In an island peopled by Knights (who always say the truth) and Liars (who obviously always lie), two persons spoke about each other.
A said: "B would say I lie."
B said: "That is true."
Can anything be deduced as to what kind is each of them?
Yes, A is the Knight and B is the Liar.
Reasoning: If A is the Liar then he must say something false and B can never agree (B only states the truth).