Implement accessibility support for reflection (#191)

docs/PRO_DEF_FREE_AS_MEM_DISPATCH.md

@@ -0,0 +1,71 @@
+# Macro `PRO_DEF_FREE_AS_MEM_DISPATCH`
+
+```cpp
+#define PRO_DEF_FREE_AS_MEM_DISPATCH // see below
+```
+
+Macro `PRO_DEF_FREE_AS_MEM_DISPATCH` defines dispatch types for free function expressions with accessibility via a member function. It supports two syntaxes:
+
+```cpp
+// (1)
+PRO_DEF_FREE_AS_MEM_DISPATCH(dispatch_name, func_name);
+
+// (2)
+PRO_DEF_FREE_AS_MEM_DISPATCH(dispatch_name, func_name, accessibility_func_name);
+```
+
+`(1)` Equivalent to `PRO_DEF_FREE_AS_MEM_DISPATCH(dispatch_name, func_name, func_name);`
+
+`(2)` Defines a class named `dispatch_name` of free function call expressions of `func_name` with accessibility via a member function. `dispatch_name` meets the [*ProAccessible*](ProAccessible.md) requirements of types `F`, `C`, and `Os...`, where `F` models concept [`facade`](facade.md), `C` is a tuple element type defined in `typename F::convention_types`, and each type `O` (possibly qualified with *cv ref noex*) in `Os...` is a tuple element type defined in `typename C::overload_types`. The member functions provided by `typename dispatch_name::template accessor<F, C, Os...>` are named `accessibility_func_name`. Let `SELF` be `std::forward<accessor cv ref>(*this)`, effectively equivalent to:
+
+```cpp
+struct dispatch_name {
+  template <class T, class... Args>
+  decltype(auto) operator()(T&& self, Args&&... args)
+      noexcept(noexcept(func_name(std::forward<T>(self), std::forward<Args>(args)...)))
+      requires(requires { func_name(std::forward<T>(self), std::forward<Args>(args)...); }) {
+    return func_name(std::forward<T>(self), std::forward<Args>(args)...);
+  }
+
+  template <class F, class C, class... Os>
+  struct accessor {
+    accessor() = delete;
+  };
+  template <class F, class C, class... Os>
+      requires(sizeof...(Os) > 1u && (std::is_trivial_v<accessor<F, C, Os>> && ...))
+  struct accessor<F, C, Os...> : accessor<F, C, Os>... {
+    using accessor<F, C, Os>::accessibility_func_name ...;
+  };
+  template <class F, class C, class R, class... Args>
+  struct accessor<F, C, R(Args...) cv ref noex> {
+    R accessibility_func_name(Args... args) cv ref noex {
+      return pro::proxy_invoke<C, R(Args...) cv ref noex>(pro::access_proxy<F>(SELF), std::forward<Args>(args)...);
+    }
+  };
+}
+```
+
+## Example
+
+```cpp
+#include <iostream>
+#include <string>
+
+#include "proxy.h"
+
+PRO_DEF_FREE_AS_MEM_DISPATCH(FreeToString, std::to_string, ToString);
+
+struct Stringable : pro::facade_builder
+    ::add_convention<FreeToString, std::string()>
+    ::build {};
+
+int main() {
+  pro::proxy<Stringable> p = pro::make_proxy<Stringable>(123);
+  std::cout << p->ToString() << "\n";  // Prints: "123"
+}
+```
+
+## See Also
+
+- [macro `PRO_DEF_FREE_DISPATCH`](PRO_DEF_FREE_DISPATCH.md)
+- [alias template `basic_facade_builder::add_convention`](basic_facade_builder/add_convention.md)

