[libcxx-commits] [libcxx] [libc++][ranges] optimize the performance of `ranges::starts_with` (PR #84570)

[Xiaoyang Liu via libcxx-commits]

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@@ -69,18 +95,41 @@ struct __fn {
     requires indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>, _Pred, _Proj1, _Proj2>
   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI static constexpr bool
   operator()(_Range1&& __range1, _Range2&& __range2, _Pred __pred = {}, _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) {
-    return __mismatch::__fn::__go(
+    if constexpr (sized_range<_Range1> && sized_range<_Range2>) {
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xiaoyang-sde wrote:

A`range` can model `sized_range` when its iterators doesn't model `sized_sentinel_for`.

https://github.com/llvm/llvm-project/pull/84570