Allocation during access to "typed" field of mutable struct

General Usage Performance
4

I’m sorry:

using Test
using BenchmarkTools

abstract type AbstractElement end

mutable struct Element{T<:AbstractElement} <: AbstractElement
           input::String
           name::UnitRange{Int64}
           attributes::Union{Nothing, Int}
           value::Union{T, Nothing}
           parent::Union{Element, Nothing}
           next::Union{Element, Nothing}
end

example(node::Element) = begin
    while !isnothing(node)
        if node.name == 1:1 return node end
        node = node.next
    end
    return error("error")
end

@testset "example" begin
    first = Element{Element}("", 2:2, nothing, nothing, nothing, nothing)
    second = Element{Element}("", 1:1, nothing, nothing, nothing, nothing)
    first.next = second
    @code_warntype example(first)
    @btime example($first)
end

You can just copypaste this snippet, it works and shows the problem