Auto merge of #115960 - GuillaumeGomez:rollup-8tky3qu, r=GuillaumeGomez

Rollup of 6 pull requests

Successful merges:

 - #112725 (rustdoc-search: add support for type parameters)
 - #114941 (Don't resolve generic impls that may be shadowed by dyn built-in impls)
 - #115625 (Explain HRTB + infer limitations of old solver)
 - #115839 (Bump libc to 0.2.148)
 - #115924 (Don't complain on a single non-exhaustive 1-ZST)
 - #115946 (panic when encountering an illegal cpumask in thread::available_parallelism)

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

Author: bors

Diff for: Cargo.lock

@@ -2142,9 +2142,9 @@ checksum = "db13adb97ab515a3691f56e4dbab09283d0b86cb45abd991d8634a9d6f501760"
 
 [[package]]
 name = "libc"
-version = "0.2.147"
+version = "0.2.148"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b4668fb0ea861c1df094127ac5f1da3409a82116a4ba74fca2e58ef927159bb3"
+checksum = "9cdc71e17332e86d2e1d38c1f99edcb6288ee11b815fb1a4b049eaa2114d369b"
 dependencies = [
  "rustc-std-workspace-core",
 ]

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

@@ -1201,25 +1201,35 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
         );
         return;
     }
-    for (span, _trivial, non_exhaustive) in field_infos {
-        if let Some((descr, def_id, args, non_exhaustive)) = non_exhaustive {
-            tcx.struct_span_lint_hir(
-                REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
-                tcx.hir().local_def_id_to_hir_id(adt.did().expect_local()),
-                span,
-                "zero-sized fields in `repr(transparent)` cannot contain external non-exhaustive types",
-                |lint| {
-                    let note = if non_exhaustive {
-                        "is marked with `#[non_exhaustive]`"
-                    } else {
-                        "contains private fields"
-                    };
-                    let field_ty = tcx.def_path_str_with_args(def_id, args);
-                    lint
-                        .note(format!("this {descr} contains `{field_ty}`, which {note}, \
-                            and makes it not a breaking change to become non-zero-sized in the future."))
-                },
-            )
+    let mut prev_non_exhaustive_1zst = false;
+    for (span, _trivial, non_exhaustive_1zst) in field_infos {
+        if let Some((descr, def_id, args, non_exhaustive)) = non_exhaustive_1zst {
+            // If there are any non-trivial fields, then there can be no non-exhaustive 1-zsts.
+            // Otherwise, it's only an issue if there's >1 non-exhaustive 1-zst.
+            if non_trivial_count > 0 || prev_non_exhaustive_1zst {
+                tcx.struct_span_lint_hir(
+                    REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
+                    tcx.hir().local_def_id_to_hir_id(adt.did().expect_local()),
+                    span,
+                    "zero-sized fields in `repr(transparent)` cannot \
+                    contain external non-exhaustive types",
+                    |lint| {
+                        let note = if non_exhaustive {
+                            "is marked with `#[non_exhaustive]`"
+                        } else {
+                            "contains private fields"
+                        };
+                        let field_ty = tcx.def_path_str_with_args(def_id, args);
+                        lint.note(format!(
+                            "this {descr} contains `{field_ty}`, which {note}, \
+                                and makes it not a breaking change to become \
+                                non-zero-sized in the future."
+                        ))
+                    },
+                )
+            } else {
+                prev_non_exhaustive_1zst = true;
+            }
         }
     }
 }

Diff for: compiler/rustc_middle/src/ty/sty.rs

@@ -2945,6 +2945,33 @@ impl<'tcx> Ty<'tcx> {
             _ => false,
         }
     }
+
+    pub fn is_known_rigid(self) -> bool {
+        match self.kind() {
+            Bool
+            | Char
+            | Int(_)
+            | Uint(_)
+            | Float(_)
+            | Adt(_, _)
+            | Foreign(_)
+            | Str
+            | Array(_, _)
+            | Slice(_)
+            | RawPtr(_)
+            | Ref(_, _, _)
+            | FnDef(_, _)
+            | FnPtr(_)
+            | Dynamic(_, _, _)
+            | Closure(_, _)
+            | Generator(_, _, _)
+            | GeneratorWitness(_)
+            | GeneratorWitnessMIR(_, _)
+            | Never
+            | Tuple(_) => true,
+            Error(_) | Infer(_) | Alias(_, _) | Param(_) | Bound(_, _) | Placeholder(_) => false,
+        }
+    }
 }
 
 /// Extra information about why we ended up with a particular variance.

