Add missing implicit SFINAE constraints (#2607)

Co-authored-by: Stephan T. Lavavej <[email protected]>

stl/inc/any

@@ -357,11 +357,13 @@ inline void swap(any& _Left, any& _Right) noexcept {
     _Left.swap(_Right);
 }
 
-template <class _ValueType, class... _Types>
+template <class _ValueType, class... _Types,
+    enable_if_t<is_constructible_v<any, in_place_type_t<_ValueType>, _Types...>, int> = 0>
 _NODISCARD any make_any(_Types&&... _Args) { // construct an any containing a _ValueType initialized with _Args...
     return any{in_place_type<_ValueType>, _STD forward<_Types>(_Args)...};
 }
-template <class _ValueType, class _Elem, class... _Types>
+template <class _ValueType, class _Elem, class... _Types,
+    enable_if_t<is_constructible_v<any, in_place_type_t<_ValueType>, initializer_list<_Elem>&, _Types...>, int> = 0>
 _NODISCARD any make_any(initializer_list<_Elem> _Ilist, _Types&&... _Args) {
     // construct an any containing a _ValueType initialized with _Ilist and _Args...
     return any{in_place_type<_ValueType>, _Ilist, _STD forward<_Types>(_Args)...};

stl/inc/memory

@@ -1623,7 +1623,7 @@ public:
         return *this;
     }
 
-    template <class _Ty2>
+    template <class _Ty2, enable_if_t<_SP_pointer_compatible<_Ty2, _Ty>::value, int> = 0>
     shared_ptr& operator=(const shared_ptr<_Ty2>& _Right) noexcept {
         shared_ptr(_Right).swap(*this);
         return *this;
@@ -1634,21 +1634,24 @@ public:
         return *this;
     }
 
-    template <class _Ty2>
+    template <class _Ty2, enable_if_t<_SP_pointer_compatible<_Ty2, _Ty>::value, int> = 0>
     shared_ptr& operator=(shared_ptr<_Ty2>&& _Right) noexcept { // take resource from _Right
         shared_ptr(_STD move(_Right)).swap(*this);
         return *this;
     }
 
 #if _HAS_AUTO_PTR_ETC
-    template <class _Ty2>
+    template <class _Ty2, enable_if_t<is_convertible_v<_Ty2*, _Ty*>, int> = 0>
     shared_ptr& operator=(auto_ptr<_Ty2>&& _Right) {
         shared_ptr(_STD move(_Right)).swap(*this);
         return *this;
     }
 #endif // _HAS_AUTO_PTR_ETC
 
-    template <class _Ux, class _Dx>
+    template <class _Ux, class _Dx,
+        enable_if_t<conjunction_v<_SP_pointer_compatible<_Ux, _Ty>,
+                        is_convertible<typename unique_ptr<_Ux, _Dx>::pointer, element_type*>>,
+            int> = 0>
     shared_ptr& operator=(unique_ptr<_Ux, _Dx>&& _Right) { // move from unique_ptr
         shared_ptr(_STD move(_Right)).swap(*this);
         return *this;
@@ -1662,17 +1665,26 @@ public:
         shared_ptr().swap(*this);
     }
 
-    template <class _Ux>
+    template <class _Ux,
+        enable_if_t<conjunction_v<conditional_t<is_array_v<_Ty>, _Can_array_delete<_Ux>, _Can_scalar_delete<_Ux>>,
+                        _SP_convertible<_Ux, _Ty>>,
+            int> = 0>
     void reset(_Ux* _Px) { // release, take ownership of _Px
         shared_ptr(_Px).swap(*this);
     }
 
-    template <class _Ux, class _Dx>
+    template <class _Ux, class _Dx,
+        enable_if_t<conjunction_v<is_move_constructible<_Dx>, _Can_call_function_object<_Dx&, _Ux*&>,
+                        _SP_convertible<_Ux, _Ty>>,
+            int> = 0>
     void reset(_Ux* _Px, _Dx _Dt) { // release, take ownership of _Px, with deleter _Dt
         shared_ptr(_Px, _Dt).swap(*this);
     }
 
