Rust: Add DB downgrade script

rust/downgrades/30a0713e5bf69c60d003e4994e5abd1c78a36826/downgrade.ql

@@ -0,0 +1,15 @@
+class Element extends @element {
+  string toString() { none() }
+}
+
+class Expr extends Element, @expr { }
+
+class ClosureExpr extends Expr, @closure_expr { }
+
+class Function extends Element, @function { }
+
+query predicate new_closure_expr_bodies(ClosureExpr ce, Expr e) {
+  closure_expr_closure_bodies(ce, e)
+}
+
+query predicate new_function_bodies(Function f, Expr e) { function_function_bodies(f, e) }

rust/downgrades/30a0713e5bf69c60d003e4994e5abd1c78a36826/upgrade.properties

@@ -0,0 +1,8 @@
+description: Rename function/closure body relations
+compatibility: backwards
+
+closure_expr_closure_bodies.rel: delete
+function_function_bodies.rel: delete
+
+closure_expr_bodies.rel: run downgrade.ql new_closure_expr_bodies
+function_bodies.rel: run downgrade.ql new_function_bodies