Move code generation into askama_derive

1 files changed, 0 insertions, 2142 deletions

diff --git a/askama_shared/src/generator.rs b/askama_shared/src/generator.rs
deleted file mode 100644
index ea95bd3..0000000
--- a/askama_shared/src/generator.rs
+++ /dev/null
@@ -1,2142 +0,0 @@
-use crate::config::{get_template_source, read_config_file, Config, WhitespaceHandling};
-use crate::heritage::{Context, Heritage};
-use crate::input::{Print, Source, TemplateInput};
-use crate::parser::{parse, Cond, CondTest, Expr, Loop, Node, Target, When, Whitespace, Ws};
-use crate::{filters, CompileError};
-
-use proc_macro2::TokenStream;
-use quote::{quote, ToTokens};
-
-use std::collections::HashMap;
-use std::path::{Path, PathBuf};
-use std::{cmp, hash, mem, str};
-
-/// The actual implementation for askama_derive::Template
-#[doc(hidden)]
-pub fn derive_template(input: TokenStream) -> TokenStream {
-    let ast: syn::DeriveInput = syn::parse2(input).unwrap();
-    match build_template(&ast) {
-        Ok(source) => source.parse().unwrap(),
-        Err(e) => e.into_compile_error(),
-    }
-}
-
-/// Takes a `syn::DeriveInput` and generates source code for it
-///
-/// Reads the metadata from the `template()` attribute to get the template
-/// metadata, then fetches the source from the filesystem. The source is
-/// parsed, and the parse tree is fed to the code generator. Will print
-/// the parse tree and/or generated source according to the `print` key's
-/// value as passed to the `template()` attribute.
-fn build_template(ast: &syn::DeriveInput) -> Result<String, CompileError> {
-    let template_args = TemplateArgs::new(ast)?;
-    let config_toml = read_config_file(&template_args.config_path)?;
-    let config = Config::new(&config_toml)?;
-    let input = TemplateInput::new(ast, &config, template_args)?;
-    let source: String = match input.source {
-        Source::Source(ref s) => s.clone(),
-        Source::Path(_) => get_template_source(&input.path)?,
-    };
-
-    let mut sources = HashMap::new();
-    find_used_templates(&input, &mut sources, source)?;
-
-    let mut parsed = HashMap::new();
-    for (path, src) in &sources {
-        parsed.insert(path.as_path(), parse(src, input.syntax)?);
-    }
-
-    let mut contexts = HashMap::new();
-    for (path, nodes) in &parsed {
-        contexts.insert(*path, Context::new(input.config, path, nodes)?);
-    }
-
-    let ctx = &contexts[input.path.as_path()];
-    let heritage = if !ctx.blocks.is_empty() || ctx.extends.is_some() {
-        Some(Heritage::new(ctx, &contexts))
-    } else {
-        None
-    };
-
-    if input.print == Print::Ast || input.print == Print::All {
-        eprintln!("{:?}", parsed[input.path.as_path()]);
-    }
-
-    let code = Generator::new(
-        &input,
-        &contexts,
-        heritage.as_ref(),
-        MapChain::new(),
-        config.whitespace,
-    )
-    .build(&contexts[input.path.as_path()])?;
-    if input.print == Print::Code || input.print == Print::All {
-        eprintln!("{}", code);
-    }
-    Ok(code)
-}
-
-#[derive(Default)]
-pub(crate) struct TemplateArgs {
-    pub(crate) source: Option<Source>,
-    pub(crate) print: Print,
-    pub(crate) escaping: Option<String>,
-    pub(crate) ext: Option<String>,
-    pub(crate) syntax: Option<String>,
-    pub(crate) config_path: Option<String>,
-}
-
-impl TemplateArgs {
-    fn new(ast: &'_ syn::DeriveInput) -> Result<Self, CompileError> {
-        // Check that an attribute called `template()` exists once and that it is
-        // the proper type (list).
-        let mut template_args = None;
-        for attr in &ast.attrs {
-            let ident = match attr.path.get_ident() {
-                Some(ident) => ident,
-                None => continue,
-            };
-
-            if ident == "template" {
-                if template_args.is_some() {
-                    return Err("duplicated 'template' attribute".into());
-                }
-
-                match attr.parse_meta() {
-                    Ok(syn::Meta::List(syn::MetaList { nested, .. })) => {
-                        template_args = Some(nested);
-                    }
-                    Ok(_) => return Err("'template' attribute must be a list".into()),
-                    Err(e) => return Err(format!("unable to parse attribute: {}", e).into()),
-                }
-            }
-        }
-        let template_args =
-            template_args.ok_or_else(|| CompileError::from("no attribute 'template' found"))?;
-
-        let mut args = Self::default();
-        // Loop over the meta attributes and find everything that we
-        // understand. Return a CompileError if something is not right.
-        // `source` contains an enum that can represent `path` or `source`.
-        for item in template_args {
-            let pair = match item {
-                syn::NestedMeta::Meta(syn::Meta::NameValue(ref pair)) => pair,
-                _ => {
-                    return Err(format!(
-                        "unsupported attribute argument {:?}",
-                        item.to_token_stream()
-                    )
-                    .into())
-                }
-            };
-            let ident = match pair.path.get_ident() {
-                Some(ident) => ident,
-                None => unreachable!("not possible in syn::Meta::NameValue(…)"),
-            };
-
-            if ident == "path" {
-                if let syn::Lit::Str(ref s) = pair.lit {
-                    if args.source.is_some() {
-                        return Err("must specify 'source' or 'path', not both".into());
-                    }
-                    args.source = Some(Source::Path(s.value()));
-                } else {
-                    return Err("template path must be string literal".into());
-                }
-            } else if ident == "source" {
-                if let syn::Lit::Str(ref s) = pair.lit {
-                    if args.source.is_some() {
-                        return Err("must specify 'source' or 'path', not both".into());
-                    }
-                    args.source = Some(Source::Source(s.value()));
-                } else {
-                    return Err("template source must be string literal".into());
-                }
-            } else if ident == "print" {
-                if let syn::Lit::Str(ref s) = pair.lit {
-                    args.print = s.value().parse()?;
-                } else {
-                    return Err("print value must be string literal".into());
-                }
-            } else if ident == "escape" {
-                if let syn::Lit::Str(ref s) = pair.lit {
-                    args.escaping = Some(s.value());
-                } else {
-                    return Err("escape value must be string literal".into());
-                }
-            } else if ident == "ext" {
-                if let syn::Lit::Str(ref s) = pair.lit {
-                    args.ext = Some(s.value());
-                } else {
-                    return Err("ext value must be string literal".into());
-                }
-            } else if ident == "syntax" {
-                if let syn::Lit::Str(ref s) = pair.lit {
-                    args.syntax = Some(s.value())
-                } else {
-                    return Err("syntax value must be string literal".into());
-                }
-            } else if ident == "config" {
-                if let syn::Lit::Str(ref s) = pair.lit {
-                    args.config_path = Some(s.value())
-                } else {
-                    return Err("config value must be string literal".into());
-                }
-            } else {
-                return Err(format!("unsupported attribute key {:?} found", ident).into());
-            }
-        }
-
-        Ok(args)
-    }
-}
-
-fn find_used_templates(
-    input: &TemplateInput<'_>,
-    map: &mut HashMap<PathBuf, String>,
-    source: String,
-) -> Result<(), CompileError> {
-    let mut dependency_graph = Vec::new();
-    let mut check = vec![(input.path.clone(), source)];
-    while let Some((path, source)) = check.pop() {
-        for n in parse(&source, input.syntax)? {
-            match n {
-                Node::Extends(Expr::StrLit(extends)) => {
-                    let extends = input.config.find_template(extends, Some(&path))?;
-                    let dependency_path = (path.clone(), extends.clone());
-                    if dependency_graph.contains(&dependency_path) {
-                        return Err(format!(
-                            "cyclic dependecy in graph {:#?}",
-                            dependency_graph
-                                .iter()
-                                .map(|e| format!("{:#?} --> {:#?}", e.0, e.1))
-                                .collect::<Vec<String>>()
-                        )
-                        .into());
-                    }
-                    dependency_graph.push(dependency_path);
-                    let source = get_template_source(&extends)?;
-                    check.push((extends, source));
-                }
-                Node::Import(_, import, _) => {
-                    let import = input.config.find_template(import, Some(&path))?;
-                    let source = get_template_source(&import)?;
-                    check.push((import, source));
-                }
-                _ => {}
-            }
-        }
-        map.insert(path, source);
-    }
-    Ok(())
-}
-struct Generator<'a, S: std::hash::BuildHasher> {
-    // The template input state: original struct AST and attributes
-    input: &'a TemplateInput<'a>,
-    // All contexts, keyed by the package-relative template path
-    contexts: &'a HashMap<&'a Path, Context<'a>, S>,
-    // The heritage contains references to blocks and their ancestry
-    heritage: Option<&'a Heritage<'a>>,
-    // Variables accessible directly from the current scope (not redirected to context)
-    locals: MapChain<'a, &'a str, LocalMeta>,
-    // Suffix whitespace from the previous literal. Will be flushed to the
-    // output buffer unless suppressed by whitespace suppression on the next
-    // non-literal.
-    next_ws: Option<&'a str>,
-    // Whitespace suppression from the previous non-literal. Will be used to
-    // determine whether to flush prefix whitespace from the next literal.
