Fix the std::in_place_type_t overload for SFINAE-unsafe facades (#223)

Author: mingxwa

.github/workflows/bvt-clang.yml

@@ -15,21 +15,14 @@ jobs:
 
     - name: install clang
       run: |
-        sudo apt install -y clang-15 clang-16 clang-17 clang-18
+        sudo apt install -y clang-16 clang-17 clang-18
 
     - name: check compiler versions
       run: |
-        clang++-15 --version
         clang++-16 --version
         clang++-17 --version
         clang++-18 --version
 
-    - name: build and run test with clang 15
-      run: |
-        cmake -B build-clang-15 -DCMAKE_C_COMPILER=clang-15 -DCMAKE_CXX_COMPILER=clang++-15 -DCMAKE_BUILD_TYPE=Release
-        cmake --build build-clang-15 -j
-        ctest --test-dir build-clang-15 -j
-
     - name: build and run test with clang 16
       run: |
         cmake -B build-clang-16 -DCMAKE_C_COMPILER=clang-16 -DCMAKE_CXX_COMPILER=clang++-16 -DCMAKE_BUILD_TYPE=Release

README.md

@@ -167,7 +167,7 @@ The "Proxy" library is a self-contained solution for runtime polymorphism in C++
 | Family     | Minimum version | Required flags |
 | ---------- | --------------- | -------------- |
 | GCC        | 13.1            | -std=c++20     |
-| Clang      | 15.0.0          | -std=c++20     |
+| Clang      | 16.0.0          | -std=c++20     |
 | MSVC       | 19.31           | /std:c++20     |
 | NVIDIA HPC | 24.1            | -std=c++20     |
 

proxy.h

@@ -520,6 +520,12 @@ template <class A1, class A2>
 using merged_composite_accessor =
     typename composite_accessor_merge_traits<A1, A2>::type;
 
+template <class T> struct in_place_type_traits : inapplicable_traits {};
+template <class T>
+struct in_place_type_traits<std::in_place_type_t<T>> : applicable_traits {};
+template <class T>
+constexpr bool is_in_place_type = in_place_type_traits<T>::applicable;
+
 template <class F>
 consteval bool is_facade_constraints_well_formed() {
   if constexpr (requires {
@@ -782,14 +788,15 @@ class proxy : public details::facade_traits<F>::direct_accessor {
   }
   template <class P>
   proxy(P&& ptr) noexcept(std::is_nothrow_constructible_v<std::decay_t<P>, P>)
-      requires(proxiable<std::decay_t<P>, F> &&
-          std::is_constructible_v<std::decay_t<P>, P>) : proxy()
-      { initialize<std::decay_t<P>>(std::forward<P>(ptr)); }
+      requires(!details::is_in_place_type<std::decay_t<P>> &&
+          proxiable<std::decay_t<P>, F> &&
+          std::is_constructible_v<std::decay_t<P>, P>)
+      : proxy() { initialize<std::decay_t<P>>(std::forward<P>(ptr)); }
   template <proxiable<F> P, class... Args>
   explicit proxy(std::in_place_type_t<P>, Args&&... args)
       noexcept(std::is_nothrow_constructible_v<P, Args...>)
-      requires(std::is_constructible_v<P, Args...>) : proxy()
-      { initialize<P>(std::forward<Args>(args)...); }
+      requires(std::is_constructible_v<P, Args...>)
+      : proxy() { initialize<P>(std::forward<Args>(args)...); }
   template <proxiable<F> P, class U, class... Args>
   explicit proxy(std::in_place_type_t<P>, std::initializer_list<U> il,
           Args&&... args)
@@ -1258,8 +1265,6 @@ template <class F, class C>
 using adl_accessor_arg_t =
     std::conditional_t<C::is_direct, proxy<F>, proxy_indirect_accessor<F>>;
 
-template <class O>
-using overload_return_type = typename overload_traits<O>::return_type;
 #define ___PRO_DEF_CAST_ACCESSOR(Q, SELF, ...) \
     template <class __F, class __C, class T> \
     struct accessor<__F, __C, T() Q> { \
@@ -1274,7 +1279,7 @@ using overload_return_type = typename overload_traits<O>::return_type;
 template <bool Expl, bool Nullable>
 struct cast_dispatch_base {
   ___PRO_DEF_MEM_ACCESSOR_TEMPLATE(___PRO_DEF_CAST_ACCESSOR,
-      operator overload_return_type<__Os>)
+      operator typename overload_traits<__Os>::return_type)
 };
 #undef ___PRO_DEF_CAST_ACCESSOR
 