docs/PRO_DEF_FREE_DISPATCH.md

@@ -39,7 +39,7 @@ struct dispatch_name {
       return pro::proxy_invoke<C, R(Args...) cv ref noex>(pro::access_proxy<F>(SELF), std::forward<Args>(args)...);
     }
   };
-};
+}
 ```
 
 ## Example
@@ -65,4 +65,5 @@ int main() {
 ## See Also
 
 - [macro `PRO_DEF_MEM_DISPATCH`](PRO_DEF_MEM_DISPATCH.md)
+- [macro `PRO_DEF_FREE_AS_MEM_DISPATCH`](PRO_DEF_FREE_AS_MEM_DISPATCH.md)
 - [alias template `basic_facade_builder::add_convention`](basic_facade_builder/add_convention.md)

docs/PRO_DEF_MEM_DISPATCH.md

@@ -42,7 +42,7 @@ struct dispatch_name {
       return pro::proxy_invoke<C, R(Args...) cv ref noex>(pro::access_proxy<F>(SELF), std::forward<Args>(args)...);
     }
   };
-};
+}
 ```
 
 ## Example

docs/PRO_DEF_WEAK_DISPATCH.md

@@ -21,7 +21,7 @@ struct dispatch_name : existing_dispatch {
       requires(requires { default_func_name(std::forward<Args>(args)...); }) {
     return default_func_name(std::forward<Args>(args)...);
   }
-};
+}
 ```
 
 ## Notes

docs/ProBasicReflection.md

@@ -0,0 +1,13 @@
+# Named requirements: *ProBasicReflection*
+
+A type `R` meets the *ProBasicReflection* requirements if the following expressions are well-formed and have the specified semantics.
+
+| Expressions                  | Semantics                                                    |
+| ---------------------------- | ------------------------------------------------------------ |
+| `R::is_direct`               | A [core constant expression](https://en.cppreference.com/w/cpp/language/constant_expression) of type `bool`, specifying whether the reflection applies to a pointer type itself (`true`), or the element type of a pointer type (`false`). |
+| `typename R::reflector_type` | A [trivial type](https://en.cppreference.com/w/cpp/named_req/TrivialType) that defines the data structure reflected from the type. |
+
+## See Also
+
+- [*ProBasicFacade* requirements](ProBasicFacade.md)
+- [*ProReflection* requirements](ProReflection.md)

docs/ProReflection.md

@@ -1,10 +1,10 @@
 # Named requirements: *ProReflection*
 
-A type `R` meets the *ProReflection* requirements of a type `P` if the following expressions are well-formed and have the specified semantics.
+A type `R` meets the *ProReflection* requirements of a type `P` if `R` meets the [*ProBasicReflection* requirements](ProBasicReflection.md), and the following expressions are well-formed and have the specified semantics (let `T` be `P` when `R::is_direct` is `true`, or otherwise `typename std::pointer_traits<P>::element_type`).
 
-| Expressions                | Semantics                                                    |
-| -------------------------- | ------------------------------------------------------------ |
-| `R{std::in_place_type<P>}` | A [core constant expression](https://en.cppreference.com/w/cpp/language/constant_expression) that constructs a value of type `R`, reflecting implementation-defined metadata of type `P`. |
+| Expressions                                         | Semantics                                                    |
+| --------------------------------------------------- | ------------------------------------------------------------ |
+| `typename R::reflector_type{std::in_place_type<T>}` | A [core constant expression](https://en.cppreference.com/w/cpp/language/constant_expression) that constructs a value of type `typename R::reflector_type`, reflecting implementation-defined metadata of type `T`. |
 
 ## See Also
 

docs/basic_facade_builder.md

@@ -36,7 +36,7 @@ using facade_builder = basic_facade_builder<std::tuple<>, std::tuple<>,
 | Name                                                         | Description                                                  |
 | ------------------------------------------------------------ | ------------------------------------------------------------ |
 | [`add_convention`<br />`add_indirect_convention`<br />`add_direct_convention`](basic_facade_builder/add_convention.md) | Adds a convention to the template parameters                 |
-| [`add_reflection`](basic_facade_builder/add_reflection.md)   | Adds a reflection to the template parameters                 |
+| [`add_reflection`<br />`add_indirect_reflection`<br />`add_direct_reflection`](basic_facade_builder/add_reflection.md) | Adds a reflection to the template parameters                 |
 | [`add_facade`](basic_facade_builder/add_facade.md)           | Adds a facade to the template parameters                     |
 | [`restrict_layout`](basic_facade_builder/restrict_layout.md) | Specifies maximum `max_size` and `max_align` of `C` in the template parameters |
 | [`support_copy`](basic_facade_builder/support_copy.md)       | Specifies minimum `copyability` of `C` in the template parameters |

docs/basic_facade_builder/add_convention.md

@@ -18,12 +18,12 @@ The alias templates `add_convention`, `add_indirect_convention`, and `add_direct
   - `IC::is_direct` is `false`.
   - `typename IC::dispatch_type` is `D`.
   - `typename IC::overload_types` is a [tuple-like](https://en.cppreference.com/w/cpp/utility/tuple/tuple-like) type of distinct types in `Os`.
-  - `typename IC::template accessor<F>` is `typename D::template accessor<F, IC, Os...>`.
+  - `typename IC::template accessor<F>` is `typename D::template accessor<F, IC, Os...>` if applicable.
 - `add_direct_convention` merges an implementation-defined convention type `IC` into `Cs`, where:
   - `IC::is_direct` is `true`.
   - `typename IC::dispatch_type` is `D`.
   - `typename IC::overload_types` is a [tuple-like](https://en.cppreference.com/w/cpp/utility/tuple/tuple-like) type of distinct types in `Os`.
-  - `typename IC::template accessor<F>` is `typename D::template accessor<F, IC, Os...>`.
+  - `typename IC::template accessor<F>` is `typename D::template accessor<F, IC, Os...>` if applicable.
 
 When `Cs` already contains a convention type `IC2` where `IC2::is_direct == IC::is_direct && std::is_same_v<typename IC2::dispatch_type, typename IC::dispatch_type>` is `true`, `Os` merges with `typename IC2::overload_types` and removes duplicates, and `std::tuple_size_v<Cs>` shall not change.
 

docs/basic_facade_builder/add_reflection.md

@@ -2,14 +2,32 @@
 
