Rollup of 9 pull requests

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -456,10 +456,15 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, '_, 'infcx, 'tcx> {
                 if let Some(def_id) = def_id
                     && self.infcx.tcx.def_kind(def_id).is_fn_like()
                     && let Some(pos) = args.iter().position(|arg| arg.hir_id == expr.hir_id)
-                    && let ty::Param(_) =
-                        self.infcx.tcx.fn_sig(def_id).skip_binder().skip_binder().inputs()
-                            [pos + offset]
-                            .kind()
+                    && let Some(arg) = self
+                        .infcx
+                        .tcx
+                        .fn_sig(def_id)
+                        .skip_binder()
+                        .skip_binder()
+                        .inputs()
+                        .get(pos + offset)
+                    && let ty::Param(_) = arg.kind()
                 {
                     let place = &self.move_data.move_paths[mpi].place;
                     let ty = place.ty(self.body, self.infcx.tcx).ty;

compiler/rustc_codegen_cranelift/src/abi/mod.rs

@@ -505,7 +505,7 @@ pub(crate) fn codegen_terminator_call<'tcx>(
                 let nop_inst = fx.bcx.ins().nop();
                 fx.add_comment(
                     nop_inst,
-                    format!("virtual call; self arg pass mode: {:?}", &fn_abi.args[0]),
+                    format!("virtual call; self arg pass mode: {:?}", fn_abi.args[0]),
                 );
             }
 

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -759,7 +759,7 @@ fn link_natively(
     sess.dcx().abort_if_errors();
 
     // Invoke the system linker
-    info!("{:?}", &cmd);
+    info!("{cmd:?}");
     let retry_on_segfault = env::var("RUSTC_RETRY_LINKER_ON_SEGFAULT").is_ok();
     let unknown_arg_regex =
         Regex::new(r"(unknown|unrecognized) (command line )?(option|argument)").unwrap();
@@ -796,7 +796,7 @@ fn link_natively(
                     cmd.arg(arg);
                 }
             }
-            info!("{:?}", &cmd);
+            info!("{cmd:?}");
             continue;
         }
 
@@ -817,7 +817,7 @@ fn link_natively(
                     cmd.arg(arg);
                 }
             }
-            info!("{:?}", &cmd);
+            info!("{cmd:?}");
             continue;
         }
 
@@ -878,7 +878,7 @@ fn link_natively(
                     cmd.arg(arg);
                 }
             }
-            info!("{:?}", &cmd);
+            info!("{cmd:?}");
             continue;
         }
 
@@ -996,7 +996,7 @@ fn link_natively(
                 sess.dcx().emit_err(errors::UnableToExeLinker {
                     linker_path,
                     error: e,
-                    command_formatted: format!("{:?}", &cmd),
+                    command_formatted: format!("{cmd:?}"),
                 });
             }
 
@@ -1567,7 +1567,7 @@ fn print_native_static_libs(
                 sess.dcx().emit_note(errors::StaticLibraryNativeArtifacts);
                 // Prefix for greppability
                 // Note: This must not be translated as tools are allowed to depend on this exact string.
-                sess.dcx().note(format!("native-static-libs: {}", &lib_args.join(" ")));
+                sess.dcx().note(format!("native-static-libs: {}", lib_args.join(" ")));
             }
         }
     }

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -328,7 +328,7 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
             sym::link_section => {
                 if let Some(val) = attr.value_str() {
                     if val.as_str().bytes().any(|b| b == 0) {
-                        let msg = format!("illegal null byte in link_section value: `{}`", &val);
+                        let msg = format!("illegal null byte in link_section value: `{val}`");
                         tcx.dcx().span_err(attr.span, msg);
                     } else {
                         codegen_fn_attrs.link_section = Some(val);
@@ -726,7 +726,7 @@ fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
         if *ordinal <= u16::MAX as u128 {
             Some(ordinal.get() as u16)
         } else {
-            let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
+            let msg = format!("ordinal value in `link_ordinal` is too large: `{ordinal}`");
             tcx.dcx()
                 .struct_span_err(attr.span, msg)
                 .with_note("the value may not exceed `u16::MAX`")

compiler/rustc_codegen_ssa/src/mono_item.rs

@@ -130,7 +130,7 @@ impl<'a, 'tcx: 'a> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
 
         let symbol_name = self.symbol_name(cx.tcx()).name;
 
