[beta] backports

.github/workflows/post-merge.yml

@@ -6,7 +6,7 @@ name: Post merge analysis
 on:
   push:
     branches:
-      - master
+      - main
 
 jobs:
   analysis:

compiler/rustc_errors/src/emitter.rs

@@ -3465,14 +3465,9 @@ impl Drop for Buffy {
 
 pub fn stderr_destination(color: ColorConfig) -> Destination {
     let buffer_writer = std::io::stderr();
-    let choice = color.to_color_choice();
     // We need to resolve `ColorChoice::Auto` before `Box`ing since
     // `ColorChoice::Auto` on `dyn Write` will always resolve to `Never`
-    let choice = if matches!(choice, ColorChoice::Auto) {
-        AutoStream::choice(&buffer_writer)
-    } else {
-        choice
-    };
+    let choice = get_stderr_color_choice(color, &buffer_writer);
     // On Windows we'll be performing global synchronization on the entire
     // system for emitting rustc errors, so there's no need to buffer
     // anything.
@@ -3487,6 +3482,11 @@ pub fn stderr_destination(color: ColorConfig) -> Destination {
     }
 }
 
+pub fn get_stderr_color_choice(color: ColorConfig, stderr: &std::io::Stderr) -> ColorChoice {
+    let choice = color.to_color_choice();
+    if matches!(choice, ColorChoice::Auto) { AutoStream::choice(stderr) } else { choice }
+}
+
 /// On Windows, BRIGHT_BLUE is hard to read on black. Use cyan instead.
 ///
 /// See #36178.

compiler/rustc_mir_transform/src/liveness.rs

@@ -45,6 +45,9 @@ struct Access {
     /// When we encounter multiple statements at the same location, we only increase the liveness,
     /// in order to avoid false positives.
     live: bool,
+    /// Is this a direct access to the place itself, no projections, or to a field?
+    /// This helps distinguish `x = ...` from `x.field = ...`
+    is_direct: bool,
 }
 
 #[tracing::instrument(level = "debug", skip(tcx), ret)]
@@ -689,15 +692,17 @@ impl<'a, 'tcx> AssignmentResult<'a, 'tcx> {
             |place: Place<'tcx>, kind, source_info: SourceInfo, live: &DenseBitSet<PlaceIndex>| {
                 if let Some((index, extra_projections)) = checked_places.get(place.as_ref()) {
                     if !is_indirect(extra_projections) {
+                        let is_direct = extra_projections.is_empty();
                         match assignments[index].entry(source_info) {
                             IndexEntry::Vacant(v) => {
-                                let access = Access { kind, live: live.contains(index) };
+                                let access = Access { kind, live: live.contains(index), is_direct };
                                 v.insert(access);
                             }
                             IndexEntry::Occupied(mut o) => {
                                 // There were already a sighting. Mark this statement as live if it
                                 // was, to avoid false positives.
                                 o.get_mut().live |= live.contains(index);
+                                o.get_mut().is_direct &= is_direct;
                             }
                         }
                     }
@@ -781,7 +786,7 @@ impl<'a, 'tcx> AssignmentResult<'a, 'tcx> {
                     continue;
                 };
                 let source_info = body.local_decls[place.local].source_info;
-                let access = Access { kind, live: live.contains(index) };
+                let access = Access { kind, live: live.contains(index), is_direct: true };
                 assignments[index].insert(source_info, access);
             }
         }
@@ -875,6 +880,33 @@ impl<'a, 'tcx> AssignmentResult<'a, 'tcx> {
         dead_captures
     }
 
