From Jason Turner

[func.wrap.ref.ctor]

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tmp/tmpb0zl0v_v/{from.md → to.md} RENAMED
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+ ##### Constructors and assignment operators <a id="func.wrap.ref.ctor">[[func.wrap.ref.ctor]]</a>
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+
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+ ``` cpp
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+ template<class... T>
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+ static constexpr bool is-invocable-using = see below;
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+ ```
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+
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+ If *noex* is `true`, *`is-invocable-using`*`<T...>` is equal to:
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+
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+ ``` cpp
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+ is_nothrow_invocable_r_v<R, T..., ArgTypes...>
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+ ```
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+
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+ Otherwise, *`is-invocable-using`*`<T...>` is equal to:
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+
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+ ``` cpp
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+ is_invocable_r_v<R, T..., ArgTypes...>
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+ ```
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+
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+ ``` cpp
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+ template<class F> function_ref(F* f) noexcept;
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+ ```
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+
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+ *Constraints:*
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+
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+ - `is_function_v<F>` is `true`, and
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+ - *`is-invocable-using`*`<F>` is `true`.
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+
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+ *Preconditions:* `f` is not a null pointer.
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+
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+ *Effects:* Initializes *bound-entity* with `f`, and *thunk-ptr* with the
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+ address of a function *`thunk`* such that
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+ *`thunk`*`(`*`bound-entity`*`, `*`call-args`*`...)` is
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+ expression-equivalent [[defns.expression.equivalent]] to
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+ `invoke_r<R>(f, `*`call-args`*`...)`.
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+
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+ ``` cpp
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+ template<class F> constexpr function_ref(F&& f) noexcept;
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+ ```
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+
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+ Let `T` be `remove_reference_t<F>`.
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+
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+ *Constraints:*
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+
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+ - `remove_cvref_t<F>` is not the same type as `function_ref`,
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+ - `is_member_pointer_v<T>` is `false`, and
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+ - *`is-invocable-using`*`<cv T&>` is `true`.
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+
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+ *Effects:* Initializes *bound-entity* with `addressof(f)`, and
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+ *thunk-ptr* with the address of a function *`thunk`* such that
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+ *`thunk`*`(`*`bound-entity`*`, `*`call-args`*`...)` is
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+ expression-equivalent [[defns.expression.equivalent]] to
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+ `invoke_r<R>(static_cast<cv T&>(f), `*`call-args`*`...)`.
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+
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+ ``` cpp
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+ template<auto f> constexpr function_ref(nontype_t<f>) noexcept;
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+ ```
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+
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+ Let `F` be `decltype(f)`.
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+
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+ *Constraints:* *`is-invocable-using`*`<F>` is `true`.
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+
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+ *Mandates:* If `is_pointer_v<F> || is_member_pointer_v<F>` is `true`,
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+ then `f != nullptr` is `true`.
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+
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+ *Effects:* Initializes *bound-entity* with a pointer to an unspecified
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+ object or null pointer value, and *thunk-ptr* with the address of a
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+ function *`thunk`* such that
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+ *`thunk`*`(`*`bound-entity`*`, `*`call-args`*`...)` is
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+ expression-equivalent [[defns.expression.equivalent]] to
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+ `invoke_r<R>(f, `*`call-args`*`...)`.
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+
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+ ``` cpp
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+ template<auto f, class U>
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+ constexpr function_ref(nontype_t<f>, U&& obj) noexcept;
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+ ```
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+
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+ Let `T` be `remove_reference_t<U>` and `F` be `decltype(f)`.
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+
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+ *Constraints:*
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+
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+ - `is_rvalue_reference_v<U&&>` is `false`, and
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+ - *`is-invocable-using`*`<F, cv T&>` is `true`.
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+
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+ *Mandates:* If `is_pointer_v<F> || is_member_pointer_v<F>` is `true`,
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+ then `f != nullptr` is `true`.
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+
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+ *Effects:* Initializes *bound-entity* with `addressof(obj)`, and
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+ *thunk-ptr* with the address of a function *`thunk`* such that
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+ *`thunk`*`(`*`bound-entity`*`, `*`call-args`*`...)` is
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+ expression-equivalent [[defns.expression.equivalent]] to
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+ `invoke_r<R>(f, static_cast<cv T&>(obj), `*`call-args`*`...)`.
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+
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+ ``` cpp
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+ template<auto f, class T>
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+ constexpr function_ref(nontype_t<f>, cv T* obj) noexcept;
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+ ```
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+
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+ Let `F` be `decltype(f)`.
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+
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+ *Constraints:* *`is-invocable-using`*`<F, cv T*>` is `true`.
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+
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+ *Mandates:* If `is_pointer_v<F> || is_member_pointer_v<F>` is `true`,
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+ then `f != nullptr` is `true`.
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+
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+ *Preconditions:* If `is_member_pointer_v<F>` is `true`, `obj` is not a
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+ null pointer.
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+
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+ *Effects:* Initializes *bound-entity* with `obj`, and *thunk-ptr* with
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+ the address of a function *`thunk`* such that
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+ *`thunk`*`(`*`bound-entity`*`, `*`call-args`*`...)` is
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+ expression-equivalent [[defns.expression.equivalent]] to
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+ `invoke_r<R>(f, obj, `*`call-args`*`...)`.
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+
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+ ``` cpp
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+ template<class T> function_ref& operator=(T) = delete;
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+ ```
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+
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+ *Constraints:*
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+
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+ - `T` is not the same type as `function_ref`,
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+ - `is_pointer_v<T>` is `false`, and
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+ - `T` is not a specialization of `nontype_t`.
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+