Method variable names and destructuring

Internals & Design
1

I am trying to fix DocStringExtensions.jl/issues/67, for which I need to get the variable names also for destructured arguments. MWE:

f((x, y), z) = x + y + z
## how to extract something like
((:x, :y), :z)
## from
first(methods(f))
2

I don’t think that x and y exists in the method signature after lowering but that this instead gets transformed to

function f(__xy, z)
    x, y = __xy
    return x + y + z
end

I guess the lowered form could be analyzed and retrieve back the original variable names but it requires a bit more work

julia> Meta.lower(Main, :(f((x, y), z) = x + y + z))
:($(Expr(:thunk, CodeInfo(
 1 ─      $(Expr(:method, :f))                                                                                      │
 │   %2 = (Core.Typeof)(f)                                                                                          │
 │   %3 = (Core.svec)(%2, Core.Any, Core.Any)                                                                       │
 │   %4 = (Core.svec)()                                                                                             │
 │   %5 = (Core.svec)(%3, %4)                                                                                       │
 │        $(Expr(:method, :f, :(%5), CodeInfo(quote                                                                 │
    (Base.indexed_iterate)(#temp#@_2, 1)
    x = (Core.getfield)(%1, 1)
    #temp#@_6 = (Core.getfield)(%1, 2)
    (Base.indexed_iterate)(#temp#@_2, 2, #temp#@_6)
    y = (Core.getfield)(%4, 1)
    #temp#@_6 = (Core.getfield)(%4, 2)
    x + y + z
    return %7
end)))
 └──      return f                                                                                                  │
))))