The "subject" of the infinitive

The doer of the action expressed by the infinitive can be:

• the subject of the sentence:
  

  I was glad to see her.
  You must be joking.
  Lucy was assumed to have left the day before.
  I want to go.
  I've come here to help you.

• the direct object of the verb in the main clause:
  

  I want you to go.
  The teacher made Jack rewrite the composition.
  I'll have her copy the document right away.
  I couldn't get her to understand the problem.
  I saw him cross the street.

• the object of the prepositions of or for:
  

  It's very kind of you to come with me to the embassy.
  We were waiting for the rain to stop.
  It's easy for an outsider to say what should be done in such a situation.

• an indefinite or generalised subject (you, one, we, people etc.):
  

  It is sometimes difficult to accept the truth.
  The rules didn't specify who to talk to in case of an emergency.

• unexpressed and understood only from the context:
  

  It must have been funny to see her in a tuxedo.
  Nice to meet you.
  It would be a mistake to hire him.