Fix #21390
Previously the interpreter's handling of RET_BCO
stack frames would
throw away the tag of the returned closure, resulting in #21390 (closed).
Add a test and fix #21390 (closed).
Previously the interpreter's handling of RET_BCO
stack frames would
throw away the tag of the returned closure, resulting in #21390 (closed).
Add a test and fix #21390 (closed).