why fastcache not do hashcode collision?

[ahfuzhang]

in file fastcache.go, func (b *bucket) Set, line 359:
b.m[h] = idx | (b.gen << bucketSizeBits)

I think the code should be:

if oldValue, ok := b.m[h]; ok{
    //do something, or the last key of same hashcode will lost
}

thanks.

[ahfuzhang]

sorry, I don't see all logic.
If there is a check, clean() will not remove expires data.
But we can still add a hashcode collision check, and tell calller the over write old value.