@@ -1468,11 +1473,10 @@ struct observer_overload_mapping_traits<F, IS_DIRECT, D, O>
     : observer_overload_mapping_traits_impl<F, IS_DIRECT, D, O> {};
 template <class F, class O>
 struct observer_overload_mapping_traits<F, true, upward_conversion_dispatch, O>
-    : std::type_identity<proxy_view<
-          std::conditional_t<std::is_const_v<F>,
-              const facade_of_t<typename overload_traits<O>::return_type>,
-              facade_of_t<typename overload_traits<O>::return_type>
-          >>() const noexcept> {};
+    : std::type_identity<proxy_view<std::conditional_t<std::is_const_v<F>,
+          const facade_of_t<typename overload_traits<O>::return_type>,
+          facade_of_t<typename overload_traits<O>::return_type>>>()
+          const noexcept> {};
 
 template <class D>
 struct observer_dispatch_reduction : std::type_identity<D> {};
@@ -1702,22 +1706,20 @@ struct basic_facade_builder {
   using support_destruction = basic_facade_builder<
       Cs, Rs, details::make_destructible(C, CL)>;
 #ifdef __cpp_rtti
-  using support_indirect_rtti =
-      basic_facade_builder<
-          details::add_conv_t<Cs, details::conv_impl<false,
-              details::proxy_cast_dispatch, void(details::proxy_cast_context) &,
-              void(details::proxy_cast_context) const&,
-              void(details::proxy_cast_context) &&>>,
-          details::add_tuple_t<Rs, details::refl_impl<false,
-              details::proxy_typeid_reflector>>, C>;
-  using support_direct_rtti =
-      basic_facade_builder<
-          details::add_conv_t<Cs, details::conv_impl<true,
-              details::proxy_cast_dispatch, void(details::proxy_cast_context) &,
-              void(details::proxy_cast_context) const&,
-              void(details::proxy_cast_context) &&>>,
-          details::add_tuple_t<Rs, details::refl_impl<true,
-              details::proxy_typeid_reflector>>, C>;
+  using support_indirect_rtti = basic_facade_builder<
+      details::add_conv_t<Cs, details::conv_impl<false,
+          details::proxy_cast_dispatch, void(details::proxy_cast_context) &,
+          void(details::proxy_cast_context) const&,
+          void(details::proxy_cast_context) &&>>,
+      details::add_tuple_t<Rs, details::refl_impl<false,
+          details::proxy_typeid_reflector>>, C>;
+  using support_direct_rtti = basic_facade_builder<
+      details::add_conv_t<Cs, details::conv_impl<true,
+          details::proxy_cast_dispatch, void(details::proxy_cast_context) &,
+          void(details::proxy_cast_context) const&,
+          void(details::proxy_cast_context) &&>>,
+      details::add_tuple_t<Rs, details::refl_impl<true,
+          details::proxy_typeid_reflector>>, C>;
   using support_rtti = support_indirect_rtti;
 #endif  // __cpp_rtti
   template <class F>
@@ -1783,17 +1785,17 @@ struct operator_dispatch;
 #define ___PRO_LHS_BINARY_OP_DISPATCH_BODY_IMPL(...) \
     template <class T, class Arg> \
     decltype(auto) operator()(T&& self, Arg&& arg) \
-        ___PRO_DIRECT_FUNC_IMPL(std::forward<T>(self) __VA_ARGS__ \
-            std::forward<Arg>(arg))
+        ___PRO_DIRECT_FUNC_IMPL( \
+            std::forward<T>(self) __VA_ARGS__ std::forward<Arg>(arg))
 #define ___PRO_LHS_ALL_OP_DISPATCH_BODY_IMPL(...) \
     ___PRO_LHS_LEFT_OP_DISPATCH_BODY_IMPL(__VA_ARGS__) \
     ___PRO_LHS_BINARY_OP_DISPATCH_BODY_IMPL(__VA_ARGS__)
 #define ___PRO_LHS_OP_DISPATCH_IMPL(TYPE, ...) \
     template <> \
     struct operator_dispatch<#__VA_ARGS__, false> { \
       ___PRO_LHS_##TYPE##_OP_DISPATCH_BODY_IMPL(__VA_ARGS__) \
-      ___PRO_DEF_MEM_ACCESSOR_TEMPLATE(___PRO_DEF_LHS_##TYPE##_OP_ACCESSOR, \
-          operator __VA_ARGS__) \
+      ___PRO_DEF_MEM_ACCESSOR_TEMPLATE( \
+          ___PRO_DEF_LHS_##TYPE##_OP_ACCESSOR, operator __VA_ARGS__) \
     };
 