Diff for: compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -986,6 +986,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                             }
                         }
 
+                        self.explain_hrtb_projection(&mut err, trait_predicate, obligation.param_env, &obligation.cause);
+
                         // Return early if the trait is Debug or Display and the invocation
                         // originates within a standard library macro, because the output
                         // is otherwise overwhelming and unhelpful (see #85844 for an

Diff for: compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -406,6 +406,14 @@ pub trait TypeErrCtxtExt<'tcx> {
         candidate_impls: &[ImplCandidate<'tcx>],
         span: Span,
     );
+
+    fn explain_hrtb_projection(
+        &self,
+        diag: &mut Diagnostic,
+        pred: ty::PolyTraitPredicate<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        cause: &ObligationCause<'tcx>,
+    );
 }
 
 fn predicate_constraint(generics: &hir::Generics<'_>, pred: ty::Predicate<'_>) -> (Span, String) {
@@ -4027,6 +4035,71 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             }
         }
     }
+
+    fn explain_hrtb_projection(
+        &self,
+        diag: &mut Diagnostic,
+        pred: ty::PolyTraitPredicate<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        cause: &ObligationCause<'tcx>,
+    ) {
+        if pred.skip_binder().has_escaping_bound_vars() && pred.skip_binder().has_non_region_infer()
+        {
+            self.probe(|_| {
+                let ocx = ObligationCtxt::new(self);
+                let pred = self.instantiate_binder_with_placeholders(pred);
+                let pred = ocx.normalize(&ObligationCause::dummy(), param_env, pred);
+                ocx.register_obligation(Obligation::new(
+                    self.tcx,
+                    ObligationCause::dummy(),
+                    param_env,
+                    pred,
+                ));
+                if !ocx.select_where_possible().is_empty() {
+                    // encountered errors.
+                    return;
+                }
+
+                if let ObligationCauseCode::FunctionArgumentObligation {
+                    call_hir_id,
+                    arg_hir_id,
+                    parent_code: _,
+                } = cause.code()
+                {
+                    let arg_span = self.tcx.hir().span(*arg_hir_id);
+                    let mut sp: MultiSpan = arg_span.into();
+
+                    sp.push_span_label(
+                        arg_span,
+                        "the trait solver is unable to infer the \
+                        generic types that should be inferred from this argument",
+                    );
+                    sp.push_span_label(
+                        self.tcx.hir().span(*call_hir_id),
+                        "add turbofish arguments to this call to \
+                        specify the types manually, even if it's redundant",
+                    );
+                    diag.span_note(
+                        sp,
+                        "this is a known limitation of the trait solver that \
+                        will be lifted in the future",
+                    );
+                } else {
+                    let mut sp: MultiSpan = cause.span.into();
+                    sp.push_span_label(
+                        cause.span,
+                        "try adding turbofish arguments to this expression to \
+                        specify the types manually, even if it's redundant",
+                    );
+                    diag.span_note(
+                        sp,
+                        "this is a known limitation of the trait solver that \
+                        will be lifted in the future",
+                    );
+                }
+            });
+        }
+    }
 }
 
 /// Add a hint to add a missing borrow or remove an unnecessary one.

Diff for: compiler/rustc_ty_utils/src/instance.rs

@@ -141,11 +141,34 @@ fn resolve_associated_item<'tcx>(
                     false
                 }
             };
-
             if !eligible {
                 return Ok(None);
             }
 
+            // HACK: We may have overlapping `dyn Trait` built-in impls and
+            // user-provided blanket impls. Detect that case here, and return
+            // ambiguity.
+            //
+            // This should not affect totally monomorphized contexts, only
+            // resolve calls that happen polymorphically, such as the mir-inliner
+            // and const-prop (and also some lints).
+            let self_ty = rcvr_args.type_at(0);
+            if !self_ty.is_known_rigid() {
+                let predicates = tcx
+                    .predicates_of(impl_data.impl_def_id)
+                    .instantiate(tcx, impl_data.args)
+                    .predicates;
+                let sized_def_id = tcx.lang_items().sized_trait();
+                // If we find a `Self: Sized` bound on the item, then we know
+                // that `dyn Trait` can certainly never apply here.
+                if !predicates.into_iter().filter_map(ty::Clause::as_trait_clause).any(|clause| {
+                    Some(clause.def_id()) == sized_def_id
+                        && clause.skip_binder().self_ty() == self_ty
+                }) {
+                    return Ok(None);
+                }
+            }
+
             // Any final impl is required to define all associated items.
             if !leaf_def.item.defaultness(tcx).has_value() {
                 let guard = tcx.sess.delay_span_bug(

