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I played around with this a few years ago in github.com/MasonProtter/PatternDispatch.jl

julia> module PatternFruitFactory
       using PatternDispatch

       abstract type Fruit end
       struct Apple <: Fruit end
       struct Orange <: Fruit end

       @pattern fruit("apple") = Apple()
       @pattern fruit("orange") = Orange()
       @pattern fruit(s) = error("unknown fruit $s")
       end

julia> @btime PatternFruitFactory.fruit("orange")
  3.449 ns (0 allocations: 0 bytes)
Main.PatternFruitFactory.Orange()

These are extensible at a later time:

julia> @btime PatternFruitFactory.fruit("banana")
  7.537 ns (0 allocations: 0 bytes)
Main.PatternFruitFactory.Banana()

PatternDispatch.jl does some stuff that's unfriendly to precompilation though so it doesn't fit very well into packages. Very much just a proof of concept.