LittleDict should overload hasfastin to be false

[oxinabox]

This function says if the checking of haskey is expected logorithmic or better.
but for LittleDict it is not, it is linear.

Default for AbstractDict is true.

https://github.com/JuliaLang/julia/blob/aa36eefa17e68dd3781b668bc40328583b161924/base/abstractset.jl#L284-L295

[kmsquire]

Technically true, but isn’t the point of LittleDicts is that they’re used when you only have a few values? In this case, the size is bounded, and the timing can be considered linear. (Of course, there isn’t a size check in the code, right?)

Technical definitions aside, what is the point of hasfastin? If it’s really concerned about speed, then the speed of key lookup in LittleDicts might be considered fast. If it’s used for inlining (or something similar), then maybe not.

[oxinabox]

See discussion in JuliaLang/julia#34672

It's exactly the same here except we know more about the type of our key container -- always tuple or vevtor