From b9f3c420392c3ff4d53dd56df8c31fb4fb9deda0 Mon Sep 17 00:00:00 2001
From: Lukasz Anforowicz <lukasza@chromium.org>
Date: Mon, 24 Mar 2025 21:28:19 +0000
Subject: [PATCH] Add an explicit conversion operator from `rust::Str` to
 `std::string_view`.

---
 book/src/binding/str.md |  3 +++
 include/cxx.h           | 14 +++++++++++---
 src/cxx.cc              |  6 ++++++
 tests/ffi/tests.cc      |  5 +++++
 4 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/book/src/binding/str.md b/book/src/binding/str.md
index e37a13dfd..214d12dfa 100644
--- a/book/src/binding/str.md
+++ b/book/src/binding/str.md
@@ -25,6 +25,9 @@ public:
   Str &operator=(const Str &) & noexcept;
 
   explicit operator std::string() const;
+#if __cplusplus >= 201703L
+  explicit operator std::string_view() const;
+#endif
 
   // Note: no null terminator.
   const char *data() const noexcept;
diff --git a/include/cxx.h b/include/cxx.h
index 9f54ecc50..4e261a355 100644
--- a/include/cxx.h
+++ b/include/cxx.h
@@ -9,9 +9,6 @@
 #include <iosfwd>
 #include <iterator>
 #include <new>
-#if __cplusplus >= 202002L
-#include <ranges>
-#endif
 #include <stdexcept>
 #include <string>
 #include <type_traits>
@@ -23,6 +20,14 @@
 #include <sys/types.h>
 #endif
 
+#if __cplusplus >= 201703L
+#include <string_view>
+#endif
+
+#if __cplusplus >= 202002L
+#include <ranges>
+#endif
+
 namespace rust {
 inline namespace cxxbridge1 {
 
@@ -123,6 +128,9 @@ class Str final {
   Str &operator=(const Str &) & noexcept = default;
 
   explicit operator std::string() const;
+#if __cplusplus >= 201703L
+  explicit operator std::string_view() const;
+#endif
 
   // Note: no null terminator.
   const char *data() const noexcept;
diff --git a/src/cxx.cc b/src/cxx.cc
index 1e3e355b2..45d9aace7 100644
--- a/src/cxx.cc
+++ b/src/cxx.cc
@@ -325,6 +325,12 @@ Str::operator std::string() const {
   return std::string(this->data(), this->size());
 }
 
+#if __cplusplus >= 201703L
+Str::operator std::string_view() const {
+  return std::string_view(this->data(), this->size());
+}
+#endif
+
 const char *Str::data() const noexcept { return cxxbridge1$str$ptr(this); }
 
 std::size_t Str::size() const noexcept { return cxxbridge1$str$len(this); }
diff --git a/tests/ffi/tests.cc b/tests/ffi/tests.cc
index ad60aacba..2ba67f87d 100644
--- a/tests/ffi/tests.cc
+++ b/tests/ffi/tests.cc
@@ -874,6 +874,11 @@ extern "C" const char *cxx_run_test() noexcept {
     rust::Str out_param;
     r_return_str_via_out_param(Shared{2020}, out_param);
     ASSERT(out_param == "2020");
+
+#if __cplusplus >= 201703L
+    std::string_view out_param_as_string_view{out_param};
+    ASSERT(out_param_as_string_view == "2020");
+#endif
   }
 
   rust::Str cstr = "test";