Why does TID require one extra bit?

[loyd]

In tid.rs LEN is defined as:

sharded-slab/src/tid.rs

Line 47 in 8ebe120

const LEN: usize = C::MAX_SHARDS.trailing_zeros() as usize + 1;

that gives for the default config (MAX_THREADS = 4096) 13 bit space instead of 12:

    assert_eq!(Tid::<crate::cfg::DefaultConfig>::LEN, 13);

Meanwhile, we have two different checks for TID overflow:

1. sharded-slab/src/tid.rs

   Line 163 in 8ebe120

   if id > Tid::<C>::BITS {

2. sharded-slab/src/shard.rs

   Line 296 in 8ebe120

   idx < self.shards.len(),

I've missed something?

[loyd]

Any thoughts? Maybe I missed something. Extra bit would be most welcome =)

[hawkw]

this might be a bug on my part, whoops!