-    skip_ws: WhitespaceHandling,
-    // If currently in a block, this will contain the name of a potential parent block
-    super_block: Option<(&'a str, usize)>,
-    // buffer for writable
-    buf_writable: Vec<Writable<'a>>,
-    // Counter for write! hash named arguments
-    named: usize,
-    // If set to `suppress`, the whitespace characters will be removed by default unless `+` is
-    // used.
-    whitespace: WhitespaceHandling,
-}
-
-impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
-    fn new<'n>(
-        input: &'n TemplateInput<'_>,
-        contexts: &'n HashMap<&'n Path, Context<'n>, S>,
-        heritage: Option<&'n Heritage<'_>>,
-        locals: MapChain<'n, &'n str, LocalMeta>,
-        whitespace: WhitespaceHandling,
-    ) -> Generator<'n, S> {
-        Generator {
-            input,
-            contexts,
-            heritage,
-            locals,
-            next_ws: None,
-            skip_ws: WhitespaceHandling::Preserve,
-            super_block: None,
-            buf_writable: vec![],
-            named: 0,
-            whitespace,
-        }
-    }
-
-    fn child(&mut self) -> Generator<'_, S> {
-        let locals = MapChain::with_parent(&self.locals);
-        Self::new(
-            self.input,
-            self.contexts,
-            self.heritage,
-            locals,
-            self.whitespace,
-        )
-    }
-
-    // Takes a Context and generates the relevant implementations.
-    fn build(mut self, ctx: &'a Context<'_>) -> Result<String, CompileError> {
-        let mut buf = Buffer::new(0);
-        if !ctx.blocks.is_empty() {
-            if let Some(parent) = self.input.parent {
-                self.deref_to_parent(&mut buf, parent)?;
-            }
-        };
-
-        self.impl_template(ctx, &mut buf)?;
-        self.impl_display(&mut buf)?;
-
-        #[cfg(feature = "actix-web")]
-        self.impl_actix_web_responder(&mut buf)?;
-        #[cfg(feature = "axum")]
-        self.impl_axum_into_response(&mut buf)?;
-        #[cfg(feature = "gotham")]
-        self.impl_gotham_into_response(&mut buf)?;
-        #[cfg(feature = "mendes")]
-        self.impl_mendes_responder(&mut buf)?;
-        #[cfg(feature = "rocket")]
-        self.impl_rocket_responder(&mut buf)?;
-        #[cfg(feature = "tide")]
-        self.impl_tide_integrations(&mut buf)?;
-        #[cfg(feature = "warp")]
-        self.impl_warp_reply(&mut buf)?;
-
-        Ok(buf.buf)
-    }
-
-    // Implement `Template` for the given context struct.
-    fn impl_template(
-        &mut self,
-        ctx: &'a Context<'_>,
-        buf: &mut Buffer,
-    ) -> Result<(), CompileError> {
-        self.write_header(buf, "::askama::Template", None)?;
-        buf.writeln(
-            "fn render_into(&self, writer: &mut (impl ::std::fmt::Write + ?Sized)) -> \
-             ::askama::Result<()> {",
-        )?;
-
-        // Make sure the compiler understands that the generated code depends on the template files.
-        for path in self.contexts.keys() {
-            // Skip the fake path of templates defined in rust source.
-            let path_is_valid = match self.input.source {
-                Source::Path(_) => true,
-                Source::Source(_) => path != &self.input.path,
-            };
-            if path_is_valid {
-                let path = path.to_str().unwrap();
-                buf.writeln(
-                    &quote! {
-                        include_bytes!(#path);
-                    }
-                    .to_string(),
-                )?;
-            }
-        }
-
-        let size_hint = if let Some(heritage) = self.heritage {
-            self.handle(heritage.root, heritage.root.nodes, buf, AstLevel::Top)
-        } else {
-            self.handle(ctx, ctx.nodes, buf, AstLevel::Top)
-        }?;
-
-        self.flush_ws(Ws(None, None));
-        buf.writeln("::askama::Result::Ok(())")?;
-        buf.writeln("}")?;
-
-        buf.writeln("const EXTENSION: ::std::option::Option<&'static ::std::primitive::str> = ")?;
-        buf.writeln(&format!("{:?}", self.input.extension()))?;
-        buf.writeln(";")?;
-
-        buf.writeln("const SIZE_HINT: ::std::primitive::usize = ")?;
-        buf.writeln(&format!("{}", size_hint))?;
-        buf.writeln(";")?;
-
-        buf.writeln("const MIME_TYPE: &'static ::std::primitive::str = ")?;
-        buf.writeln(&format!("{:?}", &self.input.mime_type))?;
-        buf.writeln(";")?;
-
-        buf.writeln("}")?;
-        Ok(())
-    }
-
-    // Implement `Deref<Parent>` for an inheriting context struct.
-    fn deref_to_parent(
-        &mut self,
-        buf: &mut Buffer,
-        parent_type: &syn::Type,
-    ) -> Result<(), CompileError> {
-        self.write_header(buf, "::std::ops::Deref", None)?;
-        buf.writeln(&format!(
-            "type Target = {};",
-            parent_type.into_token_stream()
-        ))?;
-        buf.writeln("#[inline]")?;
-        buf.writeln("fn deref(&self) -> &Self::Target {")?;
-        buf.writeln("&self._parent")?;
-        buf.writeln("}")?;
-        buf.writeln("}")
-    }
-
-    // Implement `Display` for the given context struct.
-    fn impl_display(&mut self, buf: &mut Buffer) -> Result<(), CompileError> {
-        self.write_header(buf, "::std::fmt::Display", None)?;
-        buf.writeln("#[inline]")?;
-        buf.writeln("fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {")?;
-        buf.writeln("::askama::Template::render_into(self, f).map_err(|_| ::std::fmt::Error {})")?;
-        buf.writeln("}")?;
-        buf.writeln("}")
-    }
-
-    // Implement Actix-web's `Responder`.
-    #[cfg(feature = "actix-web")]
-    fn impl_actix_web_responder(&mut self, buf: &mut Buffer) -> Result<(), CompileError> {
-        self.write_header(buf, "::askama_actix::actix_web::Responder", None)?;
-        buf.writeln("type Body = ::askama_actix::actix_web::body::BoxBody;")?;
-        buf.writeln("#[inline]")?;
-        buf.writeln(
-            "fn respond_to(self, _req: &::askama_actix::actix_web::HttpRequest) \
-             -> ::askama_actix::actix_web::HttpResponse<Self::Body> {",
-        )?;
-        buf.writeln("<Self as ::askama_actix::TemplateToResponse>::to_response(&self)")?;
-        buf.writeln("}")?;
-        buf.writeln("}")
-    }
-
-    // Implement Axum's `IntoResponse`.
-    #[cfg(feature = "axum")]
-    fn impl_axum_into_response(&mut self, buf: &mut Buffer) -> Result<(), CompileError> {
-        self.write_header(buf, "::askama_axum::IntoResponse", None)?;
-        buf.writeln("#[inline]")?;
-        buf.writeln(
-            "fn into_response(self)\
-             -> ::askama_axum::Response {",
-        )?;
-        let ext = self.input.extension().unwrap_or("txt");
-        buf.writeln(&format!("::askama_axum::into_response(&self, {:?})", ext))?;
-        buf.writeln("}")?;
-        buf.writeln("}")
-    }
-
-    // Implement gotham's `IntoResponse`.
-    #[cfg(feature = "gotham")]
-    fn impl_gotham_into_response(&mut self, buf: &mut Buffer) -> Result<(), CompileError> {
-        self.write_header(buf, "::askama_gotham::IntoResponse", None)?;
-        buf.writeln("#[inline]")?;
-        buf.writeln(
-            "fn into_response(self, _state: &::askama_gotham::State)\
-             -> ::askama_gotham::Response<::askama_gotham::Body> {",
-        )?;
-        let ext = self.input.extension().unwrap_or("txt");
-        buf.writeln(&format!("::askama_gotham::respond(&self, {:?})", ext))?;
-        buf.writeln("}")?;
-        buf.writeln("}")
-    }
-
-    // Implement mendes' `Responder`.
-    #[cfg(feature = "mendes")]
-    fn impl_mendes_responder(&mut self, buf: &mut Buffer) -> Result<(), CompileError> {
-        let param = syn::parse_str("A: ::mendes::Application").unwrap();
-
-        let mut generics = self.input.ast.generics.clone();
-        generics.params.push(param);
-        let (_, orig_ty_generics, _) = self.input.ast.generics.split_for_impl();
-        let (impl_generics, _, where_clause) = generics.split_for_impl();
-
-        let mut where_clause = match where_clause {
-            Some(clause) => clause.clone(),
-            None => syn::WhereClause {
-                where_token: syn::Token![where](proc_macro2::Span::call_site()),
-                predicates: syn::punctuated::Punctuated::new(),
-            },
-        };
-
-        where_clause
-            .predicates
-            .push(syn::parse_str("A::ResponseBody: From<String>").unwrap());
-        where_clause
-            .predicates
-            .push(syn::parse_str("A::Error: From<::askama_mendes::Error>").unwrap());
-
-        buf.writeln(
-            format!(
-                "{} {} for {} {} {{",
-                quote!(impl#impl_generics),
-                "::mendes::application::IntoResponse<A>",
-                self.input.ast.ident,
-                quote!(#orig_ty_generics #where_clause),
-            )
-            .as_ref(),
-        )?;
-
-        buf.writeln(
-            "fn into_response(self, app: &A, req: &::mendes::http::request::Parts) \
-             -> ::mendes::http::Response<A::ResponseBody> {",
-        )?;
-
-        buf.writeln(&format!(
-            "::askama_mendes::into_response(app, req, &self, {:?})",
-            self.input.extension()
-        ))?;
-        buf.writeln("}")?;
-        buf.writeln("}")?;
-        Ok(())
-    }
-
-    // Implement Rocket's `Responder`.
