JuliaSyntax: fix anonymous function parsing

[IanButterworth]

Fixes #60202

julia> function zip_missing(::Tuple{}, longer)
		      map(function (second_one)
		          (missing, second_one)
		      end, longer)
		  end
zip_missing (generic function with 1 method)

Written by Claude

[Keno]

Just for reference, @KristofferC just touched this code in JuliaLang/JuliaSyntax.jl#580

[fingolfin]

Maybe also insert a involving explicitly a tuple () as the body?

E.g. near line 622-628, where in JuliaLang/JuliaSyntax.jl#580 this test was inserted:

        "function (\n        f\n        )() end" =>  "(function (call (parens f)) (block))"

well now we want to test something like this (not sure if I got it quite right)

        "function (\n        x\n        )\n() end" =>  "(function (tuple-p x) (block (tuple-p)))"

Because for me, on master, this parses:

function(y)
  body
end

but this does not:

function(y)
  ()
end