Function parse_precision 

fn parse_precision(
    precision_pair: Pair<'_, Rule>,
    context: &'static str,
) -> Result<i32, MessageParseError>

Parse a sub-second precision type parameter.

Substrait allows any precision from 0 to 12 on a type, so this stays a plain integer. Narrowing to a precision that a value can actually be written at is crate::precision::SupportedPrecision’s job, and only literals need it.