Function toString can dump parameters

[tcr]

We can and should recover parameter names from function debug info to aid in Function toString, e.g.

function ok (a, b, c) {
    return true;
}
console.log(ok)

printing

function ok (a, b, c) {
  [compiled bytecode]
}

This is a temporary holdover until we have take in JavaScript source code directly, so this is flagged pending-jsparser for now.