ident, ok := x.(*ast.Ident)
	return ok && ident.Name == "_"
}

func simplify(f *ast.File) {
	// remove empty declarations such as "const ()", etc
	removeEmptyDeclGroups(f)

	var s simplifier
	ast.Walk(s, f)
}

func removeEmptyDeclGroups(f *ast.File) {
	i := 0
	for _, d := range f.Decls {
		if g, ok := d.(*ast.GenDecl); !ok || !isEmpty(f, g) {
			f.Decls[i] = d
			i++
		}
	}