Reordering NamedTuples

General Usage
6

I think this is pretty simple and efficient:

julia> nt1 = (; a = 1, b = 2)
(a = 1, b = 2)

julia> nt2 = (; b = 3, a = 4)
(b = 3, a = 4)

julia> NamedTuple{keys(nt1)}(nt2)
(a = 4, b = 3)

julia> @code_warntype NamedTuple{keys(nt1)}(nt2)
MethodInstance for (NamedTuple{(:a, :b)})(::NamedTuple{(:b, :a), Tuple{Int64, Int64}})
  from (NamedTuple{names})(nt::NamedTuple) where names in Base at namedtuple.jl:99
Static Parameters
  names = (:a, :b)
Arguments
  #self#::Type{NamedTuple{(:a, :b)}}
  nt::NamedTuple{(:b, :a), Tuple{Int64, Int64}}
Body::NamedTuple{(:a, :b), Tuple{Int64, Int64}}
1 ─ %1 = Core.apply_type(Base.NamedTuple, $(Expr(:static_parameter, 1)), Tuple{Int64, Int64})::Core.Const(NamedTuple{(:a, :b), Tuple{Int64, Int64}})
│   %2 = Base.getfield(nt, 2)::Int64
│   %3 = Base.getfield(nt, 1)::Int64
│   %4 = %new(%1, %2, %3)::NamedTuple{(:a, :b), Tuple{Int64, Int64}}
└──      return %4

It’s implemented in Base with a generated function.

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