Fix nested type inheritance conversion

JavaToCSharp.Tests/ConvertNestedTypeInheritanceTests.cs

@@ -0,0 +1,45 @@
+namespace JavaToCSharp.Tests;
+
+public class ConvertNestedTypeInheritanceTests
+{
+    [Fact]
+    public void Extending_Nested_Type_Keeps_Declaring_Type_Qualifier()
+    {
+        const string javaCode = """
+                                package com.example;
+                                public class GeneratorFactory {
+                                    public abstract static class AbstractXmlFeatureGeneratorFactory {
+                                    }
+                                    public interface XmlFeatureGeneratorFactory {
+                                    }
+                                    public class CachedFeatureGeneratorFactory
+                                        extends GeneratorFactory.AbstractXmlFeatureGeneratorFactory
+                                        implements GeneratorFactory.XmlFeatureGeneratorFactory {
+                                    }
+                                }
+                                """;
+
+        var parsed = Convert(javaCode);
+
+        Assert.Contains(
+            "public class CachedFeatureGeneratorFactory : GeneratorFactory.AbstractXmlFeatureGeneratorFactory, GeneratorFactory.XmlFeatureGeneratorFactory",
+            parsed);
+    }
+
+    [Fact]
+    public void Extending_Simple_Type_Is_Unaffected()
+    {
+        const string javaCode = """
+                                package com.example;
+                                public class Square extends Shape {
+                                }
+                                """;
+
+        var parsed = Convert(javaCode);
+
+        Assert.Contains("public class Square : Shape", parsed);
+    }
+
+    private static string Convert(string javaCode)
+        => JavaToCSharpConverter.ConvertText(javaCode, new JavaConversionOptions { IncludeComments = false }) ?? "";
+}

JavaToCSharp/TypeHelper.cs

@@ -171,6 +171,15 @@ public static TypeSyntax GetSyntaxFromType(ClassOrInterfaceType type)
             typeSyntax = SyntaxFactory.ParseTypeName(typeName);
         }
 
+        // Nested types (e.g. `Outer.Inner`) carry their declaring type as a scope, which
+        // getNameAsString() above does not include. Prepend it so the declaring type isn't lost.
+        if (type.getScope().FromOptional<ClassOrInterfaceType>() is { } scope
+            && typeSyntax is SimpleNameSyntax simpleName
+            && GetSyntaxFromType(scope) is NameSyntax scopeName)
+        {
+            return SyntaxFactory.QualifiedName(scopeName, simpleName);
+        }
+
         return typeSyntax;
     }