Documented check for uniqueness in Set collection

[TenzinCHW]

The documented check for whether an element is in a set is Base.isequal. However, based on the code it seems that a Dict is used as the underlying datastructure, which implies that the check is actually using Base.hash instead.

struct A
    content::Vector{UInt8}
end

Base.hash(a::A) = hash(a.content)
# vs
# Base.isequal(a::A, b::A) = all(a.content .== b.content)

s = Set([A([1]) for _ in 1:2])

If instead the content field of A is a String, defining Base.isequal is not necessary.

[KristofferC]

You need isequal to deal with hash collisions.