-    #[cfg(feature = "rocket")]
-    fn impl_rocket_responder(&mut self, buf: &mut Buffer) -> Result<(), CompileError> {
-        let lifetime = syn::Lifetime::new("'askama", proc_macro2::Span::call_site());
-        let param = syn::GenericParam::Lifetime(syn::LifetimeDef::new(lifetime));
-        self.write_header(
-            buf,
-            "::askama_rocket::Responder<'askama>",
-            Some(vec![param]),
-        )?;
-
-        buf.writeln("#[inline]")?;
-        buf.writeln(
-            "fn respond_to(self, _: &::askama_rocket::Request) \
-             -> ::askama_rocket::Result<'askama> {",
-        )?;
-        let ext = self.input.extension().unwrap_or("txt");
-        buf.writeln(&format!("::askama_rocket::respond(&self, {:?})", ext))?;
-
-        buf.writeln("}")?;
-        buf.writeln("}")?;
-        Ok(())
-    }
-
-    #[cfg(feature = "tide")]
-    fn impl_tide_integrations(&mut self, buf: &mut Buffer) -> Result<(), CompileError> {
-        let ext = self.input.extension().unwrap_or("txt");
-
-        self.write_header(
-            buf,
-            "::std::convert::TryInto<::askama_tide::tide::Body>",
-            None,
-        )?;
-        buf.writeln(
-            "type Error = ::askama_tide::askama::Error;\n\
-            #[inline]\n\
-            fn try_into(self) -> ::askama_tide::askama::Result<::askama_tide::tide::Body> {",
-        )?;
-        buf.writeln(&format!("::askama_tide::try_into_body(&self, {:?})", &ext))?;
-        buf.writeln("}")?;
-        buf.writeln("}")?;
-
-        buf.writeln("#[allow(clippy::from_over_into)]")?;
-        self.write_header(buf, "Into<::askama_tide::tide::Response>", None)?;
-        buf.writeln("#[inline]")?;
-        buf.writeln("fn into(self) -> ::askama_tide::tide::Response {")?;
-        buf.writeln(&format!("::askama_tide::into_response(&self, {:?})", ext))?;
-        buf.writeln("}\n}")
-    }
-
-    #[cfg(feature = "warp")]
-    fn impl_warp_reply(&mut self, buf: &mut Buffer) -> Result<(), CompileError> {
-        self.write_header(buf, "::askama_warp::warp::reply::Reply", None)?;
-        buf.writeln("#[inline]")?;
-        buf.writeln("fn into_response(self) -> ::askama_warp::warp::reply::Response {")?;
-        let ext = self.input.extension().unwrap_or("txt");
-        buf.writeln(&format!("::askama_warp::reply(&self, {:?})", ext))?;
-        buf.writeln("}")?;
-        buf.writeln("}")
-    }
-
-    // Writes header for the `impl` for `TraitFromPathName` or `Template`
-    // for the given context struct.
-    fn write_header(
-        &mut self,
-        buf: &mut Buffer,
-        target: &str,
-        params: Option<Vec<syn::GenericParam>>,
-    ) -> Result<(), CompileError> {
-        let mut generics = self.input.ast.generics.clone();
-        if let Some(params) = params {
-            for param in params {
-                generics.params.push(param);
-            }
-        }
-        let (_, orig_ty_generics, _) = self.input.ast.generics.split_for_impl();
-        let (impl_generics, _, where_clause) = generics.split_for_impl();
-        buf.writeln(
-            format!(
-                "{} {} for {}{} {{",
-                quote!(impl#impl_generics),
-                target,
-                self.input.ast.ident,
-                quote!(#orig_ty_generics #where_clause),
-            )
-            .as_ref(),
-        )
-    }
-
-    /* Helper methods for handling node types */
-
-    fn handle(
-        &mut self,
-        ctx: &'a Context<'_>,
-        nodes: &'a [Node<'_>],
-        buf: &mut Buffer,
-        level: AstLevel,
-    ) -> Result<usize, CompileError> {
-        let mut size_hint = 0;
-        for n in nodes {
-            match *n {
-                Node::Lit(lws, val, rws) => {
-                    self.visit_lit(lws, val, rws);
-                }
-                Node::Comment(ws) => {
-                    self.write_comment(ws);
-                }
-                Node::Expr(ws, ref val) => {
-                    self.write_expr(ws, val);
-                }
-                Node::LetDecl(ws, ref var) => {
-                    self.write_let_decl(buf, ws, var)?;
-                }
-                Node::Let(ws, ref var, ref val) => {
-                    self.write_let(buf, ws, var, val)?;
-                }
-                Node::Cond(ref conds, ws) => {
-                    self.write_cond(ctx, buf, conds, ws)?;
-                }
-                Node::Match(ws1, ref expr, ref arms, ws2) => {
-                    self.write_match(ctx, buf, ws1, expr, arms, ws2)?;
-                }
-                Node::Loop(ref loop_block) => {
-                    self.write_loop(ctx, buf, loop_block)?;
-                }
-                Node::BlockDef(ws1, name, _, ws2) => {
-                    self.write_block(buf, Some(name), Ws(ws1.0, ws2.1))?;
-                }
-                Node::Include(ws, path) => {
-                    size_hint += self.handle_include(ctx, buf, ws, path)?;
-                }
-                Node::Call(ws, scope, name, ref args) => {
-                    size_hint += self.write_call(ctx, buf, ws, scope, name, args)?;
-                }
-                Node::Macro(_, ref m) => {
-                    if level != AstLevel::Top {
-                        return Err("macro blocks only allowed at the top level".into());
-                    }
-                    self.flush_ws(m.ws1);
-                    self.prepare_ws(m.ws2);
-                }
-                Node::Raw(ws1, lws, val, rws, ws2) => {
-                    self.handle_ws(ws1);
-                    self.visit_lit(lws, val, rws);
-                    self.handle_ws(ws2);
-                }
-                Node::Import(ws, _, _) => {
-                    if level != AstLevel::Top {
-                        return Err("import blocks only allowed at the top level".into());
-                    }
-                    self.handle_ws(ws);
-                }
-                Node::Extends(_) => {
-                    if level != AstLevel::Top {
-                        return Err("extend blocks only allowed at the top level".into());
-                    }
-                    // No whitespace handling: child template top-level is not used,
-                    // except for the blocks defined in it.
-                }
-                Node::Break(ws) => {
-                    self.handle_ws(ws);
-                    self.write_buf_writable(buf)?;
-                    buf.writeln("break;")?;
-                }
-                Node::Continue(ws) => {
-                    self.handle_ws(ws);
-                    self.write_buf_writable(buf)?;
-                    buf.writeln("continue;")?;
-                }
-            }
-        }
-
-        if AstLevel::Top == level {
-            size_hint += self.write_buf_writable(buf)?;
-        }
-        Ok(size_hint)
-    }
-
-    fn write_cond(
-        &mut self,
-        ctx: &'a Context<'_>,
-        buf: &mut Buffer,
-        conds: &'a [Cond<'_>],
-        ws: Ws,
-    ) -> Result<usize, CompileError> {
-        let mut flushed = 0;
-        let mut arm_sizes = Vec::new();
-        let mut has_else = false;
-        for (i, &(cws, ref cond, ref nodes)) in conds.iter().enumerate() {
-            self.handle_ws(cws);
-            flushed += self.write_buf_writable(buf)?;
-            if i > 0 {
-                self.locals.pop();
-            }
-
-            self.locals.push();
-            let mut arm_size = 0;
-            if let Some(CondTest { target, expr }) = cond {
-                if i == 0 {
-                    buf.write("if ");
-                } else {
-                    buf.dedent()?;
-                    buf.write("} else if ");
-                }
-
-                if let Some(target) = target {
-                    let mut expr_buf = Buffer::new(0);
-                    self.visit_expr(&mut expr_buf, expr)?;
-                    buf.write("let ");
-                    self.visit_target(buf, true, true, target);
-                    buf.write(" = &(");
-                    buf.write(&expr_buf.buf);
-                    buf.write(")");
-                } else {
-                    // The following syntax `*(&(...) as &bool)` is used to
-                    // trigger Rust's automatic dereferencing, to coerce
-                    // e.g. `&&&&&bool` to `bool`. First `&(...) as &bool`
-                    // coerces e.g. `&&&bool` to `&bool`. Then `*(&bool)`
-                    // finally dereferences it to `bool`.
