Rollup of 9 pull requests

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -1557,31 +1557,46 @@ impl<'a> TraitDef<'a> {
                             }),
                         ),
                     );
-                    // In general, fields in packed structs are copied via a
-                    // block, e.g. `&{self.0}`. The one exception is `[u8]`
-                    // fields, which cannot be copied and also never cause
-                    // unaligned references. This exception is allowed to
-                    // handle the `FlexZeroSlice` type in the `zerovec` crate
-                    // within `icu4x-0.9.0`.
-                    //
-                    // Once use of `icu4x-0.9.0` has dropped sufficiently, this
-                    // exception should be removed.
-                    let is_u8_slice = if let TyKind::Slice(ty) = &struct_field.ty.kind &&
-                        let TyKind::Path(None, rustc_ast::Path { segments, .. }) = &ty.kind &&
-                        let [seg] = segments.as_slice() &&
-                        seg.ident.name == sym::u8 && seg.args.is_none()
-                    {
-                        true
-                    } else {
-                        false
-                    };
                     if is_packed {
-                        if is_u8_slice {
+                        // In general, fields in packed structs are copied via a
+                        // block, e.g. `&{self.0}`. The two exceptions are `[u8]`
+                        // and `str` fields, which cannot be copied and also never
+                        // cause unaligned references. These exceptions are allowed
+                        // to handle the `FlexZeroSlice` type in the `zerovec`
+                        // crate within `icu4x-0.9.0`.
+                        //
+                        // Once use of `icu4x-0.9.0` has dropped sufficiently, this
+                        // exception should be removed.
+                        let is_simple_path = |ty: &P<ast::Ty>, sym| {
+                            if let TyKind::Path(None, ast::Path { segments, .. }) = &ty.kind &&
+                                let [seg] = segments.as_slice() &&
+                                seg.ident.name == sym && seg.args.is_none()
+                            {
+                                true
+                            } else {
+                                false
+                            }
+                        };
+
+                        let exception = if let TyKind::Slice(ty) = &struct_field.ty.kind &&
+                            is_simple_path(ty, sym::u8)
+                        {
+                            Some("byte")
+                        } else if is_simple_path(&struct_field.ty, sym::str) {
+                            Some("string")
+                        } else {
+                            None
+                        };
+
+                        if let Some(ty) = exception {
                             cx.sess.parse_sess.buffer_lint_with_diagnostic(
                                 BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
                                 sp,
                                 ast::CRATE_NODE_ID,
-                                "byte slice in a packed struct that derives a built-in trait",
+                                &format!(
+                                    "{} slice in a packed struct that derives a built-in trait",
+                                    ty
+                                ),
                                 rustc_lint_defs::BuiltinLintDiagnostics::ByteSliceInPackedStructWithDerive
                             );
                         } else {

compiler/rustc_driver_impl/src/lib.rs

@@ -229,10 +229,6 @@ fn run_compiler(
         registry: diagnostics_registry(),
     };
 
-    if !tracing::dispatcher::has_been_set() {
-        init_rustc_env_logger_with_backtrace_option(&config.opts.unstable_opts.log_backtrace);
-    }
-
     match make_input(config.opts.error_format, &matches.free) {
         Err(reported) => return Err(reported),
         Ok(Some(input)) => {
@@ -1251,16 +1247,7 @@ pub fn install_ice_hook() {
 /// This allows tools to enable rust logging without having to magically match rustc's
 /// tracing crate version.
 pub fn init_rustc_env_logger() {
-    init_rustc_env_logger_with_backtrace_option(&None);
-}
-
-/// This allows tools to enable rust logging without having to magically match rustc's
-/// tracing crate version. In contrast to `init_rustc_env_logger` it allows you to
-/// choose a target module you wish to show backtraces along with its logging.
-pub fn init_rustc_env_logger_with_backtrace_option(backtrace_target: &Option<String>) {
-    if let Err(error) = rustc_log::init_rustc_env_logger_with_backtrace_option(backtrace_target) {
-        early_error(ErrorOutputType::default(), &error.to_string());
-    }
+    init_env_logger("RUSTC_LOG");
 }
 
