Function extern_spec_T_From_legacy_RangeFrom_T_RangeFrom_T_from 

pub fn extern_spec_T_From_legacy_RangeFrom_T_RangeFrom_T_from<T>(
    value: RangeFrom<T>,
) -> RangeFrom<T>

extern spec for RangeFrom<T>::from

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

ensures

result == RangeFrom { start: value.start }