func (p *parser) newAssignStmt(pos Pos, op Operator, lhs, rhs Expr) *AssignStmt {
	a := new(AssignStmt)
	a.pos = pos
	a.Op = op
	a.Lhs = lhs
	a.Rhs = rhs
	return a
}

func (p *parser) labeledStmtOrNil(label *Name) Stmt {
	if trace {
		defer p.trace("labeledStmt")()
	}

	s := new(LabeledStmt)
	s.pos = p.pos()
	s.Label = label

	p.want(_Colon)

	if p.tok == _Rbrace {