 /// This allows tools to enable rust logging without having to magically match rustc's
@@ -1324,6 +1311,7 @@ mod signal_handler {
 pub fn main() -> ! {
     let start_time = Instant::now();
     let start_rss = get_resident_set_size();
+    init_rustc_env_logger();
     signal_handler::install();
     let mut callbacks = TimePassesCallbacks::default();
     install_ice_hook();

compiler/rustc_interface/src/tests.rs

@@ -758,7 +758,6 @@ fn test_unstable_options_tracking_hash() {
     tracked!(link_only, true);
     tracked!(llvm_plugins, vec![String::from("plugin_name")]);
     tracked!(location_detail, LocationDetail { file: true, line: false, column: false });
-    tracked!(log_backtrace, Some("filter".to_string()));
     tracked!(maximal_hir_to_mir_coverage, true);
     tracked!(merge_functions, Some(MergeFunctions::Disabled));
     tracked!(mir_emit_retag, true);

compiler/rustc_lint_defs/src/builtin.rs

@@ -4073,7 +4073,8 @@ declare_lint! {
 
 declare_lint! {
     /// The `byte_slice_in_packed_struct_with_derive` lint detects cases where a byte slice field
-    /// (`[u8]`) is used in a `packed` struct that derives one or more built-in traits.
+    /// (`[u8]`) or string slice field (`str`) is used in a `packed` struct that derives one or
+    /// more built-in traits.
     ///
     /// ### Example
     ///
@@ -4091,11 +4092,11 @@ declare_lint! {
     /// ### Explanation
     ///
     /// This was previously accepted but is being phased out, because fields in packed structs are
-    /// now required to implement `Copy` for `derive` to work. Byte slices are a temporary
-    /// exception because certain crates depended on them.
+    /// now required to implement `Copy` for `derive` to work. Byte slices and string slices are a
+    /// temporary exception because certain crates depended on them.
     pub BYTE_SLICE_IN_PACKED_STRUCT_WITH_DERIVE,
     Warn,
-    "`[u8]` slice used in a packed struct with `derive`",
+    "`[u8]` or `str` used in a packed struct with `derive`",
     @future_incompatible = FutureIncompatibleInfo {
         reference: "issue #107457 <https://github.com/rust-lang/rust/issues/107457>",
         reason: FutureIncompatibilityReason::FutureReleaseErrorReportNow,

compiler/rustc_log/src/lib.rs

@@ -54,25 +54,12 @@ use tracing_subscriber::fmt::{
 use tracing_subscriber::layer::SubscriberExt;
 
 pub fn init_rustc_env_logger() -> Result<(), Error> {
-    init_rustc_env_logger_with_backtrace_option(&None)
-}
-
-pub fn init_rustc_env_logger_with_backtrace_option(
-    backtrace_target: &Option<String>,
-) -> Result<(), Error> {
-    init_env_logger_with_backtrace_option("RUSTC_LOG", backtrace_target)
+    init_env_logger("RUSTC_LOG")
 }
 
 /// In contrast to `init_rustc_env_logger` this allows you to choose an env var
 /// other than `RUSTC_LOG`.
 pub fn init_env_logger(env: &str) -> Result<(), Error> {
-    init_env_logger_with_backtrace_option(env, &None)
-}
-
-pub fn init_env_logger_with_backtrace_option(
-    env: &str,
-    backtrace_target: &Option<String>,
-) -> Result<(), Error> {
     let filter = match env::var(env) {
         Ok(env) => EnvFilter::new(env),
         _ => EnvFilter::default().add_directive(Directive::from(LevelFilter::WARN)),
@@ -106,16 +93,16 @@ pub fn init_env_logger_with_backtrace_option(
     let layer = layer.with_thread_ids(true).with_thread_names(true);
 
     let subscriber = tracing_subscriber::Registry::default().with(filter).with(layer);
-    match backtrace_target {
-        Some(str) => {
+    match env::var(format!("{env}_BACKTRACE")) {
+        Ok(str) => {
             let fmt_layer = tracing_subscriber::fmt::layer()
                 .with_writer(io::stderr)
                 .without_time()
                 .event_format(BacktraceFormatter { backtrace_target: str.to_string() });
             let subscriber = subscriber.with(fmt_layer);
             tracing::subscriber::set_global_default(subscriber).unwrap();
         }
-        None => {
+        Err(_) => {
             tracing::subscriber::set_global_default(subscriber).unwrap();
         }
     };

compiler/rustc_parse/src/parser/ty.rs

@@ -694,8 +694,9 @@ impl<'a> Parser<'a> {
         // `where`, so stop if it's it.
         // We also continue if we find types (not traits), again for error recovery.
         while self.can_begin_bound()
-            || self.token.can_begin_type()
-            || (self.token.is_reserved_ident() && !self.token.is_keyword(kw::Where))
+            || (self.may_recover()
+                && (self.token.can_begin_type()
+                    || (self.token.is_reserved_ident() && !self.token.is_keyword(kw::Where))))
         {
             if self.token.is_keyword(kw::Dyn) {
                 // Account for `&dyn Trait + dyn Other`.

