From 6a24ae96eaf175b048e70dfb46dfb860ee7147d9 Mon Sep 17 00:00:00 2001
From: Tobias Bucher <tobiasbucher5991@gmail.com>
Date: Mon, 18 Aug 2025 11:50:27 +0200
Subject: [PATCH 1/2] =?UTF-8?q?Simplify=20macro=20generating=20`ToString`?=
 =?UTF-8?q?=20implementations=20for=20`&=E2=80=A6&str`?=
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Use deref coercion to let the compiler remove any amount of references.
---
 library/alloc/src/string.rs | 55 ++++++++++++++-----------------------
 1 file changed, 21 insertions(+), 34 deletions(-)

diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index 9eacbf00e4233..b1f2cb598c879 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -2949,52 +2949,39 @@ impl SpecToString for i8 {
     }
 }
 
-// Generic/generated code can sometimes have multiple, nested references
-// for strings, including `&&&str`s that would never be written
-// by hand. This macro generates twelve layers of nested `&`-impl
-// for primitive strings.
-#[cfg(not(no_global_oom_handling))]
-macro_rules! to_string_str_wrap_in_ref {
-    {x $($x:ident)*} => {
-        &to_string_str_wrap_in_ref! { $($x)* }
-    };
-    {} => { str };
-}
-#[cfg(not(no_global_oom_handling))]
-macro_rules! to_string_expr_wrap_in_deref {
-    {$self:expr ; x $($x:ident)*} => {
-        *(to_string_expr_wrap_in_deref! { $self ; $($x)* })
-    };
-    {$self:expr ;} => { $self };
-}
 #[cfg(not(no_global_oom_handling))]
 macro_rules! to_string_str {
-    {$($($x:ident)*),+} => {
+    {$($type:ty,)*} => {
         $(
-            impl SpecToString for to_string_str_wrap_in_ref!($($x)*) {
+            impl SpecToString for $type {
                 #[inline]
                 fn spec_to_string(&self) -> String {
-                    String::from(to_string_expr_wrap_in_deref!(self ; $($x)*))
+                    let s: &str = self;
+                    String::from(s)
                 }
             }
-        )+
+        )*
     };
 }
 
 #[cfg(not(no_global_oom_handling))]
 to_string_str! {
-    x x x x x x x x x x x x,
-    x x x x x x x x x x x,
-    x x x x x x x x x x,
-    x x x x x x x x x,
-    x x x x x x x x,
-    x x x x x x x,
-    x x x x x x,
-    x x x x x,
-    x x x x,
-    x x x,
-    x x,
-    x,
+    // Generic/generated code can sometimes have multiple, nested references
+    // for strings, including `&&&str`s that would never be written
+    // by hand.
+    &&&&&&&&&&&&str,
+    &&&&&&&&&&&str,
+    &&&&&&&&&&str,
+    &&&&&&&&&str,
+    &&&&&&&&str,
+    &&&&&&&str,
+    &&&&&&str,
+    &&&&&str,
+    &&&&str,
+    &&&str,
+    &&str,
+    &str,
+    str,
 }
 
 #[cfg(not(no_global_oom_handling))]

From cb5a4d138a298853225d7561c243ce6e23064775 Mon Sep 17 00:00:00 2001
From: Tobias Bucher <tobiasbucher5991@gmail.com>
Date: Mon, 18 Aug 2025 11:51:31 +0200
Subject: [PATCH 2/2] Use `ToString` specialization macro also for `Cow` and
 `String`

---
 library/alloc/src/string.rs | 18 ++----------------
 1 file changed, 2 insertions(+), 16 deletions(-)

diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index b1f2cb598c879..ec4d934a5a3f6 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -2966,6 +2966,8 @@ macro_rules! to_string_str {
 
 #[cfg(not(no_global_oom_handling))]
 to_string_str! {
+    Cow<'_, str>,
+    String,
     // Generic/generated code can sometimes have multiple, nested references
     // for strings, including `&&&str`s that would never be written
     // by hand.
@@ -2984,22 +2986,6 @@ to_string_str! {
     str,
 }
 
-#[cfg(not(no_global_oom_handling))]
-impl SpecToString for Cow<'_, str> {
-    #[inline]
-    fn spec_to_string(&self) -> String {
-        self[..].to_owned()
-    }
-}
-
-#[cfg(not(no_global_oom_handling))]
-impl SpecToString for String {
-    #[inline]
-    fn spec_to_string(&self) -> String {
-        self.to_owned()
-    }
-}
-
 #[cfg(not(no_global_oom_handling))]
 impl SpecToString for fmt::Arguments<'_> {
     #[inline]