Add labelled expressions.

Restructure project (again).

Convert `Cat` and `Alt` from binary to n+2-ary.

2 files changed, 468 insertions, 311 deletions

diff --git a/src/lower/mod.rs b/src/lower/mod.rs
index 242fa47..06099e3 100644
--- a/src/lower/mod.rs
+++ b/src/lower/mod.rs
@@ -1,58 +1,488 @@
-use crate::chomp::typed::{
-    Alt, Cat, Epsilon, Fix, Literal, RawTypedExpression, TypedExpression, Variable,
+use std::{
+    collections::{BTreeSet, HashMap},
+    convert::TryInto,
 };
 
-pub mod rust;
+use heck::{CamelCase, SnakeCase};
+use proc_macro2::{Ident, Span, TokenStream, TokenTree};
+use quote::{format_ident, quote, quote_spanned};
+use syn::{Index, LitStr};
 
-pub trait Backend: Default {
-    type Id;
-    type Code;
+use crate::chomp::{
+    ast,
+    set::FirstSet,
+    typed::{
+        lower::{Backend, GenerateCode},
+        Alt, Cat, Epsilon, Fix, Literal, Type, Typed, TypedExpression, Variable,
+    },
+    Name,
+};
 
-    fn gen_epsilon(&mut self, eps: Epsilon) -> Self::Id;
+#[derive(Clone, Debug)]
+struct Ty {
+    name: TokenStream,
+    rest: TokenStream,
+    deps: BTreeSet<usize>,
+}
 
-    fn gen_literal(&mut self, lit: Literal) -> Self::Id;
+#[derive(Debug)]
+pub struct RustBackend {
+    // Indexed by ID, stores type, impl and dependencies
+    data: Vec<Ty>,
+    eps_id: Option<usize>,
+    lit_map: HashMap<String, usize>,
+    cat_map: HashMap<Vec<usize>, usize>,
+    alt_map: HashMap<Vec<usize>, usize>,
+    fix_map: HashMap<TypedExpression, usize>,
+    var_map: HashMap<usize, usize>, // Key is fix point ID
+    name_map: HashMap<Ident, usize>,
+    can_char: BTreeSet<usize>,
+    context: Vec<usize>,
+}
 
-    fn gen_cat(&mut self, cat: Cat) -> Self::Id;
+impl RustBackend {
+    fn new_type_name(&mut self, prefix: &str, name: Option<Name>, span: Span) -> (usize, Ident) {
+        let id = self.data.len();
 
-    fn gen_alt(&mut self, alt: Alt) -> Self::Id;
+        match name {
+            None => (id, format_ident!("{}{}", prefix, id + 1, span = span)),
+            Some(name) => {
+                let name = name.to_camel_case().into_ident(span);
+                let count = self.name_map.entry(name.clone()).or_insert(0);
+                *count += 1;
+                (id, format_ident!("{}{}", name, count))
+            }
+        }
+    }
 
-    fn gen_fix(&mut self, fix: Fix) -> Self::Id;
+    fn recurse_exprs<I: IntoIterator<Item = TypedExpression>>(
+        &mut self,
+        iter: I,
+    ) -> (Vec<Type>, Vec<(Option<Name>, Span)>, Vec<usize>) {
+        let (ty_name_span, ids): (Vec<_>, _) = iter
+            .into_iter()
+            .map(|e| {
+                (
+                    (
+                        e.get_type().clone(),
+                        (e.name.clone(), e.span.unwrap_or_else(Span::call_site)),
+                    ),
+                    e.gen(self),
+                )
+            })
+            .unzip();
+        let (ty, name_span) = ty_name_span.into_iter().unzip();
+        (ty, name_span, ids)
+    }
+
+    fn indexes<'a, I: 'a + IntoIterator<Item = Span>>(
+        prefix: &'a str,
+        iter: I,
+    ) -> impl Iterator<Item = (Index, Ident)> + '_ {
+        iter.into_iter().enumerate().map(move |(idx, span)| {
+            (
+                Index {
+                    index: idx.try_into().unwrap(),
+                    span,
+                },
+                format_ident!("{}{}", prefix, idx, span = span),
+            )
+        })
+    }
+
+    fn ty_names<'a, I: 'a + IntoIterator<Item = usize>>(
+        &'a self,
+        iter: I,
+    ) -> impl Iterator<Item = TokenStream> + '_ {
+        iter.into_iter().map(move |id| self.data[id].name.clone())
+    }
 
-    fn gen_variable(&mut self, var: Variable) -> Self::Id;
+    fn name_parts_snake<'a, I: 'a + IntoIterator<Item = (Option<Name>, Span)>>(
+        default: &'a str,
+        iter: I,
+    ) -> impl Iterator<Item = Ident> + '_ {
+        let mut name_map = HashMap::new();
+        iter.into_iter()
+            .enumerate()
+            .map(move |(index, (name, span))| match name {
+                None => format_ident!("{}{}", default, index + 1, span = span),
+                Some(name) => {
+                    let name = name.to_snake_case().into_ident(span);
+                    let count = name_map.entry(name.clone()).or_insert(0usize);
+                    *count += 1;
+                    format_ident!("{}{}", name, count)
+                }
+            })
+    }
 
