Auto merge of rust-lang#128719 - matthiaskrgr:rollup-rbjs7bc, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#122792 (Stabilize `min_exhaustive_patterns`)
 - rust-lang#124944 (On trait bound mismatch, detect multiple crate versions in dep tree)
 - rust-lang#128273 (Improve `Ord` violation help)
 - rust-lang#128406 (implement BufReader::peek)
 - rust-lang#128539 (Forbid unused unsafe in vxworks-specific std modules)
 - rust-lang#128692 (Add a triagebot mention for `library/Cargo.lock`)
 - rust-lang#128710 (Don't ICE when getting an input file name's stem fails)

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

Author: bors

compiler/rustc_codegen_cranelift/example/mini_core_hello_world.rs

@@ -585,6 +585,7 @@ pub enum E2<X> {
     V4,
 }
 
+#[allow(unreachable_patterns)]
 fn check_niche_behavior() {
     if let E1::V2 { .. } = (E1::V1 { f: true }) {
         intrinsics::abort();

compiler/rustc_codegen_gcc/example/mini_core_hello_world.rs

@@ -430,6 +430,7 @@ pub enum E2<X> {
     V4,
 }
 
+#[allow(unreachable_patterns)]
 fn check_niche_behavior () {
     if let E1::V2 { .. } = (E1::V1 { f: true }) {
         intrinsics::abort();

compiler/rustc_errors/src/diagnostic.rs

@@ -741,6 +741,16 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
         self
     }
 
+    #[rustc_lint_diagnostics]
+    pub fn highlighted_span_note(
+        &mut self,
+        span: impl Into<MultiSpan>,
+        msg: Vec<StringPart>,
+    ) -> &mut Self {
+        self.sub_with_highlights(Level::Note, msg, span.into());
+        self
+    }
+
     /// This is like [`Diag::note()`], but it's only printed once.
     #[rustc_lint_diagnostics]
     pub fn note_once(&mut self, msg: impl Into<SubdiagMessage>) -> &mut Self {
@@ -815,6 +825,17 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
         self
     }
 
+    /// Add a help message attached to this diagnostic with a customizable highlighted message.
+    #[rustc_lint_diagnostics]
+    pub fn highlighted_span_help(
+        &mut self,
+        span: impl Into<MultiSpan>,
+        msg: Vec<StringPart>,
+    ) -> &mut Self {
+        self.sub_with_highlights(Level::Help, msg, span.into());
+        self
+    }
+
     /// Prints the span with some help above it.
     /// This is like [`Diag::help()`], but it gets its own span.
     #[rustc_lint_diagnostics]

compiler/rustc_errors/src/diagnostic_impls.rs

@@ -66,6 +66,7 @@ macro_rules! into_diag_arg_for_number {
             impl IntoDiagArg for $ty {
                 fn into_diag_arg(self) -> DiagArgValue {
                     // Convert to a string if it won't fit into `Number`.
+                    #[allow(irrefutable_let_patterns)]
                     if let Ok(n) = TryInto::<i32>::try_into(self) {
                         DiagArgValue::Number(n)
                     } else {

compiler/rustc_errors/src/emitter.rs

@@ -1346,7 +1346,7 @@ impl HumanEmitter {
                 buffer.append(0, ": ", header_style);
                 label_width += 2;
             }
-            for (text, _) in msgs.iter() {
+            for (text, style) in msgs.iter() {
                 let text = self.translate_message(text, args).map_err(Report::new).unwrap();
                 // Account for newlines to align output to its label.
                 for (line, text) in normalize_whitespace(&text).lines().enumerate() {
@@ -1357,7 +1357,10 @@ impl HumanEmitter {
                             if line == 0 { String::new() } else { " ".repeat(label_width) },
                             text
                         ),
-                        header_style,
+                        match style {
+                            Style::Highlight => *style,
+                            _ => header_style,
+                        },
                     );
                 }
             }

compiler/rustc_feature/src/accepted.rs

@@ -267,6 +267,8 @@ declare_features! (
     (accepted, min_const_generics, "1.51.0", Some(74878)),
     /// Allows calling `const unsafe fn` inside `unsafe` blocks in `const fn` functions.
     (accepted, min_const_unsafe_fn, "1.33.0", Some(55607)),
+    /// Allows exhaustive pattern matching on uninhabited types when matched by value.
+    (accepted, min_exhaustive_patterns, "CURRENT_RUSTC_VERSION", Some(119612)),
     /// Allows using `Self` and associated types in struct expressions and patterns.
     (accepted, more_struct_aliases, "1.16.0", Some(37544)),
     /// Allows using the MOVBE target feature.

