Isn't load() in 5.2 too naive about _ENV?

[Artur Galyamov <artur-pub@...>]

Why does load(...) in 5.2 make an assumption, that _ENV is *always*
first upvalue? I think it should search for the name "_ENV" instead
(and set nothing, if not found).

------------------------------------------------------------
local upvalue

function test()
    return upvalue, global
end

assert(debug.getupvalue(test, 1) == "upvalue")
assert(debug.getupvalue(test, 2) == "_ENV")

local f = load(string.dump(test), nil, nil, "environment")
-- bad thing happened...

print(debug.getupvalue(f, 1)) -- "upvalue", "environment"
print(debug.getupvalue(f, 2)) -- "_ENV", nil
------------------------------------------------------------

-- Artur