LWG-3515: [stacktrace.basic.nonmem]: operator<< should be less temp…

…latized (#3236)
microsoft · Nov 19, 2022 · 10e1366 · 10e1366
1 parent 299abb0
commit 10e1366
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Showing 2 changed files with 35 additions and 4 deletions.
diff --git a/stl/inc/stacktrace b/stl/inc/stacktrace
@@ -339,13 +339,13 @@ _NODISCARD string to_string(const basic_stacktrace<_Alloc>& _St) {
     return _Result;
 }
 
-_EXPORT_STD template <class _CharT, class _Traits>
-basic_ostream<_CharT, _Traits>& operator<<(basic_ostream<_CharT, _Traits>& _Os, const stacktrace_entry& _Fx) {
+_EXPORT_STD template <int = 0>
+ostream& operator<<(ostream& _Os, const stacktrace_entry& _Fx) {
     return _Os << _STD to_string(_Fx);
 }
 
-_EXPORT_STD template <class _CharT, class _Traits, class _Alloc>
-basic_ostream<_CharT, _Traits>& operator<<(basic_ostream<_CharT, _Traits>& _Os, const basic_stacktrace<_Alloc>& _St) {
+_EXPORT_STD template <class _Alloc>
+ostream& operator<<(ostream& _Os, const basic_stacktrace<_Alloc>& _St) {
     return _Os << _STD to_string(_St);
 }
 

diff --git a/tests/std/tests/P0881R7_stacktrace/test.cpp b/tests/std/tests/P0881R7_stacktrace/test.cpp
@@ -2,9 +2,12 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 #include <cassert>
+#include <concepts>
 #include <cstddef>
 #include <filesystem>
 #include <iterator>
+#include <memory_resource>
+#include <ostream>
 #include <sstream>
 #include <stacktrace>
 #include <stdexcept>
@@ -20,6 +23,34 @@
 
 using namespace std;
 
+#if defined(__cpp_lib_concepts) // TRANSITION, GH-395
+template <class Ostream, class Alloc = allocator<stacktrace_entry>>
+concept CanPrintStacktrace =
+    requires(Ostream& os, const stacktrace_entry& f, const basic_stacktrace<Alloc>& st) {
+        { os << f } -> same_as<basic_ostream<typename Ostream::char_type, typename Ostream::traits_type>&>;
+        { os << st } -> same_as<basic_ostream<typename Ostream::char_type, typename Ostream::traits_type>&>;
+    };
+
+template <class CharT>
+struct FancyCharTraits : char_traits<CharT> {};
+
+static_assert(CanPrintStacktrace<ostream>);
+static_assert(CanPrintStacktrace<ostringstream>);
+static_assert(CanPrintStacktrace<ostream, pmr::polymorphic_allocator<stacktrace_entry>>);
+
+static_assert(!CanPrintStacktrace<wostream>);
+static_assert(!CanPrintStacktrace<wostringstream>);
+static_assert(!CanPrintStacktrace<wostream, pmr::polymorphic_allocator<stacktrace_entry>>);
+
+using FancyCharStream = basic_ostream<char, FancyCharTraits<char>>;
+static_assert(!CanPrintStacktrace<FancyCharStream>);
+static_assert(!CanPrintStacktrace<FancyCharStream, pmr::polymorphic_allocator<stacktrace_entry>>);
+
+using FancyWcharStream = basic_ostream<wchar_t, FancyCharTraits<wchar_t>>;
+static_assert(!CanPrintStacktrace<FancyWcharStream>);
+static_assert(!CanPrintStacktrace<FancyWcharStream, pmr::polymorphic_allocator<stacktrace_entry>>);
+#endif // defined(__cpp_lib_concepts)
+
 [[maybe_unused]] const int base_line = __LINE__;
 
 // Note: the below assumes that tail call optimization is disabled, which is the case in /Od