C++: add upgrade and downgrade scripts

Author: jketema

cpp/downgrades/73af5058c6899dcdb05754c27ca966aeb3a68c94/exprs.ql

@@ -0,0 +1,13 @@
+class Expr extends @expr {
+  string toString() { none() }
+}
+
+class Location extends @location_expr {
+  string toString() { none() }
+}
+
+from Expr expr, int kind, int kind_new, Location location
+where
+  exprs(expr, kind, location) and
+  if expr instanceof @blockassignexpr then kind_new = 0 else kind_new = kind
+select expr, kind_new, location