Function extern_spec_TryFrom_i64_u64_try_from 

pub fn extern_spec_TryFrom_i64_u64_try_from(
    value: i64,
) -> Result<u64, TryFromIntError>

extern spec for u64::try_from

This is not a real function: its only use is for documentation.

ghost

ensures

match result { Ok(val) => val@ == value@, Err(_) => value@ < 0 }