From 81c4805e8ad43352d4033d3086abca4b4ac168c5 Mon Sep 17 00:00:00 2001
From: Kornel <kornel@geekhood.net>
Date: Sun, 25 Aug 2024 11:20:42 +0100
Subject: [PATCH] Add str.as_str() for easy dereferencing of Box<str>

---
 alloc/src/lib.rs      |  1 +
 alloc/src/rc/tests.rs |  4 ++++
 core/src/str/mod.rs   | 11 +++++++++++
 3 files changed, 16 insertions(+)

diff --git a/alloc/src/lib.rs b/alloc/src/lib.rs
index f0597f295b3f0..ff5ddd16e07e3 100644
--- a/alloc/src/lib.rs
+++ b/alloc/src/lib.rs
@@ -93,6 +93,7 @@
 // tidy-alphabetical-start
 #![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
 #![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
+#![cfg_attr(test, feature(str_as_str))]
 #![feature(alloc_layout_extra)]
 #![feature(allocator_api)]
 #![feature(array_chunks)]
diff --git a/alloc/src/rc/tests.rs b/alloc/src/rc/tests.rs
index 84e8b325f71fc..333e1bde31c1e 100644
--- a/alloc/src/rc/tests.rs
+++ b/alloc/src/rc/tests.rs
@@ -448,7 +448,11 @@ fn test_from_box_str() {
     use std::string::String;
 
     let s = String::from("foo").into_boxed_str();
+    assert_eq!((&&&s).as_str(), "foo");
+
     let r: Rc<str> = Rc::from(s);
+    assert_eq!((&r).as_str(), "foo");
+    assert_eq!(r.as_str(), "foo");
 
     assert_eq!(&r[..], "foo");
 }
diff --git a/core/src/str/mod.rs b/core/src/str/mod.rs
index 9373d807f44e3..5b20e681c2409 100644
--- a/core/src/str/mod.rs
+++ b/core/src/str/mod.rs
@@ -2737,6 +2737,17 @@ impl str {
     pub fn substr_range(&self, substr: &str) -> Option<Range<usize>> {
         self.as_bytes().subslice_range(substr.as_bytes())
     }
+
+    /// Returns the same string as a string slice `&str`.
+    ///
+    /// This method is redundant when used directly on `&str`, but
+    /// it helps dereferencing other string-like types to string slices,
+    /// for example references to `Box<str>` or `Arc<str>`.
+    #[inline]
+    #[unstable(feature = "str_as_str", issue = "130366")]
+    pub fn as_str(&self) -> &str {
+        self
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]