+    /// Check if a local is referenced in any reachable basic block.
+    /// Variables in unreachable code (e.g., after `todo!()`) should not trigger unused warnings.
+    fn is_local_in_reachable_code(&self, local: Local) -> bool {
+        struct LocalVisitor {
+            target_local: Local,
+            found: bool,
+        }
+
+        impl<'tcx> Visitor<'tcx> for LocalVisitor {
+            fn visit_local(&mut self, local: Local, _context: PlaceContext, _location: Location) {
+                if local == self.target_local {
+                    self.found = true;
+                }
+            }
+        }
+
+        let mut visitor = LocalVisitor { target_local: local, found: false };
+        for (bb, bb_data) in traversal::postorder(self.body) {
+            visitor.visit_basic_block_data(bb, bb_data);
+            if visitor.found {
+                return true;
+            }
+        }
+
+        false
+    }
+
     /// Report fully unused locals, and forget the corresponding assignments.
     fn report_fully_unused(&mut self) {
         let tcx = self.tcx;
@@ -928,6 +960,10 @@ impl<'a, 'tcx> AssignmentResult<'a, 'tcx> {
 
             let statements = &mut self.assignments[index];
             if statements.is_empty() {
+                if !self.is_local_in_reachable_code(local) {
+                    continue;
+                }
+
                 let sugg = if from_macro {
                     errors::UnusedVariableSugg::NoSugg { span: def_span, name }
                 } else {
@@ -977,8 +1013,10 @@ impl<'a, 'tcx> AssignmentResult<'a, 'tcx> {
                     self.checked_places,
                     self.body,
                 ) {
-                    statements.clear();
-                    continue;
+                    statements.retain(|_, access| access.is_direct);
+                    if statements.is_empty() {
+                        continue;
+                    }
                 }
 
                 let typo = maybe_suggest_typo();
@@ -1049,26 +1087,28 @@ impl<'a, 'tcx> AssignmentResult<'a, 'tcx> {
 
             let Some((name, decl_span)) = self.checked_places.names[index] else { continue };
 
-            // We have outstanding assignments and with non-trivial drop.
-            // This is probably a drop-guard, so we do not issue a warning there.
-            if maybe_drop_guard(
+            let is_maybe_drop_guard = maybe_drop_guard(
                 tcx,
                 self.typing_env,
                 index,
                 &self.ever_dropped,
                 self.checked_places,
                 self.body,
-            ) {
-                continue;
-            }
+            );
 
             // We probed MIR in reverse order for dataflow.
             // We revert the vector to give a consistent order to the user.
-            for (source_info, Access { live, kind }) in statements.into_iter().rev() {
+            for (source_info, Access { live, kind, is_direct }) in statements.into_iter().rev() {
                 if live {
                     continue;
                 }
 
+                // If this place was dropped and has non-trivial drop,
+                // skip reporting field assignments.
+                if !is_direct && is_maybe_drop_guard {
+                    continue;
+                }
+
                 // Report the dead assignment.
                 let Some(hir_id) = source_info.scope.lint_root(&self.body.source_scopes) else {
                     continue;

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -1,11 +1,12 @@
 use core::ops::ControlFlow;
 use std::borrow::Cow;
+use std::collections::hash_set;
 use std::path::PathBuf;
 
 use rustc_abi::ExternAbi;
 use rustc_ast::ast::LitKind;
 use rustc_ast::{LitIntType, TraitObjectSyntax};
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::codes::*;
 use rustc_errors::{
@@ -1927,11 +1928,17 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         if self.tcx.visibility(did).is_accessible_from(body_def_id, self.tcx) {
                             // don't suggest foreign `#[doc(hidden)]` types
                             if !did.is_local() {
-                                while let Some(parent) = parent_map.get(&did) {
+                                let mut previously_seen_dids: FxHashSet<DefId> = Default::default();
+                                previously_seen_dids.insert(did);
+                                while let Some(&parent) = parent_map.get(&did)
+                                    && let hash_set::Entry::Vacant(v) =
+                                        previously_seen_dids.entry(parent)
+                                {
                                     if self.tcx.is_doc_hidden(did) {
                                         return false;
                                     }
-                                    did = *parent;
+                                    v.insert();
+                                    did = parent;
                                 }
                             }
                             true

