Fix for implicitly abstract interfaces and implicitly sealed structs

Author: datacute

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Interfaces are implicitly abstract, so generated partial interfaces should not be explicitly marked as abstract.
+- Structs are implicitly sealed, so generated partial structs should not be explicitly marked as sealed.
+
 ## [1.0.1] - 2025-07-27
 
 ### Fixed

IncrementalGeneratorExtensions.Content/Datacute/IncrementalGeneratorExtensions/TypeContext.cs

@@ -209,7 +209,12 @@ public static string GetAccessibilityModifier(Accessibility accessibility)
         /// Gets the abstract modifier for this type context.
         /// </summary>
         /// <returns>A string representing the abstract modifier, such as "abstract " or an empty string.</returns>
-        public string GetAbstractModifier() => GetAbstractModifier(IsAbstract);
+        public string GetAbstractModifier()
+        {
+            if (TypeDeclarationKeyword == "interface")
+                return ""; // implicitly abstract
+            return GetAbstractModifier(IsAbstract);
+        }
         /// <summary>
         /// Gets the abstract modifier for a given abstract status.
         /// </summary>
@@ -221,13 +226,18 @@ public static string GetAccessibilityModifier(Accessibility accessibility)
         /// Gets the sealed modifier for this type context.
         /// </summary>
         /// <returns>A string representing the sealed modifier, such as "sealed " or an empty string.</returns>
-        public string GetSealedModifier() => GetSealedModifier(IsSealed);
+        public string GetSealedModifier()
+        {
+            if (TypeDeclarationKeyword == "struct" || TypeDeclarationKeyword == "record struct")
+                return ""; // implicitly sealed
+            return GetSealedModifier(IsSealed);
+        }
         /// <summary>
         /// Gets the sealed modifier for a given sealed status.
         /// </summary>
-        /// <param name="isSealead">The sealed status of the type.</param>
+        /// <param name="isSealed">The sealed status of the type.</param>
         /// <returns>A string representing the sealed modifier, such as "sealed " or an empty string.</returns>
-        public static string GetSealedModifier(bool isSealead) => isSealead ? "sealed " : "";
+        public static string GetSealedModifier(bool isSealed) => isSealed ? "sealed " : "";
 
         /// <summary>
         /// Gets the type declaration string for a type symbol, determining if it is a record, struct, or class.