_id(tcx)).instantiate_identity(),
@@ -1291,6 +1295,9 @@ fn check_impl<'tcx>(
                 // therefore don't need to be WF (the trait's `Self: Trait` predicate
                 // won't hold).
                 let trait_ref = tcx.impl_trait_ref(item.owner_id).unwrap().instantiate_identity();
+                // Avoid bogus "type annotations needed `Foo: Bar`" errors on `impl Bar for Foo` in case
+                // other `Foo` impls are incoherent.
+                tcx.ensure().coherent_trait(trait_ref.def_id)?;
                 let trait_ref = wfcx.normalize(
                     ast_trait_ref.path.span,
                     Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),

Diff for: compiler/rustc_hir_analysis/src/lib.rs

@@ -169,11 +169,11 @@ pub fn check_crate(tcx: TyCtxt<'_>) -> Result<(), ErrorGuaranteed> {
 
     tcx.sess.time("coherence_checking", || {
         // Check impls constrain their parameters
-        let mut res =
+        let res =
             tcx.hir().try_par_for_each_module(|module| tcx.ensure().check_mod_impl_wf(module));
 
         for &trait_def_id in tcx.all_local_trait_impls(()).keys() {
-            res = res.and(tcx.ensure().coherent_trait(trait_def_id));
+            let _ = tcx.ensure().coherent_trait(trait_def_id);
         }
         // these queries are executed for side-effects (error reporting):
         res.and(tcx.ensure().crate_inherent_impls(()))

Diff for: compiler/rustc_lint/src/lib.rs

@@ -516,6 +516,11 @@ fn register_builtins(store: &mut LintStore) {
         "converted into hard error, see PR #118649 \
          <https://github.com/rust-lang/rust/pull/118649> for more information",
     );
+    store.register_removed(
+        "nontrivial_structural_match",
+        "no longer needed, see RFC #3535 \
+         <https://rust-lang.github.io/rfcs/3535-constants-in-patterns.html> for more information",
+    );
 }
 
 fn register_internals(store: &mut LintStore) {

Diff for: compiler/rustc_lint_defs/src/builtin.rs

@@ -3,6 +3,9 @@
 //! These are the built-in lints that are emitted direct in the main
 //! compiler code, rather than using their own custom pass. Those
 //! lints are all available in `rustc_lint::builtin`.
+//!
+//! When removing a lint, make sure to also add a call to `register_removed` in
+//! compiler/rustc_lint/src/lib.rs.
 
 use crate::{declare_lint, declare_lint_pass, FutureIncompatibilityReason};
 use rustc_span::edition::Edition;
@@ -67,7 +70,6 @@ declare_lint_pass! {
         MUST_NOT_SUSPEND,
         NAMED_ARGUMENTS_USED_POSITIONALLY,
         NON_EXHAUSTIVE_OMITTED_PATTERNS,
-        NONTRIVIAL_STRUCTURAL_MATCH,
         ORDER_DEPENDENT_TRAIT_OBJECTS,
         OVERLAPPING_RANGE_ENDPOINTS,
         PATTERNS_IN_FNS_WITHOUT_BODY,
@@ -2330,8 +2332,8 @@ declare_lint! {
     Warn,
     "constant used in pattern contains value of non-structural-match type in a field or a variant",
     @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
-        reference: "issue #62411 <https://github.com/rust-lang/rust/issues/62411>",
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
+        reference: "issue #120362 <https://github.com/rust-lang/rust/issues/120362>",
     };
 }
 
@@ -2386,47 +2388,8 @@ declare_lint! {
     Warn,
     "pointers are not structural-match",
     @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
-        reference: "issue #62411 <https://github.com/rust-lang/rust/issues/70861>",
-    };
-}
-
-declare_lint! {
-    /// The `nontrivial_structural_match` lint detects constants that are used in patterns,
-    /// whose type is not structural-match and whose initializer body actually uses values
-    /// that are not structural-match. So `Option<NotStructuralMatch>` is ok if the constant
-    /// is just `None`.
-    ///
-    /// ### Example
-    ///
-    /// ```rust,compile_fail
-    /// #![deny(nontrivial_structural_match)]
-    ///
-    /// #[derive(Copy, Clone, Debug)]
-    /// struct NoDerive(u32);
-    /// impl PartialEq for NoDerive { fn eq(&self, _: &Self) -> bool { false } }
-    /// impl Eq for NoDerive { }
-    /// fn main() {
-    ///     const INDEX: Option<NoDerive> = [None, Some(NoDerive(10))][0];
-    ///     match None { Some(_) => panic!("whoops"), INDEX => dbg!(INDEX), };
-    /// }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// Previous versions of Rust accepted constants in patterns, even if those constants' types
-    /// did not have `PartialEq` derived. Thus the compiler falls back to runtime execution of
-    /// `PartialEq`, which can report that two constants are not equal even if they are
-    /// bit-equivalent.
-    pub NONTRIVIAL_STRUCTURAL_MATCH,
-    Warn,
-    "constant used in pattern of non-structural-match type and the constant's initializer \
-    expression contains values of non-structural-match types",
-    @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
-        reference: "issue #73448 <https://github.com/rust-lang/rust/issues/73448>",
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
+        reference: "issue #120362 <https://github.com/rust-lang/rust/issues/120362>",
     };
 }
 

Diff for: compiler/rustc_middle/src/mir/query.rs

@@ -189,15 +189,14 @@ pub struct BorrowCheckResult<'tcx> {
 
 /// The result of the `mir_const_qualif` query.
 ///
-/// Each field (except `error_occurred`) corresponds to an implementer of the `Qualif` trait in
+/// Each field (except `tainted_by_errors`) corresponds to an implementer of the `Qualif` trait in
 /// `rustc_const_eval/src/transform/check_consts/qualifs.rs`. See that file for more information on each
 /// `Qualif`.
 #[derive(Clone, Copy, Debug, Default, TyEncodable, TyDecodable, HashStable)]
 pub struct ConstQualifs {
     pub has_mut_interior: bool,
     pub needs_drop: bool,
     pub needs_non_const_drop: bool,
-    pub custom_eq: bool,
     pub tainted_by_errors: Option<ErrorGuaranteed>,
 }