Rule for typed_vcat?

[ToucheSir]

Mainly because the vcat literal syntax lowers to this:

julia> Meta.@lower Int[1; 2; 3]
:($(Expr(:thunk, CodeInfo(
    @ none within `top-level scope`
1 ─ %1 = Base.typed_vcat(Int, 1, 2, 3)
└──      return %1
))))

[mcabbott]

Similarly Int[1 2 3] and Float32[1 2; 3 4]. Ideally these would share as much code as possible with the existing cat rules, perhaps just changing a few lines.

Maybe worth mentioning that typed comprehensions are much harder: Meta.@lower Int[x^2 for x in 1:3].