[Wasm GC] rtt.fresh_sub (#3936)

This is the same as rtt.sub, but creates a "new" rtt each time. See

https://docs.google.com/document/d/1DklC3qVuOdLHSXB5UXghM_syCh-4cMinQ50ICiXnK3Q/edit#

The old Literal implementation of rtts becomes a little more complex here,
as it was designed for the original spec where only structure matters. It may
be worth a complete redesign there, but for now as the spec is in flux I think
the approach here is good enough.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/wasm-interpreter.h b/src/wasm-interpreter.h
index 94230b747..c3148d9c6 100644
--- a/src/wasm-interpreter.h
+++ b/src/wasm-interpreter.h
@@ -1594,6 +1594,9 @@ public:
     auto parentValue = parent.getSingleValue();
     auto newSupers = std::make_unique<RttSupers>(parentValue.getRttSupers());
     newSupers->push_back(parentValue.type);
+    if (curr->fresh) {
+      newSupers->back().makeFresh();
+    }
     return Literal(std::move(newSupers), curr->type);
   }
   Flow visitStructNew(StructNew* curr) {