avoid some `Symbol` to `String` conversions

4 files changed, 15 insertions, 20 deletions

diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index b9cfc3732dc..146f86e5a11 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -23,7 +23,7 @@ use rustc_middle::ty::{
 use rustc_mir_dataflow::move_paths::{InitKind, MoveOutIndex, MovePathIndex};
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::symbol::sym;
-use rustc_span::{BytePos, Span};
+use rustc_span::{BytePos, Span, Symbol};
 use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::TraitEngineExt as _;
 
@@ -1227,8 +1227,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     from_closure: false,
                     region_name:
                         RegionName {
-                            source:
-                                RegionNameSource::AnonRegionFromUpvar(upvar_span, ref upvar_name),
+                            source: RegionNameSource::AnonRegionFromUpvar(upvar_span, upvar_name),
                             ..
                         },
                     span,
@@ -1702,7 +1701,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         borrow_span: Span,
         name: &Option<String>,
         upvar_span: Span,
-        upvar_name: &str,
+        upvar_name: Symbol,
         escape_span: Span,
     ) -> DiagnosticBuilder<'cx, ErrorGuaranteed> {
         let tcx = self.infcx.tcx;
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 230ccf51990..72aee0267ac 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -12,7 +12,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::adjustment::PointerCast;
 use rustc_middle::ty::{self, RegionVid, TyCtxt};
-use rustc_span::symbol::Symbol;
+use rustc_span::symbol::{kw, Symbol};
 use rustc_span::{sym, DesugaringKind, Span};
 
 use crate::region_infer::BlameConstraint;
@@ -282,7 +282,7 @@ impl<'tcx> BorrowExplanation<'tcx> {
     ) {
         if let ConstraintCategory::OpaqueType = category {
             let suggestable_name =
-                if region_name.was_named() { region_name.to_string() } else { "'_".to_string() };
+                if region_name.was_named() { region_name.name } else { kw::UnderscoreLifetime };
 
             let msg = format!(
                 "you can add a bound to the {}to make it last less than `'static` and match `{}`",
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 5d3997289bb..7b2f771288f 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -19,8 +19,7 @@ use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::Region;
 use rustc_middle::ty::TypeVisitor;
 use rustc_middle::ty::{self, RegionVid, Ty};
-use rustc_span::symbol::sym;
-use rustc_span::symbol::Ident;
+use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::Span;
 
 use crate::borrowck_errors;
@@ -758,7 +757,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 return;
             };
 
-            let lifetime = if f.has_name() { fr_name.to_string() } else { "'_".to_string() };
+            let lifetime = if f.has_name() { fr_name.name } else { kw::UnderscoreLifetime };
 
             let arg = match param.param.pat.simple_ident() {
                 Some(simple_ident) => format!("argument `{}`", simple_ident),
@@ -770,7 +769,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 self.infcx.tcx,
                 diag,
                 fn_returns,
-                lifetime,
+                lifetime.to_string(),
                 Some(arg),
                 captures,
                 Some((param.param_ty_span, param.param_ty.to_string())),
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index e60e11f11df..49f8218b222 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -34,13 +34,13 @@ pub(crate) enum RegionNameSource {
     /// The `'static` region.
     Static,
     /// The free region corresponding to the environment of a closure.
-    SynthesizedFreeEnvRegion(Span, String),
+    SynthesizedFreeEnvRegion(Span, &'static str),
     /// The region corresponding to an argument.
     AnonRegionFromArgument(RegionNameHighlight),
     /// The region corresponding to a closure upvar.
-    AnonRegionFromUpvar(Span, String),
+    AnonRegionFromUpvar(Span, Symbol),
     /// The region corresponding to the return type of a closure.
-    AnonRegionFromOutput(RegionNameHighlight, String),
+    AnonRegionFromOutput(RegionNameHighlight, &'static str),
     /// The region from a type yielded by a generator.
     AnonRegionFromYieldTy(Span, String),
     /// An anonymous region from an async fn.
@@ -110,7 +110,7 @@ impl RegionName {
             }
             RegionNameSource::SynthesizedFreeEnvRegion(span, note) => {
                 diag.span_label(*span, format!("lifetime `{self}` represents this closure's body"));
-                diag.note(note);
+                diag.note(*note);
             }
             RegionNameSource::AnonRegionFromArgument(RegionNameHighlight::CannotMatchHirTy(
                 span,
@@ -350,10 +350,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
                     Some(RegionName {
                         name: region_name,
-                        source: RegionNameSource::SynthesizedFreeEnvRegion(
-                            fn_decl_span,
-                            note.to_string(),
-                        ),
+                        source: RegionNameSource::SynthesizedFreeEnvRegion(fn_decl_span, note),
                     })
                 }
 
@@ -678,7 +675,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         Some(RegionName {
             name: region_name,
-            source: RegionNameSource::AnonRegionFromUpvar(upvar_span, upvar_name.to_string()),
+            source: RegionNameSource::AnonRegionFromUpvar(upvar_span, upvar_name),
         })
     }
 
@@ -756,7 +753,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
 
         Some(RegionName {
             name: self.synthesize_region_name(),
-            source: RegionNameSource::AnonRegionFromOutput(highlight, mir_description.to_string()),
+            source: RegionNameSource::AnonRegionFromOutput(highlight, mir_description),
         })
     }