Quotations and Dialogue

Q. How does one punctuate dialogue in which one character interrupts another in the middle of a word? The writer whose work I’m editing has used a hyphen followed by an ellipsis, which looks awful to me: “I wouldn’t go so far as to call myself an expe- . . .”

A. The conventional punctuation is a dash: “I wouldn’t go so far as to call myself an expe—”