-                    buf.write("*(&(");
-                    let expr_code = self.visit_expr_root(expr)?;
-                    buf.write(&expr_code);
-                    buf.write(") as &bool)");
-                }
-            } else {
-                buf.dedent()?;
-                buf.write("} else");
-                has_else = true;
-            }
-
-            buf.writeln(" {")?;
-
-            arm_size += self.handle(ctx, nodes, buf, AstLevel::Nested)?;
-            arm_sizes.push(arm_size);
-        }
-        self.handle_ws(ws);
-        flushed += self.write_buf_writable(buf)?;
-        buf.writeln("}")?;
-
-        self.locals.pop();
-
-        if !has_else {
-            arm_sizes.push(0);
-        }
-        Ok(flushed + median(&mut arm_sizes))
-    }
-
-    #[allow(clippy::too_many_arguments)]
-    fn write_match(
-        &mut self,
-        ctx: &'a Context<'_>,
-        buf: &mut Buffer,
-        ws1: Ws,
-        expr: &Expr<'_>,
-        arms: &'a [When<'_>],
-        ws2: Ws,
-    ) -> Result<usize, CompileError> {
-        self.flush_ws(ws1);
-        let flushed = self.write_buf_writable(buf)?;
-        let mut arm_sizes = Vec::new();
-
-        let expr_code = self.visit_expr_root(expr)?;
-        buf.writeln(&format!("match &{} {{", expr_code))?;
-
-        let mut arm_size = 0;
-        for (i, arm) in arms.iter().enumerate() {
-            let &(ws, ref target, ref body) = arm;
-            self.handle_ws(ws);
-
-            if i > 0 {
-                arm_sizes.push(arm_size + self.write_buf_writable(buf)?);
-
-                buf.writeln("}")?;
-                self.locals.pop();
-            }
-
-            self.locals.push();
-            self.visit_target(buf, true, true, target);
-            buf.writeln(" => {")?;
-
-            arm_size = self.handle(ctx, body, buf, AstLevel::Nested)?;
-        }
-
-        self.handle_ws(ws2);
-        arm_sizes.push(arm_size + self.write_buf_writable(buf)?);
-        buf.writeln("}")?;
-        self.locals.pop();
-
-        buf.writeln("}")?;
-
-        Ok(flushed + median(&mut arm_sizes))
-    }
-
-    #[allow(clippy::too_many_arguments)]
-    fn write_loop(
-        &mut self,
-        ctx: &'a Context<'_>,
-        buf: &mut Buffer,
-        loop_block: &'a Loop<'_>,
-    ) -> Result<usize, CompileError> {
-        self.handle_ws(loop_block.ws1);
-        self.locals.push();
-
-        let expr_code = self.visit_expr_root(&loop_block.iter)?;
-
-        let flushed = self.write_buf_writable(buf)?;
-        buf.writeln("{")?;
-        buf.writeln("let mut _did_loop = false;")?;
-        match loop_block.iter {
-            Expr::Range(_, _, _) => buf.writeln(&format!("let _iter = {};", expr_code)),
-            Expr::Array(..) => buf.writeln(&format!("let _iter = {}.iter();", expr_code)),
-            // If `iter` is a call then we assume it's something that returns
-            // an iterator. If not then the user can explicitly add the needed
-            // call without issues.
-            Expr::Call(..) | Expr::Index(..) => {
-                buf.writeln(&format!("let _iter = ({}).into_iter();", expr_code))
-            }
-            // If accessing `self` then it most likely needs to be
-            // borrowed, to prevent an attempt of moving.
-            _ if expr_code.starts_with("self.") => {
-                buf.writeln(&format!("let _iter = (&{}).into_iter();", expr_code))
-            }
-            // If accessing a field then it most likely needs to be
-            // borrowed, to prevent an attempt of moving.
-            Expr::Attr(..) => buf.writeln(&format!("let _iter = (&{}).into_iter();", expr_code)),
-            // Otherwise, we borrow `iter` assuming that it implements `IntoIterator`.
-            _ => buf.writeln(&format!("let _iter = ({}).into_iter();", expr_code)),
-        }?;
-        if let Some(cond) = &loop_block.cond {
-            self.locals.push();
-            buf.write("let _iter = _iter.filter(|");
-            self.visit_target(buf, true, true, &loop_block.var);
-            buf.write("| -> bool {");
-            self.visit_expr(buf, cond)?;
-            buf.writeln("});")?;
-            self.locals.pop();
-        }
-
-        self.locals.push();
-        buf.write("for (");
-        self.visit_target(buf, true, true, &loop_block.var);
-        buf.writeln(", _loop_item) in ::askama::helpers::TemplateLoop::new(_iter) {")?;
-
-        buf.writeln("_did_loop = true;")?;
-        let mut size_hint1 = self.handle(ctx, &loop_block.body, buf, AstLevel::Nested)?;
-        self.handle_ws(loop_block.ws2);
-        size_hint1 += self.write_buf_writable(buf)?;
-        self.locals.pop();
-        buf.writeln("}")?;
-
-        buf.writeln("if !_did_loop {")?;
-        self.locals.push();
-        let mut size_hint2 = self.handle(ctx, &loop_block.else_block, buf, AstLevel::Nested)?;
-        self.handle_ws(loop_block.ws3);
-        size_hint2 += self.write_buf_writable(buf)?;
-        self.locals.pop();
-        buf.writeln("}")?;
-
-        buf.writeln("}")?;
-
-        Ok(flushed + ((size_hint1 * 3) + size_hint2) / 2)
-    }
-
-    fn write_call(
-        &mut self,
-        ctx: &'a Context<'_>,
-        buf: &mut Buffer,
-        ws: Ws,
-        scope: Option<&str>,
-        name: &str,
-        args: &[Expr<'_>],
-    ) -> Result<usize, CompileError> {
-        if name == "super" {
-            return self.write_block(buf, None, ws);
-        }
-
-        let (def, own_ctx) = match scope {
-            Some(s) => {
-                let path = ctx.imports.get(s).ok_or_else(|| {
-                    CompileError::from(format!("no import found for scope {:?}", s))
-                })?;
-                let mctx = self.contexts.get(path.as_path()).ok_or_else(|| {
-                    CompileError::from(format!("context for {:?} not found", path))
-                })?;
-                let def = mctx.macros.get(name).ok_or_else(|| {
-                    CompileError::from(format!("macro {:?} not found in scope {:?}", name, s))
-                })?;
-                (def, mctx)
-            }
-            None => {
-                let def = ctx
-                    .macros
-                    .get(name)
-                    .ok_or_else(|| CompileError::from(format!("macro {:?} not found", name)))?;
-                (def, ctx)
-            }
-        };
-
-        self.flush_ws(ws); // Cannot handle_ws() here: whitespace from macro definition comes first
-        self.locals.push();
-        self.write_buf_writable(buf)?;
-        buf.writeln("{")?;
-        self.prepare_ws(def.ws1);
-
-        let mut names = Buffer::new(0);
-        let mut values = Buffer::new(0);
-        let mut is_first_variable = true;
-        for (i, arg) in def.args.iter().enumerate() {
-            let expr = args.get(i).ok_or_else(|| {
-                CompileError::from(format!("macro {:?} takes more than {} arguments", name, i))
-            })?;
-
-            match expr {
-                // If `expr` is already a form of variable then
-                // don't reintroduce a new variable. This is
-                // to avoid moving non-copyable values.
-                Expr::Var(name) => {
-                    let var = self.locals.resolve_or_self(name);
-                    self.locals.insert(arg, LocalMeta::with_ref(var));
-                }
-                Expr::Attr(obj, attr) => {
-                    let mut attr_buf = Buffer::new(0);
-                    self.visit_attr(&mut attr_buf, obj, attr)?;
-
-                    let var = self.locals.resolve(&attr_buf.buf).unwrap_or(attr_buf.buf);
-                    self.locals.insert(arg, LocalMeta::with_ref(var));
-                }
-                // Everything else still needs to become variables,
-                // to avoid having the same logic be executed
-                // multiple times, e.g. in the case of macro
-                // parameters being used multiple times.
-                _ => {
-                    if is_first_variable {
-                        is_first_variable = false
-                    } else {
-                        names.write(", ");
-                        values.write(", ");
-                    }
-                    names.write(arg);
-
-                    values.write("(");
-                    values.write(&self.visit_expr_root(expr)?);
-                    values.write(")");
-                    self.locals.insert_with_default(arg);
-                }
-            }
-        }
-
-        debug_assert_eq!(names.buf.is_empty(), values.buf.is_empty());
-        if !names.buf.is_empty() {
-            buf.writeln(&format!("let ({}) = ({});", names.buf, values.buf))?;
-        }
-
-        let mut size_hint = self.handle(own_ctx, &def.nodes, buf, AstLevel::Nested)?;
-
-        self.flush_ws(def.ws2);
-        size_hint += self.write_buf_writable(buf)?;
-        buf.writeln("}")?;
-        self.locals.pop();
-        self.prepare_ws(ws);
-        Ok(size_hint)
-    }
-
-    fn handle_include(
-        &mut self,
-        ctx: &'a Context<'_>,
-        buf: &mut Buffer,
-        ws: Ws,
-        path: &str,
-    ) -> Result<usize, CompileError> {
-        self.flush_ws(ws);
-        self.write_buf_writable(buf)?;
-        let path = self
-            .input
-            .config
-            .find_template(path, Some(&self.input.path))?;
-        let src = get_template_source(&path)?;
-        let nodes = parse(&src, self.input.syntax)?;
-
-        // Make sure the compiler understands that the generated code depends on the template file.
-        {
-            let path = path.to_str().unwrap();
-            buf.writeln(
-                &quote! {
-                    include_bytes!(#path);
-                }
-                .to_string(),
-            )?;
-        }
-
-        let size_hint = {
-            // Since nodes must not outlive the Generator, we instantiate
-            // a nested Generator here to handle the include's nodes.
