use &str / String literals instead of format!()

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -649,7 +649,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         if !assign_value.is_empty() {
             err.span_suggestion_verbose(
                 sugg_span.shrink_to_hi(),
-                format!("consider assigning a value"),
+                "consider assigning a value",
                 format!(" = {}", assign_value),
                 Applicability::MaybeIncorrect,
             );

compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs

@@ -270,7 +270,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
                 for extra in extra_info {
                     match extra {
                         ExtraConstraintInfo::PlaceholderFromPredicate(span) => {
-                            err.span_note(*span, format!("due to current limitations in the borrow checker, this implies a `'static` lifetime"));
+                            err.span_note(*span, "due to current limitations in the borrow checker, this implies a `'static` lifetime");
                         }
                     }
                 }

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -472,7 +472,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         for extra in extra_info {
             match extra {
                 ExtraConstraintInfo::PlaceholderFromPredicate(span) => {
-                    diag.span_note(span, format!("due to current limitations in the borrow checker, this implies a `'static` lifetime"));
+                    diag.span_note(span, "due to current limitations in the borrow checker, this implies a `'static` lifetime");
                 }
             }
         }

compiler/rustc_codegen_llvm/src/asm.rs

@@ -144,7 +144,7 @@ impl<'ll, 'tcx> AsmBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
                     // We prefer the latter because it matches the behavior of
                     // Clang.
                     if late && matches!(reg, InlineAsmRegOrRegClass::Reg(_)) {
-                        constraints.push(format!("{}", reg_to_llvm(reg, Some(&in_value.layout))));
+                        constraints.push(reg_to_llvm(reg, Some(&in_value.layout)).to_string());
                     } else {
                         constraints.push(format!("{}", op_idx[&idx]));
                     }

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2240,7 +2240,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     ),
                     "s",
                 ),
-                [only] => (format!("{only}"), ""),
+                [only] => (only.to_string(), ""),
                 [] => unreachable!(),
             };
             let last_span = *arg_spans.last().unwrap();

compiler/rustc_hir_typeck/src/demand.rs

@@ -406,7 +406,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
 
                     let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
-                        .then(|| format!(" (its field is private, but it's local to this crate and its privacy can be changed)"));
+                        .then(|| " (its field is private, but it's local to this crate and its privacy can be changed)".to_string());
 
                     let sole_field_ty = sole_field.ty(self.tcx, substs);
                     if self.can_coerce(expr_ty, sole_field_ty) {

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1013,7 +1013,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             } else {
                                 args_span
                             };
-                            labels.push((span, format!("multiple arguments are missing")));
+                            labels.push((span, "multiple arguments are missing".to_string()));
                             suggestion_text = match suggestion_text {
                                 SuggestionText::None | SuggestionText::Provide(_) => {
                                     SuggestionText::Provide(true)

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -319,11 +319,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
             }
 
-            err.multipart_suggestion_verbose(
-                format!("use parentheses to call these"),
-                sugg,
-                applicability,
-            );
+            err.multipart_suggestion_verbose("use parentheses to call these", sugg, applicability);
 
             true
         } else {

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -1007,7 +1007,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         if def_kind == DefKind::AssocFn && lev_candidate.fn_has_self_parameter {
                             err.span_suggestion(
                                 span,
-                                &format!("there is a method with a similar name",),
+                                "there is a method with a similar name",
                                 lev_candidate.name,
                                 Applicability::MaybeIncorrect,
                             );

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -184,7 +184,7 @@ fn msg_span_from_early_bound_and_free_regions<'tcx>(
             let text = if br.has_name() {
                 format!("the lifetime `{}` as defined here", br.name)
             } else {
-                format!("the anonymous lifetime as defined here")
+                "the anonymous lifetime as defined here".to_string()
             };
             (text, sp)
         }
@@ -203,7 +203,7 @@ fn msg_span_from_early_bound_and_free_regions<'tcx>(
                             sp = param.span;
                         }
                         let text = if name == kw::UnderscoreLifetime {
-                            format!("the anonymous lifetime as defined here")
+                            "the anonymous lifetime as defined here".to_string()
                         } else {
                             format!("the lifetime `{}` as defined here", name)
                         };

