code: func loc(parser *Parser, start int) *ast.Location {
  	if parser.Options.NoLocation {
  		return nil
  	}
  	if parser.Options.NoSource {
  		return ast.NewLocation(&ast.Location{
  			Start: start,
  			End:   parser.PrevEnd,
  		})
  	}
  	return ast.NewLocation(&ast.Location{
  		Start:  start,
  		End:    parser.PrevEnd,
  		Source: parser.Source,
  	})
  }
docs: /* Core parsing utility functions */
  // Returns a location object, used to identify the place in
  // the source that created a given parsed object.