From a407966592e8aab5c7b0757867a2f0585175fe80 Mon Sep 17 00:00:00 2001
From: Abseil Team <absl-team@google.com>
Date: Mon, 23 Feb 2026 11:30:09 -0800
Subject: [PATCH] Revert Optimize copying of matchers vector to speed up
 `ElementsAreArray` by reserving a `std::vector` copied via `push_back`.

If the iterators are forward iterators, we can measure the size and reserve the vector, avoiding reallocations and copying.

PiperOrigin-RevId: 874172640
Change-Id: Ie081fdf7952858d7e41ddda63a3ae15d9867c8c5
---
 googlemock/include/gmock/gmock-matchers.h | 18 ------------------
 1 file changed, 18 deletions(-)

diff --git a/googlemock/include/gmock/gmock-matchers.h b/googlemock/include/gmock/gmock-matchers.h
index 9f5118e8c..2532d597f 100644
--- a/googlemock/include/gmock/gmock-matchers.h
+++ b/googlemock/include/gmock/gmock-matchers.h
@@ -2821,7 +2821,6 @@ class [[nodiscard]] QuantifierMatcherImpl : public MatcherInterface<Container> {
     StlContainerReference stl_container = View::ConstReference(container);
     size_t i = 0;
     std::vector<size_t> match_elements;
-    match_elements.reserve(stl_container.size());
     for (auto it = stl_container.begin(); it != stl_container.end();
          ++it, ++i) {
       StringMatchResultListener inner_listener;
@@ -3592,18 +3591,6 @@ class [[nodiscard]] FieldsAreMatcher {
   std::tuple<Inner...> matchers_;
 };
 
-// Returns the distance between [first, last) if known, otherwise 0.
-template <typename Iter>
-size_t DistanceIfKnown(Iter first, Iter last) {
-  if constexpr (std::is_base_of_v<
-                    std::forward_iterator_tag,
-                    typename std::iterator_traits<Iter>::iterator_category>) {
-    return std::distance(first, last);
-  } else {
-    return 0;
-  }
-}
-
 // Implements ElementsAre() and ElementsAreArray().
 template <typename Container>
 class [[nodiscard]] ElementsAreMatcherImpl
@@ -3619,7 +3606,6 @@ class [[nodiscard]] ElementsAreMatcherImpl
   // element matchers.
   template <typename InputIter>
   ElementsAreMatcherImpl(InputIter first, InputIter last) {
-    matchers_.reserve(DistanceIfKnown(first, last));
     while (first != last) {
       matchers_.push_back(MatcherCast<const Element&>(*first++));
     }
@@ -3895,11 +3881,9 @@ class [[nodiscard]] UnorderedElementsAreMatcherImpl
   UnorderedElementsAreMatcherImpl(UnorderedMatcherRequire::Flags matcher_flags,
                                   InputIter first, InputIter last)
       : UnorderedElementsAreMatcherImplBase(matcher_flags) {
-    matchers_.reserve(DistanceIfKnown(first, last));
     for (; first != last; ++first) {
       matchers_.push_back(MatcherCast<const Element&>(*first));
     }
-    matcher_describers().reserve(matchers_.size());
     for (const auto& m : matchers_) {
       matcher_describers().push_back(m.GetDescriber());
     }
@@ -3933,7 +3917,6 @@ class [[nodiscard]] UnorderedElementsAreMatcherImpl
                               ::std::vector<std::string>* element_printouts,
                               MatchResultListener* listener) const {
     element_printouts->clear();
-    element_printouts->reserve(DistanceIfKnown(elem_first, elem_last));
     ::std::vector<char> did_match;
     size_t num_elements = 0;
     DummyMatchResultListener dummy;
@@ -5104,7 +5087,6 @@ UnorderedPointwise(const Tuple2Matcher& tuple2_matcher,
 
   // Create a matcher for each element in rhs_container.
   ::std::vector<internal::BoundSecondMatcher<Tuple2Matcher, Second>> matchers;
-  matchers.reserve(rhs_stl_container.size());
   for (auto it = rhs_stl_container.begin(); it != rhs_stl_container.end();
        ++it) {
     matchers.push_back(internal::MatcherBindSecond(tuple2_matcher, *it));