-        debug!("symbol {}", &symbol_name);
+        debug!("symbol {symbol_name}");
 
         match *self {
             MonoItem::Static(def_id) => {

compiler/rustc_fluent_macro/src/fluent.rs

@@ -253,7 +253,7 @@ pub(crate) fn fluent_messages(input: proc_macro::TokenStream) -> proc_macro::Tok
 
             for Attribute { id: Identifier { name: attr_name }, .. } in attributes {
                 let snake_name = Ident::new(
-                    &format!("{}{}", &crate_prefix, &attr_name.replace('-', "_")),
+                    &format!("{crate_prefix}{}", attr_name.replace('-', "_")),
                     resource_str.span(),
                 );
                 if !previous_attrs.insert(snake_name.clone()) {

compiler/rustc_hir_analysis/src/errors/wrong_number_of_generic_args.rs

@@ -651,7 +651,7 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
             self.path_segment.hir_id,
             num_params_to_take,
         );
-        debug!("suggested_args: {:?}", &suggested_args);
+        debug!("suggested_args: {suggested_args:?}");
 
         match self.angle_brackets {
             AngleBrackets::Missing => {

compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs

@@ -249,7 +249,7 @@ fn check_explicit_predicates<'tcx>(
     let explicit_predicates = explicit_map.explicit_predicates_of(tcx, def_id);
 
     for (outlives_predicate, &span) in explicit_predicates.as_ref().skip_binder() {
-        debug!("outlives_predicate = {:?}", &outlives_predicate);
+        debug!("outlives_predicate = {outlives_predicate:?}");
 
         // Careful: If we are inferring the effects of a `dyn Trait<..>`
         // type, then when we look up the predicates for `Trait`,
@@ -289,12 +289,12 @@ fn check_explicit_predicates<'tcx>(
             && let GenericArgKind::Type(ty) = outlives_predicate.0.unpack()
             && ty.walk().any(|arg| arg == self_ty.into())
         {
-            debug!("skipping self ty = {:?}", &ty);
+            debug!("skipping self ty = {ty:?}");
             continue;
         }
 
         let predicate = explicit_predicates.rebind(*outlives_predicate).instantiate(tcx, args);
-        debug!("predicate = {:?}", &predicate);
+        debug!("predicate = {predicate:?}");
         insert_outlives_predicate(tcx, predicate.0, predicate.1, span, required_predicates);
     }
 }

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1265,9 +1265,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         }
                         (
                             match parent_pred {
-                                None => format!("`{}`", &p),
+                                None => format!("`{p}`"),
                                 Some(parent_pred) => match format_pred(*parent_pred) {
-                                    None => format!("`{}`", &p),
+                                    None => format!("`{p}`"),
                                     Some((parent_p, _)) => {
                                         if !suggested
                                             && !suggested_bounds.contains(pred)

compiler/rustc_middle/src/middle/stability.rs

@@ -112,7 +112,7 @@ pub fn report_unstable(
 ) {
     let msg = match reason {
         Some(r) => format!("use of unstable library feature '{feature}': {r}"),
-        None => format!("use of unstable library feature '{}'", &feature),
+        None => format!("use of unstable library feature '{feature}'"),
     };
 
     if is_soft {

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -2627,7 +2627,7 @@ impl<'tcx> FmtPrinter<'_, 'tcx> {
             self.prepare_region_info(value);
         }
 
-        debug!("self.used_region_names: {:?}", &self.used_region_names);
+        debug!("self.used_region_names: {:?}", self.used_region_names);
 
         let mut empty = true;
         let mut start_or_continue = |cx: &mut Self, start: &str, cont: &str| {

compiler/rustc_middle/src/util/find_self_call.rs

@@ -14,7 +14,7 @@ pub fn find_self_call<'tcx>(
     local: Local,
     block: BasicBlock,
 ) -> Option<(DefId, GenericArgsRef<'tcx>)> {
-    debug!("find_self_call(local={:?}): terminator={:?}", local, &body[block].terminator);
+    debug!("find_self_call(local={:?}): terminator={:?}", local, body[block].terminator);
     if let Some(Terminator { kind: TerminatorKind::Call { func, args, .. }, .. }) =
         &body[block].terminator
     {

