From 1e3f11ff6dce092af6157b18545b3534d7e72ac3 Mon Sep 17 00:00:00 2001
From: phosit <phosit@wildfiregames.com>
Date: Sun, 19 Nov 2023 21:04:40 +0000
Subject: [PATCH] Disallow conversion in Future return

Differential Revision: https://code.wildfiregames.com/D4812
This was SVN commit r27947.
---
 source/ps/Future.h            |  5 +++--
 source/ps/tests/test_Future.h | 16 ++++------------
 2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/source/ps/Future.h b/source/ps/Future.h
index 361578e357..6c56216e4e 100644
--- a/source/ps/Future.h
+++ b/source/ps/Future.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2022 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -280,7 +280,8 @@ template<typename ResultType>
 template<typename T>
 PackagedTask<ResultType> Future<ResultType>::Wrap(T&& func)
 {
-	static_assert(std::is_convertible_v<std::invoke_result_t<T>, ResultType>, "The return type of the wrapped function cannot be converted to the type of the Future.");
+	static_assert(std::is_same_v<std::invoke_result_t<T>, ResultType>,
+		"The return type of the wrapped function is not the same as the type the Future expects.");
 	m_SharedState = std::make_shared<SharedState>(std::move(func));
 	return PackagedTask<ResultType>(m_SharedState);
 }
diff --git a/source/ps/tests/test_Future.h b/source/ps/tests/test_Future.h
index 46042941ab..7858601000 100644
--- a/source/ps/tests/test_Future.h
+++ b/source/ps/tests/test_Future.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2021 Wildfire Games.
+/* Copyright (C) 2023 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -54,14 +54,6 @@ public:
 			TS_ASSERT_EQUALS(future.Get(), 1);
 		}
 
-		// Convertible type.
-		{
-			Future<int> future;
-			std::function<void()> task = future.Wrap([]() -> u8 { return 1; });
-			task();
-			TS_ASSERT_EQUALS(future.Get(), 1);
-		}
-
 		static int destroyed = 0;
 		// No trivial constructor or destructor. Also not copiable.
 		struct NonDef
@@ -80,21 +72,21 @@ public:
 		TS_ASSERT_EQUALS(destroyed, 0);
 		{
 			Future<NonDef> future;
-			std::function<void()> task = future.Wrap([]() { return 1; });
+			std::function<void()> task = future.Wrap([]() { return NonDef{1}; });
 			task();
 			TS_ASSERT_EQUALS(future.Get().value, 1);
 		}
 		TS_ASSERT_EQUALS(destroyed, 1);
 		{
 			Future<NonDef> future;
-			std::function<void()> task = future.Wrap([]() { return 1; });
+			std::function<void()> task = future.Wrap([]() { return NonDef{1}; });
 		}
 		TS_ASSERT_EQUALS(destroyed, 1);
 		/**
 		 * TODO: find a way to test this
 		{
 			Future<NonDef> future;
-			std::function<void()> task = future.Wrap([]() { return 1; });
+			std::function<void()> task = future.Wrap([]() { return NonDef{1}; });
 			future.CancelOrWait();
 			TS_ASSERT_THROWS(future.Get(), const Future<NonDef>::BadFutureAccess&);
 		}