function_traits: more tests, fix function objects/lambdas not working with some compilers

A member function reference is not the same as a member function pointer.

1 files changed, 10 insertions, 4 deletions

diff --git a/lib/util.cpp b/lib/util.cpp
index 4c176fc7..5e7644a1 100644
--- a/lib/util.cpp
+++ b/lib/util.cpp
@@ -100,10 +100,16 @@ struct S { int mf(); };
 static_assert(is_callable_v<decltype(&S::mf)>, "Test member function");
 static_assert(returns<int, decltype(&S::mf)>(), "Test returns<> with member function");
 
-struct Fo { void operator()(int); };
-static_assert(function_traits<Fo>::arg_number == 1, "Test function object 1");
-static_assert(is_callable_v<Fo>, "Test is_callable<>");
-static_assert(std::is_same<fn_arg_t<Fo>, int>(),
+struct Fo { int operator()(); };
+static_assert(is_callable_v<Fo>, "Test is_callable<> with function object");
+static_assert(function_traits<Fo>::arg_number == 0, "Test function object");
+static_assert(std::is_same<fn_return_t<Fo>, int>::value,
+              "Test return type of function object");
+
+struct Fo1 { void operator()(int); };
+static_assert(function_traits<Fo1>::arg_number == 1, "Test function object 1");
+static_assert(is_callable_v<Fo1>, "Test is_callable<> with function object 1");
+static_assert(std::is_same<fn_arg_t<Fo1>, int>(),
               "Test fn_arg_t defaulting to first argument");
 
 static auto l = [] { return 1; };