diff --git a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
index 8b12db071b6ac..fe5e3c5a81b61 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
@@ -237,7 +237,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     err.span_suggestion_verbose(
                         span,
                         "consider changing this to be mutable",
-                        " mut ".into(),
+                        " mut ",
                         Applicability::MaybeIncorrect,
                     );
                 }
diff --git a/compiler/rustc_builtin_macros/src/deriving/default.rs b/compiler/rustc_builtin_macros/src/deriving/default.rs
index 2c5260616c7da..b49331e28753d 100644
--- a/compiler/rustc_builtin_macros/src/deriving/default.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/default.rs
@@ -235,7 +235,7 @@ fn validate_default_attribute(
             .span_suggestion_hidden(
                 attr.span,
                 "try using `#[default]`",
-                "#[default]".into(),
+                "#[default]",
                 Applicability::MaybeIncorrect,
             )
             .emit();
diff --git a/compiler/rustc_errors/src/diagnostic.rs b/compiler/rustc_errors/src/diagnostic.rs
index cd17726c78588..39cb71848ebdd 100644
--- a/compiler/rustc_errors/src/diagnostic.rs
+++ b/compiler/rustc_errors/src/diagnostic.rs
@@ -605,7 +605,7 @@ impl Diagnostic {
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self {
         self.span_suggestion_with_style(
@@ -623,13 +623,13 @@ impl Diagnostic {
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
         style: SuggestionStyle,
     ) -> &mut Self {
         self.push_suggestion(CodeSuggestion {
             substitutions: vec![Substitution {
-                parts: vec![SubstitutionPart { snippet: suggestion, span: sp }],
+                parts: vec![SubstitutionPart { snippet: suggestion.to_string(), span: sp }],
             }],
             msg: msg.into(),
             style,
@@ -643,7 +643,7 @@ impl Diagnostic {
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self {
         self.span_suggestion_with_style(
@@ -711,7 +711,7 @@ impl Diagnostic {
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self {
         self.span_suggestion_with_style(
@@ -734,7 +734,7 @@ impl Diagnostic {
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self {
         self.span_suggestion_with_style(
@@ -755,7 +755,7 @@ impl Diagnostic {
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self {
         self.span_suggestion_with_style(
diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
index d218040847704..efc7693459fc9 100644
--- a/compiler/rustc_errors/src/diagnostic_builder.rs
+++ b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -477,7 +477,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self);
     forward!(pub fn span_suggestions(
@@ -497,28 +497,28 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self);
     forward!(pub fn span_suggestion_verbose(
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self);
     forward!(pub fn span_suggestion_hidden(
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self);
     forward!(pub fn tool_only_span_suggestion(
         &mut self,
         sp: Span,
         msg: impl Into<DiagnosticMessage>,
-        suggestion: String,
+        suggestion: impl ToString,
         applicability: Applicability,
     ) -> &mut Self);
 
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index a9c7ba5d072d2..c91125105d746 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -511,7 +511,7 @@ pub fn parse_cfg<'a>(meta_item: &'a MetaItem, sess: &Session) -> Option<&'a Meta
             err.span_suggestion(
                 span,
                 "expected syntax is",
-                suggestion.into(),
+                suggestion,
                 Applicability::HasPlaceholders,
             );
         }
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index f9273cc50b70a..14555ad92559d 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -2198,7 +2198,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             err.span_suggestion(
                 span.with_hi(before_close).shrink_to_hi(),
                 msg,
-                ",".into(),
+                ",",
                 Applicability::MachineApplicable,
             );
         } else {
diff --git a/compiler/rustc_lint/src/array_into_iter.rs b/compiler/rustc_lint/src/array_into_iter.rs
index a14d602036131..dff2e31c6070c 100644
--- a/compiler/rustc_lint/src/array_into_iter.rs
+++ b/compiler/rustc_lint/src/array_into_iter.rs
