Fixed a bug in MS mode and added a test.

Signed-off-by: Dimitar Dobrev <dpldobrev@yahoo.com>

src/AST/ClassLayout.cs

@@ -99,8 +99,11 @@ namespace CppSharp.AST
             Size = classLayout.Size;
             DataSize = classLayout.DataSize;
             VFTables.AddRange(classLayout.VFTables);
-            Layout = new VTableLayout();
-            Layout.Components.AddRange(classLayout.Layout.Components);
+            if (classLayout.Layout != null)
+            {
+                Layout = new VTableLayout();
+                Layout.Components.AddRange(classLayout.Layout.Components);
+            }
         }
 
         /// <summary>

src/Generator/Generators/CSharp/CSharpTextTemplate.cs

@@ -1566,7 +1566,7 @@ namespace CppSharp.Generators.CSharp
                 case CppAbi.Microsoft:
                     i = (from table in @class.Layout.VFTables
                          let j = table.Layout.Components.FindIndex(m => m.Method == method)
-                         where j > 0
+                         where j >= 0
                          select j).First();
                     break;
                 default:

tests/Basic/Basic.Tests.cs

@@ -85,5 +85,13 @@ public class BasicTests
         Foo2 result = foo2 << 3;
         Assert.That(result.C, Is.EqualTo(16));
     }
+
+    [Test]
+    public void TestAbstractReturnType()
+    {
+        var returnsAbstractFoo = new ReturnsAbstractFoo();
+        AbstractFoo abstractFoo = returnsAbstractFoo.getFoo();
+        Assert.AreEqual(abstractFoo.pureFunction(), 5);
+    }
 }
  

tests/Basic/Basic.cpp

@@ -121,11 +121,16 @@ Bar indirectReturn()
     return Bar();
 }
 
-int ImplementAbstractFoo::pureFunction()
+int ImplementsAbstractFoo::pureFunction()
 {
     return 5;
 }
 
+const AbstractFoo& ReturnsAbstractFoo::getFoo()
+{
+    return i;
+}
+
 void DefaultParameters::Foo(int a, int b)
 {
 }

tests/Basic/Basic.h

@@ -86,12 +86,21 @@ public:
     virtual int pureFunction() = 0;
 };
 
-class DLL_API ImplementAbstractFoo : public AbstractFoo
+class DLL_API ImplementsAbstractFoo : public AbstractFoo
 {
 public:
     virtual int pureFunction();
 };
 
+class DLL_API ReturnsAbstractFoo
+{
+public:
+    const AbstractFoo& getFoo();
+
+private:
+    ImplementsAbstractFoo i;
+};
+
 DLL_API Bar operator-(const Bar &);
 DLL_API Bar operator+(const Bar &, const Bar &);