string hash significant speedup

[HyperParrow via Digitalmars-d-learn]

On Thursday, 10 August 2017 at 20:07:35 UTC, Steven Schveighoffer 
wrote:
> On 8/10/17 3:36 PM, Johnson Jones wrote:
>> when using T[string], hashing is used. Computing the hash is 
>> slow(relatively speaking).
>> 
>> Does D cache the hashes? Strings are immutable so there is 
>> absolutely no reason why the hash ever need to be computed 
>> more than once.
>
> It computes them on insertion, and caches the result in the 
> structure of the hash table.
>
> -Steve

But i think he speaks about the strings that are tested for 
inclusion (i.e opIn RHS), not those who are inserted, for which 
obviously the hash is known.