string_format.h: create the StringifySink at the correct scope and pass it along so that its lifetime gets extended to the full-expression that uses FormatArg, as would have happened if AlphaNum was used as intended (i.e. as an argument to StrCat and StrAppend).

Author: dconeybe

Firestore/core/src/util/string_format.h

@@ -65,8 +65,8 @@ struct FormatChoice<5> {};
 class FormatArg : public absl::AlphaNum {
  public:
   template <typename T>
-  FormatArg(T&& value)  // NOLINT(runtime/explicit)
-      : FormatArg{std::forward<T>(value), internal::FormatChoice<0>{}} {
+  FormatArg(T&& value, absl::strings_internal::StringifySink&& sink = {})  // NOLINT(runtime/explicit)
+      : FormatArg{std::forward<T>(value), std::move(sink), internal::FormatChoice<0>{}} {
   }
 
  private:
@@ -79,7 +79,7 @@ class FormatArg : public absl::AlphaNum {
    */
   template <typename T,
             typename = typename std::enable_if<std::is_same<bool, T>{}>::type>
-  FormatArg(T bool_value, internal::FormatChoice<0>)
+  FormatArg(T bool_value, absl::strings_internal::StringifySink&&, internal::FormatChoice<0>)
       : AlphaNum(bool_value ? "true" : "false") {
   }
 
@@ -90,15 +90,15 @@ class FormatArg : public absl::AlphaNum {
   template <
       typename T,
       typename = typename std::enable_if<objc::is_objc_pointer<T>{}>::type>
-  FormatArg(T object, internal::FormatChoice<1>)
+  FormatArg(T object, absl::strings_internal::StringifySink&&, internal::FormatChoice<1>)
       : AlphaNum(MakeStringView([object description])) {
   }
 
   /**
    * Creates a FormatArg from any Objective-C Class type. Objective-C Class
    * types are a special struct that aren't of a type derived from NSObject.
    */
-  FormatArg(Class object, internal::FormatChoice<1>)
+  FormatArg(Class object, absl::strings_internal::StringifySink&&, internal::FormatChoice<1>)
       : AlphaNum(MakeStringView(NSStringFromClass(object))) {
   }
 #endif
@@ -108,15 +108,15 @@ class FormatArg : public absl::AlphaNum {
    * handled specially to avoid ambiguity with generic pointers, which are
    * handled differently.
    */
-  FormatArg(std::nullptr_t, internal::FormatChoice<2>) : AlphaNum("null") {
+  FormatArg(std::nullptr_t, absl::strings_internal::StringifySink&&, internal::FormatChoice<2>) : AlphaNum("null") {
   }
 
   /**
    * Creates a FormatArg from a character string literal. This is
    * handled specially to avoid ambiguity with generic pointers, which are
    * handled differently.
    */
-  FormatArg(const char* string_value, internal::FormatChoice<3>)
+  FormatArg(const char* string_value, absl::strings_internal::StringifySink&&, internal::FormatChoice<3>)
       : AlphaNum(string_value == nullptr ? "null" : string_value) {
   }
 
@@ -125,16 +125,16 @@ class FormatArg : public absl::AlphaNum {
    * hexadecimal integer literal.
    */
   template <typename T>
-  FormatArg(T* pointer_value, internal::FormatChoice<4>)
-      : AlphaNum(absl::Hex(reinterpret_cast<uintptr_t>(pointer_value))) {
+  FormatArg(T* pointer_value, absl::strings_internal::StringifySink&& sink, internal::FormatChoice<4>)
+      : AlphaNum(absl::Hex(reinterpret_cast<uintptr_t>(pointer_value)), std::move(sink)) {
   }
 
   /**
    * As a final fallback, creates a FormatArg from any type of value that
    * absl::AlphaNum accepts.
    */
   template <typename T>
-  FormatArg(T&& value, internal::FormatChoice<5>)
+  FormatArg(T&& value, absl::strings_internal::StringifySink&&, internal::FormatChoice<5>)
       : AlphaNum(std::forward<T>(value)) {
   }
 };
@@ -157,8 +157,7 @@ class FormatArg : public absl::AlphaNum {
  */
 template <typename... FA>
 std::string StringFormat(const char* format, const FA&... args) {
-  return internal::StringFormatPieces(
-      format, {static_cast<const FormatArg&>(args).Piece()...});
+  return internal::StringFormatPieces(format, {static_cast<const FormatArg&>(args).Piece()...});
 }
 
 inline std::string StringFormat() {