Always null detection

compiler/testData/diagnostics/tests/smartCasts/notNullorNotNull.kt

@@ -1,6 +1,6 @@
 fun bar(x: Int?): Int {
     if (x != null) return -1
-    if (<!SENSELESS_COMPARISON!>x == null<!>) return -2
+    if (<!ALWAYS_NULL!>x<!> == null) return -2
     // Should be unreachable
     return 2 + 2
 }