compiler/rustc_trait_selection/src/lib.rs

@@ -20,6 +20,7 @@
 #![feature(associated_type_defaults)]
 #![feature(box_patterns)]
 #![feature(default_field_values)]
+#![feature(hash_set_entry)]
 #![feature(if_let_guard)]
 #![feature(iter_intersperse)]
 #![feature(iterator_try_reduce)]

library/alloc/src/collections/btree/map.rs

@@ -2414,7 +2414,7 @@ impl<K, V> Default for BTreeMap<K, V> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<K: PartialEq, V: PartialEq, A: Allocator + Clone> PartialEq for BTreeMap<K, V, A> {
     fn eq(&self, other: &BTreeMap<K, V, A>) -> bool {
-        self.iter().eq(other)
+        self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a == b)
     }
 }
 

library/alloctests/tests/collections/eq_diff_len.rs

@@ -0,0 +1,96 @@
+//! Regression tests which fail if some collections' `PartialEq::eq` impls compare
+//! elements when the collections have different sizes.
+//! This behavior is not guaranteed either way, so regressing these tests is fine
+//! if it is done on purpose.
+use std::cmp::Ordering;
+use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet, LinkedList};
+
+/// This intentionally has a panicking `PartialEq` impl, to test that various
+/// collections' `PartialEq` impls don't actually compare elements if their sizes
+/// are unequal.
+///
+/// This is not advisable in normal code.
+#[derive(Debug, Clone, Copy, Hash)]
+struct Evil;
+
+impl PartialEq for Evil {
+    fn eq(&self, _: &Self) -> bool {
+        panic!("Evil::eq is evil");
+    }
+}
+impl Eq for Evil {}
+
+impl PartialOrd for Evil {
+    fn partial_cmp(&self, _: &Self) -> Option<Ordering> {
+        Some(Ordering::Equal)
+    }
+}
+
+impl Ord for Evil {
+    fn cmp(&self, _: &Self) -> Ordering {
+        // Constructing a `BTreeSet`/`BTreeMap` uses `cmp` on the elements,
+        // but comparing it with with `==` uses `eq` on the elements,
+        // so Evil::cmp doesn't need to be evil.
+        Ordering::Equal
+    }
+}
+
+// check Evil works
+#[test]
+#[should_panic = "Evil::eq is evil"]
+fn evil_eq_works() {
+    let v1 = vec![Evil];
+    let v2 = vec![Evil];
+
+    _ = v1 == v2;
+}
+
+// check various containers don't compare if their sizes are different
+
+#[test]
+fn vec_evil_eq() {
+    let v1 = vec![Evil];
+    let v2 = vec![Evil; 2];
+
+    assert_eq!(false, v1 == v2);
+}
+
+#[test]
+fn hashset_evil_eq() {
+    let s1 = HashSet::from([(0, Evil)]);
+    let s2 = HashSet::from([(0, Evil), (1, Evil)]);
+
+    assert_eq!(false, s1 == s2);
+}
+
+#[test]
+fn hashmap_evil_eq() {
+    let m1 = HashMap::from([(0, Evil)]);
+    let m2 = HashMap::from([(0, Evil), (1, Evil)]);
+
+    assert_eq!(false, m1 == m2);
+}
+
+#[test]
+fn btreeset_evil_eq() {
+    let s1 = BTreeSet::from([(0, Evil)]);
+    let s2 = BTreeSet::from([(0, Evil), (1, Evil)]);
+
+    assert_eq!(false, s1 == s2);
+}
+
+#[test]
+fn btreemap_evil_eq() {
+    let m1 = BTreeMap::from([(0, Evil)]);
+    let m2 = BTreeMap::from([(0, Evil), (1, Evil)]);
+
+    assert_eq!(false, m1 == m2);
+}
+
+#[test]
+fn linkedlist_evil_eq() {
+    let m1 = LinkedList::from([Evil]);
+    let m2 = LinkedList::from([Evil; 2]);
+
+    assert_eq!(false, m1 == m2);
+}