-            let mut gen = self.child();
-            let mut size_hint = gen.handle(ctx, &nodes, buf, AstLevel::Nested)?;
-            size_hint += gen.write_buf_writable(buf)?;
-            size_hint
-        };
-        self.prepare_ws(ws);
-        Ok(size_hint)
-    }
-
-    fn write_let_decl(
-        &mut self,
-        buf: &mut Buffer,
-        ws: Ws,
-        var: &'a Target<'_>,
-    ) -> Result<(), CompileError> {
-        self.handle_ws(ws);
-        self.write_buf_writable(buf)?;
-        buf.write("let ");
-        self.visit_target(buf, false, true, var);
-        buf.writeln(";")
-    }
-
-    fn is_shadowing_variable(&self, var: &Target<'a>) -> Result<bool, CompileError> {
-        match var {
-            Target::Name(name) => {
-                let name = normalize_identifier(name);
-                match self.locals.get(&name) {
-                    // declares a new variable
-                    None => Ok(false),
-                    // an initialized variable gets shadowed
-                    Some(meta) if meta.initialized => Ok(true),
-                    // initializes a variable that was introduced in a LetDecl before
-                    _ => Ok(false),
-                }
-            }
-            Target::Tuple(_, targets) => {
-                for target in targets {
-                    match self.is_shadowing_variable(target) {
-                        Ok(false) => continue,
-                        outcome => return outcome,
-                    }
-                }
-                Ok(false)
-            }
-            Target::Struct(_, named_targets) => {
-                for (_, target) in named_targets {
-                    match self.is_shadowing_variable(target) {
-                        Ok(false) => continue,
-                        outcome => return outcome,
-                    }
-                }
-                Ok(false)
-            }
-            _ => Err("literals are not allowed on the left-hand side of an assignment".into()),
-        }
-    }
-
-    fn write_let(
-        &mut self,
-        buf: &mut Buffer,
-        ws: Ws,
-        var: &'a Target<'_>,
-        val: &Expr<'_>,
-    ) -> Result<(), CompileError> {
-        self.handle_ws(ws);
-        let mut expr_buf = Buffer::new(0);
-        self.visit_expr(&mut expr_buf, val)?;
-
-        let shadowed = self.is_shadowing_variable(var)?;
-        if shadowed {
-            // Need to flush the buffer if the variable is being shadowed,
-            // to ensure the old variable is used.
-            self.write_buf_writable(buf)?;
-        }
-        if shadowed
-            || !matches!(var, &Target::Name(_))
-            || matches!(var, Target::Name(name) if self.locals.get(name).is_none())
-        {
-            buf.write("let ");
-        }
-
-        self.visit_target(buf, true, true, var);
-        buf.writeln(&format!(" = {};", &expr_buf.buf))
-    }
-
-    // If `name` is `Some`, this is a call to a block definition, and we have to find
-    // the first block for that name from the ancestry chain. If name is `None`, this
-    // is from a `super()` call, and we can get the name from `self.super_block`.
-    fn write_block(
-        &mut self,
-        buf: &mut Buffer,
-        name: Option<&'a str>,
-        outer: Ws,
-    ) -> Result<usize, CompileError> {
-        // Flush preceding whitespace according to the outer WS spec
-        self.flush_ws(outer);
-
-        let prev_block = self.super_block;
-        let cur = match (name, prev_block) {
-            // The top-level context contains a block definition
-            (Some(cur_name), None) => (cur_name, 0),
-            // A block definition contains a block definition of the same name
-            (Some(cur_name), Some((prev_name, _))) if cur_name == prev_name => {
-                return Err(format!("cannot define recursive blocks ({})", cur_name).into());
-            }
-            // A block definition contains a definition of another block
-            (Some(cur_name), Some((_, _))) => (cur_name, 0),
-            // `super()` was called inside a block
-            (None, Some((prev_name, gen))) => (prev_name, gen + 1),
-            // `super()` is called from outside a block
-            (None, None) => return Err("cannot call 'super()' outside block".into()),
-        };
-        self.super_block = Some(cur);
-
-        // Get the block definition from the heritage chain
-        let heritage = self
-            .heritage
-            .as_ref()
-            .ok_or_else(|| CompileError::from("no block ancestors available"))?;
-        let (ctx, def) = heritage.blocks[cur.0].get(cur.1).ok_or_else(|| {
-            CompileError::from(match name {
-                None => format!("no super() block found for block '{}'", cur.0),
-                Some(name) => format!("no block found for name '{}'", name),
-            })
-        })?;
-
-        // Get the nodes and whitespace suppression data from the block definition
-        let (ws1, nodes, ws2) = if let Node::BlockDef(ws1, _, nodes, ws2) = def {
-            (ws1, nodes, ws2)
-        } else {
-            unreachable!()
-        };
-
-        // Handle inner whitespace suppression spec and process block nodes
-        self.prepare_ws(*ws1);
-        self.locals.push();
-        let size_hint = self.handle(ctx, nodes, buf, AstLevel::Block)?;
-
-        if !self.locals.is_current_empty() {
-            // Need to flush the buffer before popping the variable stack
-            self.write_buf_writable(buf)?;
-        }
-
-        self.locals.pop();
-        self.flush_ws(*ws2);
-
-        // Restore original block context and set whitespace suppression for
-        // succeeding whitespace according to the outer WS spec
-        self.super_block = prev_block;
-        self.prepare_ws(outer);
-        Ok(size_hint)
-    }
-
-    fn write_expr(&mut self, ws: Ws, s: &'a Expr<'a>) {
-        self.handle_ws(ws);
-        self.buf_writable.push(Writable::Expr(s));
-    }
-
-    // Write expression buffer and empty
-    fn write_buf_writable(&mut self, buf: &mut Buffer) -> Result<usize, CompileError> {
-        if self.buf_writable.is_empty() {
-            return Ok(0);
-        }
-
-        if self
-            .buf_writable
-            .iter()
-            .all(|w| matches!(w, Writable::Lit(_)))
-        {
-            let mut buf_lit = Buffer::new(0);
-            for s in mem::take(&mut self.buf_writable) {
-                if let Writable::Lit(s) = s {
-                    buf_lit.write(s);
-                };
-            }
-            buf.writeln(&format!("writer.write_str({:#?})?;", &buf_lit.buf))?;
-            return Ok(buf_lit.buf.len());
-        }
-
-        let mut size_hint = 0;
-        let mut buf_format = Buffer::new(0);
-        let mut buf_expr = Buffer::new(buf.indent + 1);
-        let mut expr_cache = HashMap::with_capacity(self.buf_writable.len());
-        for s in mem::take(&mut self.buf_writable) {
-            match s {
-                Writable::Lit(s) => {
-                    buf_format.write(&s.replace('{', "{{").replace('}', "}}"));
-                    size_hint += s.len();
-                }
-                Writable::Expr(s) => {
-                    use self::DisplayWrap::*;
-                    let mut expr_buf = Buffer::new(0);
-                    let wrapped = self.visit_expr(&mut expr_buf, s)?;
-                    let expression = match wrapped {
-                        Wrapped => expr_buf.buf,
-                        Unwrapped => format!(
-                            "::askama::MarkupDisplay::new_unsafe(&({}), {})",
-                            expr_buf.buf, self.input.escaper
-                        ),
-                    };
-
-                    use std::collections::hash_map::Entry;
-                    let id = match expr_cache.entry(expression.clone()) {
-                        Entry::Occupied(e) => *e.get(),
-                        Entry::Vacant(e) => {
-                            let id = self.named;
-                            self.named += 1;
-
-                            buf_expr.write(&format!("expr{} = ", id));
-                            buf_expr.write("&");
-                            buf_expr.write(&expression);
-                            buf_expr.writeln(",")?;
-
-                            e.insert(id);
-                            id
-                        }
-                    };
-
-                    buf_format.write(&format!("{{expr{}}}", id));
-                    size_hint += 3;
-                }
-            }
-        }
-
-        buf.writeln("::std::write!(")?;
-        buf.indent();
-        buf.writeln("writer,")?;
-        buf.writeln(&format!("{:#?},", &buf_format.buf))?;
-        buf.writeln(buf_expr.buf.trim())?;
-        buf.dedent()?;
-        buf.writeln(")?;")?;
-        Ok(size_hint)
-    }
-
-    fn visit_lit(&mut self, lws: &'a str, val: &'a str, rws: &'a str) {
