================
@@ -2113,12 +2113,63 @@ void erase(Container &C, ValueType V) {
C.erase(std::remove(C.begin(), C.end(), V), C.end());
}
+namespace detail {
+template <typename Range>
+using check_has_member_iterator_category_t =
+ typename decltype(std::declval<Range &>().begin())::iterator_category;
+
+template <typename Range>
+static constexpr bool HasMemberIteratorCategory =
+ is_detected<check_has_member_iterator_category_t, Range>::value;
+
+template <typename Container>
+using check_has_member_capacity_t =
+ decltype(std::declval<Container &>().capacity());
+
+template <typename Container>
+static constexpr bool HasMemberCapacity =
+ is_detected<check_has_member_capacity_t, Container>::value;
+
+template <typename Container>
+using check_has_member_reserve_t =
+ decltype(std::declval<Container &>().reserve(1U));
+
+template <typename Container>
+static constexpr bool HasMemberReserve =
+ is_detected<check_has_member_reserve_t, Container>::value;
+} // namespace detail
+
/// Wrapper function to append range `R` to container `C`.
///
/// C.insert(C.end(), R.begin(), R.end());
template <typename Container, typename Range>
void append_range(Container &C, Range &&R) {
+ size_t Before = 0;
+ size_t After = 0;
+
+ if constexpr (detail::HasMemberReserve<Container>) {
+ using IteratorType = decltype(adl_begin(R));
+ if constexpr (std::is_pointer<IteratorType>::value) {
+ C.reserve(C.size() + std::distance(adl_begin(R), adl_end(R)));
----------------
kuhar wrote:
The alternative would be to check that the type either has `.size()` (which we
assume to be fast) or that `llvm::size` is detected (which already requires
random access iterators)
https://github.com/llvm/llvm-project/pull/136543
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