Infer argument types

[gfwilliams]

Currently if I write:

function a(x) {
  "compiled";
  print(x|0);
}

You get something a bit like like:

void a(JsVar *x) {
  print(jsvGetInteger(x)|0);
}

We know that x|0 is an integer already, so ideally:

• x itself would get converted to an integer, which would change the argument type
• x|0 then detected as a no-op and removed (although the compiler would do this so do we care?)

void a(int x) {
  print(x);
}