Avoid Symbol to &str conversions

compiler/rustc_ast_lowering/src/asm.rs

@@ -145,7 +145,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     InlineAsmRegOrRegClass::Reg(s) => {
                         asm::InlineAsmRegOrRegClass::Reg(if let Some(asm_arch) = asm_arch {
                             asm::InlineAsmReg::parse(asm_arch, s).unwrap_or_else(|e| {
-                                let msg = format!("invalid register `{}`: {}", s.as_str(), e);
+                                let msg = format!("invalid register `{}`: {}", s, e);
                                 sess.struct_span_err(*op_sp, &msg).emit();
                                 asm::InlineAsmReg::Err
                             })
@@ -156,7 +156,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     InlineAsmRegOrRegClass::RegClass(s) => {
                         asm::InlineAsmRegOrRegClass::RegClass(if let Some(asm_arch) = asm_arch {
                             asm::InlineAsmRegClass::parse(asm_arch, s).unwrap_or_else(|e| {
-                                let msg = format!("invalid register class `{}`: {}", s.as_str(), e);
+                                let msg = format!("invalid register class `{}`: {}", s, e);
                                 sess.struct_span_err(*op_sp, &msg).emit();
                                 asm::InlineAsmRegClass::Err
                             })

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -62,9 +62,9 @@ impl<'a> PostExpansionVisitor<'a> {
         let ast::StrLit { symbol_unescaped, span, .. } = abi;
 
         if let ast::Const::Yes(_) = constness {
-            match symbol_unescaped.as_str() {
+            match symbol_unescaped {
                 // Stable
-                "Rust" | "C" => {}
+                sym::Rust | sym::C => {}
                 abi => gate_feature_post!(
                     &self,
                     const_extern_fn,

compiler/rustc_codegen_llvm/src/debuginfo/gdb.rs

@@ -55,7 +55,7 @@ pub fn get_or_insert_gdb_debug_scripts_section_global<'ll>(cx: &CodegenCx<'ll, '
             // The initial byte `4` instructs GDB that the following pretty printer
             // is defined inline as opposed to in a standalone file.
             section_contents.extend_from_slice(b"\x04");
-            let vis_name = format!("pretty-printer-{}-{}\n", crate_name.as_str(), index);
+            let vis_name = format!("pretty-printer-{}-{}\n", crate_name, index);
             section_contents.extend_from_slice(vis_name.as_bytes());
             section_contents.extend_from_slice(&visualizer.src);
 

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

@@ -228,7 +228,7 @@ pub fn suggest_adding_lifetime_params<'tcx>(
     if is_impl {
         sugg.push_str(" and update trait if needed");
     }
-    err.multipart_suggestion(sugg.as_str(), suggestions, Applicability::MaybeIncorrect);
+    err.multipart_suggestion(sugg, suggestions, Applicability::MaybeIncorrect);
 
     true
 }

compiler/rustc_passes/src/entry.rs

@@ -77,7 +77,7 @@ fn err_if_attr_found(ctxt: &EntryContext<'_>, attrs: &[Attribute], sym: Symbol)
             .sess
             .struct_span_err(
                 attr.span,
-                &format!("`{}` attribute can only be used on functions", sym.as_str()),
+                &format!("`{}` attribute can only be used on functions", sym),
             )
             .emit();
     }

compiler/rustc_resolve/src/diagnostics.rs

@@ -1630,7 +1630,7 @@ impl<'a> Resolver<'a> {
                     "{}{} `{}` defined here",
                     prefix,
                     suggestion.res.descr(),
-                    suggestion.candidate.as_str(),
+                    suggestion.candidate,
                 ),
             );
         }

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -80,7 +80,7 @@ impl ForLifetimeSpanType {
         }
     }
 
-    pub(crate) fn suggestion(&self, sugg: &str) -> String {
+    pub(crate) fn suggestion(&self, sugg: impl std::fmt::Display) -> String {
         match self {
             Self::BoundEmpty | Self::TypeEmpty => format!("for<{}> ", sugg),
             Self::BoundTail | Self::TypeTail => format!(", {}", sugg),
@@ -2311,8 +2311,8 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
 
