Handle comparison between std::expected and nullptr

rollbear · Jun 30, 2024 · 2498c74 · 2498c74 · subbota-a · Jun 30, 2024
1 parent 8f36c45
commit 2498c74
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diff --git a/ChangeLog b/ChangeLog
@@ -1,3 +1,6 @@
+	* Fixed issue with std::expected causing compilation error. Thank you
+	  @subbota-a for reporting
+
 v47 2024-01-01
 
 	* Coroutines are conditionally supported by the __cpp_impl_coroutine

diff --git a/include/trompeloeil/mock.hpp b/include/trompeloeil/mock.hpp
@@ -139,6 +139,19 @@
 #include <coroutine>
 #endif
 
+
+#if TROMPELOEIL_CPLUSPLUS >= 202211L
+#  if __has_include(<expected>)
+#    include <expected>
+#  endif
+#  if defined(__cpp_lib_expected)
+#    define   TROMPELOEIL_HAS_EXPECTED 1
+#  else
+#    define TROMPELOEIL_HAS_EXPECTED 0
+#  endif
+#else
+#define TROMPELOEIL_HAS_EXPECTED 0
+#endif
 #ifndef TROMPELOEIL_CUSTOM_ATOMIC
 #include <atomic>
 namespace trompeloeil { using std::atomic; }
@@ -1008,6 +1021,22 @@ template <typename T>
     return is_null(t.get());
   }
 
+#if TROMPELOEIL_HAS_EXPECTED
+  template <typename T, typename E>
+  constexpr
+  bool
+  is_null(const std::expected<T, E>& e)
+  {
+    if constexpr (requires { e.value() == nullptr; }) {
+      return e == nullptr;
+    }
+    else
+    {
+      return false;
+    }
+  }
+#endif
+
   template <typename T>
   void
   print(

diff --git a/test/compiling_tests_14.cpp b/test/compiling_tests_14.cpp
@@ -5167,4 +5167,34 @@ TEST_CASE_METHOD(
   REQUIRE(okReports.empty());
 }
 
+#if TROMPELOEIL_HAS_EXPECTED
+TEST_CASE_METHOD(
+  Fixture,
+  "C++23: is_null with expected",
+  "[C++23][is_null]")
+{
+  WHEN("value type of expected is not comparable to null")
+  {
+    THEN("is null is false")
+    {
+      REQUIRE_FALSE(trompeloeil::is_null(std::expected<int,int>{}));
+    }
+  }
+  AND_WHEN("value type is comparable with nullptr but false")
+  {
+    THEN("is null is false")
+    {
+      REQUIRE_FALSE(trompeloeil::is_null(std::expected<const void*, int>{"foo"}));
+    }
+  }
+  AND_WHEN("value type is comparable with nullptr and true")
+  {
+    THEN("is null is true")
+    {
+      REQUIRE(trompeloeil::is_null(std::expected<const void*, int>{}));
+    }
+  }
+}
+#endif
+
 #endif /* TROMPELOEIL_CPLUSPLUS > 201103L */