code: func sourceCoordinates(asm map[int][]assemblyInstruction) (start, end int) {
  	for l := range asm {
  		if start == 0 || l < start {
  			start = l
  		}
  		if end == 0 || l > end {
  			end = l
  		}
  	}
  	return start, end
  }
docs: // sourceCoordinates returns the lowest and highest line numbers from
  // a set of assembly statements.