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<format>: Move the major part of visit_format_arg into a member function of basic_format_arg #3787

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Merged
Stephan T. Lavavej (StephanTLavavej) merged 1 commit into from
Jun 22, 2023
Merged

<format>: Move the major part of visit_format_arg into a member function of basic_format_arg #3787

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75 changes: 39 additions & 36 deletions stl/inc/format
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Original file line number Diff line number Diff line change
Expand Up @@ -745,10 +745,45 @@ public:
}
}

private:
template <class _Visitor, class _Ctx>
friend decltype(auto) visit_format_arg(_Visitor&&, basic_format_arg<_Ctx>);
template <class _Visitor>
decltype(auto) _Visit(_Visitor&& _Vis) {
switch (_Active_state) {
case _Basic_format_arg_type::_None:
return _STD forward<_Visitor>(_Vis)(_No_state);
case _Basic_format_arg_type::_Int_type:
return _STD forward<_Visitor>(_Vis)(_Int_state);
case _Basic_format_arg_type::_UInt_type:
return _STD forward<_Visitor>(_Vis)(_UInt_state);
case _Basic_format_arg_type::_Long_long_type:
return _STD forward<_Visitor>(_Vis)(_Long_long_state);
case _Basic_format_arg_type::_ULong_long_type:
return _STD forward<_Visitor>(_Vis)(_ULong_long_state);
case _Basic_format_arg_type::_Bool_type:
return _STD forward<_Visitor>(_Vis)(_Bool_state);
case _Basic_format_arg_type::_Char_type:
return _STD forward<_Visitor>(_Vis)(_Char_state);
case _Basic_format_arg_type::_Float_type:
return _STD forward<_Visitor>(_Vis)(_Float_state);
case _Basic_format_arg_type::_Double_type:
return _STD forward<_Visitor>(_Vis)(_Double_state);
case _Basic_format_arg_type::_Long_double_type:
return _STD forward<_Visitor>(_Vis)(_Long_double_state);
case _Basic_format_arg_type::_Pointer_type:
return _STD forward<_Visitor>(_Vis)(_Pointer_state);
case _Basic_format_arg_type::_CString_type:
return _STD forward<_Visitor>(_Vis)(_CString_state);
case _Basic_format_arg_type::_String_type:
return _STD forward<_Visitor>(_Vis)(_String_state);
case _Basic_format_arg_type::_Custom_type:
return _STD forward<_Visitor>(_Vis)(_Custom_state);
default:
_STL_VERIFY(false, "basic_format_arg is in impossible state");
int _Dummy{};
return _STD forward<_Visitor>(_Vis)(_Dummy);
}
}

private:
friend basic_format_args<_Context>;
friend _Format_handler<_CharType>;
friend _Format_arg_traits<_Context>;
Expand Down Expand Up @@ -838,39 +873,7 @@ auto _Format_arg_traits<_Context>::_Type_eraser() {

_EXPORT_STD template <class _Visitor, class _Context>
decltype(auto) visit_format_arg(_Visitor&& _Vis, basic_format_arg<_Context> _Arg) {
switch (_Arg._Active_state) {
case _Basic_format_arg_type::_None:
return _STD forward<_Visitor>(_Vis)(_Arg._No_state);
case _Basic_format_arg_type::_Int_type:
return _STD forward<_Visitor>(_Vis)(_Arg._Int_state);
case _Basic_format_arg_type::_UInt_type:
return _STD forward<_Visitor>(_Vis)(_Arg._UInt_state);
case _Basic_format_arg_type::_Long_long_type:
return _STD forward<_Visitor>(_Vis)(_Arg._Long_long_state);
case _Basic_format_arg_type::_ULong_long_type:
return _STD forward<_Visitor>(_Vis)(_Arg._ULong_long_state);
case _Basic_format_arg_type::_Bool_type:
return _STD forward<_Visitor>(_Vis)(_Arg._Bool_state);
case _Basic_format_arg_type::_Char_type:
return _STD forward<_Visitor>(_Vis)(_Arg._Char_state);
case _Basic_format_arg_type::_Float_type:
return _STD forward<_Visitor>(_Vis)(_Arg._Float_state);
case _Basic_format_arg_type::_Double_type:
return _STD forward<_Visitor>(_Vis)(_Arg._Double_state);
case _Basic_format_arg_type::_Long_double_type:
return _STD forward<_Visitor>(_Vis)(_Arg._Long_double_state);
case _Basic_format_arg_type::_Pointer_type:
return _STD forward<_Visitor>(_Vis)(_Arg._Pointer_state);
case _Basic_format_arg_type::_CString_type:
return _STD forward<_Visitor>(_Vis)(_Arg._CString_state);
case _Basic_format_arg_type::_String_type:
return _STD forward<_Visitor>(_Vis)(_Arg._String_state);
case _Basic_format_arg_type::_Custom_type:
return _STD forward<_Visitor>(_Vis)(_Arg._Custom_state);
default:
_STL_VERIFY(false, "basic_format_arg is in impossible state");
return _STD forward<_Visitor>(_Vis)(0);
}
return _Arg._Visit(_STD forward<_Visitor>(_Vis));
}

// we need to implement this ourselves because from_chars does not work with wide characters and isn't constexpr
Expand Down
16 changes: 16 additions & 0 deletions tests/std/tests/P0645R10_text_formatting_args/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -252,13 +252,29 @@ void test_lwg3810() {
static_assert(same_as<decltype(basic_format_args{args_store}), basic_format_args<Context>>);
}

struct lvalue_only_visitor {
template <class T>
void operator()(T&&) const = delete;
template <class T>
void operator()(T&) const noexcept {}
};

template <class Context>
void test_lvalue_only_visitation() {
visit_format_arg(lvalue_only_visitor{}, basic_format_arg<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>();

test_lvalue_only_visitation<format_context>();
test_lvalue_only_visitation<wformat_context>();
}