[llvm] [EquivClasses] Introduce members iterator-helper (PR #130139)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-armv8-quick` running on `linaro-clang-armv8-quick` while building `llvm` at step 5 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/154/builds/12966

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 5 (ninja check 1) failure: stage 1 checked (failure)
...
----------------------------------------------------------------------
Ran 154 tests in 2.317s

OK
[20/126] Linking CXX executable unittests/DebugInfo/GSYM/DebugInfoGSYMTests
[21/126] Linking CXX executable unittests/Bitcode/BitcodeTests
[22/126] Linking CXX executable tools/clang/tools/extra/unittests/clang-tidy/ClangTidyTests
[23/126] Linking CXX executable tools/clang/unittests/Format/FormatTests
[24/126] Linking CXX executable unittests/DebugInfo/PDB/DebugInfoPDBTests
[25/126] Building CXX object unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o
FAILED: unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o 
/usr/local/bin/c++ -DGTEST_HAS_RTTI=0 -DLLVM_BUILD_STATIC -D_DEBUG -D_FILE_OFFSET_BITS=64 -D_GLIBCXX_ASSERTIONS -D_GNU_SOURCE -D_LARGEFILE_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/unittests/ADT -I/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/llvm/unittests/ADT -I/home/tcwg-buildbot/worker/clang-armv8-quick/stage1/include -I/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/llvm/include -I/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/third-party/unittest/googletest/include -I/home/tcwg-buildbot/worker/clang-armv8-quick/llvm/third-party/unittest/googlemock/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -std=c++17  -Wno-variadic-macros -Wno-gnu-zero-variadic-macro-arguments -fno-exceptions -funwind-tables -fno-rtti -UNDEBUG -Wno-suggest-override -MD -MT unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o -MF unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o.d -o unittests/ADT/CMakeFiles/ADTTests.dir/EquivalenceClassesTest.cpp.o -c /home/tcwg-buildbot/worker/clang-armv8-quick/llvm/llvm/unittests/ADT/EquivalenceClassesTest.cpp
In file included from ../llvm/llvm/unittests/ADT/EquivalenceClassesTest.cpp:10:
In file included from ../llvm/third-party/unittest/googlemock/include/gmock/gmock.h:61:
../llvm/third-party/unittest/googlemock/include/gmock/gmock-more-matchers.h:73:40: error: no member named 'size' in 'llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator>'
   73 |     *listener << "whose size is " << c.size();
      |                                      ~ ^
../llvm/third-party/unittest/googletest/include/gtest/gtest-matchers.h:647:20: note: in instantiation of function template specialization 'testing::internal::IsEmptyMatcher::MatchAndExplain<llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator>>' requested here
  647 |       return impl_.MatchAndExplain(x, listener);
      |                    ^
../llvm/third-party/unittest/googletest/include/gtest/gtest-matchers.h:638:14: note: in instantiation of member function 'testing::PolymorphicMatcher<testing::internal::IsEmptyMatcher>::MonomorphicImpl<const llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator> &>::MatchAndExplain' requested here
  638 |     explicit MonomorphicImpl(const Impl& impl) : impl_(impl) {}
      |              ^
../llvm/third-party/unittest/googletest/include/gtest/gtest-matchers.h:631:27: note: in instantiation of member function 'testing::PolymorphicMatcher<testing::internal::IsEmptyMatcher>::MonomorphicImpl<const llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator> &>::MonomorphicImpl' requested here
  631 |     return Matcher<T>(new MonomorphicImpl<const T&>(impl_));
      |                           ^
../llvm/third-party/unittest/googlemock/include/gmock/gmock-matchers.h:373:12: note: in instantiation of function template specialization 'testing::PolymorphicMatcher<testing::internal::IsEmptyMatcher>::operator Matcher<const llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator> &>' requested here
  373 |     return polymorphic_matcher_or_value;
      |            ^
../llvm/third-party/unittest/googlemock/include/gmock/gmock-matchers.h:355:12: note: in instantiation of function template specialization 'testing::internal::MatcherCastImpl<const llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator> &, testing::PolymorphicMatcher<testing::internal::IsEmptyMatcher>>::CastImpl<false>' requested here
  355 |     return CastImpl(polymorphic_matcher_or_value,
      |            ^
../llvm/third-party/unittest/googlemock/include/gmock/gmock-matchers.h:515:43: note: in instantiation of member function 'testing::internal::MatcherCastImpl<const llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator> &, testing::PolymorphicMatcher<testing::internal::IsEmptyMatcher>>::Cast' requested here
  515 |   return internal::MatcherCastImpl<T, M>::Cast(matcher);
      |                                           ^
../llvm/third-party/unittest/googlemock/include/gmock/gmock-matchers.h:522:10: note: in instantiation of function template specialization 'testing::MatcherCast<const llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator> &, testing::PolymorphicMatcher<testing::internal::IsEmptyMatcher>>' requested here
  522 |   return MatcherCast<T>(polymorphic_matcher_or_value);
      |          ^
../llvm/third-party/unittest/googlemock/include/gmock/gmock-matchers.h:1591:39: note: in instantiation of function template specialization 'testing::SafeMatcherCast<const llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator> &, testing::PolymorphicMatcher<testing::internal::IsEmptyMatcher>>' requested here
 1591 |     const Matcher<const T&> matcher = SafeMatcherCast<const T&>(matcher_);
      |                                       ^
../llvm/llvm/unittests/ADT/EquivalenceClassesTest.cpp:80:3: note: in instantiation of function template specialization 'testing::internal::PredicateFormatterFromMatcher<testing::PolymorphicMatcher<testing::internal::IsEmptyMatcher>>::operator()<llvm::iterator_range<llvm::EquivalenceClasses<int>::member_iterator>>' requested here
   80 |   EXPECT_THAT(EC.members(EC.end()), testing::IsEmpty());
      |   ^
../llvm/third-party/unittest/googlemock/include/gmock/gmock-matchers.h:5495:3: note: expanded from macro 'EXPECT_THAT'
 5495 |   EXPECT_PRED_FORMAT1(              \
      |   ^
../llvm/third-party/unittest/googletest/include/gtest/gtest_pred_impl.h:109:3: note: expanded from macro 'EXPECT_PRED_FORMAT1'
  109 |   GTEST_PRED_FORMAT1_(pred_format, v1, GTEST_NONFATAL_FAILURE_)

```

</details>

https://github.com/llvm/llvm-project/pull/130139