-        assert!(self.next_ws.is_none());
-        if !lws.is_empty() {
-            match self.skip_ws {
-                WhitespaceHandling::Suppress => {
-                    self.skip_ws = WhitespaceHandling::Preserve;
-                }
-                _ if val.is_empty() => {
-                    assert!(rws.is_empty());
-                    self.next_ws = Some(lws);
-                }
-                WhitespaceHandling::Preserve => self.buf_writable.push(Writable::Lit(lws)),
-                WhitespaceHandling::Minimize => {
-                    self.buf_writable
-                        .push(Writable::Lit(match lws.contains('\n') {
-                            true => "\n",
-                            false => " ",
-                        }))
-                }
-            }
-        }
-
-        if !val.is_empty() {
-            self.buf_writable.push(Writable::Lit(val));
-        }
-
-        if !rws.is_empty() {
-            self.next_ws = Some(rws);
-        }
-    }
-
-    fn write_comment(&mut self, ws: Ws) {
-        self.handle_ws(ws);
-    }
-
-    /* Visitor methods for expression types */
-
-    fn visit_expr_root(&mut self, expr: &Expr<'_>) -> Result<String, CompileError> {
-        let mut buf = Buffer::new(0);
-        self.visit_expr(&mut buf, expr)?;
-        Ok(buf.buf)
-    }
-
-    fn visit_expr(
-        &mut self,
-        buf: &mut Buffer,
-        expr: &Expr<'_>,
-    ) -> Result<DisplayWrap, CompileError> {
-        Ok(match *expr {
-            Expr::BoolLit(s) => self.visit_bool_lit(buf, s),
-            Expr::NumLit(s) => self.visit_num_lit(buf, s),
-            Expr::StrLit(s) => self.visit_str_lit(buf, s),
-            Expr::CharLit(s) => self.visit_char_lit(buf, s),
-            Expr::Var(s) => self.visit_var(buf, s),
-            Expr::Path(ref path) => self.visit_path(buf, path),
-            Expr::Array(ref elements) => self.visit_array(buf, elements)?,
-            Expr::Attr(ref obj, name) => self.visit_attr(buf, obj, name)?,
-            Expr::Index(ref obj, ref key) => self.visit_index(buf, obj, key)?,
-            Expr::Filter(name, ref args) => self.visit_filter(buf, name, args)?,
-            Expr::Unary(op, ref inner) => self.visit_unary(buf, op, inner)?,
-            Expr::BinOp(op, ref left, ref right) => self.visit_binop(buf, op, left, right)?,
-            Expr::Range(op, ref left, ref right) => self.visit_range(buf, op, left, right)?,
-            Expr::Group(ref inner) => self.visit_group(buf, inner)?,
-            Expr::Call(ref obj, ref args) => self.visit_call(buf, obj, args)?,
-            Expr::RustMacro(name, args) => self.visit_rust_macro(buf, name, args),
-            Expr::Try(ref expr) => self.visit_try(buf, expr.as_ref())?,
-            Expr::Tuple(ref exprs) => self.visit_tuple(buf, exprs)?,
-        })
-    }
-
-    fn visit_try(
-        &mut self,
-        buf: &mut Buffer,
-        expr: &Expr<'_>,
-    ) -> Result<DisplayWrap, CompileError> {
-        buf.write("::core::result::Result::map_err(");
-        self.visit_expr(buf, expr)?;
-        buf.write(", |err| ::askama::shared::Error::Custom(::core::convert::Into::into(err)))?");
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_rust_macro(&mut self, buf: &mut Buffer, name: &str, args: &str) -> DisplayWrap {
-        buf.write(name);
-        buf.write("!(");
-        buf.write(args);
-        buf.write(")");
-
-        DisplayWrap::Unwrapped
-    }
-
-    #[cfg(not(feature = "markdown"))]
-    fn _visit_markdown_filter(
-        &mut self,
-        _buf: &mut Buffer,
-        _args: &[Expr<'_>],
-    ) -> Result<DisplayWrap, CompileError> {
-        Err("the `markdown` filter requires the `markdown` feature to be enabled".into())
-    }
-
-    #[cfg(feature = "markdown")]
-    fn _visit_markdown_filter(
-        &mut self,
-        buf: &mut Buffer,
-        args: &[Expr<'_>],
-    ) -> Result<DisplayWrap, CompileError> {
-        let (md, options) = match args {
-            [md] => (md, None),
-            [md, options] => (md, Some(options)),
-            _ => return Err("markdown filter expects no more than one option argument".into()),
-        };
-
-        buf.write(&format!(
-            "::askama::filters::markdown({}, ",
-            self.input.escaper
-        ));
-        self.visit_expr(buf, md)?;
-        match options {
-            Some(options) => {
-                buf.write(", ::core::option::Option::Some(");
-                self.visit_expr(buf, options)?;
-                buf.write(")");
-            }
-            None => buf.write(", ::core::option::Option::None"),
-        }
-        buf.write(")?");
-
-        Ok(DisplayWrap::Wrapped)
-    }
-
-    fn visit_filter(
-        &mut self,
-        buf: &mut Buffer,
-        mut name: &str,
-        args: &[Expr<'_>],
-    ) -> Result<DisplayWrap, CompileError> {
-        if matches!(name, "escape" | "e") {
-            self._visit_escape_filter(buf, args)?;
-            return Ok(DisplayWrap::Wrapped);
-        } else if name == "format" {
-            self._visit_format_filter(buf, args)?;
-            return Ok(DisplayWrap::Unwrapped);
-        } else if name == "fmt" {
-            self._visit_fmt_filter(buf, args)?;
-            return Ok(DisplayWrap::Unwrapped);
-        } else if name == "join" {
-            self._visit_join_filter(buf, args)?;
-            return Ok(DisplayWrap::Unwrapped);
-        } else if name == "markdown" {
-            return self._visit_markdown_filter(buf, args);
-        }
-
-        if name == "tojson" {
-            name = "json";
-        }
-
-        #[cfg(not(feature = "json"))]
-        if name == "json" {
-            return Err("the `json` filter requires the `serde-json` feature to be enabled".into());
-        }
-        #[cfg(not(feature = "yaml"))]
-        if name == "yaml" {
-            return Err("the `yaml` filter requires the `serde-yaml` feature to be enabled".into());
-        }
-
-        const FILTERS: [&str; 2] = ["safe", "yaml"];
-        if FILTERS.contains(&name) {
-            buf.write(&format!(
-                "::askama::filters::{}({}, ",
-                name, self.input.escaper
-            ));
-        } else if filters::BUILT_IN_FILTERS.contains(&name) {
-            buf.write(&format!("::askama::filters::{}(", name));
-        } else {
-            buf.write(&format!("filters::{}(", name));
-        }
-
-        self._visit_args(buf, args)?;
-        buf.write(")?");
-        Ok(match FILTERS.contains(&name) {
-            true => DisplayWrap::Wrapped,
-            false => DisplayWrap::Unwrapped,
-        })
-    }
-
-    fn _visit_escape_filter(
-        &mut self,
-        buf: &mut Buffer,
-        args: &[Expr<'_>],
-    ) -> Result<(), CompileError> {
-        if args.len() > 2 {
-            return Err("only two arguments allowed to escape filter".into());
-        }
-        let opt_escaper = match args.get(1) {
-            Some(Expr::StrLit(name)) => Some(*name),
-            Some(_) => return Err("invalid escaper type for escape filter".into()),
-            None => None,
-        };
-        let escaper = match opt_escaper {
-            Some(name) => self
-                .input
-                .config
-                .escapers
-                .iter()
-                .find_map(|(escapers, escaper)| escapers.contains(name).then(|| escaper))
-                .ok_or_else(|| CompileError::from("invalid escaper for escape filter"))?,
-            None => self.input.escaper,
-        };
-        buf.write("::askama::filters::escape(");
-        buf.write(escaper);
-        buf.write(", ");
-        self._visit_args(buf, &args[..1])?;
-        buf.write(")?");
-        Ok(())
-    }
-
-    fn _visit_format_filter(
-        &mut self,
-        buf: &mut Buffer,
-        args: &[Expr<'_>],
-    ) -> Result<(), CompileError> {
-        buf.write("format!(");
-        if let Some(Expr::StrLit(v)) = args.first() {
-            self.visit_str_lit(buf, v);
-            if args.len() > 1 {
-                buf.write(", ");
-            }
-        } else {
-            return Err("invalid expression type for format filter".into());
-        }
-        self._visit_args(buf, &args[1..])?;
-        buf.write(")");
-        Ok(())
-    }
-
-    fn _visit_fmt_filter(
-        &mut self,
-        buf: &mut Buffer,
-        args: &[Expr<'_>],
-    ) -> Result<(), CompileError> {
-        buf.write("format!(");
-        if let Some(Expr::StrLit(v)) = args.get(1) {
-            self.visit_str_lit(buf, v);
-            buf.write(", ");
-        } else {
-            return Err("invalid expression type for fmt filter".into());
-        }
-        self._visit_args(buf, &args[0..1])?;
-        if args.len() > 2 {
-            return Err("only two arguments allowed to fmt filter".into());
-        }
-        buf.write(")");
-        Ok(())
-    }
-
-    // Force type coercion on first argument to `join` filter (see #39).
