Static fieldnames

General Usage
2 
julia> @generated f(obj) = :(string($((:(getfield(obj, $i)) for i in 1:fieldcount(obj))...)))
f (generic function with 1 method)

julia> f(1im)
"01"

julia> f((1, 2, 2.4))
"122.4"

julia> @code_warntype f(1im)
Variables:
  #self# <optimized out>
  obj::Complex{Int64}

Body:
  begin
      #= REPL[4]:1 =#
      # meta: location REPL[4] @generated body
      return $(Expr(:invoke, MethodInstance for #print_to_string#245(::Void, ::Function, ::Int64, ::Vararg{Int64,N} where N), :(Base.#print_to_string#245), :($(QuoteNode(nothing))), :($(QuoteNode(Base.print_to_string))), :((Main.getfield)(obj, 1)::Int64), :((Main.getfield)(obj, 2)::Int64)))::String
      # meta: pop location
  end::String

julia> @code_warntype f((1, 2, "", 3))
Variables:
  #self# <optimized out>
  obj::Tuple{Int64,Int64,String,Int64}

Body:
  begin
      #= REPL[4]:1 =#
      # meta: location REPL[4] @generated body
      return $(Expr(:invoke, MethodInstance for #print_to_string#245(::Void, ::Function, ::Int64, ::Vararg{Any,N} where N), :(Base.#print_to_string#245), :($(QuoteNode(nothing))), :($(QuoteNode(Base.print_to_string))), :((Main.getfield)(obj, 1)::Int64), :((Main.getfield)(obj, 2)::Int64), :((Main.getfield)(obj, 3)::String), :((Main.getfield)(obj, 4)::Int64)))::String
      # meta: pop location
  end::String

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