func (p *parser) expect(tok rune) scanner.Position {
pos := p.pos
if p.tok != tok {
p.errorExpected(pos, scanner.TokenString(tok))
}
// make progress in any case
p.next()
return pos
}
func (p *parser) errorExpected(pos scanner.Position, msg string) {
msg = `expected "` + msg + `"`
if pos.Offset == p.pos.Offset {
// the error happened at the current position; make the error message more
// specific
msg += ", found " + scanner.TokenString(p.tok)
if p.tok < 0 {
msg += " " + p.lit
}
}
p.error(pos, msg)
}