4 files changed, 18 insertions, 17 deletions
diff --git a/compiler/rustc_middle/src/lint.rs b/compiler/rustc_middle/src/lint.rs
index 14343ac1108..caf3fc26039 100644
--- a/compiler/rustc_middle/src/lint.rs
+++ b/compiler/rustc_middle/src/lint.rs
@@ -251,7 +251,7 @@ pub fn explain_lint_level_source(
         }
         LintLevelSource::Node { name: lint_attr_name, span, reason, .. } => {
             if let Some(rationale) = reason {
-                err.note(rationale.as_str());
+                err.note(rationale.to_string());
             }
             err.span_note_once(span, "the lint level is defined here");
             if lint_attr_name.as_str() != name {
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 6354c0aabde..60844c17e47 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -104,7 +104,7 @@ pub fn report_unstable(
     suggestion: Option<(Span, String, String, Applicability)>,
     is_soft: bool,
     span: Span,
-    soft_handler: impl FnOnce(&'static Lint, Span, &str),
+    soft_handler: impl FnOnce(&'static Lint, Span, String),
 ) {
     let msg = match reason {
         Some(r) => format!("use of unstable library feature '{}': {}", feature, r),
@@ -112,7 +112,7 @@ pub fn report_unstable(
     };
 
     if is_soft {
-        soft_handler(SOFT_UNSTABLE, span, &msg)
+        soft_handler(SOFT_UNSTABLE, span, msg)
     } else {
         let mut err =
             feature_err_issue(&sess.parse_sess, feature, span, GateIssue::Library(issue), msg);
@@ -225,7 +225,7 @@ pub fn deprecation_message_and_lint(
 
 pub fn early_report_deprecation(
     lint_buffer: &mut LintBuffer,
-    message: &str,
+    message: String,
     suggestion: Option<Symbol>,
     lint: &'static Lint,
     span: Span,
@@ -241,7 +241,7 @@ pub fn early_report_deprecation(
 
 fn late_report_deprecation(
     tcx: TyCtxt<'_>,
-    message: &str,
+    message: String,
     suggestion: Option<Symbol>,
     lint: &'static Lint,
     span: Span,
@@ -396,7 +396,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
                         late_report_deprecation(
                             self,
-                            &deprecation_message(
+                            deprecation_message(
                                 is_in_effect,
                                 depr_attr.since,
                                 depr_attr.note,
@@ -619,7 +619,7 @@ impl<'tcx> TyCtxt<'tcx> {
         allow_unstable: AllowUnstable,
         unmarked: impl FnOnce(Span, DefId),
     ) -> bool {
-        let soft_handler = |lint, span, msg: &_| {
+        let soft_handler = |lint, span, msg: String| {
             self.struct_span_lint_hir(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, msg, |lint| lint)
         };
         let eval_result =
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 2bde55bc4fd..0464336627f 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -732,7 +732,11 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Constructs a `RegionKind::ReError` lifetime and registers a `delay_span_bug` with the given
     /// `msg` to ensure it gets used.
     #[track_caller]
-    pub fn mk_re_error_with_message<S: Into<MultiSpan>>(self, span: S, msg: &str) -> Region<'tcx> {
+    pub fn mk_re_error_with_message<S: Into<MultiSpan>>(
+        self,
+        span: S,
+        msg: &'static str,
+    ) -> Region<'tcx> {
         let reported = self.sess.delay_span_bug(span, msg);
         self.mk_re_error(reported)
     }
@@ -759,7 +763,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         ty: Ty<'tcx>,
         span: S,
-        msg: &str,
+        msg: &'static str,
     ) -> Const<'tcx> {
         let reported = self.sess.delay_span_bug(span, msg);
         self.mk_const(ty::ConstKind::Error(reported), ty)
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index 6a29063b80d..9c91b778403 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -1,5 +1,6 @@
 //! Diagnostics related methods for `Ty`.
 
+use std::borrow::Cow;
 use std::ops::ControlFlow;
 
 use crate::ty::{
@@ -384,22 +385,18 @@ pub fn suggest_constraining_type_params<'a>(
 
     if suggestions.len() == 1 {
         let (span, suggestion, msg) = suggestions.pop().unwrap();
-
-        let s;
         let msg = match msg {
             SuggestChangingConstraintsMessage::RestrictBoundFurther => {
-                "consider further restricting this bound"
+                Cow::from("consider further restricting this bound")
             }
             SuggestChangingConstraintsMessage::RestrictType { ty } => {
-                s = format!("consider restricting type parameter `{}`", ty);
-                &s
+                Cow::from(format!("consider restricting type parameter `{}`", ty))
             }
             SuggestChangingConstraintsMessage::RestrictTypeFurther { ty } => {
-                s = format!("consider further restricting type parameter `{}`", ty);
-                &s
+                Cow::from(format!("consider further restricting type parameter `{}`", ty))
             }
             SuggestChangingConstraintsMessage::RemovingQSized => {
-                "consider removing the `?Sized` bound to make the type parameter `Sized`"
+                Cow::from("consider removing the `?Sized` bound to make the type parameter `Sized`")
             }
         };