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_relation.rs

@@ -44,7 +44,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
                         );
                     }
                     (Some(sub_span), Some(sup_span), _, Some(sup_symbol)) => {
-                        err.span_note(sub_span, format!("the lifetime defined here..."));
+                        err.span_note(sub_span, "the lifetime defined here...");
                         err.span_note(
                             sup_span,
                             format!("...must outlive the lifetime `{sup_symbol}` defined here"),
@@ -55,17 +55,11 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
                             sub_span,
                             format!("the lifetime `{sub_symbol}` defined here..."),
                         );
-                        err.span_note(
-                            sup_span,
-                            format!("...must outlive the lifetime defined here"),
-                        );
+                        err.span_note(sup_span, "...must outlive the lifetime defined here");
                     }
                     (Some(sub_span), Some(sup_span), _, _) => {
-                        err.span_note(sub_span, format!("the lifetime defined here..."));
-                        err.span_note(
-                            sup_span,
-                            format!("...must outlive the lifetime defined here"),
-                        );
+                        err.span_note(sub_span, "the lifetime defined here...");
+                        err.span_note(sup_span, "...must outlive the lifetime defined here");
                     }
                     _ => {}
                 }

compiler/rustc_lint/src/for_loops_over_fallibles.rs

@@ -71,11 +71,11 @@ impl<'tcx> LateLintPass<'tcx> for ForLoopsOverFallibles {
                 );
             } else {
                 lint.multipart_suggestion_verbose(
-                    format!("to check pattern in a loop use `while let`"),
+                    "to check pattern in a loop use `while let`",
                     vec![
                         // NB can't use `until` here because `expr.span` and `pat.span` have different syntax contexts
                         (expr.span.with_hi(pat.span.lo()), format!("while let {var}(")),
-                        (pat.span.between(arg.span), format!(") = ")),
+                        (pat.span.between(arg.span), ") = ".to_string()),
                     ],
                     Applicability::MaybeIncorrect
                 );
@@ -95,7 +95,7 @@ impl<'tcx> LateLintPass<'tcx> for ForLoopsOverFallibles {
                 vec![
                     // NB can't use `until` here because `expr.span` and `pat.span` have different syntax contexts
                     (expr.span.with_hi(pat.span.lo()), format!("if let {var}(")),
-                    (pat.span.between(arg.span), format!(") = ")),
+                    (pat.span.between(arg.span), ") = ".to_string()),
                 ],
                 Applicability::MaybeIncorrect,
             )

compiler/rustc_macros/src/diagnostics/diagnostic.rs

@@ -39,10 +39,8 @@ impl<'a> DiagnosticDerive<'a> {
             let init = match builder.slug.value_ref() {
                 None => {
                     span_err(builder.span, "diagnostic slug not specified")
-                        .help(format!(
-                            "specify the slug as the first argument to the `#[diag(...)]` \
-                            attribute, such as `#[diag(hir_analysis_example_error)]`",
-                        ))
+                        .help("specify the slug as the first argument to the `#[diag(...)]` \
+                            attribute, such as `#[diag(hir_analysis_example_error)]`")
                         .emit();
                     return DiagnosticDeriveError::ErrorHandled.to_compile_error();
                 }
@@ -133,10 +131,8 @@ impl<'a> LintDiagnosticDerive<'a> {
             match builder.slug.value_ref() {
                 None => {
                     span_err(builder.span, "diagnostic slug not specified")
-                        .help(format!(
-                            "specify the slug as the first argument to the attribute, such as \
-                            `#[diag(compiletest_example)]`",
-                        ))
+                        .help("specify the slug as the first argument to the attribute, such as \
+                            `#[diag(compiletest_example)]`")
                         .emit();
                     DiagnosticDeriveError::ErrorHandled.to_compile_error()
                 }

