bangbang in assignment if needed

src/org/jetbrains/jet/j2k/visitors/ExpressionVisitor.kt

@@ -46,7 +46,7 @@ public open class ExpressionVisitor(converter: Converter): StatementVisitor(conv
         }
 
         val lhs = getConverter().expressionToExpression(expression?.getLExpression()!!)
-        val rhs = getConverter().expressionToExpression(expression?.getRExpression()!!)
+        val rhs = getConverter().expressionToExpression(expression?.getRExpression()!!, expression?.getRExpression()?.getType())
         if (!secondOp.isEmpty()) {
             myResult = AssignmentExpression(lhs, BinaryExpression(lhs, rhs, secondOp), "=")
         }

tests/testData/ast/assignmentExpression/file/nullability.jav

@@ -0,0 +1,9 @@
+import java.util.BitSet;
+
+class Foo {
+  void foo(BitSet o) {
+    BitSet o2 = o;
+    int foo = 0;
+    foo = o2.size();
+  }
+}

tests/testData/ast/assignmentExpression/file/nullability.kt

@@ -0,0 +1,8 @@
+import java.util.BitSet
+open class Foo() {
+open fun foo(o : BitSet?) : Unit {
+var o2 : BitSet? = o
+var foo : Int = 0
+foo = o2?.size()!!
+}
+}