219 lines
8.9 KiB
Rust
219 lines
8.9 KiB
Rust
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// Copyright (c) 2024 Jonas Schäfer <jonas@zombofant.net>
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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//! Handling of structs
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use proc_macro2::TokenStream;
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use quote::quote;
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use syn::*;
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use crate::meta::{NameRef, NamespaceRef, XmlCompoundMeta};
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/// Parts necessary to construct a `::xso::FromXml` implementation.
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pub(crate) struct FromXmlParts {
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/// Additional items necessary for the implementation.
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pub(crate) defs: TokenStream,
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/// The body of the `::xso::FromXml::from_xml` function.
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pub(crate) from_events_body: TokenStream,
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/// The name of the type which is the `::xso::FromXml::Builder`.
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pub(crate) builder_ty_ident: Ident,
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}
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/// Parts necessary to construct a `::xso::IntoXml` implementation.
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pub(crate) struct IntoXmlParts {
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/// Additional items necessary for the implementation.
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pub(crate) defs: TokenStream,
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/// The body of the `::xso::IntoXml::into_event_iter` function.
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pub(crate) into_event_iter_body: TokenStream,
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/// The name of the type which is the `::xso::IntoXml::EventIter`.
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pub(crate) event_iter_ty_ident: Ident,
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}
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/// Definition of a struct and how to parse it.
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pub(crate) struct StructDef {
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/// The XML namespace of the element to map the struct to.
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namespace: NamespaceRef,
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/// The XML name of the element to map the struct to.
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name: NameRef,
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/// Name of the target type.
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target_ty_ident: Ident,
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/// Name of the builder type.
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builder_ty_ident: Ident,
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/// Name of the iterator type.
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event_iter_ty_ident: Ident,
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}
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impl StructDef {
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/// Create a new struct from its name, meta, and fields.
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pub(crate) fn new(ident: &Ident, meta: XmlCompoundMeta, fields: &Fields) -> Result<Self> {
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let Some(namespace) = meta.namespace else {
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return Err(Error::new(meta.span, "`namespace` is required on structs"));
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};
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let Some(name) = meta.name else {
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return Err(Error::new(meta.span, "`name` is required on structs"));
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};
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match fields {
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Fields::Unit => (),
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other => {
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return Err(Error::new_spanned(
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other,
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"cannot derive on non-unit struct (yet!)",
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))
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}
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}
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Ok(Self {
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namespace,
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name,
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target_ty_ident: ident.clone(),
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builder_ty_ident: quote::format_ident!("{}FromXmlBuilder", ident),
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event_iter_ty_ident: quote::format_ident!("{}IntoXmlIterator", ident),
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})
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}
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pub(crate) fn make_from_events_builder(
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&self,
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vis: &Visibility,
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name_ident: &Ident,
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attrs_ident: &Ident,
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) -> Result<FromXmlParts> {
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let xml_namespace = &self.namespace;
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let xml_name = &self.name;
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let target_ty_ident = &self.target_ty_ident;
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let builder_ty_ident = &self.builder_ty_ident;
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let state_ty_name = quote::format_ident!("{}State", builder_ty_ident);
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let unknown_attr_err = format!(
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"Unknown attribute in {} element.",
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xml_name.repr_to_string()
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);
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let unknown_child_err = format!("Unknown child in {} element.", xml_name.repr_to_string());
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let docstr = format!("Build a [`{}`] from XML events", target_ty_ident);
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Ok(FromXmlParts {
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defs: quote! {
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enum #state_ty_name {
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Default,
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}
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#[doc = #docstr]
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#vis struct #builder_ty_ident(::core::option::Option<#state_ty_name>);
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impl ::xso::FromEventsBuilder for #builder_ty_ident {
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type Output = #target_ty_ident;
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fn feed(
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&mut self,
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ev: ::xso::exports::rxml::Event
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) -> ::core::result::Result<::core::option::Option<Self::Output>, ::xso::error::Error> {
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match self.0 {
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::core::option::Option::None => panic!("feed() called after it returned a non-None value"),
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::core::option::Option::Some(#state_ty_name::Default) => match ev {
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::xso::exports::rxml::Event::StartElement(..) => {
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::core::result::Result::Err(::xso::error::Error::Other(#unknown_child_err))
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}
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::xso::exports::rxml::Event::EndElement(..) => {
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self.0 = ::core::option::Option::None;
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::core::result::Result::Ok(::core::option::Option::Some(#target_ty_ident))
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}
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::xso::exports::rxml::Event::Text(..) => {
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::core::result::Result::Err(::xso::error::Error::Other("Unexpected text content".into()))
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}
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// we ignore these: a correct parser only generates
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// them at document start, and there we want to indeed
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// not worry about them being in front of the first
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// element.
