CHECKCAST always succeeds on null

eval4j/src/org/jetbrains/eval4j/interpreter.kt

@@ -172,7 +172,9 @@ class SingleInstructionInterpreter(private val eval: Eval) : Interpreter<Value>(
 
             CHECKCAST -> {
                 val targetType = Type.getObjectType((insn as TypeInsnNode).desc)
-                if (eval.isInstanceOf(value, targetType)) {
+                if (value == NULL_VALUE) {
+                    NULL_VALUE
+                } else if (eval.isInstanceOf(value, targetType)) {
                     ObjectValue(value.obj(), targetType)
                 }
                 else {

eval4j/test/org/jetbrains/eval4j/test/TestData.java

@@ -48,6 +48,22 @@ class TestData {
         return "str";
     }
 
+    static void checkCastNull() {
+        CheckCastToNull klass = new CheckCastToNull();
+        klass.f1(null);
+        klass.f2(null);
+        klass.f3(null);
+
+        Integer integer = (Integer) null;
+        Object object = (Object) null;
+    }
+
+    static class CheckCastToNull {
+        void f1(Integer p) {}
+        void f2(Integer[] p) {}
+        void f3(Integer[][] p) {}
+    }
+
     static Integer integerValueOf() { return 1; }
 
     static Byte byteValueOf() { return 1; }
@@ -549,3 +565,5 @@ class TestData {
         int[] i = (int[]) null;
     }
 }
+
+