Make absl::from_chars_result compatible with C++20 and C++26

absl/strings/charconv.h

@@ -47,6 +47,15 @@ enum class chars_format {
 struct from_chars_result {
   const char* absl_nonnull ptr;
   std::errc ec;
+
+  constexpr friend bool operator==(const from_chars_result& l,
+                                   const from_chars_result& r) noexcept {
+    return l.ptr == r.ptr && l.ec == r.ec;
+  }
+
+  constexpr explicit operator bool() const noexcept {
+    return ec == std::errc{};
+  }
 };
 
 // Workalike compatibility version of std::from_chars from C++17.  Currently

absl/strings/charconv_test.cc

@@ -784,4 +784,117 @@ TEST(FromChars, DecimalFloatLimits) {
   TestOverflowAndUnderflow<float>(input_gen, expected_gen, -45, 38);
 }
 
+#if !defined(ABSL_INTERNAL_CPLUSPLUS_LANG) || \
+    ABSL_INTERNAL_CPLUSPLUS_LANG < 202002L
+constexpr bool operator!=(const absl::from_chars_result& l,
+                          const absl::from_chars_result& r) noexcept {
+  return !(l == r);
+}
+#endif
+// Check that the operator== for from_chars_result works as expected.
+//
+// EXPECT_TRUE and EXPECT_FALSE used intentionally to check operator== and
+// operator!= explicitly.
+// Before C++20 we need to define the operator!= explicitly, as it is not
+// automatically generated by the compiler.
+TEST(FromChars, ResultOperatorEqual) {
+  {
+    absl::from_chars_result result1{};
+    absl::from_chars_result result2{};
+    EXPECT_TRUE(result1 == result2);
+    EXPECT_FALSE(result1 != result2);
+  }
+
+  {
+    absl::from_chars_result result1{};
+    result1.ec = std::errc::result_out_of_range;
+    absl::from_chars_result result2{};
+    result2.ec = std::errc::result_out_of_range;
+    EXPECT_TRUE(result1 == result2);
+    EXPECT_FALSE(result1 != result2);
+  }
+  {
+    absl::from_chars_result result1{};
+    result1.ec = std::errc::result_out_of_range;
+    absl::from_chars_result result2{};
+    EXPECT_FALSE(result1 == result2);
+    EXPECT_TRUE(result1 != result2);
+  }
+  {
+    absl::from_chars_result result1{};
+    absl::from_chars_result result2{};
+    result2.ec = std::errc::result_out_of_range;
+    EXPECT_FALSE(result1 == result2);
+    EXPECT_TRUE(result1 != result2);
+  }
+
+  {
+    absl::from_chars_result result1{};
+    result1.ptr = "";
+    absl::from_chars_result result2{};
+    result2.ptr = "";
+    EXPECT_TRUE(result1 == result2);
+    EXPECT_FALSE(result1 != result2);
+  }
+  {
+    absl::from_chars_result result1{};
+    result1.ptr = "";
+    absl::from_chars_result result2{};
+    EXPECT_FALSE(result1 == result2);
+    EXPECT_TRUE(result1 != result2);
+  }
+  {
+    absl::from_chars_result result1{};
+    absl::from_chars_result result2{};
+    result2.ptr = "";
+    EXPECT_FALSE(result1 == result2);
+    EXPECT_TRUE(result1 != result2);
+  }
+
+  {
+    absl::from_chars_result result1{"", std::errc::result_out_of_range};
+    absl::from_chars_result result2{"", std::errc::result_out_of_range};
+    EXPECT_TRUE(result1 == result2);
+    EXPECT_FALSE(result1 != result2);
+  }
+  {
+    absl::from_chars_result result1{"", std::errc::result_out_of_range};
+    absl::from_chars_result result2{};
+    EXPECT_FALSE(result1 == result2);
+    EXPECT_TRUE(result1 != result2);
+  }
+  {
+    absl::from_chars_result result1{};
+    absl::from_chars_result result2{"", std::errc::result_out_of_range};
+    EXPECT_FALSE(result1 == result2);
+    EXPECT_TRUE(result1 != result2);
+  }
+}
+
+// Check that the operator bool for from_chars_result works as expected.
+TEST(FromChars, ResultOperatorBool) {
+  {
+    absl::from_chars_result result{};
+    EXPECT_TRUE(result);
+    EXPECT_FALSE(!result);
+  }
+  {
+    absl::from_chars_result result{};
+    result.ec = std::errc::result_out_of_range;
+    EXPECT_FALSE(result);
+    EXPECT_TRUE(!result);
+  }
+  {
+    absl::from_chars_result result{};
+    result.ptr = "";
+    EXPECT_TRUE(result);
+    EXPECT_FALSE(!result);
+  }
+  {
+    absl::from_chars_result result{"", std::errc::result_out_of_range};
+    EXPECT_FALSE(result);
+    EXPECT_TRUE(!result);
+  }
+}
+
 }  // namespace