[libcxx-commits] [libcxx] [libc++] Remove [[nodiscard]] from map etc. operator[] (PR #172444)

[A. Jiang via libcxx-commits]

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@@ -465,13 +465,13 @@ class flat_map {
   }
 
   // [flat.map.access], element access
-  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 mapped_type& operator[](const key_type& __x)
+  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 mapped_type& operator[](const key_type& __x)
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frederick-vs-ja wrote:

I'm not sure whether value-discarding `m[k]` is intended. If one only wants the side effects, `m.try_emplace(k)` can be used instead to express this more clearly.

For `map` and `unordered_map`, `m[k]` is possibly a workaround because `try_emplace` wasn't present before C++17. So I just want to keep `[[nodiscard]]` for `flat_map::operator[]`.

https://github.com/llvm/llvm-project/pull/172444