src/jdk.scripting.nashorn/share/classes/jdk/nashorn/internal/runtime/linker/NashornLinker.java

*** 155,170 ****
       * @throws Exception if something goes wrong; generally, if there's an issue with creation of the SAM proxy type
       * constructor.
       */
      private static GuardedInvocation getSamTypeConverter(final Class<?> sourceType, final Class<?> targetType, final Supplier<MethodHandles.Lookup> lookupSupplier) throws Exception {
          // If source type is more generic than ScriptFunction class, we'll need to use a guard
!         final boolean isSourceTypeGeneric = sourceType.isAssignableFrom(ScriptFunction.class);
  
          if ((isSourceTypeGeneric || ScriptFunction.class.isAssignableFrom(sourceType)) && isAutoConvertibleFromFunction(targetType)) {
!             final MethodHandle ctor = JavaAdapterFactory.getConstructor(ScriptFunction.class, targetType, getCurrentLookup(lookupSupplier));
              assert ctor != null; // if isAutoConvertibleFromFunction() returned true, then ctor must exist.
!             return new GuardedInvocation(ctor, isSourceTypeGeneric ? IS_SCRIPT_FUNCTION : null);
          }
          return null;
      }
  
      private static MethodHandles.Lookup getCurrentLookup(final Supplier<MethodHandles.Lookup> lookupSupplier) {
--- 155,175 ----
       * @throws Exception if something goes wrong; generally, if there's an issue with creation of the SAM proxy type
       * constructor.
       */
      private static GuardedInvocation getSamTypeConverter(final Class<?> sourceType, final Class<?> targetType, final Supplier<MethodHandles.Lookup> lookupSupplier) throws Exception {
          // If source type is more generic than ScriptFunction class, we'll need to use a guard
!         final boolean isSourceTypeGeneric = sourceType.isAssignableFrom(ScriptObject.class);
  
          if ((isSourceTypeGeneric || ScriptFunction.class.isAssignableFrom(sourceType)) && isAutoConvertibleFromFunction(targetType)) {
!             final Class<?> paramType = isSourceTypeGeneric ? Object.class : ScriptFunction.class;
!             // Using Object.class as constructor source type means we're getting an overloaded constructor handle,
!             // which is safe but slower than a single constructor handle. If the actual argument is a ScriptFunction it
!             // would be nice if we could change the formal parameter to ScriptFunction.class and add a guard for it
!             // in the main invocation.
!             final MethodHandle ctor = JavaAdapterFactory.getConstructor(paramType, targetType, getCurrentLookup(lookupSupplier));
              assert ctor != null; // if isAutoConvertibleFromFunction() returned true, then ctor must exist.
!             return new GuardedInvocation(ctor, isSourceTypeGeneric ? IS_FUNCTION : null);
          }
          return null;
      }
  
      private static MethodHandles.Lookup getCurrentLookup(final Supplier<MethodHandles.Lookup> lookupSupplier) {
*** 313,323 ****
      private static boolean isList(final Class<?> clazz) {
          return clazz == List.class || clazz == Deque.class;
      }
  
      private static final MethodHandle IS_SCRIPT_OBJECT = Guards.isInstance(ScriptObject.class, MH.type(Boolean.TYPE, Object.class));
!     private static final MethodHandle IS_SCRIPT_FUNCTION = Guards.isInstance(ScriptFunction.class, MH.type(Boolean.TYPE, Object.class));
      private static final MethodHandle IS_NATIVE_ARRAY = Guards.isOfClass(NativeArray.class, MH.type(Boolean.TYPE, Object.class));
  
      private static final MethodHandle IS_NASHORN_OR_UNDEFINED_TYPE = findOwnMH("isNashornTypeOrUndefined", Boolean.TYPE, Object.class);
      private static final MethodHandle CREATE_MIRROR = findOwnMH("createMirror", Object.class, Object.class);
  
--- 318,328 ----
      private static boolean isList(final Class<?> clazz) {
          return clazz == List.class || clazz == Deque.class;
      }
  
      private static final MethodHandle IS_SCRIPT_OBJECT = Guards.isInstance(ScriptObject.class, MH.type(Boolean.TYPE, Object.class));
!     private static final MethodHandle IS_FUNCTION = findOwnMH("isFunction", boolean.class, Object.class);
      private static final MethodHandle IS_NATIVE_ARRAY = Guards.isOfClass(NativeArray.class, MH.type(Boolean.TYPE, Object.class));
  
      private static final MethodHandle IS_NASHORN_OR_UNDEFINED_TYPE = findOwnMH("isNashornTypeOrUndefined", Boolean.TYPE, Object.class);
      private static final MethodHandle CREATE_MIRROR = findOwnMH("createMirror", Object.class, Object.class);
  
*** 346,355 ****
--- 351,365 ----
      @SuppressWarnings("unused")
      private static Object createMirror(final Object obj) {
          return obj instanceof ScriptObject? ScriptUtils.wrap((ScriptObject)obj) : obj;
      }
  
+     @SuppressWarnings("unused")
+     private static boolean isFunction(final Object obj) {
+         return obj instanceof ScriptFunction || obj instanceof ScriptObjectMirror && ((ScriptObjectMirror) obj).isFunction();
+     }
+ 
      private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) {
          return MH.findStatic(MethodHandles.lookup(), NashornLinker.class, name, MH.type(rtype, types));
      }
  }