-    template <class _Ux, class _Dx, class _Alloc>
+    template <class _Ux, class _Dx, class _Alloc,
+        enable_if_t<conjunction_v<is_move_constructible<_Dx>, _Can_call_function_object<_Dx&, _Ux*&>,
+                        _SP_convertible<_Ux, _Ty>>,
+            int> = 0>
     void reset(_Ux* _Px, _Dx _Dt, _Alloc _Ax) { // release, take ownership of _Px, with deleter _Dt, allocator _Ax
         shared_ptr(_Px, _Dt, _Ax).swap(*this);
     }
@@ -3023,7 +3035,7 @@ public:
         return *this;
     }
 
-    template <class _Ty2>
+    template <class _Ty2, enable_if_t<_SP_pointer_compatible<_Ty2, _Ty>::value, int> = 0>
     weak_ptr& operator=(const weak_ptr<_Ty2>& _Right) noexcept {
         weak_ptr(_Right).swap(*this);
         return *this;
@@ -3034,13 +3046,13 @@ public:
         return *this;
     }
 
-    template <class _Ty2>
+    template <class _Ty2, enable_if_t<_SP_pointer_compatible<_Ty2, _Ty>::value, int> = 0>
     weak_ptr& operator=(weak_ptr<_Ty2>&& _Right) noexcept {
         weak_ptr(_STD move(_Right)).swap(*this);
         return *this;
     }
 
-    template <class _Ty2>
+    template <class _Ty2, enable_if_t<_SP_pointer_compatible<_Ty2, _Ty>::value, int> = 0>
     weak_ptr& operator=(const shared_ptr<_Ty2>& _Right) noexcept {
         weak_ptr(_Right).swap(*this);
         return *this;

stl/inc/optional

@@ -853,15 +853,16 @@ _CONSTEXPR20 void swap(optional<_Ty>& _Left, optional<_Ty>& _Right) noexcept(noe
     _Left.swap(_Right);
 }
 
-template <class _Ty>
+template <class _Ty, enable_if_t<is_constructible_v<decay_t<_Ty>, _Ty>, int> = 0> // LWG-3627
 _NODISCARD constexpr optional<decay_t<_Ty>> make_optional(_Ty&& _Value) {
     return optional<decay_t<_Ty>>{_STD forward<_Ty>(_Value)};
 }
-template <class _Ty, class... _Types>
+template <class _Ty, class... _Types, enable_if_t<is_constructible_v<_Ty, _Types...>, int> = 0>
 _NODISCARD constexpr optional<_Ty> make_optional(_Types&&... _Args) {
     return optional<_Ty>{in_place, _STD forward<_Types>(_Args)...};
 }
-template <class _Ty, class _Elem, class... _Types>
+template <class _Ty, class _Elem, class... _Types,
+    enable_if_t<is_constructible_v<_Ty, initializer_list<_Elem>&, _Types...>, int> = 0>
 _NODISCARD constexpr optional<_Ty> make_optional(initializer_list<_Elem> _Ilist, _Types&&... _Args) {
     return optional<_Ty>{in_place, _Ilist, _STD forward<_Types>(_Args)...};
 }

tests/std/test.lst

@@ -191,6 +191,7 @@ tests\GH_002030_asan_annotate_vector
 tests\GH_002039_byte_is_not_trivially_swappable
 tests\GH_002058_debug_iterator_race
 tests\GH_002120_streambuf_seekpos_and_seekoff
+tests\GH_002299_implicit_sfinae_constraints
 tests\GH_002488_promise_not_default_constructible_types
 tests\GH_002581_common_reference_workaround
 tests\LWG2597_complex_branch_cut