compiler/rustc_session/src/options.rs

@@ -1413,8 +1413,6 @@ options! {
         "what location details should be tracked when using caller_location, either \
         `none`, or a comma separated list of location details, for which \
         valid options are `file`, `line`, and `column` (default: `file,line,column`)"),
-    log_backtrace: Option<String> = (None, parse_opt_string, [TRACKED],
-        "add a backtrace along with logging"),
     ls: bool = (false, parse_bool, [UNTRACKED],
         "list the symbols defined by a library crate (default: no)"),
     macro_backtrace: bool = (false, parse_bool, [UNTRACKED],

compiler/rustc_trait_selection/src/solve/assembly.rs

@@ -3,7 +3,7 @@
 use super::infcx_ext::InferCtxtExt;
 #[cfg(doc)]
 use super::trait_goals::structural_traits::*;
-use super::{CanonicalResponse, Certainty, EvalCtxt, Goal, QueryResult};
+use super::{CanonicalResponse, Certainty, EvalCtxt, Goal, MaybeCause, QueryResult};
 use rustc_hir::def_id::DefId;
 use rustc_infer::traits::query::NoSolution;
 use rustc_infer::traits::util::elaborate_predicates;
@@ -399,10 +399,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             ty::Alias(_, alias_ty) => alias_ty,
         };
 
-        for (assumption, _) in self
-            .tcx()
-            .bound_explicit_item_bounds(alias_ty.def_id)
-            .subst_iter_copied(self.tcx(), alias_ty.substs)
+        for assumption in self.tcx().item_bounds(alias_ty.def_id).subst(self.tcx(), alias_ty.substs)
         {
             match G::consider_assumption(self, goal, assumption) {
                 Ok(result) => {
@@ -462,4 +459,78 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             }
         }
     }
+
+    #[instrument(level = "debug", skip(self), ret)]
+    pub(super) fn merge_candidates_and_discard_reservation_impls(
+        &mut self,
+        mut candidates: Vec<Candidate<'tcx>>,
+    ) -> QueryResult<'tcx> {
+        match candidates.len() {
+            0 => return Err(NoSolution),
+            1 => return Ok(self.discard_reservation_impl(candidates.pop().unwrap()).result),
+            _ => {}
+        }
+
+        if candidates.len() > 1 {
+            let mut i = 0;
+            'outer: while i < candidates.len() {
+                for j in (0..candidates.len()).filter(|&j| i != j) {
+                    if self.trait_candidate_should_be_dropped_in_favor_of(
+                        &candidates[i],
+                        &candidates[j],
+                    ) {
+                        debug!(candidate = ?candidates[i], "Dropping candidate #{}/{}", i, candidates.len());
+                        candidates.swap_remove(i);
+                        continue 'outer;
+                    }
+                }
+
+                debug!(candidate = ?candidates[i], "Retaining candidate #{}/{}", i, candidates.len());
+                i += 1;
+            }
+
+            // If there are *STILL* multiple candidates, give up
+            // and report ambiguity.
+            if candidates.len() > 1 {
+                let certainty = if candidates.iter().all(|x| {
+                    matches!(x.result.value.certainty, Certainty::Maybe(MaybeCause::Overflow))
+                }) {
+                    Certainty::Maybe(MaybeCause::Overflow)
+                } else {
+                    Certainty::AMBIGUOUS
+                };
+                return self.make_canonical_response(certainty);
+            }
+        }
+
+        Ok(self.discard_reservation_impl(candidates.pop().unwrap()).result)
+    }
+
+    fn trait_candidate_should_be_dropped_in_favor_of(
+        &self,
+        candidate: &Candidate<'tcx>,
+        other: &Candidate<'tcx>,
+    ) -> bool {
+        // FIXME: implement this
+        match (candidate.source, other.source) {
+            (CandidateSource::Impl(_), _)
+            | (CandidateSource::ParamEnv(_), _)
+            | (CandidateSource::AliasBound, _)
+            | (CandidateSource::BuiltinImpl, _) => false,
+        }
+    }
+
+    fn discard_reservation_impl(&self, mut candidate: Candidate<'tcx>) -> Candidate<'tcx> {
+        if let CandidateSource::Impl(def_id) = candidate.source {
+            if let ty::ImplPolarity::Reservation = self.tcx().impl_polarity(def_id) {
+                debug!("Selected reservation impl");
+                // We assemble all candidates inside of a probe so by
+                // making a new canonical response here our result will
+                // have no constraints.
+                candidate.result = self.make_canonical_response(Certainty::AMBIGUOUS).unwrap();
+            }
+        }
+
+        candidate
+    }
 }

