Do not wrap flexible types into Nullable/NotNull types

compiler/testData/diagnostics/tests/platformTypes/getParentOfType.kt

@@ -0,0 +1,36 @@
+// FILE: p/PsiElement.java
+
+package p;
+
+public interface PsiElement {}
+
+// FILE: p/JetExpression.java
+
+package p;
+
+public interface JetExpression extends PsiElement {}
+
+// FILE: p/Util.java
+
+package p;
+
+public class Util {
+
+    public static <T extends PsiElement> T getParentOfType(@Nullable PsiElement element, @NotNull Class<T> aClass) {
+        return null;
+    }
+
+    public static void on(JetExpression e) {}
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test(e: JetExpression) {
+    Util.on(
+        Util.getParentOfType(e, javaClass<JetExpression>()) ?: e
+    )
+}
+
+fun <T> javaClass(): Class<T> = null!!