Function dial_early_without_offer 

pub async fn dial_early_without_offer(
    endpoint: &Handle,
    target: Target,
    to: &Uri,
    options: &DialOptions,
) -> Result<Dialing>

Place an offerless INVITE and answer an offer from a reliable provisional in PRACK.

This is RFC 3262 section 5’s delayed-offer shape. An SDP-bearing reliable provisional is not merely observed: it is answered on the same dialog sequence and the resulting media is retained through confirmation. Like dial_early, this function can return for a bodiless provisional; Dialing::has_early_session distinguishes that case from a negotiated early session.

Errors

The same transport, timeout and final-response errors as dial_early, plus the SDP or media error produced while answering the provisional offer. DTLS-SRTP is refused because its active handshake cannot be started safely before the final response on this path.