library/alloctests/tests/collections/mod.rs

@@ -1 +1,2 @@
 mod binary_heap;
+mod eq_diff_len;

src/ci/citool/src/jobs.rs

@@ -123,7 +123,7 @@ pub fn load_job_db(db: &str) -> anyhow::Result<JobDatabase> {
 /// modulo certain carve-outs" in [`validate_job_database`].
 ///
 /// This invariant is important to make sure that it's not easily possible (without modifying
-/// `citool`) to have PRs with red PR-only CI jobs merged into `master`, causing all subsequent PR
+/// `citool`) to have PRs with red PR-only CI jobs merged into `main`, causing all subsequent PR
 /// CI runs to be red until the cause is fixed.
 fn register_pr_jobs_as_auto_jobs(db: &mut JobDatabase) -> anyhow::Result<()> {
     for pr_job in &db.pr_jobs {
@@ -273,7 +273,7 @@ pub enum RunType {
     /// Merge attempt workflow
     AutoJob,
     /// Fake job only used for sharing Github Actions cache.
-    MasterJob,
+    MainJob,
 }
 
 /// Maximum number of custom try jobs that can be requested in a single
@@ -323,7 +323,7 @@ fn calculate_jobs(
             (jobs, "try", &db.envs.try_env)
         }
         RunType::AutoJob => (db.auto_jobs.clone(), "auto", &db.envs.auto_env),
-        RunType::MasterJob => return Ok(vec![]),
+        RunType::MainJob => return Ok(vec![]),
     };
     let jobs = substitute_github_vars(jobs.clone())
         .context("Failed to substitute GitHub context variables in jobs")?;
@@ -376,15 +376,15 @@ pub fn calculate_job_matrix(
     eprintln!("Run type: {run_type:?}");
 
     let jobs = calculate_jobs(&run_type, &db, channel)?;
-    if jobs.is_empty() && !matches!(run_type, RunType::MasterJob) {
+    if jobs.is_empty() && !matches!(run_type, RunType::MainJob) {
         return Err(anyhow::anyhow!("Computed job list is empty"));
     }
 
     let run_type = match run_type {
         RunType::PullRequest => "pr",
         RunType::TryJob { .. } => "try",
         RunType::AutoJob => "auto",
-        RunType::MasterJob => "master",
+        RunType::MainJob => "main",
     };
 
     eprintln!("Output");

src/ci/citool/src/main.rs

@@ -47,7 +47,7 @@ impl GitHubContext {
                 Some(RunType::TryJob { job_patterns: patterns })
             }
             ("push", "refs/heads/auto") => Some(RunType::AutoJob),
-            ("push", "refs/heads/master") => Some(RunType::MasterJob),
+            ("push", "refs/heads/main") => Some(RunType::MainJob),
             _ => None,
         }
     }

src/ci/citool/tests/jobs.rs

@@ -46,11 +46,11 @@ fn pr_jobs() {
 }
 
 #[test]
-fn master_jobs() {
-    let stdout = get_matrix("push", "commit", "refs/heads/master");
+fn main_jobs() {
+    let stdout = get_matrix("push", "commit", "refs/heads/main");
     insta::assert_snapshot!(stdout, @r#"
     jobs=[]
-    run_type=master
+    run_type=main
     "#);
 }
 

src/ci/scripts/checkout-submodules.sh

@@ -17,7 +17,7 @@ ci_dir=$(cd $(dirname $0) && pwd)/..
 # On the beta channel we'll be automatically calculating the prerelease version
 # via the git history, so unshallow our shallow clone from CI.
 if [ "$(releaseChannel)" = "beta" ]; then
-  git fetch origin --unshallow beta master
+  git fetch origin --unshallow beta main
 fi
 
 function fetch_github_commit_archive {