A practical english grammar - Vyssaja skola 1978

Contractions of HAVE with the subject pronouns
Sound symbols

When forms of have, as an auxiliary verb, and the subject pronouns occur together, the form of have is usually spoken as a contraction, as shown in Table 6-1.

Table 6-1

Notice that the contractions of has and the subject pronouns are the same as those with is; only the rest of the sentence will let you know which is which.

He’s going. (= he is)

He’s gone. (= he has)