CTFE get_alloc_extra_mut: also provide ref to MemoryExtra This would let me use mutable references in more places in Stacked Borrows, avoiding some `RefCell` overhead. :) r? `@oli-obk`
CTFE get_alloc_extra_mut: also provide ref to MemoryExtra This would let me use mutable references in more places in Stacked Borrows, avoiding some `RefCell` overhead. :) r? `@oli-obk`