compiler/rustc_feature/src/unstable.rs

@@ -519,9 +519,6 @@ declare_features! (
     (unstable, macro_metavar_expr_concat, "1.81.0", Some(124225)),
     /// Allows `#[marker]` on certain traits allowing overlapping implementations.
     (unstable, marker_trait_attr, "1.30.0", Some(29864)),
-    /// Allows exhaustive pattern matching on types that contain uninhabited types in cases that are
-    /// unambiguously sound.
-    (unstable, min_exhaustive_patterns, "1.77.0", Some(119612)),
     /// A minimal, sound subset of specialization intended to be used by the
     /// standard library until the soundness issues with specialization
     /// are fixed.

compiler/rustc_middle/src/lib.rs

@@ -28,6 +28,7 @@
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(rustc::potential_query_instability)]
 #![allow(rustc::untranslatable_diagnostic)]
+#![cfg_attr(bootstrap, feature(min_exhaustive_patterns))]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(allocator_api)]
@@ -48,7 +49,6 @@
 #![feature(iter_from_coroutine)]
 #![feature(let_chains)]
 #![feature(macro_metavar_expr)]
-#![feature(min_exhaustive_patterns)]
 #![feature(min_specialization)]
 #![feature(negative_impls)]
 #![feature(never_type)]

compiler/rustc_mir_build/src/build/matches/match_pair.rs

@@ -208,14 +208,11 @@ impl<'pat, 'tcx> MatchPairTree<'pat, 'tcx> {
                 subpairs = cx.field_match_pairs(downcast_place, subpatterns);
 
                 let irrefutable = adt_def.variants().iter_enumerated().all(|(i, v)| {
-                    i == variant_index || {
-                        (cx.tcx.features().exhaustive_patterns
-                            || cx.tcx.features().min_exhaustive_patterns)
-                            && !v
-                                .inhabited_predicate(cx.tcx, adt_def)
-                                .instantiate(cx.tcx, args)
-                                .apply_ignore_module(cx.tcx, cx.param_env)
-                    }
+                    i == variant_index
+                        || !v
+                            .inhabited_predicate(cx.tcx, adt_def)
+                            .instantiate(cx.tcx, args)
+                            .apply_ignore_module(cx.tcx, cx.param_env)
                 }) && (adt_def.did().is_local()
                     || !adt_def.is_variant_list_non_exhaustive());
                 if irrefutable {

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -695,9 +695,7 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
 
         // Emit an extra note if the first uncovered witness would be uninhabited
         // if we disregard visibility.
-        let witness_1_is_privately_uninhabited = if (self.tcx.features().exhaustive_patterns
-            || self.tcx.features().min_exhaustive_patterns)
-            && let Some(witness_1) = witnesses.get(0)
+        let witness_1_is_privately_uninhabited = if let Some(witness_1) = witnesses.get(0)
             && let ty::Adt(adt, args) = witness_1.ty().kind()
             && adt.is_enum()
             && let Constructor::Variant(variant_index) = witness_1.ctor()
@@ -1059,7 +1057,7 @@ fn report_non_exhaustive_match<'p, 'tcx>(
                 err.note("`&str` cannot be matched exhaustively, so a wildcard `_` is necessary");
             } else if cx.is_foreign_non_exhaustive_enum(ty) {
                 err.note(format!("`{ty}` is marked as non-exhaustive, so a wildcard `_` is necessary to match exhaustively"));
-            } else if cx.is_uninhabited(ty.inner()) && cx.tcx.features().min_exhaustive_patterns {
+            } else if cx.is_uninhabited(ty.inner()) {
                 // The type is uninhabited yet there is a witness: we must be in the `MaybeInvalid`
                 // case.
                 err.note(format!("`{ty}` is uninhabited but is not being matched by value, so a wildcard `_` is required"));

compiler/rustc_pattern_analysis/src/lib.rs

@@ -54,7 +54,6 @@ pub trait PatCx: Sized + fmt::Debug {
     type PatData: Clone;
 
     fn is_exhaustive_patterns_feature_on(&self) -> bool;
-    fn is_min_exhaustive_patterns_feature_on(&self) -> bool;
 
     /// The number of fields for this constructor.
     fn ctor_arity(&self, ctor: &Constructor<Self>, ty: &Self::Ty) -> usize;

