Feature request: type annotation on variables in @unpack

[jishnub]

E.g.

julia> d1 = Dict(:a=>3, :b=>2.0)
Dict{Symbol, Real} with 2 entries:
  :a => 3
  :b => 2.0

julia> function f(d1)
           @unpack a = d1
           a
       end
f (generic function with 1 method)

julia> @code_typed f(d1)
CodeInfo(
1 ─ %1 = invoke Base.getindex(d1::Dict{Symbol, Real}, :a::Symbol)::Real
└──      return %1
) => Real

In this case, if I know that a must be an Int, I might want to specify this as a::Int in the @unpack, but the following doesn't work:

julia> function f(d1)
           @unpack a::Int = d1
           a
       end
f (generic function with 1 method)

julia> f(d1)
ERROR: KeyError: key :Int not found
Stacktrace:
 [1] getindex(h::Dict{Symbol, Real}, key::Symbol)
   @ Base ./dict.jl:484
 [2] unpack
   @ ~/.julia/packages/UnPack/EkESO/src/UnPack.jl:35 [inlined]
 [3] macro expansion
   @ ~/.julia/packages/UnPack/EkESO/src/UnPack.jl:101 [inlined]
 [4] f(d1::Dict{Symbol, Real})
   @ Main ./REPL[290]:2
 [5] top-level scope
   @ REPL[291]:1

[mauro3]

Thanks! Yes that would be a good feature, PR welcome.

Work-arounds:

julia> function f(d1)
           local a::Int
           @unpack a = d1
           a
       end
f (generic function with 1 method)

julia> function f(d1)
           (;a::Int) = d1
           a
       end
f (generic function with 1 method)