-    fn _visit_join_filter(
-        &mut self,
-        buf: &mut Buffer,
-        args: &[Expr<'_>],
-    ) -> Result<(), CompileError> {
-        buf.write("::askama::filters::join((&");
-        for (i, arg) in args.iter().enumerate() {
-            if i > 0 {
-                buf.write(", &");
-            }
-            self.visit_expr(buf, arg)?;
-            if i == 0 {
-                buf.write(").into_iter()");
-            }
-        }
-        buf.write(")?");
-        Ok(())
-    }
-
-    fn _visit_args(&mut self, buf: &mut Buffer, args: &[Expr<'_>]) -> Result<(), CompileError> {
-        if args.is_empty() {
-            return Ok(());
-        }
-
-        for (i, arg) in args.iter().enumerate() {
-            if i > 0 {
-                buf.write(", ");
-            }
-
-            let borrow = !arg.is_copyable();
-            if borrow {
-                buf.write("&(");
-            }
-
-            match arg {
-                Expr::Call(left, _) if !matches!(left.as_ref(), Expr::Path(_)) => {
-                    buf.writeln("{")?;
-                    self.visit_expr(buf, arg)?;
-                    buf.writeln("}")?;
-                }
-                _ => {
-                    self.visit_expr(buf, arg)?;
-                }
-            }
-
-            if borrow {
-                buf.write(")");
-            }
-        }
-        Ok(())
-    }
-
-    fn visit_attr(
-        &mut self,
-        buf: &mut Buffer,
-        obj: &Expr<'_>,
-        attr: &str,
-    ) -> Result<DisplayWrap, CompileError> {
-        if let Expr::Var(name) = *obj {
-            if name == "loop" {
-                if attr == "index" {
-                    buf.write("(_loop_item.index + 1)");
-                    return Ok(DisplayWrap::Unwrapped);
-                } else if attr == "index0" {
-                    buf.write("_loop_item.index");
-                    return Ok(DisplayWrap::Unwrapped);
-                } else if attr == "first" {
-                    buf.write("_loop_item.first");
-                    return Ok(DisplayWrap::Unwrapped);
-                } else if attr == "last" {
-                    buf.write("_loop_item.last");
-                    return Ok(DisplayWrap::Unwrapped);
-                } else {
-                    return Err("unknown loop variable".into());
-                }
-            }
-        }
-        self.visit_expr(buf, obj)?;
-        buf.write(&format!(".{}", normalize_identifier(attr)));
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_index(
-        &mut self,
-        buf: &mut Buffer,
-        obj: &Expr<'_>,
-        key: &Expr<'_>,
-    ) -> Result<DisplayWrap, CompileError> {
-        buf.write("&");
-        self.visit_expr(buf, obj)?;
-        buf.write("[");
-        self.visit_expr(buf, key)?;
-        buf.write("]");
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_call(
-        &mut self,
-        buf: &mut Buffer,
-        left: &Expr<'_>,
-        args: &[Expr<'_>],
-    ) -> Result<DisplayWrap, CompileError> {
-        match left {
-            Expr::Attr(left, method) if **left == Expr::Var("loop") => match *method {
-                "cycle" => match args {
-                    [arg] => {
-                        if matches!(arg, Expr::Array(arr) if arr.is_empty()) {
-                            return Err("loop.cycle(…) cannot use an empty array".into());
-                        }
-                        buf.write("({");
-                        buf.write("let _cycle = &(");
-                        self.visit_expr(buf, arg)?;
-                        buf.writeln(");")?;
-                        buf.writeln("let _len = _cycle.len();")?;
-                        buf.writeln("if _len == 0 {")?;
-                        buf.writeln("return ::core::result::Result::Err(::askama::Error::Fmt(::core::fmt::Error));")?;
-                        buf.writeln("}")?;
-                        buf.writeln("_cycle[_loop_item.index % _len]")?;
-                        buf.writeln("})")?;
-                    }
-                    _ => return Err("loop.cycle(…) expects exactly one argument".into()),
-                },
-                s => return Err(format!("unknown loop method: {:?}", s).into()),
-            },
-            left => {
-                match left {
-                    Expr::Var(name) => match self.locals.resolve(name) {
-                        Some(resolved) => buf.write(&resolved),
-                        None => buf.write(&format!("(&self.{})", normalize_identifier(name))),
-                    },
-                    left => {
-                        self.visit_expr(buf, left)?;
-                    }
-                }
-
-                buf.write("(");
-                self._visit_args(buf, args)?;
-                buf.write(")");
-            }
-        }
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_unary(
-        &mut self,
-        buf: &mut Buffer,
-        op: &str,
-        inner: &Expr<'_>,
-    ) -> Result<DisplayWrap, CompileError> {
-        buf.write(op);
-        self.visit_expr(buf, inner)?;
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_range(
-        &mut self,
-        buf: &mut Buffer,
-        op: &str,
-        left: &Option<Box<Expr<'_>>>,
-        right: &Option<Box<Expr<'_>>>,
-    ) -> Result<DisplayWrap, CompileError> {
-        if let Some(left) = left {
-            self.visit_expr(buf, left)?;
-        }
-        buf.write(op);
-        if let Some(right) = right {
-            self.visit_expr(buf, right)?;
-        }
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_binop(
-        &mut self,
-        buf: &mut Buffer,
-        op: &str,
-        left: &Expr<'_>,
-        right: &Expr<'_>,
-    ) -> Result<DisplayWrap, CompileError> {
-        self.visit_expr(buf, left)?;
-        buf.write(&format!(" {} ", op));
-        self.visit_expr(buf, right)?;
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_group(
-        &mut self,
-        buf: &mut Buffer,
-        inner: &Expr<'_>,
-    ) -> Result<DisplayWrap, CompileError> {
-        buf.write("(");
-        self.visit_expr(buf, inner)?;
-        buf.write(")");
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_tuple(
-        &mut self,
-        buf: &mut Buffer,
-        exprs: &[Expr<'_>],
-    ) -> Result<DisplayWrap, CompileError> {
-        buf.write("(");
-        for (index, expr) in exprs.iter().enumerate() {
-            if index > 0 {
-                buf.write(" ");
-            }
-            self.visit_expr(buf, expr)?;
-            buf.write(",");
-        }
-        buf.write(")");
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_array(
-        &mut self,
-        buf: &mut Buffer,
-        elements: &[Expr<'_>],
-    ) -> Result<DisplayWrap, CompileError> {
-        buf.write("[");
-        for (i, el) in elements.iter().enumerate() {
-            if i > 0 {
-                buf.write(", ");
-            }
-            self.visit_expr(buf, el)?;
-        }
-        buf.write("]");
-        Ok(DisplayWrap::Unwrapped)
-    }
-
-    fn visit_path(&mut self, buf: &mut Buffer, path: &[&str]) -> DisplayWrap {
-        for (i, part) in path.iter().enumerate() {
-            if i > 0 {
-                buf.write("::");
-            }
-            buf.write(part);
-        }
-        DisplayWrap::Unwrapped
-    }
-
-    fn visit_var(&mut self, buf: &mut Buffer, s: &str) -> DisplayWrap {
-        if s == "self" {
-            buf.write(s);
-            return DisplayWrap::Unwrapped;
-        }
-
-        buf.write(normalize_identifier(&self.locals.resolve_or_self(s)));
-        DisplayWrap::Unwrapped
-    }
-
-    fn visit_bool_lit(&mut self, buf: &mut Buffer, s: &str) -> DisplayWrap {
-        buf.write(s);
-        DisplayWrap::Unwrapped
-    }
-
-    fn visit_str_lit(&mut self, buf: &mut Buffer, s: &str) -> DisplayWrap {
-        buf.write(&format!("\"{}\"", s));
-        DisplayWrap::Unwrapped
-    }
-
-    fn visit_char_lit(&mut self, buf: &mut Buffer, s: &str) -> DisplayWrap {
-        buf.write(&format!("'{}'", s));
-        DisplayWrap::Unwrapped
-    }
-
-    fn visit_num_lit(&mut self, buf: &mut Buffer, s: &str) -> DisplayWrap {
-        buf.write(s);
-        DisplayWrap::Unwrapped
-    }
-
-    fn visit_target(
-        &mut self,
-        buf: &mut Buffer,
-        initialized: bool,
-        first_level: bool,
-        target: &Target<'a>,
-    ) {
-        match target {
-            Target::Name("_") => {
-                buf.write("_");
-            }
-            Target::Name(name) => {
-                let name = normalize_identifier(name);
-                match initialized {
-                    true => self.locals.insert(name, LocalMeta::initialized()),
-                    false => self.locals.insert_with_default(name),
-                }
-                buf.write(name);
-            }
-            Target::Tuple(path, targets) => {
-                buf.write(&path.join("::"));
-                buf.write("(");
-                for target in targets {
-                    self.visit_target(buf, initialized, false, target);
-                    buf.write(",");
-                }
-                buf.write(")");
-            }
-            Target::Struct(path, targets) => {
-                buf.write(&path.join("::"));
-                buf.write(" { ");
-                for (name, target) in targets {
-                    buf.write(normalize_identifier(name));
-                    buf.write(": ");
-                    self.visit_target(buf, initialized, false, target);
-                    buf.write(",");
-                }
-                buf.write(" }");
-            }
-            Target::Path(path) => {
-                self.visit_path(buf, path);
-            }
-            Target::StrLit(s) => {
-                if first_level {
-                    buf.write("&");
-                }
-                self.visit_str_lit(buf, s);
-            }
-            Target::NumLit(s) => {
-                if first_level {
-                    buf.write("&");
-                }
-                self.visit_num_lit(buf, s);
-            }
-            Target::CharLit(s) => {
-                if first_level {
-                    buf.write("&");
-                }
-                self.visit_char_lit(buf, s);
-            }
-            Target::BoolLit(s) => {
-                if first_level {
-                    buf.write("&");
-                }
-                buf.write(s);
-            }
-        }
-    }
-
-    /* Helper methods for dealing with whitespace nodes */
-
-    // Combines `flush_ws()` and `prepare_ws()` to handle both trailing whitespace from the
-    // preceding literal and leading whitespace from the succeeding literal.
