From 77ba7ca9d2a523ef9f1837e53554fa65c232abc8 Mon Sep 17 00:00:00 2001
From: Abseil Team <absl-team@google.com>
Date: Fri, 2 Jun 2023 13:49:30 -0700
Subject: Lifetime checks for `absl::StrSplit()`

PiperOrigin-RevId: 537400816
Change-Id: I06794a6b8b6a441e34121047024380190d42869a
---
 absl/strings/internal/str_split_internal.h | 62 +++++++++++++++++++++++++++---
 1 file changed, 56 insertions(+), 6 deletions(-)

(limited to 'absl/strings/internal/str_split_internal.h')

diff --git a/absl/strings/internal/str_split_internal.h b/absl/strings/internal/str_split_internal.h
index 35edf3aa..081ad85a 100644
--- a/absl/strings/internal/str_split_internal.h
+++ b/absl/strings/internal/str_split_internal.h
@@ -235,6 +235,24 @@ struct SplitterIsConvertibleTo
           HasMappedType<C>::value> {
 };
 
+template <typename StringType, typename Container, typename = void>
+struct ShouldUseLifetimeBound : std::false_type {};
+
+template <typename StringType, typename Container>
+struct ShouldUseLifetimeBound<
+    StringType, Container,
+    std::enable_if_t<
+        std::is_same<StringType, std::string>::value &&
+        std::is_same<typename Container::value_type, absl::string_view>::value>>
+    : std::true_type {};
+
+template <typename StringType, typename First, typename Second>
+using ShouldUseLifetimeBoundForPair = std::integral_constant<
+    bool, std::is_same<StringType, std::string>::value &&
+              (std::is_same<First, absl::string_view>::value ||
+               std::is_same<Second, absl::string_view>::value)>;
+
+
 // This class implements the range that is returned by absl::StrSplit(). This
 // class has templated conversion operators that allow it to be implicitly
 // converted to a variety of types that the caller may have specified on the
@@ -281,10 +299,24 @@ class Splitter {
 
   // An implicit conversion operator that is restricted to only those containers
   // that the splitter is convertible to.
-  template <typename Container,
-            typename = typename std::enable_if<
-                SplitterIsConvertibleTo<Container>::value>::type>
-  operator Container() const {  // NOLINT(runtime/explicit)
+  template <
+      typename Container,
+      std::enable_if_t<ShouldUseLifetimeBound<StringType, Container>::value &&
+                           SplitterIsConvertibleTo<Container>::value,
+                       std::nullptr_t> = nullptr>
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  operator Container() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return ConvertToContainer<Container, typename Container::value_type,
+                              HasMappedType<Container>::value>()(*this);
+  }
+
+  template <
+      typename Container,
+      std::enable_if_t<!ShouldUseLifetimeBound<StringType, Container>::value &&
+                           SplitterIsConvertibleTo<Container>::value,
+                       std::nullptr_t> = nullptr>
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  operator Container() const {
     return ConvertToContainer<Container, typename Container::value_type,
                               HasMappedType<Container>::value>()(*this);
   }
@@ -293,8 +325,27 @@ class Splitter {
   // strings returned by the begin() iterator. Either/both of .first and .second
   // will be constructed with empty strings if the iterator doesn't have a
   // corresponding value.
+  template <typename First, typename Second,
+            std::enable_if_t<
+                ShouldUseLifetimeBoundForPair<StringType, First, Second>::value,
+                std::nullptr_t> = nullptr>
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  operator std::pair<First, Second>() const ABSL_ATTRIBUTE_LIFETIME_BOUND {
+    return ConvertToPair<First, Second>();
+  }
+
+  template <typename First, typename Second,
+            std::enable_if_t<!ShouldUseLifetimeBoundForPair<StringType, First,
+                                                            Second>::value,
+                             std::nullptr_t> = nullptr>
+  // NOLINTNEXTLINE(google-explicit-constructor)
+  operator std::pair<First, Second>() const {
+    return ConvertToPair<First, Second>();
+  }
+
+ private:
   template <typename First, typename Second>
-  operator std::pair<First, Second>() const {  // NOLINT(runtime/explicit)
+  std::pair<First, Second> ConvertToPair() const {
     absl::string_view first, second;
     auto it = begin();
     if (it != end()) {
@@ -306,7 +357,6 @@ class Splitter {
     return {First(first), Second(second)};
   }
 
- private:
   // ConvertToContainer is a functor converting a Splitter to the requested
   // Container of ValueType. It is specialized below to optimize splitting to
   // certain combinations of Container and ValueType.
-- 
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