Class template argument deduction for absl::AnyInvocable?

[jiawen]

C++17 added CTAD to std::function by way of a deduction guide. This permits writing:

std::function f = []() { return 3; };

But absl::AnyInvocable does not current have this facility. E.g., the following fails to compile:

absl::AnyInvocable g = []() { return 3; };

Is there thought to adding such a facility?

[higher-performance]

The closer comparison to make here is with std::move_only_function, not std::function. It does not have deduction guides: https://en.cppreference.com/w/cpp/utility/functional/move_only_function

This is likely intentional, not an oversight -- both std::move_only_function and absl::AnyInvocable support distinguishing void() from void()&&, for example, but those can't be inferred.

I would also argue CTAD here hurts readability.