 ```cpp
 template <class R>
-using add_reflection = basic_facade_builder</* see below */>;
+using add_reflection = add_indirect_reflection<R>;
+
+template <class R>
+using add_indirect_reflection = basic_facade_builder</* see below */>;
+
+template <class R>
+using add_direct_reflection = basic_facade_builder</* see below */>;
 ```
 
-The alias template `add_reflection` of `basic_facade_builder<Cs, Rs, C>` incorporates reflection types (see [named requirements: *ProReflection*](../ProReflection.md)) into the template parameters. It merges `R` into `Rs` if `Rs` does not already contain `R`.
+The alias templates `add_reflection`, `add_indirect_reflection` and `add_direct_reflection` of `basic_facade_builder<Cs, Rs, C>` add reflection types to the template parameters. Specifically,
+
+- `add_reflection` is equivalent to `add_indirect_reflection`.
+- `add_indirect_reflection` merges an implementation-defined reflection type `R2` into `Rs`, where:
+  - `R2::is_direct` is `false`.
+  - `typename R2::reflector_type` is `R`.
+  - `typename R2::template accessor<F>` is `typename R2::template accessor<F, R2>` if applicable.
+- `add_direct_reflection` merges an implementation-defined reflection type `R2` into `Rs`, where:
+  - `R2::is_direct` is `true`.
+  - `typename R2::reflector_type` is `R`.
+  - `typename R2::template accessor<F>` is `typename R2::template accessor<F, R2>` if applicable.
+
+When `Rs` already contains `R2`, the template parameters shall not change.
 
 ## Notes
 
-Adding duplicate reflection types is well-defined, whether done directly via `add_reflection` or indirectly via [`add_facade`](add_facade.md). This process does not affect the behavior of [`build`](build.md) at either compile-time or runtime.
+Adding duplicate reflection types is well-defined, whether done directly via `add_reflection`, `add_indirect_reflection`, `add_direct_reflection`, or indirectly via [`add_facade`](add_facade.md). This process does not affect the behavior of [`build`](build.md) at either compile-time or runtime.
 
 ## Example
 
@@ -19,36 +37,33 @@ Adding duplicate reflection types is well-defined, whether done directly via `ad
 
 #include "proxy.h"
 
-class DebugReflection {
+class RttiReflector {
  public:
-  template <class P>
-  constexpr explicit DebugReflection(std::in_place_type_t<P>)
-      : pointer_type_(typeid(P)),
-        element_type_(typeid(typename std::pointer_traits<P>::element_type)) {}
+  template <class T>
+  constexpr explicit RttiReflector(std::in_place_type_t<T>) : type_(typeid(T)) {}
 
-  void PrintDebugInfo() const {
-    std::cout << "Pointer type: " << pointer_type_.name() << "\n";
-    std::cout << "Element type: " << element_type_.name() << "\n";
-  }
+  template <class F, class R>
+  struct accessor {
+    const char* GetTypeName() const noexcept {
+      const RttiReflector& self = pro::proxy_reflect<R>(pro::access_proxy<F>(*this));
+      return self.type_.name();
+    }
+  };
 
  private:
-  const std::type_info& pointer_type_;
-  const std::type_info& element_type_;
+  const std::type_info& type_;
 };
 
-struct TestFacade : pro::facade_builder
-    ::add_reflection<DebugReflection>
+struct RttiAware : pro::facade_builder
+    ::add_direct_reflection<RttiReflector>
+    ::add_indirect_reflection<RttiReflector>
     ::build {};
 
 int main() {
-  pro::proxy<TestFacade> p1 = std::make_shared<int>(123);
-  pro::proxy_reflect<DebugReflection>(p1).PrintDebugInfo();  // Prints: "Pointer type: St10shared_ptrIiE"
-                                                             //         "Element type: i" (assuming GCC)
-
-  double v = 3.14;
-  pro::proxy<TestFacade> p2 = &v;
-  pro::proxy_reflect<DebugReflection>(p2).PrintDebugInfo();  // Prints: "Pointer type: Pd"
-                                                             //         "Element type: d" (assuming GCC)
+  int a = 123;
+  pro::proxy<RttiAware> p = &a;
+  std::cout << p.GetTypeName() << "\n";  // Prints: "Pi" (assuming GCC)
+  std::cout << p->GetTypeName() << "\n";  // Prints: "i" (assuming GCC)
 }
 ```
 