@@ -129,7 +129,7 @@ impl<'tcx> LateLintPass<'tcx> for ArrayIntoIter {
                 diag.span_suggestion(
                     call.ident.span,
                     "use `.iter()` instead of `.into_iter()` to avoid ambiguity",
-                    "iter".into(),
+                    "iter",
                     Applicability::MachineApplicable,
                 );
                 if self.for_expr_span == expr.span {
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 0ffa65b79b584..d7cd5ec04f323 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -738,7 +738,7 @@ pub trait LintContext: Sized {
                     db.span_suggestion_verbose(
                         span.shrink_to_hi(),
                         "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
-                        " ".into(),
+                        " ",
                         Applicability::MachineApplicable,
                     );
                 }
diff --git a/compiler/rustc_lint/src/non_fmt_panic.rs b/compiler/rustc_lint/src/non_fmt_panic.rs
index f21f25c35847e..71769fceec1f2 100644
--- a/compiler/rustc_lint/src/non_fmt_panic.rs
+++ b/compiler/rustc_lint/src/non_fmt_panic.rs
@@ -176,7 +176,7 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
                 l.span_suggestion_verbose(
                     arg_span.shrink_to_lo(),
                     "add a \"{}\" format string to Display the message",
-                    "\"{}\", ".into(),
+                    "\"{}\", ",
                     fmt_applicability,
                 );
             } else if suggest_debug {
@@ -186,7 +186,7 @@ fn check_panic<'tcx>(cx: &LateContext<'tcx>, f: &'tcx hir::Expr<'tcx>, arg: &'tc
                         "add a \"{{:?}}\" format string to use the Debug implementation of `{}`",
                         ty,
                     ),
-                    "\"{:?}\", ".into(),
+                    "\"{:?}\", ",
                     fmt_applicability,
                 );
             }
@@ -266,13 +266,13 @@ fn check_panic_str<'tcx>(
                 l.span_suggestion(
                     arg.span.shrink_to_hi(),
                     &format!("add the missing argument{}", pluralize!(n_arguments)),
-                    ", ...".into(),
+                    ", ...",
                     Applicability::HasPlaceholders,
                 );
                 l.span_suggestion(
                     arg.span.shrink_to_lo(),
                     "or add a \"{}\" format string to use the message literally",
-                    "\"{}\", ".into(),
+                    "\"{}\", ",
                     Applicability::MachineApplicable,
                 );
             }
@@ -297,7 +297,7 @@ fn check_panic_str<'tcx>(
                 l.span_suggestion(
                     arg.span.shrink_to_lo(),
                     "add a \"{}\" format string to use the message literally",
-                    "\"{}\", ".into(),
+                    "\"{}\", ",
                     Applicability::MachineApplicable,
                 );
             }
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index e585c61bf2ee1..ee54dd44f7194 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -612,14 +612,14 @@ impl<'a> StringReader<'a> {
                 err.span_suggestion_verbose(
                     prefix_span,
                     "use `br` for a raw byte string",
-                    "br".to_string(),
+                    "br",
                     Applicability::MaybeIncorrect,
                 );
             } else if expn_data.is_root() {
                 err.span_suggestion_verbose(
                     prefix_span.shrink_to_hi(),
                     "consider inserting whitespace here",
-                    " ".into(),
+                    " ",
                     Applicability::MaybeIncorrect,
                 );
             }
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index bdbc25af7fa1e..13e9a5e660fe6 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -1771,7 +1771,7 @@ impl<'a> Parser<'a> {
             .span_suggestion(
                 token.span,
                 "must have an integer part",
-                pprust::token_to_string(token).into(),
+                pprust::token_to_string(token),
                 Applicability::MachineApplicable,
             )
             .emit();
@@ -2324,7 +2324,7 @@ impl<'a> Parser<'a> {
             .span_suggestion_short(
                 span,
                 msg,
-                sugg.into(),
+                sugg,
                 // Has been misleading, at least in the past (closed Issue #48492).