Diff for: library/std/Cargo.toml

@@ -17,7 +17,7 @@ cfg-if = { version = "1.0", features = ['rustc-dep-of-std'] }
 panic_unwind = { path = "../panic_unwind", optional = true }
 panic_abort = { path = "../panic_abort" }
 core = { path = "../core", public = true }
-libc = { version = "0.2.146", default-features = false, features = ['rustc-dep-of-std'], public = true }
+libc = { version = "0.2.148", default-features = false, features = ['rustc-dep-of-std'], public = true }
 compiler_builtins = { version = "0.1.100" }
 profiler_builtins = { path = "../profiler_builtins", optional = true }
 unwind = { path = "../unwind" }

Diff for: library/std/src/sys/unix/thread.rs

@@ -324,8 +324,10 @@ pub fn available_parallelism() -> io::Result<NonZeroUsize> {
                     if libc::sched_getaffinity(0, mem::size_of::<libc::cpu_set_t>(), &mut set) == 0 {
                         let count = libc::CPU_COUNT(&set) as usize;
                         let count = count.min(quota);
-                        // SAFETY: affinity mask can't be empty and the quota gets clamped to a minimum of 1
-                        return Ok(NonZeroUsize::new_unchecked(count));
+                        // reported to occur on MIPS kernels older than our minimum supported kernel version for those targets
+                        let count = NonZeroUsize::new(count)
+                            .expect("CPU count must be > 0. This may be a bug in sched_getaffinity(); try upgrading the kernel.");
+                        return Ok(count);
                     }
                 }
             }

Diff for: src/doc/rustdoc/src/SUMMARY.md

@@ -4,6 +4,7 @@
 - [Command-line arguments](command-line-arguments.md)
 - [How to read rustdoc output](how-to-read-rustdoc.md)
     - [In-doc settings](read-documentation/in-doc-settings.md)
+    - [Search](read-documentation/search.md)
 - [How to write documentation](how-to-write-documentation.md)
     - [What to include (and exclude)](write-documentation/what-to-include.md)
     - [The `#[doc]` attribute](write-documentation/the-doc-attribute.md)

Diff for: src/doc/rustdoc/src/how-to-read-rustdoc.md

@@ -75,56 +75,11 @@ or the current item whose documentation is being displayed.
 ## The Theme Picker and Search Interface
 
 When viewing `rustdoc`'s output in a browser with JavaScript enabled,
-a dynamic interface appears at the top of the page composed of the search
-interface, help screen, and options.
-
-### The Search Interface
-
-Typing in the search bar instantly searches the available documentation for
-the string entered with a fuzzy matching algorithm that is tolerant of minor
-typos.
-
-By default, the search results given are "In Names",
-meaning that the fuzzy match is made against the names of items.
-Matching names are shown on the left, and the first few words of their
-descriptions are given on the right.
-By clicking an item, you will navigate to its particular documentation.
-
-There are two other sets of results, shown as tabs in the search results pane.
-"In Parameters" shows matches for the string in the types of parameters to
-functions, and "In Return Types" shows matches in the return types of functions.
-Both are very useful when looking for a function whose name you can't quite
-bring to mind when you know the type you have or want.
-
-Names in the search interface can be prefixed with an item type followed by a
-colon (such as `mod:`) to restrict the results to just that kind of item. Also,
-searching for `println!` will search for a macro named `println`, just like
-searching for `macro:println` does.
-
-Function signature searches can query generics, wrapped in angle brackets, and
-traits are normalized like types in the search engine. For example, a function
-with the signature `fn my_function<I: Iterator<Item=u32>>(input: I) -> usize`
-can be matched with the following queries:
-
-* `Iterator<u32> -> usize`
-* `trait:Iterator<primitive:u32> -> primitive:usize`
-* `Iterator -> usize`
-
-Generics and function parameters are order-agnostic, but sensitive to nesting
-and number of matches. For example, a function with the signature
-`fn read_all(&mut self: impl Read) -> Result<Vec<u8>, Error>`
-will match these queries:
-
-* `Read -> Result<Vec<u8>, Error>`
-* `Read -> Result<Error, Vec>`
-* `Read -> Result<Vec<u8>>`
-
-But it *does not* match `Result<Vec, u8>` or `Result<u8<Vec>>`.
-
-Function signature searches also support arrays and slices. The explicit name
-`primitive:slice<u8>` and `primitive:array<u8>` can be used to match a slice
-or array of bytes, while square brackets `[u8]` will match either one. Empty
-square brackets, `[]`, will match any slice regardless of what it contains.
+a dynamic interface appears at the top of the page composed of the [search]
+interface, help screen, and [options].
+
+[options]: read-documentation/in-doc-settings.html
+[search]: read-documentation/search.md
 
 Paths are supported as well, you can look for `Vec::new` or `Option::Some` or
 even `module::module_child::another_child::struct::field`. Whitespace characters