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

@@ -2162,92 +2162,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
 
         self.ascribe_types(block, ascriptions);
 
-        // rust-lang/rust#27282: The `autoref` business deserves some
-        // explanation here.
-        //
-        // The intent of the `autoref` flag is that when it is true,
-        // then any pattern bindings of type T will map to a `&T`
-        // within the context of the guard expression, but will
-        // continue to map to a `T` in the context of the arm body. To
-        // avoid surfacing this distinction in the user source code
-        // (which would be a severe change to the language and require
-        // far more revision to the compiler), when `autoref` is true,
-        // then any occurrence of the identifier in the guard
-        // expression will automatically get a deref op applied to it.
-        //
-        // So an input like:
-        //
-        // ```
-        // let place = Foo::new();
-        // match place { foo if inspect(foo)
-        //     => feed(foo), ... }
-        // ```
-        //
-        // will be treated as if it were really something like:
-        //
-        // ```
-        // let place = Foo::new();
-        // match place { Foo { .. } if { let tmp1 = &place; inspect(*tmp1) }
-        //     => { let tmp2 = place; feed(tmp2) }, ... }
-        // ```
-        //
-        // And an input like:
-        //
-        // ```
-        // let place = Foo::new();
-        // match place { ref mut foo if inspect(foo)
-        //     => feed(foo), ... }
-        // ```
-        //
-        // will be treated as if it were really something like:
-        //
-        // ```
-        // let place = Foo::new();
-        // match place { Foo { .. } if { let tmp1 = & &mut place; inspect(*tmp1) }
-        //     => { let tmp2 = &mut place; feed(tmp2) }, ... }
-        // ```
-        //
-        // In short, any pattern binding will always look like *some*
-        // kind of `&T` within the guard at least in terms of how the
-        // MIR-borrowck views it, and this will ensure that guard
-        // expressions cannot mutate their the match inputs via such
-        // bindings. (It also ensures that guard expressions can at
-        // most *copy* values from such bindings; non-Copy things
-        // cannot be moved via pattern bindings in guard expressions.)
-        //
-        // ----
-        //
-        // Implementation notes (under assumption `autoref` is true).
-        //
-        // To encode the distinction above, we must inject the
-        // temporaries `tmp1` and `tmp2`.
-        //
-        // There are two cases of interest: binding by-value, and binding by-ref.
-        //
-        // 1. Binding by-value: Things are simple.
-        //
-        //    * Establishing `tmp1` creates a reference into the
-        //      matched place. This code is emitted by
-        //      bind_matched_candidate_for_guard.
-        //
-        //    * `tmp2` is only initialized "lazily", after we have
-        //      checked the guard. Thus, the code that can trigger
-        //      moves out of the candidate can only fire after the
-        //      guard evaluated to true. This initialization code is
-        //      emitted by bind_matched_candidate_for_arm.
-        //
-        // 2. Binding by-reference: Things are tricky.
-        //
-        //    * Here, the guard expression wants a `&&` or `&&mut`
-        //      into the original input. This means we need to borrow
-        //      the reference that we create for the arm.
-        //    * So we eagerly create the reference for the arm and then take a
-        //      reference to that.
+        // Lower an instance of the arm guard (if present) for this candidate,
+        // and then perform bindings for the arm body.
         if let Some((arm, match_scope)) = arm_match_scope
             && let Some(guard) = arm.guard
         {
             let tcx = self.tcx;
 
+            // Bindings for guards require some extra handling to automatically
+            // insert implicit references/dereferences.
             self.bind_matched_candidate_for_guard(block, schedule_drops, bindings.clone());
             let guard_frame = GuardFrame {
                 locals: bindings.clone().map(|b| GuardFrameLocal::new(b.var_id)).collect(),
@@ -2387,6 +2310,82 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         }
     }
 