compiler/rustc_trait_selection/src/solve/project_goals.rs

@@ -1,6 +1,6 @@
 use crate::traits::{specialization_graph, translate_substs};
 
-use super::assembly::{self, Candidate, CandidateSource};
+use super::assembly;
 use super::infcx_ext::InferCtxtExt;
 use super::trait_goals::structural_traits;
 use super::{Certainty, EvalCtxt, Goal, QueryResult};
@@ -34,7 +34,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         // projection cache in the solver.
         if self.term_is_fully_unconstrained(goal) {
             let candidates = self.assemble_and_evaluate_candidates(goal);
-            self.merge_project_candidates(candidates)
+            self.merge_candidates_and_discard_reservation_impls(candidates)
         } else {
             let predicate = goal.predicate;
             let unconstrained_rhs = match predicate.term.unpack() {
@@ -153,59 +153,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
 
         self.make_canonical_response(normalization_certainty.unify_and(rhs_certainty))
     }
-
-    fn merge_project_candidates(
-        &mut self,
-        mut candidates: Vec<Candidate<'tcx>>,
-    ) -> QueryResult<'tcx> {
-        match candidates.len() {
-            0 => return Err(NoSolution),
-            1 => return Ok(candidates.pop().unwrap().result),
-            _ => {}
-        }
-
-        if candidates.len() > 1 {
-            let mut i = 0;
-            'outer: while i < candidates.len() {
-                for j in (0..candidates.len()).filter(|&j| i != j) {
-                    if self.project_candidate_should_be_dropped_in_favor_of(
-                        &candidates[i],
-                        &candidates[j],
-                    ) {
-                        debug!(candidate = ?candidates[i], "Dropping candidate #{}/{}", i, candidates.len());
-                        candidates.swap_remove(i);
-                        continue 'outer;
-                    }
-                }
-
-                debug!(candidate = ?candidates[i], "Retaining candidate #{}/{}", i, candidates.len());
-                // If there are *STILL* multiple candidates, give up
-                // and report ambiguity.
-                i += 1;
-                if i > 1 {
-                    debug!("multiple matches, ambig");
-                    // FIXME: return overflow if all candidates overflow, otherwise return ambiguity.
-                    unimplemented!();
-                }
-            }
-        }
-
-        Ok(candidates.pop().unwrap().result)
-    }
-
-    fn project_candidate_should_be_dropped_in_favor_of(
-        &self,
-        candidate: &Candidate<'tcx>,
-        other: &Candidate<'tcx>,
-    ) -> bool {
-        // FIXME: implement this
-        match (candidate.source, other.source) {
-            (CandidateSource::Impl(_), _)
-            | (CandidateSource::ParamEnv(_), _)
-            | (CandidateSource::BuiltinImpl, _)
-            | (CandidateSource::AliasBound, _) => unimplemented!(),
-        }
-    }
 }
 
 impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
@@ -452,7 +399,8 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
                         [ty::GenericArg::from(goal.predicate.self_ty())],
                     ));
 
-                    let is_sized_certainty = ecx.evaluate_goal(goal.with(tcx, sized_predicate))?.1;
+                    let (_, is_sized_certainty) =
+                        ecx.evaluate_goal(goal.with(tcx, sized_predicate))?;
                     return ecx.eq_term_and_make_canonical_response(
                         goal,
                         is_sized_certainty,