deepcopy typestablility

[jw3126]

The return type of deepcopy is always the same as its input type, right? So why not make it typestable?

 @code_warntype deepcopy(randn(3))
Variables:
  #self#::Base.#deepcopy
  x::Array{Float64,1}
  ####dims#1300#7496::Tuple{Int64}

Body:
  begin  # deepcopy.jl, line 8: # dict.jl, line 330: # array.jl, line 163: # boot.jl, line 349: # boot.jl, line 331:
      GenSym(0) = (Core.convert)(Core.Int,32)::Any
      GenSym(1) = (top(ccall))(:jl_alloc_array_1d,(top(apply_type))(Core.Array,Any,1)::Type{Array{Any,1}},(top(svec))(Core.Any,Core.Int)::SimpleVector,Array{Any,1},0,(top(unsafe_convert))(Core.Int,GenSym(0))::Int64,GenSym(0))::Array{Any,1} # array.jl, line 195:
      return (Base.deepcopy_internal)(x::Array{Float64,1},$(Expr(:new, :((top(getfield))(Base,:ObjectIdDict)::Type{ObjectIdDict}), GenSym(1))))::Any
  end::Any

[timholy]

#13323