 #define ___PRO_DEF_RHS_OP_ACCESSOR(Q, NE, SELF_ARG, SELF, ...) \
@@ -1817,10 +1819,10 @@ ___PRO_DEBUG( \
     struct operator_dispatch<#__VA_ARGS__, true> { \
       template <class T, class Arg> \
       decltype(auto) operator()(T&& self, Arg&& arg) \
-          ___PRO_DIRECT_FUNC_IMPL(std::forward<Arg>(arg) __VA_ARGS__ \
-              std::forward<T>(self)) \
-      ___PRO_DEF_FREE_ACCESSOR_TEMPLATE(___PRO_DEF_RHS_OP_ACCESSOR, \
-          __VA_ARGS__) \
+          ___PRO_DIRECT_FUNC_IMPL( \
+              std::forward<Arg>(arg) __VA_ARGS__ std::forward<T>(self)) \
+      ___PRO_DEF_FREE_ACCESSOR_TEMPLATE( \
+          ___PRO_DEF_RHS_OP_ACCESSOR, __VA_ARGS__) \
     };
 
 #define ___PRO_EXTENDED_BINARY_OP_DISPATCH_IMPL(...) \
@@ -1873,8 +1875,8 @@ ___PRO_DEBUG( \
     struct operator_dispatch<#__VA_ARGS__, true> { \
       template <class T, class Arg> \
       decltype(auto) operator()(T&& self, Arg&& arg) \
-          ___PRO_DIRECT_FUNC_IMPL(std::forward<Arg>(arg) __VA_ARGS__ \
-              std::forward<T>(self)) \
+          ___PRO_DIRECT_FUNC_IMPL( \
+              std::forward<Arg>(arg) __VA_ARGS__ std::forward<T>(self)) \
       ___PRO_DEF_FREE_ACCESSOR_TEMPLATE(___PRO_DEF_RHS_ASSIGNMENT_OP_ACCESSOR, \
           __VA_ARGS__) \
     };
@@ -1960,8 +1962,7 @@ struct implicit_conversion_dispatch
   template <class T>
   T&& operator()(T&& self) noexcept { return std::forward<T>(self); }
 };
-struct explicit_conversion_dispatch
-    : details::cast_dispatch_base<true, false> {
+struct explicit_conversion_dispatch : details::cast_dispatch_base<true, false> {
   template <class T>
   auto operator()(T&& self) noexcept
       { return details::explicit_conversion_adapter<T>{std::forward<T>(self)}; }

tests/proxy_creation_tests.cpp

@@ -80,6 +80,16 @@ static_assert(!pro::inplace_proxiable_target<utils::LifetimeTracker::Session, Te
 static_assert(!noexcept(pro::make_proxy_inplace<TestLargeStringable, utils::LifetimeTracker::Session>(std::declval<utils::LifetimeTracker*>())));
 static_assert(noexcept(pro::make_proxy_inplace<TestLargeStringable, int>(123)));
 
+template <class T>
+void SfinaeUnsafeIncrementImpl(T&& value) { ++value; }
+
+PRO_DEF_FREE_DISPATCH(FreeSfinaeUnsafeIncrement, SfinaeUnsafeIncrementImpl, Increment);
+
+struct SfinaeUnsafeFacade : pro::facade_builder
+    ::support_rtti
+    ::add_convention<FreeSfinaeUnsafeIncrement, void()>
+    ::build {};
+
 }  // namespace proxy_creation_tests_details
 
 namespace details = proxy_creation_tests_details;
@@ -535,3 +545,9 @@ TEST(ProxyCreationTests, TestMakeProxy_WithoutSBO_Lifetime_Move) {
   expected_ops.emplace_back(1, utils::LifetimeOperationType::kDestruction);
   ASSERT_TRUE(tracker.GetOperations() == expected_ops);
 }
+
+TEST(ProxyCreationTests, TestMakeProxy_SfinaeUnsafe) {
+  pro::proxy<details::SfinaeUnsafeFacade> p = pro::make_proxy<details::SfinaeUnsafeFacade, int>();
+  Increment(*p);
+  ASSERT_EQ(proxy_cast<int>(*p), 1);
+}