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[meta] Add in-house impl of hb_is_convertible()

This commit is contained in:
Behdad Esfahbod 2021-11-02 00:49:40 -06:00
parent 7a078c395a
commit b8724c6023
2 changed files with 1 additions and 39 deletions
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26
src/hb-meta.hh
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@ -132,31 +132,7 @@ template <typename T> using hb_add_pointer = decltype (_hb_try_add_pointer<T> (h
/* TODO Add feature-parity to std::decay. */
template <typename T> using hb_decay = hb_remove_const<hb_remove_reference<T>>;
template <typename From, typename To>
struct hb_is_convertible
{
private:
static constexpr bool from_void = hb_is_same (void, hb_decay<From>);
static constexpr bool to_void = hb_is_same (void, hb_decay<To> );
static constexpr bool either_void = from_void || to_void;
static constexpr bool both_void = from_void && to_void;
static hb_true_type impl2 (typename std::conditional<to_void, int, To>::type);
template <typename T>
static auto impl (hb_priority<1>) -> decltype (impl2 (hb_declval (T)));
template <typename T>
static hb_false_type impl (hb_priority<0>);
public:
static constexpr bool value = both_void ||
(!either_void &&
decltype (impl<typename std::conditional<from_void, int, From>::type> (hb_prioritize))::value);
};
#define hb_is_convertible(From,To) hb_is_convertible<From, To>::value
template <typename Base, typename Derived>
using hb_is_base_of = hb_is_convertible<hb_decay<Derived> *, hb_decay<Base> *>;
#define hb_is_base_of(Base,Derived) hb_is_base_of<Base, Derived>::value
#define hb_is_convertible(From,To) std::is_convertible<From, To>::value
template <typename From, typename To>
using hb_is_cr_convertible = hb_bool_constant<

14
src/test-meta.cc
View File

@ -81,20 +81,6 @@ main (int argc, char **argv)
static_assert (hb_is_convertible (int *, void *), "");
static_assert (!hb_is_convertible (void *, int *), "");
static_assert (hb_is_base_of (void, void), "");
static_assert (hb_is_base_of (void, int), "");
static_assert (!hb_is_base_of (int, void), "");
static_assert (hb_is_base_of (int, int), "");
static_assert (hb_is_base_of (const int, int), "");
static_assert (hb_is_base_of (int, const int), "");
static_assert (hb_is_base_of (X, X), "");
static_assert (hb_is_base_of (X, Y), "");
static_assert (hb_is_base_of (const X, Y), "");
static_assert (hb_is_base_of (X, const Y), "");
static_assert (!hb_is_base_of (Y, X), "");
/* TODO Add more meaningful tests. */
return 0;