compiler/rustc_middle/src/mir/pretty.rs

@@ -448,15 +448,15 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
 
             // FIXME: this is a poor version of `pretty_print_const_value`.
             let fmt_val = |val: &ConstValue<'tcx>| match val {
-                ConstValue::ZeroSized => format!("<ZST>"),
+                ConstValue::ZeroSized => "<ZST>".to_string(),
                 ConstValue::Scalar(s) => format!("Scalar({:?})", s),
-                ConstValue::Slice { .. } => format!("Slice(..)"),
-                ConstValue::ByRef { .. } => format!("ByRef(..)"),
+                ConstValue::Slice { .. } => "Slice(..)".to_string(),
+                ConstValue::ByRef { .. } => "ByRef(..)".to_string(),
             };
 
             let fmt_valtree = |valtree: &ty::ValTree<'tcx>| match valtree {
                 ty::ValTree::Leaf(leaf) => format!("ValTree::Leaf({:?})", leaf),
-                ty::ValTree::Branch(_) => format!("ValTree::Branch(..)"),
+                ty::ValTree::Branch(_) => "ValTree::Branch(..)".to_string(),
             };
 
             let val = match literal {

compiler/rustc_mir_build/src/build/custom/parse/instruction.rs

@@ -76,7 +76,7 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
         let Some((otherwise, rest)) = arms.split_last() else {
             return Err(ParseError {
                 span,
-                item_description: format!("no arms"),
+                item_description: "no arms".to_string(),
                 expected: "at least one arm".to_string(),
             })
         };

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -277,11 +277,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                 let override_suggestion =
                     if ["true", "false"].contains(&item_str.to_string().to_lowercase().as_str()) {
                         let item_typo = item_str.to_string().to_lowercase();
-                        Some((
-                            item_span,
-                            "you may want to use a bool value instead",
-                            format!("{}", item_typo),
-                        ))
+                        Some((item_span, "you may want to use a bool value instead", item_typo))
                     // FIXME(vincenzopalazzo): make the check smarter,
                     // and maybe expand with levenshtein distance checks
                     } else if item_str.as_str() == "printf" {
@@ -2324,7 +2320,7 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                         let message = format!("consider introducing lifetime `{}` here", name);
                         should_continue = suggest(err, false, span, &message, sugg);
                     } else {
-                        let message = format!("consider introducing a named lifetime parameter");
+                        let message = "consider introducing a named lifetime parameter";
                         should_continue = suggest(err, false, span, &message, sugg);
                     }
                 }

compiler/rustc_trait_selection/src/traits/const_evaluatable.rs

@@ -138,10 +138,10 @@ pub fn is_const_evaluatable<'tcx>(
                 } else if uv.has_non_region_param() {
                     NotConstEvaluatable::MentionsParam
                 } else {
-                    let guar = infcx.tcx.sess.delay_span_bug(
-                        span,
-                        format!("Missing value for constant, but no error reported?"),
-                    );
+                    let guar = infcx
+                        .tcx
+                        .sess
+                        .delay_span_bug(span, "Missing value for constant, but no error reported?");
                     NotConstEvaluatable::Error(guar)
                 };
 

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

@@ -2332,9 +2332,9 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                 // get rid of :: between Trait and <type>
                                 // must be '::' between them, otherwise the parser won't accept the code
                                 suggestions.push((between_span, "".to_string(),));
-                                suggestions.push((generic_arg.span_ext.shrink_to_hi(), format!(">")));
+                                suggestions.push((generic_arg.span_ext.shrink_to_hi(), ">".to_string()));
                             } else {
-                                suggestions.push((trait_path_segment.ident.span.shrink_to_hi(), format!(">")));
+                                suggestions.push((trait_path_segment.ident.span.shrink_to_hi(), ">".to_string()));
                             }
                             err.multipart_suggestion(
                                 message,

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

@@ -2740,7 +2740,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                             }
                             ty::Closure(def_id, _) => err.span_note(
                                 self.tcx.def_span(def_id),
-                                &format!("required because it's used within this closure"),
+                                "required because it's used within this closure",
                             ),
                             _ => err.note(&msg),
                         };
@@ -3386,7 +3386,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             }
             err.span_note(
                 multi_span,
-                format!("the method call chain might not have had the expected associated types"),
+                "the method call chain might not have had the expected associated types",
             );
         }
     }