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LWG-3810: CTAD for basic_format_args #3421

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Merged
Stephan T. Lavavej (StephanTLavavej) merged 2 commits into from
Feb 14, 2023
Merged

LWG-3810: CTAD for basic_format_args #3421

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7cc2c8c
Implement LWG-3810
JMazurkiewicz Feb 12, 2023
9e22d24
Simplify CTAD test.
StephanTLavavej Feb 13, 2023
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3 changes: 3 additions & 0 deletions stl/inc/format
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Original file line number Diff line number Diff line change
Expand Up @@ -1991,6 +1991,9 @@ private:
const _Format_arg_index* _Index_array = nullptr;
};

template <class _Context, class... _Args>
basic_format_args(_Format_arg_store<_Context, _Args...>) -> basic_format_args<_Context>;
Comment on lines +1994 to +1995

@StephanTLavavej Stephan T. Lavavej (StephanTLavavej) Feb 12, 2023

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No change requested, note to other reviewers: Deduction guides can't be exported for modules, they're just automatically available if the class is exported (which is the case here), so the lack of any _EXPORT_STD is normal.


// _Lazy_locale is used instead of a std::locale so that the locale is only
// constructed when needed, and is never constructed if the format string does not
// contain locale-sensitive format specifiers. Note that this means that a new locale
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8 changes: 8 additions & 0 deletions tests/std/tests/P0645R10_text_formatting_args/test.cpp
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Expand Up @@ -229,11 +229,19 @@ void test_visit_monostate() {
assert(visit_format_arg(visitor<Context>, basic_format_arg<Context>()) == Arg_type::none);
}

template <class Context>
void test_lwg3810() {
[[maybe_unused]] auto args_store = make_format_args<Context>(1, 2, 3);
static_assert(same_as<decltype(basic_format_args{args_store}), basic_format_args<Context>>);
}

int main() {
test_basic_format_arg<format_context>();
test_basic_format_arg<wformat_context>();
test_format_arg_store<format_context>();
test_format_arg_store<wformat_context>();
test_visit_monostate<format_context>();
test_visit_monostate<wformat_context>();
test_lwg3810<format_context>();
test_lwg3810<wformat_context>();
}