Avoid ref when using format! in compiler

Clean up a few minor refs in `format!` macro, as it has a performance cost. Apparently the compiler is unable to inline `format!("{}", &variable)`, and does a run-time double-reference instead (format macro already does one level referencing).  Inlining format args prevents accidental `&` misuse.

Author: nyurik

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_dataflow/src/impls/initialized.rs

@@ -688,7 +688,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for EverInitializedPlaces<'_, '_, 'tcx> {
         let init_loc_map = &move_data.init_loc_map;
         let rev_lookup = &move_data.rev_lookup;
 
-        debug!("initializes move_indexes {:?}", &init_loc_map[location]);
+        debug!("initializes move_indexes {:?}", init_loc_map[location]);
         trans.gen_all(init_loc_map[location].iter().copied());
 
         if let mir::StatementKind::StorageDead(local) = stmt.kind {

compiler/rustc_mir_transform/src/dead_store_elimination.rs

@@ -102,7 +102,7 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
                 | StatementKind::Nop => (),
 
                 StatementKind::FakeRead(_) | StatementKind::AscribeUserType(_, _) => {
-                    bug!("{:?} not found in this MIR phase!", &statement.kind)
+                    bug!("{:?} not found in this MIR phase!", statement.kind)
                 }
             }
         }

compiler/rustc_mir_transform/src/early_otherwise_branch.rs

@@ -106,11 +106,11 @@ impl<'tcx> MirPass<'tcx> for EarlyOtherwiseBranch {
             let parent = BasicBlock::from_usize(i);
             let Some(opt_data) = evaluate_candidate(tcx, body, parent) else { continue };
 
-            if !tcx.consider_optimizing(|| format!("EarlyOtherwiseBranch {:?}", &opt_data)) {
+            if !tcx.consider_optimizing(|| format!("EarlyOtherwiseBranch {opt_data:?}")) {
                 break;
             }
 
-            trace!("SUCCESS: found optimization possibility to apply: {:?}", &opt_data);
+            trace!("SUCCESS: found optimization possibility to apply: {opt_data:?}");
 
             should_cleanup = true;
 

compiler/rustc_pattern_analysis/src/constructor.rs

@@ -904,7 +904,7 @@ impl<Cx: PatCx> Constructor<Cx> {
             // be careful to detect strings here. However a string literal pattern will never
             // be reported as a non-exhaustiveness witness, so we can ignore this issue.
             Ref => {
-                write!(f, "&{:?}", &fields.next().unwrap())?;
+                write!(f, "&{:?}", fields.next().unwrap())?;
             }
             Slice(slice) => {
                 write!(f, "[")?;

compiler/rustc_resolve/src/diagnostics.rs

@@ -149,7 +149,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     BuiltinLintDiag::AmbiguousGlobImports { diag },
                 );
             } else {
-                let mut err = struct_span_code_err!(self.dcx(), diag.span, E0659, "{}", &diag.msg);
+                let mut err = struct_span_code_err!(self.dcx(), diag.span, E0659, "{}", diag.msg);
                 report_ambiguity_error(&mut err, diag);
                 err.emit();
             }
@@ -798,7 +798,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             }
             ResolutionError::FailedToResolve { segment, label, suggestion, module } => {
                 let mut err =
-                    struct_span_code_err!(self.dcx(), span, E0433, "failed to resolve: {}", &label);
+                    struct_span_code_err!(self.dcx(), span, E0433, "failed to resolve: {label}");
                 err.span_label(span, label);
 
                 if let Some((suggestions, msg, applicability)) = suggestion {
@@ -2893,7 +2893,7 @@ fn show_candidates(
                     ""
                 };
                 candidate.0 =
-                    format!("{add_use}{}{append}{trailing}{additional_newline}", &candidate.0);
+                    format!("{add_use}{}{append}{trailing}{additional_newline}", candidate.0);
             }
 
             match mode {

compiler/rustc_resolve/src/imports.rs

@@ -694,7 +694,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             .collect::<Vec<_>>();
         let msg = format!("unresolved import{} {}", pluralize!(paths.len()), paths.join(", "),);
 
