Swift: add upgrade/downgrade scripts

Author: redsun82

swift/downgrades/be2357fd0023261478871eff5df5c57df559aa3b/downgrade.ql

@@ -0,0 +1,40 @@
+class Element extends @element {
+  string toString() { none() }
+}
+
+predicate removedClass(Element e, string name, Element child) {
+  current_context_isolation_exprs(e, child) and name = "CurrentContextIsolationExpr"
+  or
+  extract_function_isolation_exprs(e, child) and name = "ExtractFunctionIsolationExpr"
+  or
+  (
+    actor_isolation_erasure_exprs(e) and name = "ActorIsolationErasureExpr"
+    or
+    unreachable_exprs(e) and name = "UnreachableExpr"
+  ) and
+  implicit_conversion_exprs(e, child)
+}
+
+query predicate new_unspecified_elements(Element e, string property, string error) {
+  unspecified_elements(e, property, error)
+  or
+  exists(string name |
+    removedClass(e, name, _) and
+    property = "" and
+    error = name + " nodes removed during database downgrade. Please update your CodeQL code."
+  )
+}
+
+query predicate new_unspecified_element_children(Element e, int index, Element child) {
+  unspecified_element_children(e, index, child)
+  or
+  removedClass(e, _, child) and index = 0
+}
+
+query predicate new_implicit_conversion_exprs(Element e, Element child) {
+  implicit_conversion_exprs(e, child) and not removedClass(e, _, _)
+}
+
+query predicate new_expr_types(Element e, Element type) {
+  expr_types(e, type) and not removedClass(e, _, _)
+}