Function prepare_bodyless 

pub fn prepare_bodyless(
    parts: &Parts,
    is_end_stream: bool,
    _: &SizeHint,
) -> Option<CollectOptions>

Available on crate features http and std only.

Prepare only safe, truly empty requests for automatic early-data recovery.

A zero byte hint does not suffice: trailers can follow. Payload-bearing or unsafe requests stream once under this initial policy. Applications needing ordinary payload retries can supply a different preparation function; the early-send admission checks remain safe-method and empty-body only.