         let suggest_existing =
             |err: &mut Diagnostic,
-             name: &str,
-             formatters: Vec<Option<Box<dyn Fn(&str) -> String>>>| {
+             name: Symbol,
+             formatters: Vec<Option<Box<dyn Fn(Symbol) -> String>>>| {
                 if let Some(MissingLifetimeSpot::HigherRanked { span: for_span, span_type }) =
                     self.missing_named_lifetime_spots.iter().rev().next()
                 {
@@ -2332,7 +2332,8 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                     // If all single char lifetime names are present, we wrap around and double the chars.
                     let lt_name = (1..)
                         .flat_map(a_to_z_repeat_n)
-                        .find(|lt| !lifetime_names.contains(&Symbol::intern(&lt)))
+                        .map(|lt| Symbol::intern(&lt))
+                        .find(|lt| !lifetime_names.contains(lt))
                         .unwrap();
                     let msg = format!(
                         "consider making the {} lifetime-generic with a new `{}` lifetime",
@@ -2359,7 +2360,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                     introduce_suggestion.push((*for_span, for_sugg));
                     for ((span, _), formatter) in spans_with_counts.iter().zip(formatters.iter()) {
                         if let Some(formatter) = formatter {
-                            introduce_suggestion.push((*span, formatter(&lt_name)));
+                            introduce_suggestion.push((*span, formatter(lt_name)));
                         }
                     }
                     err.multipart_suggestion_verbose(
@@ -2582,15 +2583,19 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
         let lifetime_names: Vec<_> = lifetime_names.iter().collect();
         match &lifetime_names[..] {
             [name] => {
-                let mut suggs: Vec<Option<Box<dyn Fn(&str) -> String>>> = Vec::new();
+                let mut suggs: Vec<Option<Box<dyn Fn(Symbol) -> String>>> = Vec::new();
                 for (snippet, (_, count)) in snippets.iter().zip(spans_with_counts.iter().copied())
                 {
                     suggs.push(match snippet.as_deref() {
                         Some("&") => Some(Box::new(|name| format!("&{} ", name))),
                         Some("'_") => Some(Box::new(|n| n.to_string())),
                         Some("") => Some(Box::new(move |n| format!("{}, ", n).repeat(count))),
                         Some("<") => Some(Box::new(move |n| {
-                            std::iter::repeat(n).take(count).collect::<Vec<_>>().join(", ")
+                            std::iter::repeat(n)
+                                .take(count)
+                                .map(|n| n.to_string())
+                                .collect::<Vec<_>>()
+                                .join(", ")
                         })),
                         Some(snippet) if !snippet.ends_with('>') => Some(Box::new(move |name| {
                             format!(
@@ -2605,7 +2610,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                         _ => None,
                     });
                 }
-                suggest_existing(err, name.as_str(), suggs);
+                suggest_existing(err, **name, suggs);
             }
             [] => {
                 let mut suggs = Vec::new();

compiler/rustc_resolve/src/macros.rs

@@ -325,7 +325,7 @@ impl<'a> ResolverExpand for Resolver<'a> {
                 UNUSED_MACROS,
                 node_id,
                 ident.span,
-                &format!("unused macro definition: `{}`", ident.as_str()),
+                &format!("unused macro definition: `{}`", ident.name),
             );
         }
         for (&(def_id, arm_i), &(ident, rule_span)) in self.unused_macro_rules.iter() {
@@ -341,7 +341,7 @@ impl<'a> ResolverExpand for Resolver<'a> {
                 &format!(
                     "{} rule of macro `{}` is never used",
                     crate::diagnostics::ordinalize(arm_i + 1),
-                    ident.as_str()
+                    ident.name
                 ),
             );
         }

compiler/rustc_span/src/symbol.rs

@@ -257,6 +257,7 @@ symbols! {
         Result,
         Return,
         Right,
+        Rust,
         RustcDecodable,
         RustcEncodable,
         Send,

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

@@ -474,7 +474,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                         if let Some(ref s) = label {
                             // If it has a custom `#[rustc_on_unimplemented]`
                             // error message, let's display it as the label!
-                            err.span_label(span, s.as_str());
+                            err.span_label(span, s);
                             if !matches!(trait_ref.skip_binder().self_ty().kind(), ty::Param(_)) {
                                 // When the self type is a type param We don't need to "the trait
                                 // `std::marker::Sized` is not implemented for `T`" as we will point
@@ -531,7 +531,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                             let enclosing_scope_span =
                                 tcx.hir().span_with_body(tcx.hir().local_def_id_to_hir_id(body));
 
-                            err.span_label(enclosing_scope_span, s.as_str());
+                            err.span_label(enclosing_scope_span, s);
                         }
 
                         self.suggest_floating_point_literal(&obligation, &mut err, &trait_ref);

compiler/rustc_typeck/src/check/_match.rs

@@ -259,7 +259,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             &cause,
             &mut |err| {
                 if let Some((span, msg)) = &ret_reason {
-                    err.span_label(*span, msg.as_str());
+                    err.span_label(*span, msg);
                 } else if let ExprKind::Block(block, _) = &then_expr.kind
                     && let Some(expr) = &block.expr
                 {

compiler/rustc_typeck/src/check/op.rs

@@ -395,8 +395,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 false,
                             ),
                         };
-                        let mut err =
-                            struct_span_err!(self.tcx.sess, op.span, E0369, "{}", message.as_str());
+                        let mut err = struct_span_err!(self.tcx.sess, op.span, E0369, "{message}");
                         if !lhs_expr.span.eq(&rhs_expr.span) {
                             self.add_type_neq_err_label(
                                 &mut err,