Support range-like non-awaitable coroutines

include/trompeloeil/coro.hpp

@@ -14,13 +14,18 @@
 #ifndef TROMPELOEIL_CORO_HPP
 #define TROMPELOEIL_CORO_HPP
 
+#if __cplusplus < 202002L
+#  error "C++20 is required"
+#endif
+
 #if defined(__cpp_impl_coroutine)
 #  define TROMPELOEIL_COROUTINES_SUPPORTED 1
 #else
 #  error "Coroutines are not supported by this compiler"
 #endif
 
 #ifdef TROMPELOEIL_COROUTINES_SUPPORTED
+#include <ranges>
 
 #ifndef TROMPELOEIL_MOCK_HPP_
 #include "mock.hpp"
@@ -45,14 +50,22 @@ namespace trompeloeil
   {
     static auto func()
     {
-      if constexpr (requires {std::declval<T>().operator co_await();})
+      if constexpr (requires(T coro){ coro.operator co_await(); })
       {
         return type_wrapper<decltype(std::declval<T>().operator co_await().await_resume())>{};
       }
       else
+      if constexpr (requires(T coro){ coro.await_resume(); })
       {
         return type_wrapper<decltype(std::declval<T>().await_resume())>{};
       }
+      else
+      {
+        static_assert(
+            std::ranges::input_range<T>,
+            "non-awaitable coroutine shall be a range");
+        return type_wrapper<std::ranges::range_value_t<T>>{};
+      }
     }
     using type = typename decltype(func())::type;
   };

test/test_co_mock.cpp

@@ -25,6 +25,11 @@
 #include "test_reporter.hpp"
 #include <optional>
 
+#include <version>
+#ifdef __cpp_lib_generator
+#include <generator>
+#endif
+
 using trompeloeil::_;
 
 namespace {
@@ -35,6 +40,10 @@ namespace {
     MAKE_MOCK0 (voidret, coro::task<void>());
     MAKE_MOCK1 (unique, coro::task<iptr>(iptr));
     MAKE_MOCK0 (gen, coro::generator<int>());
+
+#ifdef __cpp_lib_generator
+    MAKE_MOCK0 (stdgen, std::generator<int>());
+#endif // __cpp_lib_generator
   };
 }
 
@@ -198,4 +207,46 @@ TEST_CASE_METHOD(
     REQUIRE(v == 3);
     REQUIRE(reports.empty());
 }
+
+#ifdef __cpp_lib_generator
+TEST_CASE_METHOD(
+  Fixture,
+  "CO_YIELD with std::generator",
+  "[coro]")
+{
+  co_mock m;
+  REQUIRE_CALL(m, stdgen())
+      .CO_YIELD(5)
+      .CO_YIELD(8)
+      .CO_YIELD(3)
+      .CO_YIELD(0)
+      .CO_RETURN();
+
+  auto gen = m.stdgen();
+
+  SECTION("as iterator")
+  {
+    auto it = std::ranges::begin(gen);
+    REQUIRE(*it == 5);
+    ++it;
+    REQUIRE(it != std::ranges::end(gen));
+    REQUIRE(*it == 8);
+    ++it;
+    REQUIRE(it != std::ranges::end(gen));
+    REQUIRE(*it == 3);
+    ++it;
+    REQUIRE(it != std::ranges::end(gen));
+    REQUIRE(*it == 0);
+    ++it;
+    REQUIRE(it == std::ranges::end(gen));
+  }
+
+  SECTION("as range")
+  {
+    REQUIRE(std::ranges::equal(gen, std::array{5, 8, 3, 0}));
+  }
+
+  REQUIRE(reports.empty());
+}
+#endif // __cpp_lib_generator
 #endif