diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 926b0da2ec610..96042ea30787e 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -386,7 +386,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ).span_suggestion_verbose(
                 lhs.span.shrink_to_lo(),
                 "you might have meant to introduce a new binding",
-                "let ".to_string(),
+                "let ",
                 Applicability::MachineApplicable,
             ).emit();
         }
diff --git a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
index ea58ad5ae3e34..5e4c7292e590d 100644
--- a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
@@ -467,7 +467,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 err.span_suggestion_verbose(
                     span.shrink_to_lo(),
                     "consider borrowing here",
-                    "&".to_string(),
+                    '&',
                     Applicability::MaybeIncorrect,
                 );
             }
diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index 9f37b915b773a..ef0542b57add5 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -385,7 +385,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     err.span_suggestion_verbose(
                         local_decl.source_info.span.shrink_to_lo(),
                         "consider changing this to be mutable",
-                        "mut ".to_string(),
+                        "mut ",
                         Applicability::MachineApplicable,
                     );
                     let tcx = self.infcx.tcx;