Revise design of conversion_dispatch

.github/workflows/bvt-gcc.yml

@@ -15,27 +15,13 @@ jobs:
 
     - name: install gcc
       run: |
-        sudo apt install -y gcc-11 g++-11 gcc-12 g++-12 gcc-13 g++-13 gcc-14 g++-14
+        sudo apt install -y gcc-13 g++-13 gcc-14 g++-14
 
     - name: check compiler versions
       run: |
-        g++-11 --version
-        g++-12 --version
         g++-13 --version
         g++-14 --version
 
-    - name: build and run test with gcc 11
-      run: |
-        cmake -B build-gcc-11 -DCMAKE_C_COMPILER=gcc-11 -DCMAKE_CXX_COMPILER=g++-11 -DCMAKE_BUILD_TYPE=Release
-        cmake --build build-gcc-11 -j
-        ctest --test-dir build-gcc-11 -j
-
-    - name: build and run test with gcc 12
-      run: |
-        cmake -B build-gcc-12 -DCMAKE_C_COMPILER=gcc-12 -DCMAKE_CXX_COMPILER=g++-12 -DCMAKE_BUILD_TYPE=Release
-        cmake --build build-gcc-12 -j
-        ctest --test-dir build-gcc-12 -j
-
     - name: build and run test with gcc 13
       run: |
         cmake -B build-gcc-13 -DCMAKE_C_COMPILER=gcc-13 -DCMAKE_CXX_COMPILER=g++-13 -DCMAKE_BUILD_TYPE=Release

README.md

@@ -166,9 +166,9 @@ The "Proxy" library is a self-contained solution for runtime polymorphism in C++
 
 | Family     | Minimum version | Required flags |
 | ---------- | --------------- | -------------- |
-| GCC        | 11.2            | -std=c++20     |
+| GCC        | 13.1            | -std=c++20     |
 | Clang      | 15.0.0          | -std=c++20     |
-| MSVC       | 19.30           | /std:c++20     |
+| MSVC       | 19.31           | /std:c++20     |
 | NVIDIA HPC | 24.1            | -std=c++20     |
 
 ## Build and Run Tests with CMake

docs/PRO_DEF_FREE_AS_MEM_DISPATCH.md

@@ -32,7 +32,7 @@ struct dispatch_name {
     accessor() = delete;
   };
   template <class F, class C, class... Os>
-      requires(sizeof...(Os) > 1u && (std::is_trivial_v<accessor<F, C, Os>> && ...))
+      requires(sizeof...(Os) > 1u && (std::is_constructible_v<accessor<F, C, Os>> && ...))
   struct accessor<F, C, Os...> : accessor<F, C, Os>... {
     using accessor<F, C, Os>::accessibility_func_name ...;
   };

docs/PRO_DEF_FREE_DISPATCH.md

@@ -31,7 +31,7 @@ struct dispatch_name {
     accessor() = delete;
   };
   template <class F, class C, class... Os>
-      requires(sizeof...(Os) > 1u && (std::is_trivial_v<accessor<F, C, Os>> && ...))
+      requires(sizeof...(Os) > 1u && (std::is_constructible_v<accessor<F, C, Os>> && ...))
   struct accessor<F, C, Os...> : accessor<F, C, Os>... {};
   template <class F, class C, class R, class... Args>
   struct accessor<F, C, R(Args...) cv ref noex> {

docs/PRO_DEF_MEM_DISPATCH.md

@@ -32,7 +32,7 @@ struct dispatch_name {
     accessor() = delete;
   };
   template <class F, class C, class... Os>
-      requires(sizeof...(Os) > 1u && (std::is_trivial_v<accessor<F, C, Os>> && ...))
+      requires(sizeof...(Os) > 1u && (std::is_constructible_v<accessor<F, C, Os>> && ...))
   struct accessor<F, C, Os...> : accessor<F, C, Os>... {
     using accessor<F, C, Os>::accessibility_func_name ...;
   };

docs/basic_facade_builder/add_convention.md

@@ -49,8 +49,7 @@ struct BasicStringable : pro::facade_builder
 struct Stringable : pro::facade_builder
     ::add_facade<BasicStringable>
     ::support_copy<pro::constraint_level::nontrivial>
-    ::add_direct_convention<pro::conversion_dispatch<pro::proxy<BasicStringable>>,
-        pro::proxy<BasicStringable>() &&>
+    ::add_direct_convention<pro::conversion_dispatch, pro::proxy<BasicStringable>() &&>
     ::build {};
 
