different Dicts hash to same value

[stevengj]

As reported on discourse, it looks like there is a bug in hash(a::Associative, h::UInt):

hash(Dict(Dict(1=>2) => 3, Dict(4=>5) => 6)) == hash(Dict(Dict(4=>5) => 3, Dict(1=>2) => 6))

returns true even though the dictionaries are different.

[stevengj]

Note that it seems specific to Dict keys. hash(Dict(1 => 3, 4 => 6)) == hash(Dict(4 => 3, 1 => 6)) returns false as expected, as does hash(Dict(3 => Dict(1=>2), 6 => Dict(4=>5))) == hash(Dict(3 => Dict(4=>5), 6 => Dict(1=>2))).

[stevengj]

@ScottPJones found an easy fix for this: ScottPJones@8a2a869

[StefanKarpinski]

We should cherry-pick that commit so as to preserve his authorship of the fix.

[StefanKarpinski]

Oh, already done that way, I see. Carry on.