You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: field.rs
    path of file: ./repos/diesel/diesel_derives/src
    
    the code of the file until where you have to start completion: use proc_macro2::{Span, TokenStream};
use syn::spanned::Spanned;
use syn::{Expr, Field as SynField, Ident, Index, Result, Type};

use crate::attrs::{parse_attributes, AttributeSpanWrapper, FieldAttr, SqlIdentifier};

pub struct Field {
    pub ty: Type,
    pub span: Span,
    pub name: FieldName,
    column_name: Option<AttributeSpanWrapper<SqlIdentifier>>,
    pub sql_type: Option<AttributeSpanWrapper<Type>>,
    pub treat_none_as_default_value: Option<AttributeSpanWrapper<bool>>,
    pub treat_none_as_null: Option<AttributeSpanWrapper<bool>>,
 
    
    pub fn from_struct_field(field: &SynField, index: usize) -> Result<Self> {
        let SynField {
            ident, attrs, ty, ..
        } = field;

        let mut column_name = None;
        let mut sql_type = None;
        let mut serialize_as = None;
        let mut deserialize_as = None;
        let mut embed = None;
        let mut skip_insertion = None;
        let mut select_expression = None;
        let mut select_expression_type = None;
        let mut treat_none_as_default_value = None;
        let mut treat_none_as_null = None;

        for attr in parse_attributes(attrs)? {
            let attribute_span = attr.attribute_span;
            let ident_span = attr.ident_span;
            match attr.item {
                FieldAttr::ColumnName(_, value) => {
                    column_name = Some(AttributeSpanWrapper {
                        item: value,
                        attribute_span,
                        ident_span,
                    })
                }
                FieldAttr::SqlType(_, value) => {
                    sql_type = Some(AttributeSpanWrapper {
                        item: Type::Path(value),
                        attribute_span,
                        ident_span,
                    })
                }
                FieldAttr::TreatNoneAsDefaultValue(_, value) => {
                    treat_none_as_default_value = Some(AttributeSpanWrapper {
                        item: value.value,
                        attribute_span,
                        ident_span,
                    })
                }
                FieldAttr::TreatNoneAsNull(_, value) => {
                    treat_none_as_null = Some(AttributeSpanWrapper {
                        item: value.value,
                        attribute_span,
                        ident_span,
                    })
                }
                FieldAttr::SerializeAs(_, value) => {
                    serialize_as = Some(AttributeSpanWrapper {
                        item: Type::Path(value),
                        attribute_span,
                        ident_span,
                    })
                }
                FieldAttr::DeserializeAs(_, value) => {
                    deserialize_as = Some(AttributeSpanWrapper {
                        item: Type::Path(value),
                        attribute_span,
                        ident_span,
                    })
                }
                FieldAttr::SelectExpression(_, value) => {
                    select_expression = Some(AttributeSpanWrapper {
                        item: value,
                        attribute_span,
                        ident_span,
                    })
                }
                FieldAttr::SelectExpressionType(_, value) => {
                    select_expression_type = Some(AttributeSpanWrapper {
                        item: value,
                        attribute_span,
                        ident_span,
                    })
                }
                FieldAttr::Embed(_) => {
                    embed = Some(AttributeSpanWrapper {
                        item: true,
                        attribute_span,
                        ident_span,
                    })
                }
                FieldAttr::SkipInsertion(_) => {
                    skip_insertion = Some(AttributeSpanWrapper {
                        item: true,
                        attribute_span,
                        ident_span,
                    })
                }
            }
        }

        let name = match ident.clone() {
            Some(x) => FieldName::Named(x),
            None => FieldName::Unnamed(index.into()),
        };

        let span = match name {
            FieldName::Named(ref ident) => ident.span(),
            FieldName::Unnamed(_) => ty.span(),
        };

        Ok(Self {
            ty: ty.clone(),
            span,
            name,
            column_name,
            sql_type,
            treat_none_as_default_value,
            treat_none_as_null,
            serialize_as,
            deserialize_as,
            select_expression,
            select_expression_type,
            embed,
            skip_insertion,
        })
    }