Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

Move-assign an any_completion_handler from another.

any_completion_handler & operator=(
    any_completion_handler && other);
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Assignment operator that sets the polymorphic wrapper to the empty state.

any_completion_handler & operator=(
    nullptr_t );
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