Inlining behavior: constant prop. fails, I need help in understanding "why"

General Usage Performance
4

This is how I usually benchmark constant propagation:

julia> function f(x)
           D = 1
           reconstruct(x, D)
       end
f (generic function with 1 method)

julia> @btime f($x)
  871.847 ns (2 allocations: 112 bytes)
50.48725909006644