docs/proxy.md

@@ -7,7 +7,7 @@ class proxy;
 
 Class template `proxy` is a general-purpose polymorphic wrapper for C++ objects. Unlike other polymorphic wrappers in the C++ standard (e.g., [`std::function`](https://en.cppreference.com/w/cpp/utility/functional/function), [`std::move_only_function`](https://en.cppreference.com/w/cpp/utility/functional/move_only_function), [`std::any`](https://en.cppreference.com/w/cpp/utility/any), etc.), `proxy` is based on pointer semantics. It supports flexible lifetime management without runtime [garbage collection (GC)](https://en.wikipedia.org/wiki/Garbage_collection_(computer_science)) at runtime, and offers best-in-class code generation quality, extendibility and accessibility.
 
-To instantiate `proxy<F>`, `F` shall model [concept `facade`](facade.md). As per `facade<F>`, `typename F::convention_types` shall be a [tuple-like](https://en.cppreference.com/w/cpp/utility/tuple/tuple-like) type containing any number of distinct types `Cs`. For each type `C` in `Cs`, if `C` meets the [*ProAccessible* requirements](ProAccessible.md) of `F`, `typename C::template accessor<F>` is inherited by `proxy<F>` when `C::is_direct` is `true`. Otherwise, it is inherited by the return type of [`operator*`](proxy/indirection.md) when `C::is_direct` is `false`. Implementation of accessors can call [`access_proxy`](access_proxy.md) to access the `proxy` object. It is recommended to use [`facade_builder`](basic_facade_builder.md) to define a facade type.
+To instantiate `proxy<F>`, `F` shall model [concept `facade`](facade.md). As per `facade<F>`, `typename F::convention_types` shall be a [tuple-like](https://en.cppreference.com/w/cpp/utility/tuple/tuple-like) type containing any number of distinct types `Cs`, and `typename F::reflection_types` shall be a [tuple-like](https://en.cppreference.com/w/cpp/utility/tuple/tuple-like) type containing any number of distinct types `Rs`. For each type `T` in `Cs` or `Rs`, if `T` meets the [*ProAccessible* requirements](ProAccessible.md) of `F`, `typename T::template accessor<F>` is inherited by `proxy<F>` when `T::is_direct` is `true`. Otherwise, it is inherited by the return type of [`operator*`](proxy/indirection.md) when `T::is_direct` is `false`. Implementation of accessors can call [`access_proxy`](access_proxy.md) to access the `proxy` object. It is recommended to use [`facade_builder`](basic_facade_builder.md) to define a facade type.
 