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::xso::exports::rxml::Event::XmlDeclaration(_, ::xso::exports::rxml::XmlVersion::V1_0) => ::core::result::Result::Ok(::core::option::Option::None)
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}
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}
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}
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}
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},
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from_events_body: quote! {
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if #name_ident.0 != #xml_namespace || #name_ident.1 != #xml_name {
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return ::core::result::Result::Err(::xso::error::FromEventsError::Mismatch {
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name: #name_ident,
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attrs: #attrs_ident,
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});
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}
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if attrs.len() > 0 {
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return ::core::result::Result::Err(::xso::error::Error::Other(
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#unknown_attr_err,
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).into());
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}
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::core::result::Result::Ok(#builder_ty_ident(::core::option::Option::Some(#state_ty_name::Default)))
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},
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builder_ty_ident: builder_ty_ident.clone(),
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})
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}
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pub(crate) fn make_into_event_iter(&self, vis: &Visibility) -> Result<IntoXmlParts> {
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let xml_namespace = &self.namespace;
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let xml_name = &self.name;
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let target_ty_ident = &self.target_ty_ident;
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let event_iter_ty_ident = &self.event_iter_ty_ident;
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let state_ty_name = quote::format_ident!("{}State", event_iter_ty_ident);
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let docstr = format!("Decompose a [`{}`] into XML events", target_ty_ident);
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Ok(IntoXmlParts {
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defs: quote! {
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enum #state_ty_name {
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Header,
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Footer,
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}
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#[doc = #docstr]
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#vis struct #event_iter_ty_ident(::core::option::Option<#state_ty_name>);
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impl ::std::iter::Iterator for #event_iter_ty_ident {
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type Item = ::core::result::Result<::xso::exports::rxml::Event, ::xso::error::Error>;
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fn next(&mut self) -> ::core::option::Option<Self::Item> {
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match self.0 {
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::core::option::Option::Some(#state_ty_name::Header) => {
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self.0 = ::core::option::Option::Some(#state_ty_name::Footer);
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::core::option::Option::Some(::core::result::Result::Ok(::xso::exports::rxml::Event::StartElement(
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::xso::exports::rxml::parser::EventMetrics::zero(),
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(
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::xso::exports::rxml::Namespace::from_str(#xml_namespace),
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#xml_name.to_owned(),
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),
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::xso::exports::rxml::AttrMap::new(),
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)))
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}
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::core::option::Option::Some(#state_ty_name::Footer) => {
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self.0 = ::core::option::Option::None;
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::core::option::Option::Some(::core::result::Result::Ok(::xso::exports::rxml::Event::EndElement(
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::xso::exports::rxml::parser::EventMetrics::zero(),
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)))
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}
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::core::option::Option::None => ::core::option::Option::None,
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}
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}
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}
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},
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into_event_iter_body: quote! {
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::core::result::Result::Ok(#event_iter_ty_ident(::core::option::Option::Some(#state_ty_name::Header)))
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},
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event_iter_ty_ident: event_iter_ty_ident.clone(),
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})
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}
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}
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