code: func (l *State) SetField(index int, key string) {
  	l.checkElementCount(1)
  	t := l.indexToValue(index)
  	l.push(key)
  	l.setTableAt(t, key, l.stack[l.top-2])
  	l.top -= 2
  }
docs: // SetField does the equivalent of table[key]=v where table is the value at
  // index and v is the value on top of the stack.
  //
  // This function pops the value from the stack. As in Lua, this function may
  // trigger a metamethod for the __newindex event.
  //
  // http://www.lua.org/manual/5.2/manual.html#lua_setfield