 int main() {

docs/explicit_conversion_dispatch.md

@@ -0,0 +1,44 @@
+# Class `explicit_conversion_dispatch`
+
+```cpp
+class explicit_conversion_dispatch;
+
+using conversion_dispatch = explicit_conversion_dispatch;
+```
+
+Class `explicit_conversion_dispatch` models a [dispatch](ProDispatch.md) type for explicit type conversion expressions. It meets the [*ProAccessible* requirements](ProAccessible.md) of applicable types. `conversion_dispatch` is an alias of `explicit_conversion_dispatch`.
+
+## Member Functions
+
+| Name                                                         | Description                                         |
+| ------------------------------------------------------------ | --------------------------------------------------- |
+| (constructor) [nothrow]                                      | constructs an `explicit_conversion_dispatch` object |
+| [`operator()`](explicit_conversion_dispatch/operator_call.md) | invokes the dispatch                                |
+
+## Member Types
+
+| Name                                                   | Description                       |
+| ------------------------------------------------------ | --------------------------------- |
+| [`accessor`](explicit_conversion_dispatch/accessor.md) | provides accessibility to `proxy` |
+
+## Example
+
+```cpp
+#include <iostream>
+
+#include "proxy.h"
+
+struct IntConvertible : pro::facade_builder
+    ::add_convention<pro::conversion_dispatch, int() const>
+    ::build {};
+
+int main() {
+  pro::proxy<IntConvertible> p = pro::make_proxy<IntConvertible, short>(123);  // p holds a short
+  std::cout << static_cast<int>(*p) << "\n";  // Prints: "123"
+}
+```
+
+## See Also
+
+- [class `implicit_conversion_dispatch`](implicit_conversion_dispatch.md)
+- [class template `operator_dispatch`](operator_dispatch.md)

docs/explicit_conversion_dispatch/accessor.md

@@ -0,0 +1,30 @@
+# Class template `explicit_conversion_dispatch::accessor`
+
+```cpp
+// (1)
+template <class F, class C, class... Os>
+struct accessor {
+  accessor() = delete;
+};
+
+// (2)
+template <class F, class C, class... Os>
+    requires(sizeof...(Os) > 1u && (std::is_constructible_v<accessor<F, C, Os>> && ...))
+struct accessor<F, C, Os...> : accessor<F, C, Os>... {
+  using accessor<F, C, Os>::operator return-type-of<Os>...;
+};
+
+// (3)
+template <class F, class C>
+struct accessor<F, C, T() cv ref noex> {
+  explicit operator T() cv ref noex;
+};
+```
+
+Let `SELF` be `std::forward<accessor cv ref>(*this)`.
+
+`(1)` The default implementation of `accessor` is not constructible.
+
+`(2)` When `sizeof...(Os)` is greater than `1`, and `accessor<F, C, Os>...` are default-constructible, inherits all `accessor<F, C, Os>...` types and `using` their `operator return-type-of<Os>`. `return-type-of<O>` denotes the *return type* of the overload type `O`.
+
+`(3)` When `sizeof...(Os)` is `1` and the only type `O` in `Os` is `T() cv ref noex`, provides an explicit  `operator T()` with the same *cv ref noex* specifiers. `accessor::operator T()` is equivalent to `return proxy_invoke<C, T() cv ref noex>(access_proxy<F>(SELF))`.

docs/explicit_conversion_dispatch/operator_call.md

@@ -0,0 +1,8 @@
+# `explicit_conversion_dispatch::operator()`
+
+```cpp
+template <class T>
+/* see below */ operator()(T&& value) noexcept;
+```
+
+Returns a value that is implicitly convertible to any type `U` with expression `U{std::forward<T>(value)}` when `T` is explicitly convertible to type `U`.

