Kotlin: Exclude operands of NotNullExpr from NullMaybe query

Author: tamasvajk

java/ql/src/Likely Bugs/Nullness/NullMaybe.ql

@@ -21,6 +21,8 @@ from VarAccess access, SsaSourceVariable var, string msg, Expr reason
 where
   nullDeref(var, access, msg, reason) and
   // Exclude definite nulls here, as these are covered by `NullAlways.ql`.
-  not alwaysNullDeref(var, access)
+  not alwaysNullDeref(var, access) and
+  // Exclude operands of `!!` in Kotlin, as `!!` means explicit opt out by the user.
+  not access.getParent() instanceof NotNullExpr
 select access, "Variable $@ may be null here " + msg + ".", var.getVariable(),
   var.getVariable().getName(), reason, "this"

java/ql/test/kotlin/query-tests/NullMaybe/NullMaybe.expected

@@ -1 +0,0 @@
-| Test.kt:6:13:6:13 | d | Variable $@ may be null here because of $@ assignment. | Test.kt:2:5:2:25 | Double d | d | Test.kt:2:5:2:25 | d | this |