Make gmock-matchers.h auto-detect the value_type of ranges that don't have a typedef for it based on the ranges' iterators

This is needed for ranges such as [`std::ranges::subrange`](https://en.cppreference.com/w/cpp/ranges/subrange.html) that don't expose the typical typedefs.

PiperOrigin-RevId: 879124865
Change-Id: Ie89e6ff249ee861d1b2d880079dc162bb9801679

googlemock/include/gmock/gmock-matchers.h

@@ -2602,9 +2602,9 @@ class [[nodiscard]] WhenSortedByMatcher {
     typedef typename LhsView::const_reference LhsStlContainerReference;
     // Transforms std::pair<const Key, Value> into std::pair<Key, Value>
     // so that we can match associative containers.
-    typedef
+    typedef typename RemoveConstFromKey<
-        typename RemoveConstFromKey<typename LhsStlContainer::value_type>::type
+        typename internal::RangeTraits<LhsStlContainer>::value_type>::type
-            LhsValue;
+        LhsValue;
 
     Impl(const Comparator& comparator, const ContainerMatcher& matcher)
         : comparator_(comparator), matcher_(matcher) {}
@@ -2670,7 +2670,7 @@ class [[nodiscard]] PointwiseMatcher {
  public:
   typedef internal::StlContainerView<RhsContainer> RhsView;
   typedef typename RhsView::type RhsStlContainer;
-  typedef typename RhsStlContainer::value_type RhsValue;
+  typedef typename internal::RangeTraits<RhsStlContainer>::value_type RhsValue;
 
   static_assert(!std::is_const<RhsContainer>::value,
                 "RhsContainer type must not be const");
@@ -2700,7 +2700,8 @@ class [[nodiscard]] PointwiseMatcher {
         LhsView;
     typedef typename LhsView::type LhsStlContainer;
     typedef typename LhsView::const_reference LhsStlContainerReference;
-    typedef typename LhsStlContainer::value_type LhsValue;
+    typedef
+        typename internal::RangeTraits<LhsStlContainer>::value_type LhsValue;
     // We pass the LHS value and the RHS value to the inner matcher by
     // reference, as they may be expensive to copy.  We must use tuple
     // instead of pair here, as a pair cannot hold references (C++ 98,
@@ -2786,7 +2787,7 @@ class [[nodiscard]] QuantifierMatcherImpl : public MatcherInterface<Container> {
   typedef StlContainerView<RawContainer> View;
   typedef typename View::type StlContainer;
   typedef typename View::const_reference StlContainerReference;
-  typedef typename StlContainer::value_type Element;
+  typedef typename internal::RangeTraits<StlContainer>::value_type Element;
 
   template <typename InnerMatcher>
   explicit QuantifierMatcherImpl(InnerMatcher inner_matcher)
@@ -3600,7 +3601,7 @@ class [[nodiscard]] ElementsAreMatcherImpl
   typedef internal::StlContainerView<RawContainer> View;
   typedef typename View::type StlContainer;
   typedef typename View::const_reference StlContainerReference;
-  typedef typename StlContainer::value_type Element;
+  typedef typename internal::RangeTraits<StlContainer>::value_type Element;
 
   // Constructs the matcher from a sequence of element values or
   // element matchers.
@@ -3875,7 +3876,7 @@ class [[nodiscard]] UnorderedElementsAreMatcherImpl
   typedef internal::StlContainerView<RawContainer> View;
   typedef typename View::type StlContainer;
   typedef typename View::const_reference StlContainerReference;
-  typedef typename StlContainer::value_type Element;
+  typedef typename internal::RangeTraits<StlContainer>::value_type Element;
 
   template <typename InputIter>
   UnorderedElementsAreMatcherImpl(UnorderedMatcherRequire::Flags matcher_flags,
@@ -3963,8 +3964,7 @@ class [[nodiscard]] UnorderedElementsAreMatcher {
   template <typename Container>
   operator Matcher<Container>() const {
     typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
-    typedef typename internal::StlContainerView<RawContainer>::type View;
+    typedef typename internal::RangeTraits<RawContainer>::value_type Element;
-    typedef typename View::value_type Element;
     typedef ::std::vector<Matcher<const Element&>> MatcherVec;
     MatcherVec matchers;
     matchers.reserve(::std::tuple_size<MatcherTuple>::value);
@@ -3995,7 +3995,7 @@ class [[nodiscard]] ElementsAreMatcher {
 
     typedef GTEST_REMOVE_REFERENCE_AND_CONST_(Container) RawContainer;
     typedef typename internal::StlContainerView<RawContainer>::type View;
-    typedef typename View::value_type Element;
+    typedef typename internal::RangeTraits<View>::value_type Element;
     typedef ::std::vector<Matcher<const Element&>> MatcherVec;
     MatcherVec matchers;
     matchers.reserve(::std::tuple_size<MatcherTuple>::value);
@@ -5081,7 +5081,7 @@ UnorderedPointwise(const Tuple2Matcher& tuple2_matcher,
   // STL-style container and it being a native C-style array.
   typedef typename internal::StlContainerView<RhsContainer> RhsView;
   typedef typename RhsView::type RhsStlContainer;
-  typedef typename RhsStlContainer::value_type Second;
+  typedef typename internal::RangeTraits<RhsStlContainer>::value_type Second;
   const RhsStlContainer& rhs_stl_container =
       RhsView::ConstReference(rhs_container);
 

googlemock/include/gmock/internal/gmock-internal-utils.h

@@ -41,6 +41,7 @@
 
 #include <stdio.h>
 
+#include <iterator>
 #include <ostream>  // NOLINT
 #include <string>
 #include <type_traits>
@@ -322,6 +323,24 @@ inline T Invalid() {
 #endif
 }
 
+void GetValueType(const void*);
+
+template <class T>
+typename std::iterator_traits<
+    decltype(std::begin(std::declval<T&>()))>::value_type
+GetValueType(T*);
+
+template <class T, class = void>
+struct RangeTraits {
+  typedef decltype(internal::GetValueType(
+      static_cast<std::remove_reference_t<T>*>(nullptr))) value_type;
+};
+
+template <class T>
+struct RangeTraits<T, std::conditional_t<true, void, typename T::value_type>> {
+  typedef typename T::value_type value_type;
+};
+
 // Given a raw type (i.e. having no top-level reference or const
 // modifier) RawContainer that's either an STL-style container or a
 // native array, class StlContainerView<RawContainer> has the