 Any instance of `proxy<F>` at any given point in time either *contains a value* or *does not contain a value*. If a `proxy<F>` *contains a value*, the type of the value shall be a pointer type `P`  where [`proxiable<P, F>`](proxiable.md) is `true`, and the value is guaranteed to be allocated as part of the `proxy` object footprint, i.e. no dynamic memory allocation occurs. However, `P` may allocate during its construction, depending on its implementation.
 

docs/proxy_reflect.md

@@ -2,10 +2,10 @@
 
 ```cpp
 template <class R, class F>
-const R& proxy_reflect(const proxy<F>& p) noexcept;
+/* see below */ proxy_reflect(const proxy<F>& p) noexcept;
 ```
 
-Retrieves a value of type `R` constructed from [`std::in_place_type<P>`](https://en.cppreference.com/w/cpp/utility/in_place), where `P` is the type of the contained value of `p`. `R` is required to be defined in `typename F::reflection_types`. The behavior is undefined if `p` does not contain a value.
+Let `P` be the type of the contained value of `p`. Retrieves a value of type `const typename R::reflector_type&` constructed from [`std::in_place_type<T>`](https://en.cppreference.com/w/cpp/utility/in_place), where `T` is `P` when `R::is_direct` is `true`, or otherwise `T` is `typename std::pointer_traits<P>::element_type` when `R::is_direct` is `false`. `R` is required to be defined in `typename F::reflection_types`. The behavior is undefined if `p` does not contain a value.
 
 The reference obtained from `proxy_reflect()` may be invalidated if `p` is subsequently modified.
 
@@ -22,24 +22,34 @@ This function is useful when only metadata deduced from a type is needed. While
 
 #include "proxy.h"
 
-struct TraitsRefl {
-  template <class P>
-  constexpr explicit TraitsRefl(std::in_place_type_t<P>)
-      : Copyable(std::is_copy_constructible_v<P>) {}
-
-  const bool Copyable;
+class CopyabilityReflector {
+ public:
+  template <class T>
+  constexpr explicit CopyabilityReflector(std::in_place_type_t<T>)
+      : copyable_(std::is_copy_constructible_v<T>) {}
+
+  template <class F, class R>
+  struct accessor {
+    bool IsCopyable() const noexcept {
+      const CopyabilityReflector& self = pro::proxy_reflect<R>(pro::access_proxy<F>(*this));
+      return self.copyable_;
+    }
+  };
+
+ private:
+  bool copyable_;
 };
 
-struct TestFacade : pro::facade_builder
-    ::add_reflection<TraitsRefl>
+struct CopyabilityAware : pro::facade_builder
+    ::add_direct_reflection<CopyabilityReflector>
     ::build {};
 
 int main() {
-  pro::proxy<TestFacade> p1 = std::make_unique<int>();
-  std::cout << std::boolalpha << pro::proxy_reflect<TraitsRefl>(p1).Copyable << "\n";  // Prints: "false"
+  pro::proxy<CopyabilityAware> p1 = std::make_unique<int>();
+  std::cout << std::boolalpha << p1.IsCopyable() << "\n";  // Prints: "false"
 
-  pro::proxy<TestFacade> p2 = std::make_shared<int>();
-  std::cout << pro::proxy_reflect<TraitsRefl>(p2).Copyable << "\n";  // Prints: "true"
+  pro::proxy<CopyabilityAware> p2 = std::make_shared<int>();
+  std::cout << p2.IsCopyable() << "\n";  // Prints: "true"
 }
 ```