Can we skip writing the key into a `Dict` if we know it's already present?

[Zentrik]

julia/base/dict.jl

Lines 404 to 417 in e7345b8

	function setindex!(h::Dict{K,Any}, v, key::K) where K
	@nospecialize v
	index, sh = ht_keyindex2_shorthash!(h, key)
	if index > 0
	h.age += 1
	@inbounds h.keys[index] = key
	@inbounds h.vals[index] = v
	else
	@inbounds _setindex!(h, v, key, -index, sh)
	end
	return h
	end

ht_keyindex2_shorthash!only returnsindex > 0` if

julia/base/dict.jl

Line 326 in e7345b8

if key === k || isequal(key, k)

As isequal(x,y) implies hash(x) == hash(y) and the Dict docs say 'Keys are compared with isequal and hashed with hash', seems like it should be fine to skip the h.keys[index] = key.

[Zentrik]

The dict testsuite passes if I remove this write and a couple of similar ones.

[vtjnash]

No, the key still needs to be updated to the current object, even if the objects are isequal

[vtjnash]

we should add a test though, if that is lacking

julia> d = Dict(); d[1] = 'a'; d[1.0] = 'b'; only(d) === Pair{Any,Any}(1.0, 'b')
true