Function with_current_heap 

pub fn with_current_heap<R>(f: impl for<'a> FnOnce(Option<&'a Heap>) -> R) -> R

Runs f with a reference to the currently-active heap, or None if no HeapGuard is in scope.

The heap reference is deliberately scoped to the closure. This avoids the previous current_heap() -> Option<&'static Heap> lifetime lie while still supporting legacy GcRef::new call sites that do not receive &mut LuaState.