-    fn handle_ws(&mut self, ws: Ws) {
-        self.flush_ws(ws);
-        self.prepare_ws(ws);
-    }
-
-    fn should_trim_ws(&self, ws: Option<Whitespace>) -> WhitespaceHandling {
-        match ws {
-            Some(Whitespace::Suppress) => WhitespaceHandling::Suppress,
-            Some(Whitespace::Preserve) => WhitespaceHandling::Preserve,
-            Some(Whitespace::Minimize) => WhitespaceHandling::Minimize,
-            None => self.whitespace,
-        }
-    }
-
-    // If the previous literal left some trailing whitespace in `next_ws` and the
-    // prefix whitespace suppressor from the given argument, flush that whitespace.
-    // In either case, `next_ws` is reset to `None` (no trailing whitespace).
-    fn flush_ws(&mut self, ws: Ws) {
-        if self.next_ws.is_none() {
-            return;
-        }
-
-        // If `whitespace` is set to `suppress`, we keep the whitespace characters only if there is
-        // a `+` character.
-        match self.should_trim_ws(ws.0) {
-            WhitespaceHandling::Preserve => {
-                let val = self.next_ws.unwrap();
-                if !val.is_empty() {
-                    self.buf_writable.push(Writable::Lit(val));
-                }
-            }
-            WhitespaceHandling::Minimize => {
-                let val = self.next_ws.unwrap();
-                if !val.is_empty() {
-                    self.buf_writable
-                        .push(Writable::Lit(match val.contains('\n') {
-                            true => "\n",
-                            false => " ",
-                        }));
-                }
-            }
-            WhitespaceHandling::Suppress => {}
-        }
-        self.next_ws = None;
-    }
-
-    // Sets `skip_ws` to match the suffix whitespace suppressor from the given
-    // argument, to determine whether to suppress leading whitespace from the
-    // next literal.
-    fn prepare_ws(&mut self, ws: Ws) {
-        self.skip_ws = self.should_trim_ws(ws.1);
-    }
-}
-
-struct Buffer {
-    // The buffer to generate the code into
-    buf: String,
-    // The current level of indentation (in spaces)
-    indent: u8,
-    // Whether the output buffer is currently at the start of a line
-    start: bool,
-}
-
-impl Buffer {
-    fn new(indent: u8) -> Self {
-        Self {
-            buf: String::new(),
-            indent,
-            start: true,
-        }
-    }
-
-    fn writeln(&mut self, s: &str) -> Result<(), CompileError> {
-        if s == "}" {
-            self.dedent()?;
-        }
-        if !s.is_empty() {
-            self.write(s);
-        }
-        self.buf.push('\n');
-        if s.ends_with('{') {
-            self.indent();
-        }
-        self.start = true;
-        Ok(())
-    }
-
-    fn write(&mut self, s: &str) {
-        if self.start {
-            for _ in 0..(self.indent * 4) {
-                self.buf.push(' ');
-            }
-            self.start = false;
-        }
-        self.buf.push_str(s);
-    }
-
-    fn indent(&mut self) {
-        self.indent += 1;
-    }
-
-    fn dedent(&mut self) -> Result<(), CompileError> {
-        if self.indent == 0 {
-            return Err("dedent() called while indentation == 0".into());
-        }
-        self.indent -= 1;
-        Ok(())
-    }
-}
-
-#[derive(Clone, Default)]
-struct LocalMeta {
-    refs: Option<String>,
-    initialized: bool,
-}
-
-impl LocalMeta {
-    fn initialized() -> Self {
-        Self {
-            refs: None,
-            initialized: true,
-        }
-    }
-
-    fn with_ref(refs: String) -> Self {
-        Self {
-            refs: Some(refs),
-            initialized: true,
-        }
-    }
-}
-
-// type SetChain<'a, T> = MapChain<'a, T, ()>;
-
-#[derive(Debug)]
-struct MapChain<'a, K, V>
-where
-    K: cmp::Eq + hash::Hash,
-{
-    parent: Option<&'a MapChain<'a, K, V>>,
-    scopes: Vec<HashMap<K, V>>,
-}
-
-impl<'a, K: 'a, V: 'a> MapChain<'a, K, V>
-where
-    K: cmp::Eq + hash::Hash,
-{
-    fn new() -> MapChain<'a, K, V> {
-        MapChain {
-            parent: None,
-            scopes: vec![HashMap::new()],
-        }
-    }
-
-    fn with_parent<'p>(parent: &'p MapChain<'_, K, V>) -> MapChain<'p, K, V> {
-        MapChain {
-            parent: Some(parent),
-            scopes: vec![HashMap::new()],
-        }
-    }
-
-    /// Iterates the scopes in reverse and returns `Some(LocalMeta)`
-    /// from the first scope where `key` exists.
-    fn get(&self, key: &K) -> Option<&V> {
-        let scopes = self.scopes.iter().rev();
-        scopes
-            .filter_map(|set| set.get(key))
-            .next()
-            .or_else(|| self.parent.and_then(|set| set.get(key)))
-    }
-
-    fn is_current_empty(&self) -> bool {
-        self.scopes.last().unwrap().is_empty()
-    }
-
-    fn insert(&mut self, key: K, val: V) {
-        self.scopes.last_mut().unwrap().insert(key, val);
-
-        // Note that if `insert` returns `Some` then it implies
-        // an identifier is reused. For e.g. `{% macro f(a, a) %}`
-        // and `{% let (a, a) = ... %}` then this results in a
-        // generated template, which when compiled fails with the
-        // compile error "identifier `a` used more than once".
-    }
-
-    fn insert_with_default(&mut self, key: K)
-    where
-        V: Default,
-    {
-        self.insert(key, V::default());
-    }
-
-    fn push(&mut self) {
-        self.scopes.push(HashMap::new());
-    }
-
-    fn pop(&mut self) {
-        self.scopes.pop().unwrap();
-        assert!(!self.scopes.is_empty());
-    }
-}
-
-impl MapChain<'_, &str, LocalMeta> {
-    fn resolve(&self, name: &str) -> Option<String> {
-        let name = normalize_identifier(name);
-        self.get(&name).map(|meta| match &meta.refs {
-            Some(expr) => expr.clone(),
-            None => name.to_string(),
-        })
-    }
-
-    fn resolve_or_self(&self, name: &str) -> String {
-        let name = normalize_identifier(name);
-        self.resolve(name)
-            .unwrap_or_else(|| format!("self.{}", name))
-    }
-}
-
-fn median(sizes: &mut [usize]) -> usize {
-    sizes.sort_unstable();
-    if sizes.len() % 2 == 1 {
-        sizes[sizes.len() / 2]
-    } else {
-        (sizes[sizes.len() / 2 - 1] + sizes[sizes.len() / 2]) / 2
-    }
-}
-
-#[derive(Clone, PartialEq)]
-enum AstLevel {
-    Top,
-    Block,
-    Nested,
-}
-
-impl Copy for AstLevel {}
-
-#[derive(Clone)]
-enum DisplayWrap {
-    Wrapped,
-    Unwrapped,
-}
-
-impl Copy for DisplayWrap {}
-
-#[derive(Debug)]
-enum Writable<'a> {
-    Lit(&'a str),
-    Expr(&'a Expr<'a>),
-}
-
-// Identifiers to be replaced with raw identifiers, so as to avoid
-// collisions between template syntax and Rust's syntax. In particular
-// [Rust keywords](https://doc.rust-lang.org/reference/keywords.html)
-// should be replaced, since they're not reserved words in Askama
-// syntax but have a high probability of causing problems in the
-// generated code.
-//
-// This list excludes the Rust keywords *self*, *Self*, and *super*
-// because they are not allowed to be raw identifiers, and *loop*
-// because it's used something like a keyword in the template
-// language.
-static USE_RAW: [(&str, &str); 47] = [
-    ("as", "r#as"),
-    ("break", "r#break"),
-    ("const", "r#const"),
-    ("continue", "r#continue"),
-    ("crate", "r#crate"),
-    ("else", "r#else"),
-    ("enum", "r#enum"),
-    ("extern", "r#extern"),
-    ("false", "r#false"),
-    ("fn", "r#fn"),
-    ("for", "r#for"),
-    ("if", "r#if"),
-    ("impl", "r#impl"),
-    ("in", "r#in"),
-    ("let", "r#let"),
-    ("match", "r#match"),
-    ("mod", "r#mod"),
-    ("move", "r#move"),
-    ("mut", "r#mut"),
-    ("pub", "r#pub"),
-    ("ref", "r#ref"),
-    ("return", "r#return"),
-    ("static", "r#static"),
-    ("struct", "r#struct"),
-    ("trait", "r#trait"),
-    ("true", "r#true"),
-    ("type", "r#type"),
-    ("unsafe", "r#unsafe"),
-    ("use", "r#use"),
-    ("where", "r#where"),
-    ("while", "r#while"),
-    ("async", "r#async"),
-    ("await", "r#await"),
-    ("dyn", "r#dyn"),
-    ("abstract", "r#abstract"),
-    ("become", "r#become"),
-    ("box", "r#box"),
-    ("do", "r#do"),
-    ("final", "r#final"),
-    ("macro", "r#macro"),
-    ("override", "r#override"),
-    ("priv", "r#priv"),
-    ("typeof", "r#typeof"),
-    ("unsized", "r#unsized"),
-    ("virtual", "r#virtual"),
-    ("yield", "r#yield"),
-    ("try", "r#try"),
-];
-
-fn normalize_identifier(ident: &str) -> &str {
-    if let Some(word) = USE_RAW.iter().find(|x| x.0 == ident) {
-        word.1
-    } else {
-        ident
-    }
-}