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: lib.rs
    path of file: ./repos/strata/strata-derive/src
    
    the code of the file until where you have to start completion: use proc_macro::TokenStream;
use quote::{
	quote,
	quote_spanned,
	spanned::Spanned,
};
use syn::Attribute;

struct ConfigAttrs {
	is_flat: bool,
	from_type: Option<syn::Type>,
}

impl<'a, T> From<T> for ConfigAttrs
where
	T: IntoIterator<Item = &'a Attribute>,
{
	fn from(iter: T) -> Self {
		let mut ret = Self { is_flat: false, from_type: None };

		for attr in iter {
			attr.parse_nested_meta(|meta| {
				if meta.path.is_ident("from") {
					ret.from_type = Some(meta.value()?.parse()?);
				} else if meta.path.is_ident("flat") {
					ret.is_flat = true;
				} else {
					panic!("unknown attribute");
				}
				Ok(())
			})
			.expect("failed to parse attribute");
		}

		ret
	}
}

/// Procedural macro to derive a wrapper with optional fields around a struct.
#[proc_macro_derive(Config, attributes(config))]
pub fn config_derive(input: TokenStream) -> TokenStream {
	let input = syn::parse_macro_input!(input as syn::DeriveInput);

	match input.d
    
pub fn config_derive(input: TokenStream) -> TokenStream {
	let input = syn::parse_macro_input!(input as syn::DeriveInput);

	match input.data {
		syn::Data::Struct(ref struct_data) => {
			let struct_name = input.ident;
			let fields = struct_data.fields.iter().map(|field| {
				let attrs = ConfigAttrs::from(
					field.attrs.iter().filter(|attr| attr.path().is_ident("config")),
				);
				(field.ident.as_ref().unwrap(), &field.ty, attrs)
			});

			let from_lua_fields = fields.clone().map(|(field_name, field_type, attrs)| {
				let field_type = attrs.from_type.as_ref().unwrap_or(field_type);
				let field_value = if attrs.is_flat {
					quote! {
						table.get::<_, #field_type>(stringify!(#field_name))?.into()
					}
				} else {
					quote! {
						table
							.get::<_, Option<#field_type>>(stringify!(#field_name))?
							.map(Into::into)
							.unwrap_or_default()
					}
				};

				quote! {
					#field_name: #field_value
				}
			});

			let update_from_lua_fields = fields.map(|(field_name, _field_type, attrs)| {
				match (attrs.is_flat, attrs.from_type) {
					(true, None) => {
						quote! {
							self.#field_name.update_from_lua(table.get(stringify!(#field_name))?, lua)?;
						}
					}
					(true, Some(from_type)) => {
						quote! {
							self.#field_name = table.get::<_, #from_type>(stringify!(#field_name))?.into();
						}
					}
					(false, None) => {
						quote! {
							if let Some(value) = table.get::<_, Option<mlua::Value>>(stringify!(#field_name))? {
								self.#field_name.update_from_lua(value, lua)?;
							}
						}
					}
					(false, Some(from_type)) => {
						quote! {
							if let Some(value) = table.get::<_, Option<#from_type>>(stringify!(#field_name))? {
								self.#field_name = value.into();
							}
						}
					}
				}
			});

			quote! {
				impl<'lua> mlua::FromLua<'lua> for #struct_name {
					fn from_lua(value: mlua::Value<'lua>, lua: &'lua mlua::Lua) -> mlua::Result<Self> {
						let table = mlua::Table::from_lua(value, lua)?;
						Ok(Self {
							#(#from_lua_fields),*
						})
					}
				}

				impl<'lua> strata_core::UpdateFromLua<'lua> for #struct_name {
					fn update_from_lua(&mut self, value: mlua::Value<'lua>, lua: &'lua mlua::Lua) -> mlua::Result<()> {
						let table = mlua::Table::from_lua(value, lua)?;
						#(#update_from_lua_fields)*
						Ok(())
					}
				}
			}
		}
		syn::Data::Enum(_) => {
			let enum_name = input.ident;
			quote! {
				impl<'lua> mlua::FromLua<'lua> for #enum_name {
					fn from_lua(value: mlua::Value<'lua>, lua: &'lua mlua::Lua) -> mlua::Result<Self> {
						let str = String::from_lua(value, lua)?;
						 std::str::FromStr::from_str(&str).map_err(|_| mlua::Error::FromLuaConversionError {
							from: "string",
							to: stringify!(#enum_name),
							message: Some("invalid variant".to_owned()),
						})
					}
				}

				impl<'lua> strata_core::UpdateFromLua<'lua> for #enum_name {
					fn update_from_lua(&mut self, value: mlua::Value<'lua>, lua: &'lua mlua::Lua) -> mlua::Result<()> {
						*self = Self::from_lua(value, lua)?;
						Ok(())
					}
				}
			}
		}
		_ => {
			quote_spanned! {
				input.ident.__span() => compile_error!("Config can only be derived for structs and enums");
			}
		}
	}
	.into()
}