From 6707989cd529be0e1441b0fcdd6863f9817103bb Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Fri, 14 Jun 2024 00:15:48 +0300
Subject: [PATCH] BAN: Implement same_as and add requires for BAN::Function
 with lambda

BAN::Function(lambda) now requires that the object is callable and
returns the correct type. This allows overloads with different
callback formats.
---
 BAN/include/BAN/Function.h | 2 +-
 BAN/include/BAN/Traits.h   | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/BAN/include/BAN/Function.h b/BAN/include/BAN/Function.h
index 94e083d7..b2ed0c9a 100644
--- a/BAN/include/BAN/Function.h
+++ b/BAN/include/BAN/Function.h
@@ -32,7 +32,7 @@ namespace BAN
 			new (m_storage) CallableMemberConst<Own>(function, owner);
 		}
 		template<typename Lambda>
-		Function(Lambda lambda)
+		Function(Lambda lambda) requires requires(Lambda lamda, Args... args) { { lambda(args...) } -> BAN::same_as<Ret>; }
 		{
 			static_assert(sizeof(CallableLambda<Lambda>) <= m_size);
 			new (m_storage) CallableLambda<Lambda>(lambda);
diff --git a/BAN/include/BAN/Traits.h b/BAN/include/BAN/Traits.h
index 646e5af0..976cf8b3 100644
--- a/BAN/include/BAN/Traits.h
+++ b/BAN/include/BAN/Traits.h
@@ -42,6 +42,7 @@ namespace BAN
 	template<typename T, typename S>	struct is_same			: false_type {};
 	template<typename T>				struct is_same<T, T>	: true_type {};
 	template<typename T, typename S> inline constexpr bool is_same_v = is_same<T, S>::value;
+	template<typename T, typename S> concept same_as = BAN::is_same_v<T, S>;
 
 	template<typename T> struct is_lvalue_reference		: false_type {};
 	template<typename T> struct is_lvalue_reference<T&>	: true_type {};