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Simplify formattability check

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This commit is contained in:
Victor Zverovich 2021-03-27 18:57:18 -07:00
parent 35c71ff536
commit 1b23e25f95
1 changed files with 7 additions and 13 deletions
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20
include/fmt/core.h
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@ -1451,24 +1451,18 @@ FMT_CONSTEXPR basic_format_arg<Context> make_arg(const T& value) {
return arg; return arg;
} }
template <typename T> int check(unformattable) {
static_assert(
formattable<T>(),
"Cannot format an argument. To make type T formattable provide a "
"formatter<T> specialization: https://fmt.dev/latest/api.html#udt");
return 0;
}
template <typename T, typename U> constexpr const U& check(const U& val) {
return val;
}
// The type template parameter is there to avoid an ODR violation when using // The type template parameter is there to avoid an ODR violation when using
// a fallback formatter in one translation unit and an implicit conversion in // a fallback formatter in one translation unit and an implicit conversion in
// another (not recommended). // another (not recommended).
template <bool IS_PACKED, typename Context, type, typename T, template <bool IS_PACKED, typename Context, type, typename T,
FMT_ENABLE_IF(IS_PACKED)> FMT_ENABLE_IF(IS_PACKED)>
constexpr value<Context> make_arg(const T& val) { FMT_CONSTEXPR value<Context> make_arg(const T& val) {
return detail::check<T>(arg_mapper<Context>().map(val)); const auto& arg = arg_mapper<Context>().map(val);
static_assert(
!std::is_same<decltype(arg), const unformattable&>::value,
"Cannot format an argument. To make type T formattable provide a "
"formatter<T> specialization: https://fmt.dev/latest/api.html#udt");
return arg;
} }
template <bool IS_PACKED, typename Context, type, typename T, template <bool IS_PACKED, typename Context, type, typename T,