external gc interface

tests/compiler/gc.ts

@@ -0,0 +1,39 @@
+import "allocator/arena";
+import { link_count, unlink_count, collect_count } from "./gc/_dummy";
+export { gc };
+
+class Ref {}
+
+@start export function main(): void {
+  var ref = new Ref();
+
+  assert(gc.implemented);
+
+  var previous_link_count = link_count;
+  var previous_unlink_count = unlink_count;
+  var previous_collect_count = collect_count;
+
+  gc.retain(changetype<usize>(ref));
+
+  assert(link_count == previous_link_count + 1);
+  assert(unlink_count == previous_unlink_count);
+  assert(collect_count == previous_collect_count);
+  previous_link_count = link_count;
+  previous_unlink_count = unlink_count;
+  previous_collect_count = collect_count;
+
+  gc.release(changetype<usize>(ref));
+
+  assert(link_count == previous_link_count);
+  assert(unlink_count == previous_unlink_count + 1);
+  assert(collect_count == previous_collect_count);
+  previous_link_count = link_count;
+  previous_unlink_count = unlink_count;
+  previous_collect_count = collect_count;
+
+  gc.collect();
+
+  assert(link_count == previous_link_count);
+  assert(unlink_count == previous_unlink_count);
+  assert(collect_count == previous_collect_count + 1);
+}