+    /// Binding for guards is a bit different from binding for the arm body,
+    /// because an extra layer of implicit reference/dereference is added.
+    ///
+    /// The idea is that any pattern bindings of type T will map to a `&T` within
+    /// the context of the guard expression, but will continue to map to a `T`
+    /// in the context of the arm body. To avoid surfacing this distinction in
+    /// the user source code (which would be a severe change to the language and
+    /// require far more revision to the compiler), any occurrence of the
+    /// identifier in the guard expression will automatically get a deref op
+    /// applied to it. (See the caller of [`Self::is_bound_var_in_guard`].)
+    ///
+    /// So an input like:
+    ///
+    /// ```ignore (illustrative)
+    /// let place = Foo::new();
+    /// match place { foo if inspect(foo)
+    ///     => feed(foo), ... }
+    /// ```
+    ///
+    /// will be treated as if it were really something like:
+    ///
+    /// ```ignore (illustrative)
+    /// let place = Foo::new();
+    /// match place { Foo { .. } if { let tmp1 = &place; inspect(*tmp1) }
+    ///     => { let tmp2 = place; feed(tmp2) }, ... }
+    /// ```
+    ///
+    /// And an input like:
+    ///
+    /// ```ignore (illustrative)
+    /// let place = Foo::new();
+    /// match place { ref mut foo if inspect(foo)
+    ///     => feed(foo), ... }
+    /// ```
+    ///
+    /// will be treated as if it were really something like:
+    ///
+    /// ```ignore (illustrative)
+    /// let place = Foo::new();
+    /// match place { Foo { .. } if { let tmp1 = & &mut place; inspect(*tmp1) }
+    ///     => { let tmp2 = &mut place; feed(tmp2) }, ... }
+    /// ```
+    /// ---
+    ///
+    /// ## Implementation notes
+    ///
+    /// To encode the distinction above, we must inject the
+    /// temporaries `tmp1` and `tmp2`.
+    ///
+    /// There are two cases of interest: binding by-value, and binding by-ref.
+    ///
+    /// 1. Binding by-value: Things are simple.
+    ///
+    ///    * Establishing `tmp1` creates a reference into the
+    ///      matched place. This code is emitted by
+    ///      [`Self::bind_matched_candidate_for_guard`].
+    ///
+    ///    * `tmp2` is only initialized "lazily", after we have
+    ///      checked the guard. Thus, the code that can trigger
+    ///      moves out of the candidate can only fire after the
+    ///      guard evaluated to true. This initialization code is
+    ///      emitted by [`Self::bind_matched_candidate_for_arm_body`].
+    ///
+    /// 2. Binding by-reference: Things are tricky.
+    ///
+    ///    * Here, the guard expression wants a `&&` or `&&mut`
+    ///      into the original input. This means we need to borrow
+    ///      the reference that we create for the arm.
+    ///    * So we eagerly create the reference for the arm and then take a
+    ///      reference to that.
+    ///
+    /// ---
+    ///
+    /// See these PRs for some historical context:
+    /// - <https://github.com/rust-lang/rust/pull/49870> (introduction of autoref)
+    /// - <https://github.com/rust-lang/rust/pull/59114> (always use autoref)
     fn bind_matched_candidate_for_guard<'b>(
         &mut self,
         block: BasicBlock,
@@ -2418,10 +2417,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             );
             match binding.binding_mode.0 {
                 ByRef::No => {
+                    // The arm binding will be by value, so for the guard binding
+                    // just take a shared reference to the matched place.
                     let rvalue = Rvalue::Ref(re_erased, BorrowKind::Shared, binding.source);
                     self.cfg.push_assign(block, source_info, ref_for_guard, rvalue);
                 }
                 ByRef::Yes(mutbl) => {
+                    // The arm binding will be by reference, so eagerly create it now.
                     let value_for_arm = self.storage_live_binding(
                         block,
                         binding.var_id,
@@ -2433,6 +2435,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     let rvalue =
                         Rvalue::Ref(re_erased, util::ref_pat_borrow_kind(mutbl), binding.source);
                     self.cfg.push_assign(block, source_info, value_for_arm, rvalue);
+                    // For the guard binding, take a shared reference to that reference.
                     let rvalue = Rvalue::Ref(re_erased, BorrowKind::Shared, value_for_arm);
                     self.cfg.push_assign(block, source_info, ref_for_guard, rvalue);
                 }