getNewIdent := ast.NewIdent
	if addPosition {
		getNewIdent = func(newName string) *ast.Ident {
			mangledIdent := ast.NewIdent(newName)
			if len(newName) == len(r.Name.Go) {
				return mangledIdent
			}
			p := fset.Position((*r.Expr).End())
			if p.Column == 0 {
				return mangledIdent
			}
			return ast.NewIdent(fmt.Sprintf("%s /*line :%d:%d*/", newName, p.Line, p.Column))

		err := &ast.Field{Type: ast.NewIdent("error")}
		l := gtype.Results.List
		if len(l) == 0 {
			l = []*ast.Field{err}
		} else {
			l = []*ast.Field{l[0], err}
		}
		t := new(ast.FuncType)
		*t = *gtype
		t.Results = &ast.FieldList{List: l}
		gtype = t
	}

	// Go func declaration.
	d := &ast.FuncDecl{
		Name: ast.NewIdent(n.Mangle),
		Type: gtype,
	}

		for i := len(list) - 1; i >= 0; i-- {
			if par := &list[i]; par.typ != nil {
				typ = par.typ
				if par.name == nil {
					errPos = typ.Pos()
					n := ast.NewIdent("_")
					n.NamePos = errPos // correct position
					par.name = n
				}
			} else if typ != nil {
				par.typ = typ
			} else {
				// par.typ == nil && typ == nil => we only have a par.name