Interfaces should not have a base type

Cpp2IL.Core.Tests/MethodOverridesTests.cs

@@ -1,5 +1,4 @@
 using System.Linq;
-using Cpp2IL.Core.Model.Contexts;
 
 namespace Cpp2IL.Core.Tests;
 
@@ -39,4 +38,62 @@ public void OverridesTests()
             Assert.That(iList.Methods.Select(m => m.Overrides.Count()), Is.All.EqualTo(0));
         }
     }
+
+    [Test]
+    public void InterfaceMethodsShouldNotOverrideAnything()
+    {
+        var appContext = TestGameLoader.LoadSimple2019Game();
+
+        using (Assert.EnterMultipleScope())
+        {
+            var count = 0;
+            foreach (var assembly in appContext.Assemblies)
+            {
+                foreach (var type in assembly.Types)
+                {
+                    if (!type.IsInterface)
+                        continue;
+
+                    foreach (var method in type.Methods)
+                    {
+                        if (!method.IsVirtual && !method.IsAbstract)
+                            continue;
+
+                        if (method.IsStatic || !method.IsNewSlot)
+                            continue;
+
+                        Assert.That(method.Overrides, Is.Empty);
+                        count++;
+                    }
+                }
+            }
+            Assert.That(count, Is.GreaterThan(0));
+        }
+    }
+
+    [Test]
+    public void InterfaceMethodsShouldHaveNoBaseMethod()
+    {
+        var appContext = TestGameLoader.LoadSimple2019Game();
+
+        using (Assert.EnterMultipleScope())
+        {
+            var count = 0;
+            foreach (var assembly in appContext.Assemblies)
+            {
+                foreach (var type in assembly.Types)
+                {
+                    if (!type.IsInterface)
+                        continue;
+
+                    foreach (var method in type.Methods)
+                    {
+                        Assert.That(method.BaseMethod, Is.Null);
+                        count++;
+                    }
+                }
+            }
+            Assert.That(count, Is.GreaterThan(0));
+        }
+    }
 }

Cpp2IL.Core.Tests/TypeAnalysisContextTests.cs

@@ -0,0 +1,52 @@
+namespace Cpp2IL.Core.Tests;
+
+public class TypeAnalysisContextTests
+{
+    [Test]
+    public void InterfacesHaveNoBaseType()
+    {
+        var appContext = TestGameLoader.LoadSimple2019Game();
+
+        using (Assert.EnterMultipleScope())
+        {
+            var count = 0;
+            foreach (var assembly in appContext.Assemblies)
+            {
+                foreach (var type in assembly.Types)
+                {
+                    if (!type.IsInterface)
+                        continue;
+
+                    Assert.That(type.DefaultBaseType, Is.Null);
+                    Assert.That(type.BaseType, Is.Null);
+                    count++;
+                }
+            }
+            Assert.That(count, Is.GreaterThan(0));
+        }
+    }
+
+    [Test]
+    public void StaticClassesHaveObjectBaseType()
+    {
+        var appContext = TestGameLoader.LoadSimple2019Game();
+
+        using (Assert.EnterMultipleScope())
+        {
+            var count = 0;
+            foreach (var assembly in appContext.Assemblies)
+            {
+                foreach (var type in assembly.Types)
+                {
+                    if (!type.IsStatic)
+                        continue;
+
+                    Assert.That(type.DefaultBaseType, Is.EqualTo(appContext.SystemTypes.SystemObjectType));
+                    Assert.That(type.BaseType, Is.EqualTo(appContext.SystemTypes.SystemObjectType));
+                    count++;
+                }
+            }
+            Assert.That(count, Is.GreaterThan(0));
+        }
+    }
+}

Cpp2IL.Core/Model/Contexts/MethodAnalysisContext.cs

@@ -64,6 +64,10 @@ public class MethodAnalysisContext : HasGenericParameters, IMethodInfoProvider
 
     public bool IsVirtual => (Attributes & MethodAttributes.Virtual) != 0;
 
+    public bool IsAbstract => (Attributes & MethodAttributes.Abstract) != 0;
+
+    public bool IsNewSlot => (Attributes & MethodAttributes.NewSlot) != 0;
+
     protected override int CustomAttributeIndex => Definition?.customAttributeIndex ?? throw new("Subclasses of MethodAnalysisContext should override CustomAttributeIndex if they have custom attributes");
 
     public override AssemblyAnalysisContext CustomAttributeAssembly => DeclaringType?.DeclaringAssembly ?? throw new("Subclasses of MethodAnalysisContext should override CustomAttributeAssembly if they have custom attributes");

Cpp2IL.Core/Model/Contexts/TypeAnalysisContext.cs

@@ -71,7 +71,7 @@ public class TypeAnalysisContext : HasGenericParameters, ITypeInfoProvider, ICSh
 
     public TypeAttributes Attributes => OverrideAttributes ?? DefaultAttributes;
 
-    public virtual TypeAnalysisContext? DefaultBaseType => Definition == null ? null : DeclaringAssembly.ResolveIl2CppType(Definition.RawBaseType);
+    public virtual TypeAnalysisContext? DefaultBaseType => Definition == null || DefaultAttributes.HasFlag(TypeAttributes.Interface) ? null : DeclaringAssembly.ResolveIl2CppType(Definition.RawBaseType);
 
     public TypeAnalysisContext? OverrideBaseType { get; set; }