Merge pull request llvm#38 from Yaraslaut/example_universal_formatter

Add test for universal_formatter

Author: katzdm

libcxx/test/std/experimental/reflection/p2996-ex-universal-formatter.sh.cpp

@@ -0,0 +1,91 @@
+//===----------------------------------------------------------------------===//
+//
+// Copyright 2024 Bloomberg Finance L.P.
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03 || c++11 || c++14 || c++17 || c++20
+// ADDITIONAL_COMPILE_FLAGS: -freflection
+// ADDITIONAL_COMPILE_FLAGS: -Wno-inconsistent-missing-override
+
+// <experimental/reflection>
+//
+// [reflection]
+//
+// RUN: %{build}
+// RUN: %{exec} %t.exe > %t.stdout
+
+#include <experimental/meta>
+#include <format>
+#include <print>
+
+namespace __impl {
+  template<auto... vals>
+  struct replicator_type {
+    template<typename F>
+      constexpr void operator>>(F body) const {
+        (body.template operator()<vals>(), ...);
+      }
+  };
+
+  template<auto... vals>
+  replicator_type<vals...> replicator = {};
+}
+
+template<typename R>
+consteval auto expand(R range) {
+  std::vector<std::meta::info> args;
+  for (auto r : range) {
+    args.push_back(reflect_value(r));
+  }
+  return substitute(^__impl::replicator, args);
+}
+
+struct universal_formatter {
+  constexpr auto parse(auto& ctx) { return ctx.begin(); }
+
+  template <typename T>
+  auto format(T const& t, auto& ctx) const {
+    auto out = std::format_to(ctx.out(), "{}{{", name_of(^T));
+
+    auto delim = [first=true, &out]() mutable {
+      if (!first) {
+        *out++ = ',';
+        *out++ = ' ';
+      }
+      first = false;
+    };
+
+    [: expand(bases_of(^T)) :] >> [&]<auto base>{
+        delim();
+        out = std::format_to(out, "{}", (typename [: type_of(base) :] const&)(t));
+    };
+
+    [: expand(nonstatic_data_members_of(^T)) :] >> [&]<auto mem>{
+      delim();
+      out = std::format_to(out, ".{}={}", name_of(mem), t.[:mem:]);
+    };
+
+    *out++ = '}';
+    return out;
+  }
+};
+
+struct B { int m0 = 0; };
+struct X : B { int m1 = 1; };
+struct Y : B { int m2 = 2; };
+class Z : public X, private Y { int m3 = 3; int m4 = 4; };
+
+template <> struct std::formatter<B> : universal_formatter { };
+template <> struct std::formatter<X> : universal_formatter { };
+template <> struct std::formatter<Y> : universal_formatter { };
+template <> struct std::formatter<Z> : universal_formatter { };
+
+int main() {
+  // RUN: grep "Z{X{B{.m0=0}, .m1=1}, Y{B{.m0=0}, .m2=2}, .m3=3, .m4=4}" %t.stdout | wc -l
+  std::println("{}", Z());
+}