-        let mut diag = struct_span_code_err!(self.dcx(), span, E0432, "{}", &msg);
+        let mut diag = struct_span_code_err!(self.dcx(), span, E0432, "{msg}");
 
         if let Some((_, UnresolvedImportError { note: Some(note), .. })) = errors.iter().last() {
             diag.note(note.clone());

compiler/rustc_resolve/src/rustdoc.rs

@@ -339,7 +339,7 @@ pub fn strip_generics_from_path(path_str: &str) -> Result<Box<str>, MalformedGen
         }
     }
 
-    debug!("path_str: {:?}\nstripped segments: {:?}", path_str, &stripped_segments);
+    debug!("path_str: {path_str:?}\nstripped segments: {stripped_segments:?}");
 
     let stripped_path = stripped_segments.join("::");
 

compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/encode.rs

@@ -238,12 +238,12 @@ fn encode_predicate<'tcx>(
     match predicate.as_ref().skip_binder() {
         ty::ExistentialPredicate::Trait(trait_ref) => {
             let name = encode_ty_name(tcx, trait_ref.def_id);
-            let _ = write!(s, "u{}{}", name.len(), &name);
+            let _ = write!(s, "u{}{}", name.len(), name);
             s.push_str(&encode_args(tcx, trait_ref.args, trait_ref.def_id, true, dict, options));
         }
         ty::ExistentialPredicate::Projection(projection) => {
             let name = encode_ty_name(tcx, projection.def_id);
-            let _ = write!(s, "u{}{}", name.len(), &name);
+            let _ = write!(s, "u{}{}", name.len(), name);
             s.push_str(&encode_args(tcx, projection.args, projection.def_id, true, dict, options));
             match projection.term.unpack() {
                 TermKind::Ty(ty) => s.push_str(&encode_ty(tcx, ty, dict, options)),
@@ -258,7 +258,7 @@ fn encode_predicate<'tcx>(
         }
         ty::ExistentialPredicate::AutoTrait(def_id) => {
             let name = encode_ty_name(tcx, *def_id);
-            let _ = write!(s, "u{}{}", name.len(), &name);
+            let _ = write!(s, "u{}{}", name.len(), name);
         }
     };
     compress(dict, DictKey::Predicate(*predicate.as_ref().skip_binder()), &mut s);
@@ -416,7 +416,7 @@ pub fn encode_ty<'tcx>(
             // A<array-length><element-type>
             let len = len.eval_target_usize(tcx, ty::ParamEnv::reveal_all());
             let mut s = String::from("A");
-            let _ = write!(s, "{}", &len);
+            let _ = write!(s, "{len}");
             s.push_str(&encode_ty(tcx, *ty0, dict, options));
             compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
             typeid.push_str(&s);
@@ -492,13 +492,13 @@ pub fn encode_ty<'tcx>(
                 // calling convention (or extern types [i.e., ty::Foreign]) as <length><name>, where
                 // <name> is <unscoped-name>.
                 let name = tcx.item_name(def_id).to_string();
-                let _ = write!(s, "{}{}", name.len(), &name);
+                let _ = write!(s, "{}{}", name.len(), name);
                 compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
             } else {
                 // u<length><name>[I<element-type1..element-typeN>E], where <element-type> is
                 // <subst>, as vendor extended type.
                 let name = encode_ty_name(tcx, def_id);
-                let _ = write!(s, "u{}{}", name.len(), &name);
+                let _ = write!(s, "u{}{}", name.len(), name);
                 s.push_str(&encode_args(tcx, args, def_id, false, dict, options));
                 compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
             }
@@ -530,7 +530,7 @@ pub fn encode_ty<'tcx>(
                 }
             } else {
                 let name = tcx.item_name(*def_id).to_string();
-                let _ = write!(s, "{}{}", name.len(), &name);
+                let _ = write!(s, "{}{}", name.len(), name);
             }
             compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
             typeid.push_str(&s);
@@ -542,7 +542,7 @@ pub fn encode_ty<'tcx>(
             // as vendor extended type.
             let mut s = String::new();
             let name = encode_ty_name(tcx, *def_id);
-            let _ = write!(s, "u{}{}", name.len(), &name);
+            let _ = write!(s, "u{}{}", name.len(), name);
             s.push_str(&encode_args(tcx, args, *def_id, false, dict, options));
             compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
             typeid.push_str(&s);
@@ -553,7 +553,7 @@ pub fn encode_ty<'tcx>(
             // as vendor extended type.
             let mut s = String::new();
             let name = encode_ty_name(tcx, *def_id);
-            let _ = write!(s, "u{}{}", name.len(), &name);
+            let _ = write!(s, "u{}{}", name.len(), name);
             let parent_args = tcx.mk_args(args.as_coroutine_closure().parent_args());
             s.push_str(&encode_args(tcx, parent_args, *def_id, false, dict, options));
             compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
@@ -565,7 +565,7 @@ pub fn encode_ty<'tcx>(
             // as vendor extended type.
             let mut s = String::new();
             let name = encode_ty_name(tcx, *def_id);
-            let _ = write!(s, "u{}{}", name.len(), &name);
+            let _ = write!(s, "u{}{}", name.len(), name);
             // Encode parent args only
             s.push_str(&encode_args(
                 tcx,
@@ -588,7 +588,7 @@ pub fn encode_ty<'tcx>(
             s.push('E');
             compress(dict, DictKey::Ty(Ty::new_imm_ref(tcx, *region, *ty0), TyQ::None), &mut s);
             if ty.is_mutable_ptr() {
-                s = format!("{}{}", "U3mut", &s);
+                s = format!("{}{}", "U3mut", s);
                 compress(dict, DictKey::Ty(ty, TyQ::Mut), &mut s);
             }
             typeid.push_str(&s);
@@ -600,10 +600,10 @@ pub fn encode_ty<'tcx>(
             let mut s = String::new();
             s.push_str(&encode_ty(tcx, *ptr_ty, dict, options));
             if !ty.is_mutable_ptr() {
-                s = format!("{}{}", "K", &s);
+                s = format!("{}{}", "K", s);
                 compress(dict, DictKey::Ty(*ptr_ty, TyQ::Const), &mut s);
             };
-            s = format!("{}{}", "P", &s);
+            s = format!("{}{}", "P", s);
             compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
             typeid.push_str(&s);
         }
@@ -722,7 +722,7 @@ fn encode_ty_name(tcx: TyCtxt<'_>, def_id: DefId) -> String {
     s.push('C');
     s.push_str(&to_disambiguator(tcx.stable_crate_id(def_path.krate).as_u64()));
     let crate_name = tcx.crate_name(def_path.krate).to_string();
-    let _ = write!(s, "{}{}", crate_name.len(), &crate_name);
+    let _ = write!(s, "{}{}", crate_name.len(), crate_name);
 
     // Disambiguators and names
     def_path.data.reverse();

compiler/rustc_type_ir/src/const_kind.rs

@@ -65,15 +65,13 @@ impl<I: Interner> fmt::Debug for ConstKind<I> {
 
         match self {
             Param(param) => write!(f, "{param:?}"),
-            Infer(var) => write!(f, "{:?}", &var),
+            Infer(var) => write!(f, "{var:?}"),
             Bound(debruijn, var) => crate::debug_bound_var(f, *debruijn, var),
             Placeholder(placeholder) => write!(f, "{placeholder:?}"),
-            Unevaluated(uv) => {
-                write!(f, "{:?}", &uv)
-            }
-            Value(ty, valtree) => write!(f, "({valtree:?}: {:?})", &ty),
+            Unevaluated(uv) => write!(f, "{uv:?}"),
+            Value(ty, valtree) => write!(f, "({valtree:?}: {ty:?})"),
             Error(_) => write!(f, "{{const error}}"),
-            Expr(expr) => write!(f, "{:?}", &expr),
+            Expr(expr) => write!(f, "{expr:?}"),
         }
     }
 }