From 06eee55671e86c67fcf52e22d93f50ea135e2fca Mon Sep 17 00:00:00 2001
From: Boondorl <boondorl@live.com>
Date: Fri, 8 Mar 2024 13:54:02 -0500
Subject: [PATCH] Fix for Morph virtual

Allows class<MorphedMonster> to be used as an argument type in place of class<Actor> within the third argument for backwards compatibility.
---
 src/common/objects/dobjtype.cpp        |  4 +++-
 src/namedef_custom.h                   |  1 +
 src/scripting/backend/codegen_doom.cpp | 13 +++++++++++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/common/objects/dobjtype.cpp b/src/common/objects/dobjtype.cpp
index 4c2a1bd4d0..0d1bfdf9a8 100644
--- a/src/common/objects/dobjtype.cpp
+++ b/src/common/objects/dobjtype.cpp
@@ -667,6 +667,8 @@ PClass *PClass::FindClassTentative(FName name)
 //
 //==========================================================================
 
+bool ShouldAllowGameSpecificVirtual(FName name, unsigned index, PType* arg, PType* varg);
+
 int PClass::FindVirtualIndex(FName name, PFunction::Variant *variant, PFunction *parentfunc, bool exactReturnType, bool ignorePointerReadOnly)
 {
 	auto proto = variant->Proto;
@@ -698,7 +700,7 @@ int PClass::FindVirtualIndex(FName name, PFunction::Variant *variant, PFunction
 							break;
 						}
 					}
-					else
+					else if(!ShouldAllowGameSpecificVirtual(name, a, proto->ArgumentTypes[a], vproto->ArgumentTypes[a]))
 					{
 						fail = true;
 						break;
diff --git a/src/namedef_custom.h b/src/namedef_custom.h
index 1beb0d2357..7d6d095f2c 100644
--- a/src/namedef_custom.h
+++ b/src/namedef_custom.h
@@ -462,6 +462,7 @@ xx(WBobSpeed)
 xx(WBobFire)
 xx(PlayerClass)
 xx(MonsterClass)
+xx(Morph)
 xx(MorphedMonster)
 xx(Wi_NoAutostartMap)
 
diff --git a/src/scripting/backend/codegen_doom.cpp b/src/scripting/backend/codegen_doom.cpp
index 60e0cc6141..0e52790d72 100644
--- a/src/scripting/backend/codegen_doom.cpp
+++ b/src/scripting/backend/codegen_doom.cpp
@@ -57,6 +57,19 @@ PFunction* FindBuiltinFunction(FName funcname);
 //
 //==========================================================================
 
+bool ShouldAllowGameSpecificVirtual(FName name, unsigned index, PType* arg, PType* varg)
+{
+	return (name == NAME_Morph && index == 3u && arg->isClassPointer() && varg->isClassPointer()
+			&& PType::toClassPointer(varg)->ClassRestriction->TypeName == NAME_Actor
+			&& PType::toClassPointer(arg)->ClassRestriction->TypeName == NAME_MorphedMonster);
+}
+
+//==========================================================================
+//
+//
+//
+//==========================================================================
+
 bool isActor(PContainerType *type)
 {
 	auto cls = PType::toClass(type);