Java to Kotlin converter: more smartness about nullability

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull4.kt

@@ -0,0 +1,14 @@
+trait I {
+    public fun getString(): String
+}
+
+class C() {
+    fun foo(i: I, b: Boolean) {
+        val result = i.getString()
+        if (b)
+            result = null
+        if (result != null) {
+            print(result)
+        }
+    }
+}