Auto merge of rust-lang#111933 - matthiaskrgr:rollup-m10k3ts, r=matthiaskrgr

Rollup of 4 pull requests

Successful merges:

 - rust-lang#95198 (Add slice::{split_,}{first,last}_chunk{,_mut})
 - rust-lang#109899 (Use apple-m1 as target CPU for aarch64-apple-darwin.)
 - rust-lang#111624 (Emit diagnostic for privately uninhabited uncovered witnesses.)
 - rust-lang#111875 (Don't leak the function that is called on drop)

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

Author: bors

compiler/rustc_data_structures/src/lib.rs

@@ -102,21 +102,27 @@ pub mod unord;
 pub use ena::undo_log;
 pub use ena::unify;
 
-pub struct OnDrop<F: Fn()>(pub F);
+/// Returns a structure that calls `f` when dropped.
+pub fn defer<F: FnOnce()>(f: F) -> OnDrop<F> {
+    OnDrop(Some(f))
+}
+
+pub struct OnDrop<F: FnOnce()>(Option<F>);
 
-impl<F: Fn()> OnDrop<F> {
-    /// Forgets the function which prevents it from running.
-    /// Ensure that the function owns no memory, otherwise it will be leaked.
+impl<F: FnOnce()> OnDrop<F> {
+    /// Disables on-drop call.
     #[inline]
-    pub fn disable(self) {
-        std::mem::forget(self);
+    pub fn disable(mut self) {
+        self.0.take();
     }
 }
 
-impl<F: Fn()> Drop for OnDrop<F> {
+impl<F: FnOnce()> Drop for OnDrop<F> {
     #[inline]
     fn drop(&mut self) {
-        (self.0)();
+        if let Some(f) = self.0.take() {
+            f();
+        }
     }
 }
 

compiler/rustc_data_structures/src/owned_slice/tests.rs

@@ -7,8 +7,8 @@ use std::{
 };
 
 use crate::{
+    defer,
     owned_slice::{slice_owned, try_slice_owned, OwnedSlice},
-    OnDrop,
 };
 
 #[test]
@@ -66,7 +66,7 @@ fn boxed() {
 fn drop_drops() {
     let flag = Arc::new(AtomicBool::new(false));
     let flag_prime = Arc::clone(&flag);
-    let d = OnDrop(move || flag_prime.store(true, atomic::Ordering::Relaxed));
+    let d = defer(move || flag_prime.store(true, atomic::Ordering::Relaxed));
 
     let slice = slice_owned(d, |_| &[]);
 

compiler/rustc_interface/src/interface.rs

@@ -3,9 +3,9 @@ use crate::util;
 use rustc_ast::token;
 use rustc_ast::{self as ast, LitKind, MetaItemKind};
 use rustc_codegen_ssa::traits::CodegenBackend;
+use rustc_data_structures::defer;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::sync::Lrc;
-use rustc_data_structures::OnDrop;
 use rustc_errors::registry::Registry;
 use rustc_errors::{ErrorGuaranteed, Handler};
 use rustc_lint::LintStore;
@@ -325,7 +325,7 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
 
             rustc_span::set_source_map(compiler.sess.parse_sess.clone_source_map(), move || {
                 let r = {
-                    let _sess_abort_error = OnDrop(|| {
+                    let _sess_abort_error = defer(|| {
                         compiler.sess.finish_diagnostics(registry);
                     });
 

compiler/rustc_middle/src/ty/context/tls.rs

@@ -78,7 +78,7 @@ where
 {
     TLV.with(|tlv| {
         let old = tlv.replace(erase(context));
-        let _reset = rustc_data_structures::OnDrop(move || tlv.set(old));
+        let _reset = rustc_data_structures::defer(move || tlv.set(old));
         f()
     })
 }

compiler/rustc_mir_build/messages.ftl

@@ -340,6 +340,8 @@ mir_build_uncovered = {$count ->
         *[other] patterns `{$witness_1}`, `{$witness_2}`, `{$witness_3}` and {$remainder} more
     } not covered
 
+mir_build_privately_uninhabited = pattern `{$witness_1}` is currently uninhabited, but this variant contains private fields which may become inhabited in the future
+
 mir_build_pattern_not_covered = refutable pattern in {$origin}
     .pattern_ty = the matched value is of type `{$pattern_ty}`
 

compiler/rustc_mir_build/src/errors.rs

@@ -781,6 +781,8 @@ pub(crate) struct PatternNotCovered<'s, 'tcx> {
     pub interpreted_as_const: Option<InterpretedAsConst>,
     #[subdiagnostic]
     pub adt_defined_here: Option<AdtDefinedHere<'tcx>>,
+    #[note(mir_build_privately_uninhabited)]
+    pub witness_1_is_privately_uninhabited: Option<()>,
     #[note(mir_build_pattern_ty)]
     pub _p: (),
     pub pattern_ty: Ty<'tcx>,

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

@@ -479,12 +479,30 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
             AdtDefinedHere { adt_def_span, ty, variants }
         };
 
+        // Emit an extra note if the first uncovered witness is
+        // visibly uninhabited anywhere in the current crate.
+        let witness_1_is_privately_uninhabited =
+            if cx.tcx.features().exhaustive_patterns
+                && let Some(witness_1) = witnesses.get(0)
+                && let ty::Adt(adt, substs) = witness_1.ty().kind()
+                && adt.is_enum()
+                && let Constructor::Variant(variant_index) = witness_1.ctor()
+            {
+                let variant = adt.variant(*variant_index);
+                let inhabited = variant.inhabited_predicate(cx.tcx, *adt).subst(cx.tcx, substs);
+                assert!(inhabited.apply(cx.tcx, cx.param_env, cx.module));
+                !inhabited.apply_ignore_module(cx.tcx, cx.param_env)
+            } else {
+                false
+            };
+
         self.error = Err(self.tcx.sess.emit_err(PatternNotCovered {
             span: pat.span,
             origin,
             uncovered: Uncovered::new(pat.span, &cx, witnesses),
             inform,
             interpreted_as_const,
+            witness_1_is_privately_uninhabited: witness_1_is_privately_uninhabited.then_some(()),
             _p: (),
             pattern_ty,
             let_suggestion,

compiler/rustc_query_system/src/query/job.rs

@@ -22,7 +22,7 @@ use {
     rustc_data_structures::fx::FxHashSet,
     rustc_data_structures::sync::Lock,
     rustc_data_structures::sync::Lrc,
-    rustc_data_structures::{jobserver, OnDrop},
+    rustc_data_structures::{defer, jobserver},
     rustc_span::DUMMY_SP,
     std::iter,
     std::process,
@@ -530,7 +530,7 @@ fn remove_cycle<D: DepKind>(
 /// all active queries for cycles before finally resuming all the waiters at once.
 #[cfg(parallel_compiler)]
 pub fn deadlock<D: DepKind>(query_map: QueryMap<D>, registry: &rayon_core::Registry) {
-    let on_panic = OnDrop(|| {
+    let on_panic = defer(|| {
         eprintln!("deadlock handler panicked, aborting process");
         process::abort();
     });

compiler/rustc_target/src/spec/aarch64_apple_darwin.rs

@@ -4,7 +4,7 @@ use crate::spec::{FramePointer, SanitizerSet, Target, TargetOptions};
 pub fn target() -> Target {
     let arch = Arch::Arm64;
     let mut base = opts("macos", arch);
-    base.cpu = "apple-a14".into();
+    base.cpu = "apple-m1".into();
     base.max_atomic_width = Some(128);
 
     // FIXME: The leak sanitizer currently fails the tests, see #88132.