}
	return nil
}

func (f *WorkFile) SortBlocks() {
	f.removeDups() // otherwise sorting is unsafe

	for _, stmt := range f.Syntax.Stmt {
		block, ok := stmt.(*LineBlock)
		if !ok {
			continue
		}
		sort.SliceStable(block.Line, func(i, j int) bool {
			return lineLess(block.Line[i], block.Line[j])
		})
	}
}

// removeDups removes duplicate replace directives.
//

// logic (MVS).
//
// retract directives are not de-duplicated since comments are
// meaningful, and versions may be retracted multiple times.
func (f *File) removeDups() {
	removeDups(f.Syntax, &f.Exclude, &f.Replace)
}

func removeDups(syntax *FileSyntax, exclude *[]*Exclude, replace *[]*Replace) {
	kill := make(map[*Line]bool)

	// Remove duplicate excludes.
	if exclude != nil {