[libcxx-commits] [libcxx] [libcxx] Optimize std::generate for segmented iterators (PR #163006)

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@@ -20,8 +21,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 template <class _ForwardIterator, class _Generator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void
 generate(_ForwardIterator __first, _ForwardIterator __last, _Generator __gen) {
-  for (; __first != __last; ++__first)
-    *__first = __gen();
+  std::for_each(__first, __last, [&](auto& __element) { __element = __gen(); });
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c8ef wrote:

```
# | C://llvm-project/build/libcxx/test-suite-install/include/c++/v1/__type_traits/invoke.h:88:69: note: candidate template i
gnored: substitution failure [with _Args = <(lambda at C://llvm-project/build/libcxx/test-suite-install/include/c++/v1/__alg
orithm/generate.h:24:34) &, LifetimeIterator::Reference>]: no type named 'type' in 'std::__invoke_result_impl<void, (lambda at C:/Users/Mario/Doc
uments/llvm-project/build/libcxx/test-suite-install/include/c++/v1/__algorithm/generate.h:24:34) &, LifetimeIterator::Reference>'
```

Thank you for the suggestions! I have made updates to the implementations.

Just to clarify, is it because when dereferencing `LifetimeIterator`, we get a type named `Reference` which is itself an rvalue, so `auto&` cannot bind to it?

I have also included a release note based on a previous related patch.

https://github.com/llvm/llvm-project/pull/163006