Re: [boost] delayed_forward: good, bad, ugly?

Alexander Grund wrote:

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See `std::map::try_emplace(k, args…)`.

https://en.cppreference.com/w/cpp/container/map/try_emplace

Notes: Unlike insert or emplace, these functions do not move from rvalue arguments if the insertion does not happen.

Yes, however at the callsite you can clearly see the different semantics: "try_" That's much harder for a constructor. Although a well-named factory method might be a solution if this semantic is useful.

For a constructor example, see https://eel.is/c++draft/util.smartptr.shared.const#29.