a little modification of https://gist.github.com/ildar/e5e9676f62a6b96ef2ac7b81be74ca12

traits2.tl

local record Sheep
    _naked: boolean
    _name: string
    metamethod __call: function(Sheep, Sheep): Sheep
end

-- impl Sheep
function Sheep:shear()
    print(self._name, "gets a haircut!");

    self._naked = true;
end

local Sheep_mt: metatable<Sheep> = {
    __call = function(self, initvals: Sheep): Sheep
        local res: Sheep = { _name=initvals._name, _naked=false }
        return setmetatable(res, {__index=self})
    end
}
setmetatable(Sheep, Sheep_mt)

-- fn main()
local dolly = Sheep { _name="Dolly" }

dolly:shear();