                 Applicability::MaybeIncorrect,
             )
@@ -2828,7 +2828,7 @@ impl<'a> Parser<'a> {
                             e.span_suggestion(
                                 self.prev_token.span.shrink_to_hi(),
                                 "try adding a comma",
-                                ",".into(),
+                                ",",
                                 Applicability::MachineApplicable,
                             );
                         }
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 746861933d2f0..10f1daf112951 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -332,7 +332,7 @@ impl<'a> Parser<'a> {
             err.span_suggestion_short(
                 sp,
                 &msg,
-                " struct ".into(),
+                " struct ",
                 Applicability::MaybeIncorrect, // speculative
             );
             Err(err)
@@ -532,13 +532,13 @@ impl<'a> Parser<'a> {
                 .span_suggestion(
                     span,
                     "add a trait here",
-                    " Trait ".into(),
+                    " Trait ",
                     Applicability::HasPlaceholders,
                 )
                 .span_suggestion(
                     span.to(self.token.span),
                     "for an inherent impl, drop this `for`",
-                    "".into(),
+                    "",
                     Applicability::MaybeIncorrect,
                 )
                 .emit();
@@ -1459,7 +1459,7 @@ impl<'a> Parser<'a> {
                         err.span_suggestion(
                             sp,
                             "missing comma here",
-                            ",".into(),
+                            ",",
                             Applicability::MachineApplicable,
                         );
                     }
@@ -1498,7 +1498,7 @@ impl<'a> Parser<'a> {
                     err.span_suggestion(
                         sp,
                         "try adding a comma",
-                        ",".into(),
+                        ",",
                         Applicability::MachineApplicable,
                     );
                     err.emit();
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 96cca68257e7f..cd61584a87662 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -802,7 +802,7 @@ impl<'a> Parser<'a> {
                                     .span_suggestion_verbose(
                                         self.prev_token.span.shrink_to_hi().until(self.token.span),
                                         &msg,
-                                        " @ ".to_string(),
+                                        " @ ",
                                         Applicability::MaybeIncorrect,
                                     )
                                     .emit();
@@ -818,7 +818,7 @@ impl<'a> Parser<'a> {
                                         .span_suggestion_short(
                                             sp,
                                             &format!("missing `{}`", token_str),
-                                            token_str.into(),
+                                            token_str,
                                             Applicability::MaybeIncorrect,
                                         )
                                         .emit();
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index c7b929bf367dc..8019c5fb67cb9 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -606,7 +606,7 @@ impl<'a> Parser<'a> {
             .span_suggestion(
                 mutref_span,
                 "try switching the order",
-                "ref mut".into(),
+                "ref mut",
                 Applicability::MachineApplicable,
             )
             .emit();
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index 291b6645d9aa6..650a0dc82ce23 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -851,7 +851,7 @@ impl<'a, 'b> BuildReducedGraphVisitor<'a, 'b> {
                 .span_suggestion(
                     item.span,
                     "rename the `self` crate to be able to import it",
-                    "extern crate self as name;".into(),
+                    "extern crate self as name;",
                     Applicability::HasPlaceholders,
                 )
                 .emit();
diff --git a/src/tools/clippy/clippy_lints/src/functions/must_use.rs b/src/tools/clippy/clippy_lints/src/functions/must_use.rs
index 0709580c8adfd..5462d913fb441 100644
--- a/src/tools/clippy/clippy_lints/src/functions/must_use.rs
+++ b/src/tools/clippy/clippy_lints/src/functions/must_use.rs
@@ -108,7 +108,7 @@ fn check_needless_must_use(
                 diag.span_suggestion(
                     attr.span,
                     "remove the attribute",
-                    "".into(),
+                    "",
                     Applicability::MachineApplicable,
                 );
             },
diff --git a/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs b/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
index 9c734221ebcea..4034079a90c0d 100644
--- a/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
+++ b/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
@@ -241,7 +241,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
                                                 |x| Cow::from(format!("change `{}` to", x)),
                                             )
                                             .as_ref(),
-                                        suggestion.into(),
+                                        suggestion,
                                         Applicability::Unspecified,
                                     );
                                 }
@@ -271,7 +271,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
                                                 |x| Cow::from(format!("change `{}` to", x))
                                             )
                                             .as_ref(),
-                                        suggestion.into(),
+                                        suggestion,
                                         Applicability::Unspecified,
                                     );
                                 }