code: func srcLine(src []byte, p token.Position) string {
  	// Run to end of line in both directions if not at line start/end.
  	lo, hi := p.Offset, p.Offset+1
  	for lo > 0 && src[lo-1] != '\n' {
  		lo--
  	}
  	for hi < len(src) && src[hi-1] != '\n' {
  		hi++
  	}
  	return string(src[lo:hi])
  }
docs: // srcLine returns the complete line at p, including the terminating newline.