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Add support for incomplete types

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This commit is contained in:
LocalSpook
2025-03-11 20:28:11 -07:00
committed by Victor Zverovich
parent db405954cd
commit c709138359
2 changed files with 32 additions and 1 deletions
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7
include/fmt/base.h
View File

@ -1033,6 +1033,11 @@ enum {
struct view {};
template <typename T, typename Enable = std::true_type>
struct is_view : std::false_type {};
template <typename T>
struct is_view<T, bool_constant<sizeof(T) != 0>> : std::is_base_of<view, T> {};
template <typename Char, typename T> struct named_arg;
template <typename T> struct is_named_arg : std::false_type {};
template <typename T> struct is_static_named_arg : std::false_type {};
@ -2726,7 +2731,7 @@ template <typename... T> struct fstring {
template <size_t N>
FMT_CONSTEVAL FMT_ALWAYS_INLINE fstring(const char (&s)[N]) : str(s, N - 1) {
using namespace detail;
static_assert(count<(std::is_base_of<view, remove_reference_t<T>>::value &&
static_assert(count<(is_view<remove_cvref_t<T>>::value &&
std::is_reference<T>::value)...>() == 0,
"passing views as lvalues is disallowed");
if (FMT_USE_CONSTEVAL) parse_format_string<char>(s, checker(s, arg_pack()));

26
test/format-test.cc
View File

@ -2540,3 +2540,29 @@ TEST(base_test, format_byte) {
EXPECT_EQ(s, "42");
}
#endif
// Only defined after the test case.
struct incomplete_type;
extern const incomplete_type& external_instance;
FMT_BEGIN_NAMESPACE
template <> struct formatter<incomplete_type> : formatter<int> {
auto format(const incomplete_type& x, context& ctx) const -> appender;
};
FMT_END_NAMESPACE
TEST(incomplete_type_test, format) {
EXPECT_EQ(fmt::format("{}", external_instance), "42");
}
struct incomplete_type {
int i;
};
const incomplete_type& external_instance = {42};
auto fmt::formatter<incomplete_type>::format(const incomplete_type& x,
fmt::context& ctx) const
-> fmt::appender {
return formatter<int>::format(x.i, ctx);
}