Flatten anonymous types to avoid empty names

This improves our generated API as we no longer need "_0"-like names and also prevents conflicts between an anonymous type and a property of this type.

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

src/Generator/Driver.cs

@@ -247,6 +247,7 @@ namespace CppSharp
             Generator.SetupPasses();
 
             TranslationUnitPasses.AddPass(new CleanInvalidDeclNamesPass());
+            TranslationUnitPasses.AddPass(new FlattenAnonymousTypesToFields());
             TranslationUnitPasses.AddPass(new FieldToPropertyPass());
             TranslationUnitPasses.AddPass(new CheckIgnoredDeclsPass());
             TranslationUnitPasses.AddPass(new CheckFlagEnumsPass());

src/Generator/Generators/CSharp/CSharpSources.cs

@@ -925,12 +925,12 @@ namespace CppSharp.Generators.CSharp
             }
             else
             {
-                var name = @class.Layout.Fields.First(f => f.FieldPtr == field.OriginalPtr).Name;
+                var name = ((Class) field.Namespace).Layout.Fields.First(
-                var identifier = name;
+                    f => f.FieldPtr == field.OriginalPtr).Name;
                 if (@class.IsValueType)
-                    returnVar = $"{Helpers.InstanceField}.{identifier}";
+                    returnVar = $"{Helpers.InstanceField}.{name}";
                 else
-                    returnVar = $"(({TypePrinter.PrintNative(@class)}*){Helpers.InstanceIdentifier})->{identifier}";
+                    returnVar = $"(({TypePrinter.PrintNative(@class)}*){Helpers.InstanceIdentifier})->{name}";
             }
 
             var param = new Parameter
@@ -1210,7 +1210,8 @@ namespace CppSharp.Generators.CSharp
 
         private void GenerateFieldGetter(Field field, Class @class, QualifiedType returnType)
         {
-            var name = @class.Layout.Fields.First(f => f.FieldPtr == field.OriginalPtr).Name;
+            var name = ((Class) field.Namespace).Layout.Fields.First(
+                f => f.FieldPtr == field.OriginalPtr).Name;
             string returnVar;
             var arrayType = field.Type.Desugar() as ArrayType;
             if (@class.IsValueType)

src/Generator/Passes/FlattenAnonymousTypesToFields.cs

@@ -0,0 +1,81 @@
+using CppSharp.AST;
+using CppSharp.AST.Extensions;
+
+namespace CppSharp.Passes
+{
+    /// <summary>
+    /// Replaces anonymous types with their contained fields
+    /// in class layouts and properties in order to avoid generating
+    /// these very same anonymous types which is useless and
+    /// also forces unappealing names.
+    /// </summary>
+    public class FlattenAnonymousTypesToFields : TranslationUnitPass
+    {
+        public FlattenAnonymousTypesToFields()
+        {
+            VisitOptions.VisitClassBases = false;
+            VisitOptions.VisitClassFields = false;
+            VisitOptions.VisitClassMethods = false;
+            VisitOptions.VisitClassProperties = false;
+            VisitOptions.VisitEventParameters = false;
+            VisitOptions.VisitFunctionParameters = false;
+            VisitOptions.VisitFunctionReturnType = false;
+            VisitOptions.VisitNamespaceEnums = false;
+            VisitOptions.VisitNamespaceTemplates = false;
+            VisitOptions.VisitNamespaceTypedefs = false;
+            VisitOptions.VisitNamespaceVariables = false;
+            VisitOptions.VisitPropertyAccessors = false;
+            VisitOptions.VisitTemplateArguments = false;
+        }
+
+        public override bool VisitClassDecl(Class @class)
+        {
+            if (!base.VisitClassDecl(@class) || @class.Ignore || @class.IsDependent)
+                return false;
+
+            for (int i = @class.Fields.Count - 1; i >= 0; i--)
+            {
+                Field field = @class.Fields[i];
+                Class fieldType;
+                if (!string.IsNullOrEmpty(field.OriginalName) ||
+                    !field.Type.Desugar().TryGetClass(out fieldType) ||
+                    !string.IsNullOrEmpty(fieldType.OriginalName))
+                    continue;
+
+                ReplaceField(@class, i, fieldType);
+                ReplaceLayoutField(@class, field, fieldType);
+                fieldType.Fields.Clear();
+                fieldType.ExplicitlyIgnore();
+            }
+
+            return true;
+        }
+
+        private static void ReplaceField(Class @class, int i, Class fieldType)
+        {
+            @class.Fields.RemoveAt(i);
+
+            for (int j = 0; j < fieldType.Fields.Count; j++)
+            {
+                Field nestedField = fieldType.Fields[j];
+                nestedField.Namespace = @class;
+                @class.Fields.Insert(i + j, nestedField);
+            }
+        }
+
+        private static void ReplaceLayoutField(Class @class, Field field, Class fieldType)
+        {
+            LayoutField layoutField = @class.Layout.Fields.Find(
+                                f => f.FieldPtr == field.OriginalPtr);
+            int layoutIndex = @class.Layout.Fields.IndexOf(layoutField);
+            @class.Layout.Fields.RemoveAt(layoutIndex);
+
+            for (int j = 0; j < fieldType.Layout.Fields.Count; j++)
+            {
+                LayoutField nestedlayoutField = fieldType.Layout.Fields[j];
+                nestedlayoutField.Offset += layoutField.Offset;
+                @class.Layout.Fields.Insert(layoutIndex + j, nestedlayoutField);
+            }
+        }
+    }
+}

tests/Common/Common.Tests.cs

@@ -354,6 +354,22 @@ public class CommonTests : GeneratorTestFixture
         Assert.That(nestedPublic.G, Is.Not.EqualTo(0));
     }
 
+    [Test]
+    public void TestNestedAnonymousTypes()
+    {
+        using (TestNestedTypes testNestedTypes = new TestNestedTypes())
+        {
+            testNestedTypes.ToVerifyCorrectLayoutBefore = 5;
+            Assert.That(testNestedTypes.ToVerifyCorrectLayoutBefore, Is.EqualTo(5));
+            testNestedTypes.I = 10;
+            Assert.That(testNestedTypes.I, Is.EqualTo(10));
+            testNestedTypes.C = 'D';
+            Assert.That(testNestedTypes.C, Is.EqualTo('D'));
+            testNestedTypes.ToVerifyCorrectLayoutAfter = 15;
+            Assert.That(testNestedTypes.ToVerifyCorrectLayoutAfter, Is.EqualTo(15));
+        }
+    }
+
     [Test]
     public void TestPropertyChains()
     {

tests/Common/Common.cpp

@@ -412,6 +412,14 @@ void va_listFunction(va_list v)
 {
 }
 
+TestNestedTypes::TestNestedTypes()
+{
+}
+
+TestNestedTypes::~TestNestedTypes()
+{
+}
+
 void TestDelegates::MarshalUnattributedDelegate(DelegateInGlobalNamespace del)
 {
 }

tests/Common/Common.h

@@ -827,6 +827,8 @@ DLL_API void va_listFunction(va_list v);
 struct DLL_API TestNestedTypes
 {
 public:
+    TestNestedTypes();
+    ~TestNestedTypes();
     union as_types
     {
         int as_int;
@@ -835,6 +837,13 @@ public:
             unsigned char blue, green, red, alpha;
         } as_uchar;
     };
+    int toVerifyCorrectLayoutBefore;
+    union
+    {
+        int i;
+        char c;
+    };
+    int toVerifyCorrectLayoutAfter;
 };
 
 class DLL_API HasStdString