Body[36m::Union{}[39m
          [33m @ foobar.jl:2 within `foo`[39m
          [33m┌ @ boot.jl: within `Box`[39m
[90m1 ──[39m[32m    0[39m [33m│[39m %1  = Core.Box[36m::Core.Const(Core.Box)[39m
[90m│   [39m[32m    0[39m [33m│[39m %2  = %new(%1)[91m[1m::Core.Box[22m[39m
[90m│ [39m        [33m└[39m
[90m│ [39m        [33m┌ @ int.jl: within `+`[39m
[90m│   [39m[32m    1[39m [33m│[39m %3  = Base.add_int(_2, _3)[36m::Int64[39m
[90m│ [39m        [33m└[39m
[90m└───[39m[32m    3[39m        Core.setfield!(%2, :contents, %3)
          [33m @ foobar.jl:3 within `foo`[39m
[90m2 ┄─[39m[32m    1[39m  %5  = Core.isdefined(%2, :contents)[36m::Bool[39m
[90m└───[39m[32m    0[39m        goto #4 if not %5
[90m3 ──[39m[32m    0[39m        goto #5
[90m4 ──[39m[32m    0[39m        $(Expr(:throw_undef_if_not, :z, false))
[90m5 ┄─[39m[32m    0[39m  %9  = Core.getfield(%2, :contents)[91m[1m::Any[22m[39m
[90m│   [39m[32m 1000[39m  %10 = (%9 < 4)[91m[1m::Any[22m[39m
[90m└───[39m[32m    0[39m        goto #10 if not %10
          [33m @ foobar.jl:4 within `foo`[39m
[90m6 ──[39m[32m    1[39m  %12 = Core.isdefined(%2, :contents)[36m::Bool[39m
[90m└───[39m[32m    0[39m        goto #8 if not %12
[90m7 ──[39m[32m    0[39m        goto #9
[90m8 ──[39m[32m    0[39m        $(Expr(:throw_undef_if_not, :z, false))
[90m9 ┄─[39m[32m    0[39m  %16 = Core.getfield(%2, :contents)[91m[1m::Any[22m[39m
[90m│   [39m[32m 1000[39m  %17 = (%16 + 1)[91m[1m::Any[22m[39m
[90m│   [39m[32m    3[39m        Core.setfield!(%2, :contents, %17)
[90m└───[39m[32m   40[39m        goto #2
          [33m @ foobar.jl:6 within `foo`[39m
[90m10 ─[39m[32m    0[39m  %20 = %new(Main.anonymous.:(var"#1#2"), %2)[36m::Main.anonymous.var"#1#2"[39m
[90m│   [39m[32m   20[39m        invoke %20(_2::Int64)
[90m│ [39m        [33m @ foobar.jl:7 within `foo`[39m
[90m│ [39m        [33m┌ @ refpointer.jl: within `Ref`[39m
[90m│ [39m        [33m│┌ @ refvalue.jl: within `RefValue`[39m
[90m│   [39m[32m    0[39m [33m││[39m %22 = %new(Base.RefValue{Union{Missing, Int64}}, _2)[36m::Base.RefValue{Union{Missing, Int64}}[39m
[90m│ [39m        [33m└└[39m
[90m│   [39m[32m    0[39m        (%22 + _3)
[90m└───[39m[32m    0[39m        unreachable
