It is Julia all the way down.

  julia> @which randn(1000)
  randn(dims::Integer...) in Random at ~/Software/Julia/share/julia/stdlib/v1.5/Random/src/normal.jl:210

  julia> @edit randn(1000)
  # Opens the normal.jl file in your editor

  julia> @run randn(1000)
  # Starts the debugger in VSCode

Digging deeper, at least one of the PRs [1] is based on a 2018 paper [2]

[1] https://github.com/JuliaLang/julia/pull/29240 [2] https://arxiv.org/abs/1805.10941