tests/std/tests/GH_002299_implicit_sfinae_constraints/env.lst

@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_matrix.lst

tests/std/tests/GH_002299_implicit_sfinae_constraints/test.compile.pass.cpp

@@ -0,0 +1,100 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+#if _HAS_CXX17
+#include <any>
+#include <initializer_list>
+#include <optional>
+#endif // _HAS_CXX17
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+using namespace std;
+
+// tests for shared_ptr<T>::operator=
+template <class T, class U, class = void>
+constexpr bool can_shared_ptr_assign = false;
+
+template <class T, class U>
+constexpr bool can_shared_ptr_assign<T, U, void_t<decltype(declval<shared_ptr<T>&>() = declval<U>())>> = true;
+
+STATIC_ASSERT(can_shared_ptr_assign<int, shared_ptr<int>>);
+STATIC_ASSERT(!can_shared_ptr_assign<int, shared_ptr<long>>);
+STATIC_ASSERT(!can_shared_ptr_assign<int, const shared_ptr<long>&>);
+STATIC_ASSERT(!can_shared_ptr_assign<int, unique_ptr<long>>);
+#if _HAS_AUTO_PTR_ETC
+STATIC_ASSERT(!can_shared_ptr_assign<int, auto_ptr<long>>);
+#endif
+
+// tests for shared_ptr<T>::reset
+template <class Void, class T, class... Us>
+constexpr bool can_shared_ptr_reset_impl = false;
+
+template <class T, class... Us>
+constexpr bool
+    can_shared_ptr_reset_impl<void_t<decltype(declval<shared_ptr<T>&>().reset(declval<Us>()...))>, T, Us...> = true;
+
+template <class T, class... Us>
+constexpr bool can_shared_ptr_reset = can_shared_ptr_reset_impl<void, T, Us...>;
+
+STATIC_ASSERT(can_shared_ptr_reset<int, int*>);
+STATIC_ASSERT(!can_shared_ptr_reset<int, long*>);
+STATIC_ASSERT(!can_shared_ptr_reset<int, long*, default_delete<long>>);
+STATIC_ASSERT(!can_shared_ptr_reset<int, long*, default_delete<long>, allocator<long>>);
+
+// tests for weak_ptr<T>::operator=
+template <class T, class U, class = void>
+constexpr bool can_weak_ptr_assign = false;
+
+template <class T, class U>
+constexpr bool can_weak_ptr_assign<T, U, void_t<decltype(declval<weak_ptr<T>&>() = declval<U>())>> = true;
+
+STATIC_ASSERT(can_weak_ptr_assign<int, weak_ptr<int>>);
+STATIC_ASSERT(!can_weak_ptr_assign<int, weak_ptr<long>>);
+STATIC_ASSERT(!can_weak_ptr_assign<int, const weak_ptr<long>&>);
+STATIC_ASSERT(!can_weak_ptr_assign<int, const shared_ptr<long>&>);
+
+#if _HAS_CXX17
+// tests for make_optional
+template <class T, class = void>
+constexpr bool can_make_optional_decay = false;
+
+template <class T>
+constexpr bool can_make_optional_decay<T, void_t<decltype(make_optional(declval<T>()))>> = true;
+
+template <class Void, class T, class... Us>
+constexpr bool can_make_optional_impl = false;
+
+template <class T, class... Us>
+constexpr bool can_make_optional_impl<void_t<decltype(make_optional<T>(declval<Us>()...))>, T, Us...> = true;
+
+template <class T, class... Us>
+constexpr bool can_make_optional_usual = can_make_optional_impl<void, T, Us...>;
+
+STATIC_ASSERT(can_make_optional_decay<unique_ptr<int>>);
+STATIC_ASSERT(!can_make_optional_decay<const unique_ptr<int>&>); // LWG-3627
+STATIC_ASSERT(can_make_optional_usual<int, int>);
+STATIC_ASSERT(!can_make_optional_usual<int, int, int>);
+STATIC_ASSERT(!can_make_optional_usual<int, initializer_list<int>&>);
+
+// tests for make_any
+template <class Void, class T, class... Us>
+constexpr bool can_make_any_impl = false;
+
+template <class T, class... Us>
+constexpr bool can_make_any_impl<void_t<decltype(make_any<T>(declval<Us>()...))>, T, Us...> = true;
+
+template <class T, class... Us>
+constexpr bool can_make_any = can_make_any_impl<void, T, Us...>;
+
+STATIC_ASSERT(can_make_any<int, int>);
+STATIC_ASSERT(!can_make_any<unique_ptr<int>, const unique_ptr<int>&>);
+STATIC_ASSERT(!can_make_any<int, int, int>);
+STATIC_ASSERT(!can_make_any<int, initializer_list<int>&>);
+#endif // _HAS_CXX17
+
+int main() {} // COMPILE-ONLY