docs/implicit_conversion_dispatch.md

@@ -0,0 +1,57 @@
+# Class `implicit_conversion_dispatch`
+
+```cpp
+class explicit_conversion_dispatch;
+```
+
+Class `implicit_conversion_dispatch` models a [dispatch](ProDispatch.md) type for implicit type conversion expressions. It meets the [*ProAccessible* requirements](ProAccessible.md) of applicable types.
+
+## Member Functions
+
+| Name                                                         | Description                                         |
+| ------------------------------------------------------------ | --------------------------------------------------- |
+| (constructor) [nothrow]                                      | constructs an `implicit_conversion_dispatch` object |
+| [`operator()`](implicit_conversion_dispatch/operator_call.md) | invokes the dispatch                                |
+
+## Member Types
+
+| Name                                                   | Description                       |
+| ------------------------------------------------------ | --------------------------------- |
+| [`accessor`](implicit_conversion_dispatch/accessor.md) | provides accessibility to `proxy` |
+
+## Example
+
+```cpp
+#include <iomanip>
+#include <iostream>
+
+#include "proxy.h"
+
+struct Runnable : pro::facade_builder
+    ::add_convention<pro::operator_dispatch<"()">, void()>
+    ::build {};
+
+struct CopyableRunnable : pro::facade_builder
+    ::support_copy<pro::constraint_level::nontrivial>
+    ::add_facade<Runnable>
+    ::add_direct_convention<pro::implicit_conversion_dispatch,
+        pro::proxy<Runnable>() const&, pro::proxy<Runnable>() &&>
+    ::build {};
+
+int main() {
+  pro::proxy<CopyableRunnable> p1 = pro::make_proxy<CopyableRunnable>(
+      [] { std::cout << "Lambda expression invoked\n"; });
+  auto p2 = p1;  // Copy construction
+  pro::proxy<Runnable> p3 = p2;  // Implicit conversion via const reference of pro::proxy<CopyableRunnable>
+  std::cout << std::boolalpha << p2.has_value() << "\n";  // Prints: "true"
+  // auto p4 = p3;  // Won't compile because pro::proxy<Runnable> is not copy-constructible
+  pro::proxy<Runnable> p5 = std::move(p2);  // Implicit conversion via rvalue reference of pro::proxy<CopyableRunnable>
+  std::cout << p2.has_value() << "\n";  // Prints: "false"
+  (*p5)();  // Prints: "Lambda expression invoked"
+}
+```
+
+## See Also
+
+- [class `explicit_conversion_dispatch`](explicit_conversion_dispatch.md)
+- [class template `operator_dispatch`](operator_dispatch.md)

docs/implicit_conversion_dispatch/accessor.md

@@ -0,0 +1,30 @@
+# Class template `implicit_conversion_dispatch::accessor`
+
+```cpp
+// (1)
+template <class F, class C, class... Os>
+struct accessor {
+  accessor() = delete;
+};
+
+// (2)
+template <class F, class C, class... Os>
+    requires(sizeof...(Os) > 1u && (std::is_constructible_v<accessor<F, C, Os>> && ...))
+struct accessor<F, C, Os...> : accessor<F, C, Os>... {
+  using accessor<F, C, Os>::operator return-type-of<Os>...;
+};
+
+// (3)
+template <class F, class C>
+struct accessor<F, C, T() cv ref noex> {
+  operator T() cv ref noex;
+};
+```
+
+Let `SELF` be `std::forward<accessor cv ref>(*this)`.
+
+`(1)` The default implementation of `accessor` is not constructible.
+
+`(2)` When `sizeof...(Os)` is greater than `1`, and `accessor<F, C, Os>...` are default-constructible, inherits all `accessor<F, C, Os>...` types and `using` their `operator return-type-of<Os>`. `return-type-of<O>` denotes the *return type* of the overload type `O`.
+
+`(3)` When `sizeof...(Os)` is `1` and the only type `O` in `Os` is `T() cv ref noex`, provides an implicit  `operator T()` with the same *cv ref noex* specifiers. `accessor::operator T()` is equivalent to `return proxy_invoke<C, T() cv ref noex>(access_proxy<F>(SELF))`.

docs/implicit_conversion_dispatch/operator_call.md

@@ -0,0 +1,8 @@
+# `implicit_conversion_dispatch::operator()`
+
+```cpp
+template <class T>
+T&& operator()(T&& value) noexcept;
+```
+
+Returns `std::forward<T>(value)`.

docs/operator_dispatch.md

@@ -104,7 +104,7 @@ Let `self` be the operand of [`proxy`](proxy.md), and `other` and `others...` be
 
 | Name                                               | Description                              |
 | -------------------------------------------------- | ---------------------------------------- |
-| (constructor) [trivial]                            | constructs an `operator_dispatch` object |
+| (constructor) [nothrow]                            | constructs an `operator_dispatch` object |
 | [`operator()`](operator_dispatch/operator_call.md) | invokes the dispatch                     |
 
 ## Member Types