Suggestion: implementation of FromPest for std::str::FromStr #19

impl<'pest, T: std::str::FromStr> FromPest<'pest> for T {
    type Rule = /* Rule */;
    type FatalError = T::Err;
    fn from_pest(pest: &mut Pairs<'pest, Self::Rule>) -> Result<T, ConversionError<Self::FatalError>> {
        pest.next().ok_or(ConversionError::NoMatch)?.as_str().parse::<T>().ok_or_else(|e|ConversionError::Malformed(e))
    }
}

#[derive(Debug, FromPest)]
#[pest_ast(rule(Rule::field))]
pub struct Field {
    #[pest_ast(outer(with(span_into_str), with(str::parse), with(Result::unwrap)))]
    pub value: f64,
}

#[derive(Debug, FromPest)]
#[pest_ast(rule(Rule::field))]
pub struct Field {
    pub value: f64,
}