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -237,9 +237,7 @@ impl<'p, 'tcx: 'p> RustcPatCtxt<'p, 'tcx> {
                         let tys = cx.variant_sub_tys(ty, variant).map(|(field, ty)| {
                             let is_visible =
                                 adt.is_enum() || field.vis.is_accessible_from(cx.module, cx.tcx);
-                            let is_uninhabited = (cx.tcx.features().exhaustive_patterns
-                                || cx.tcx.features().min_exhaustive_patterns)
-                                && cx.is_uninhabited(*ty);
+                            let is_uninhabited = cx.is_uninhabited(*ty);
                             let skip = is_uninhabited && (!is_visible || is_non_exhaustive);
                             (ty, PrivateUninhabitedField(skip))
                         });
@@ -925,9 +923,6 @@ impl<'p, 'tcx: 'p> PatCx for RustcPatCtxt<'p, 'tcx> {
     fn is_exhaustive_patterns_feature_on(&self) -> bool {
         self.tcx.features().exhaustive_patterns
     }
-    fn is_min_exhaustive_patterns_feature_on(&self) -> bool {
-        self.tcx.features().min_exhaustive_patterns
-    }
 
     fn ctor_arity(&self, ctor: &crate::constructor::Constructor<Self>, ty: &Self::Ty) -> usize {
         self.ctor_arity(ctor, *ty)

compiler/rustc_pattern_analysis/src/usefulness.rs

@@ -543,13 +543,11 @@
 //! recurse into subpatterns. That second part is done through [`PlaceValidity`], most notably
 //! [`PlaceValidity::specialize`].
 //!
-//! Having said all that, in practice we don't fully follow what's been presented in this section.
-//! Let's call "toplevel exception" the case where the match scrutinee itself has type `!` or
-//! `EmptyEnum`. First, on stable rust, we require `_` patterns for empty types in all cases apart
-//! from the toplevel exception. The `exhaustive_patterns` and `min_exaustive_patterns` allow
-//! omitting patterns in the cases described above. There's a final detail: in the toplevel
-//! exception or with the `exhaustive_patterns` feature, we ignore place validity when checking
-//! whether a pattern is required for exhaustiveness. I (Nadrieril) hope to deprecate this behavior.
+//! Having said all that, we don't fully follow what's been presented in this section. For
+//! backwards-compatibility, we ignore place validity when checking whether a pattern is required
+//! for exhaustiveness in two cases: when the `exhaustive_patterns` feature gate is on, or when the
+//! match scrutinee itself has type `!` or `EmptyEnum`. I (Nadrieril) hope to deprecate this
+//! exception.
 //!
 //!
 //!
@@ -953,13 +951,10 @@ impl<Cx: PatCx> PlaceInfo<Cx> {
             self.is_scrutinee && matches!(ctors_for_ty, ConstructorSet::NoConstructors);
         // Whether empty patterns are counted as useful or not. We only warn an empty arm unreachable if
         // it is guaranteed unreachable by the opsem (i.e. if the place is `known_valid`).
-        let empty_arms_are_unreachable = self.validity.is_known_valid()
-            && (is_toplevel_exception
-                || cx.is_exhaustive_patterns_feature_on()
-                || cx.is_min_exhaustive_patterns_feature_on());
+        let empty_arms_are_unreachable = self.validity.is_known_valid();
         // Whether empty patterns can be omitted for exhaustiveness. We ignore place validity in the
         // toplevel exception and `exhaustive_patterns` cases for backwards compatibility.
-        let can_omit_empty_arms = empty_arms_are_unreachable
+        let can_omit_empty_arms = self.validity.is_known_valid()
             || is_toplevel_exception
             || cx.is_exhaustive_patterns_feature_on();
 

compiler/rustc_pattern_analysis/tests/common/mod.rs

@@ -152,10 +152,6 @@ impl PatCx for Cx {
         false
     }
 
-    fn is_min_exhaustive_patterns_feature_on(&self) -> bool {
-        true
-    }
-
     fn ctor_arity(&self, ctor: &Constructor<Self>, ty: &Self::Ty) -> usize {
         ty.sub_tys(ctor).len()
     }

compiler/rustc_session/src/config.rs

@@ -838,10 +838,14 @@ pub enum Input {
 
 impl Input {
     pub fn filestem(&self) -> &str {
-        match *self {
-            Input::File(ref ifile) => ifile.file_stem().unwrap().to_str().unwrap(),
-            Input::Str { .. } => "rust_out",
+        if let Input::File(ifile) = self {
+            // If for some reason getting the file stem as a UTF-8 string fails,
+            // then fallback to a fixed name.
+            if let Some(name) = ifile.file_stem().and_then(OsStr::to_str) {
+                return name;
+            }
         }
+        "rust_out"
     }
 
     pub fn source_name(&self) -> FileName {

compiler/rustc_target/src/lib.rs

@@ -9,12 +9,12 @@
 
 // tidy-alphabetical-start
 #![allow(internal_features)]
+#![cfg_attr(bootstrap, feature(min_exhaustive_patterns))]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![doc(rust_logo)]
 #![feature(assert_matches)]
 #![feature(iter_intersperse)]
 #![feature(let_chains)]
-#![feature(min_exhaustive_patterns)]
 #![feature(rustc_attrs)]
 #![feature(rustdoc_internals)]
 // tidy-alphabetical-end