3 files changed, 15 insertions, 1 deletions
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/javatypes/JavaTypesGenerator.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/javatypes/JavaTypesGenerator.java
index 8f6bd48..867ba23 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/javatypes/JavaTypesGenerator.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/javatypes/JavaTypesGenerator.java
@@ -139,6 +139,7 @@ public class JavaTypesGenerator implements Generator {
                         packageParts,
                         new JavaInterfaceDeclaration(
                             sumDefinition.name(),
+                            JavaInterfaceDeclaration.Openness.SEALED,
                             sumDefinition.variants().stream()
                                 .map(variant -> generateTypeRef(variant.type(), context))
                                 .toList(),
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriter.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriter.java
index 3cf58ce..677b1a6 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriter.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriter.java
@@ -155,7 +155,15 @@ public class JavaWriter implements AutoCloseable {
     private void writeInterfaceDeclaration(JavaInterfaceDeclaration interfaceDeclaration) throws IOException {
         writeDocComment(interfaceDeclaration.docComment());
 
-        this.writer.write("public sealed interface ");
+        this.writer.write("public ");
+        switch (interfaceDeclaration.openness()) {
+            case OPEN -> {
+            }
+            case SEALED -> {
+                this.writer.write("sealed ");
+            }
+        }
+        this.writer.write("interface ");
         this.writer.write(interfaceDeclaration.name());
         this.writer.write(" ");
 
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaInterfaceDeclaration.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaInterfaceDeclaration.java
index d0bd0a1..a35de51 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaInterfaceDeclaration.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaInterfaceDeclaration.java
@@ -6,9 +6,14 @@ import java.util.List;
 
 public record JavaInterfaceDeclaration(
     String name,
+    Openness openness,
     List<JavaTypeRef> permitsTypes,
     List<JavaClassBodyDeclaration> body,
     JavaCustomArea customArea,
     DocComment docComment
 ) implements JavaTypeDeclaration {
+    public enum Openness {
+        OPEN,
+        SEALED
+    }
 }