From 6d01ed5d74ff0a911416d5ceaa17df22787c88bc Mon Sep 17 00:00:00 2001
From: Desour <ds.desour@proton.me>
Date: Mon, 10 Jul 2023 00:00:00 +0200
Subject: [PATCH] irr_ptr: Allow to use with forward-declared types

Also add [[nodiscard]] to ::grab() (because similar named irr_ptr::grab() returns void).
And use new std::is_convertible_v.
---
 src/irr_ptr.h                | 30 ++++++++++++++++--------------
 src/unittest/test_irrptr.cpp |  1 +
 2 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/src/irr_ptr.h b/src/irr_ptr.h
index fc4a0f558..48717976b 100644
--- a/src/irr_ptr.h
+++ b/src/irr_ptr.h
@@ -20,8 +20,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #pragma once
 #include <type_traits>
 #include <utility>
-#include "irrlichttypes.h"
-#include "IReferenceCounted.h"
+namespace irr { class IReferenceCounted; }
 
 /** Shared pointer for IrrLicht objects.
  *
@@ -37,15 +36,13 @@ with this program; if not, write to the Free Software Foundation, Inc.,
  * from such object is a bug and may lead to a crash. Indirect construction
  * is possible though; see the @c grab free function for details and use cases.
  */
-template <class ReferenceCounted,
-		class = typename std::enable_if<std::is_base_of<IReferenceCounted,
-				ReferenceCounted>::value>::type>
+template <class ReferenceCounted>
 class irr_ptr
 {
 	ReferenceCounted *value = nullptr;
 
 public:
-	irr_ptr() {}
+	irr_ptr() noexcept = default;
 
 	irr_ptr(std::nullptr_t) noexcept {}
 
@@ -53,15 +50,15 @@ public:
 
 	irr_ptr(irr_ptr &&b) noexcept { reset(b.release()); }
 
-	template <typename B, class = typename std::enable_if<std::is_convertible<B *,
-					      ReferenceCounted *>::value>::type>
+	template <typename B,
+			std::enable_if_t<std::is_convertible_v<B *, ReferenceCounted *>, bool> = true>
 	irr_ptr(const irr_ptr<B> &b) noexcept
 	{
 		grab(b.get());
 	}
 
-	template <typename B, class = typename std::enable_if<std::is_convertible<B *,
-					      ReferenceCounted *>::value>::type>
+	template <typename B,
+			std::enable_if_t<std::is_convertible_v<B *, ReferenceCounted *>, bool> = true>
 	irr_ptr(irr_ptr<B> &&b) noexcept
 	{
 		reset(b.release());
@@ -88,16 +85,16 @@ public:
 		return *this;
 	}
 
-	template <typename B, class = typename std::enable_if<std::is_convertible<B *,
-					      ReferenceCounted *>::value>::type>
+	template <typename B,
+			std::enable_if_t<std::is_convertible_v<B *, ReferenceCounted *>, bool> = true>
 	irr_ptr &operator=(const irr_ptr<B> &b) noexcept
 	{
 		grab(b.get());
 		return *this;
 	}
 
-	template <typename B, class = typename std::enable_if<std::is_convertible<B *,
-					      ReferenceCounted *>::value>::type>
+	template <typename B,
+			std::enable_if_t<std::is_convertible_v<B *, ReferenceCounted *>, bool> = true>
 	irr_ptr &operator=(irr_ptr<B> &&b) noexcept
 	{
 		reset(b.release());
@@ -128,6 +125,8 @@ public:
 	 */
 	void reset(ReferenceCounted *object = nullptr) noexcept
 	{
+		static_assert(std::is_base_of_v<irr::IReferenceCounted, ReferenceCounted>,
+				"Class is not an IReferenceCounted");
 		if (value)
 			value->drop();
 		value = object;
@@ -138,6 +137,8 @@ public:
 	 */
 	void grab(ReferenceCounted *object) noexcept
 	{
+		static_assert(std::is_base_of_v<irr::IReferenceCounted, ReferenceCounted>,
+				"Class is not an IReferenceCounted");
 		if (object)
 			object->grab();
 		reset(object);
@@ -152,6 +153,7 @@ public:
  * in this function and decreased when the returned pointer is destroyed.
  */
 template <class ReferenceCounted>
+[[nodiscard]]
 irr_ptr<ReferenceCounted> grab(ReferenceCounted *object) noexcept
 {
 	irr_ptr<ReferenceCounted> ptr;
diff --git a/src/unittest/test_irrptr.cpp b/src/unittest/test_irrptr.cpp
index befeefc73..61d1e302c 100644
--- a/src/unittest/test_irrptr.cpp
+++ b/src/unittest/test_irrptr.cpp
@@ -21,6 +21,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "exceptions.h"
 #include "irr_ptr.h"
+#include "IReferenceCounted.h"
 
 class TestIrrPtr : public TestBase
 {