-    fn emit_code(self, id: Self::Id) -> Self::Code;
+    fn name_parts_camel<'a, I: 'a + IntoIterator<Item = (Option<Name>, Span)>>(
+        default: &'a str,
+        iter: I,
+    ) -> impl Iterator<Item = Ident> + '_ {
+        let mut name_map = HashMap::new();
+        iter.into_iter()
+            .enumerate()
+            .map(move |(index, (name, span))| match name {
+                None => format_ident!("{}{}", default, index + 1, span = span),
+                Some(name) => {
+                    let name = name.to_camel_case().into_ident(span);
+                    let count = name_map.entry(name.clone()).or_insert(0usize);
+                    *count += 1;
+                    format_ident!("{}{}", name, count)
+                }
+            })
+    }
 }
 
-pub trait GenerateCode {
-    fn gen<B: Backend>(self, backend: &mut B) -> B::Id;
+impl Default for RustBackend {
+    fn default() -> Self {
+        Self {
+            data: Vec::new(),
+            eps_id: None,
+            lit_map: HashMap::new(),
+            cat_map: HashMap::new(),
+            alt_map: HashMap::new(),
+            fix_map: HashMap::new(),
+            var_map: HashMap::new(),
+            name_map: HashMap::new(),
+            can_char: BTreeSet::new(),
+            context: Vec::new(),
+        }
+    }
 }
 
-macro_rules! generate_leaf {
-    ($ty:ty, $gen:ident) => {
-        impl GenerateCode for $ty {
-            fn gen<B: Backend>(self, backend: &mut B) -> B::Id {
-                backend.$gen(self)
+impl Backend for RustBackend {
+    type Id = usize;
+
+    type Code = TokenStream;
+
+    fn gen_epsilon(&mut self, _name: Option<Name>, _span: Option<Span>, _eps: Epsilon) -> Self::Id {
+        if let Some(id) = self.eps_id {
+            return id;
+        }
+
+        let id = self.data.len();
+        self.data.push(Ty {
+            name: quote! {Epsilon},
+            rest: TokenStream::new(),
+            deps: BTreeSet::new(),
+        });
+        id
+    }
+
+    fn gen_literal(&mut self, name: Option<Name>, span: Option<Span>, lit: Literal) -> Self::Id {
+        let span = span.unwrap_or_else(Span::call_site);
+
+        let lit: ast::Literal = lit.into();
+        if let Some(&id) = self.lit_map.get(&lit) {
+            return id;
+        }
+
+        let (id, name) = self.new_type_name("Lit", name, span);
+        let doc_name = format!(r#"The literal string `{:?}`."#, lit);
+        let lit = LitStr::new(&lit, span);
+
+        let mut rest = quote_spanned! {span=>
+            #[doc=#doc_name]
+            #[derive(Clone, Debug, Eq, Hash, PartialEq)]
+            pub struct #name;
+
+            impl ::std::fmt::Display for #name {
+                fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                    write!(f, "{}", #lit)
+                }
+            }
+
+            impl Parse for #name {
+                fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
+                    input.consume_str(#lit).map(|()| #name)
+                }
             }
+        };
+
+        if lit.value().len() == 1 {
+            self.can_char.insert(id);
+            let c = lit.value().chars().next().unwrap();
+            rest.extend(quote_spanned! {span=>
+                impl From<#name> for char {
+                    fn from(_: #name) -> Self {
+                        #c
+                    }
+                }
+            });
         }
-    };
-}
 
-generate_leaf!(Epsilon, gen_epsilon);
-generate_leaf!(Literal, gen_literal);
-generate_leaf!(Cat, gen_cat);
-generate_leaf!(Alt, gen_alt);
-generate_leaf!(Fix, gen_fix);
-generate_leaf!(Variable, gen_variable);
-
-impl GenerateCode for TypedExpression {
-    fn gen<B: Backend>(self, backend: &mut B) -> B::Id {
-        match self.inner {
-            RawTypedExpression::Epsilon(e) => e.gen(backend),
-            RawTypedExpression::Literal(l) => l.gen(backend),
-            RawTypedExpression::Cat(c) => c.gen(backend),
-            RawTypedExpression::Alt(a) => a.gen(backend),
-            RawTypedExpression::Fix(f) => f.gen(backend),
-            RawTypedExpression::Variable(v) => v.gen(backend),
+        self.lit_map.insert(lit.value(), id);
+        self.data.push(Ty {
+            name: TokenTree::from(name).into(),
+            rest,
+            deps: BTreeSet::new(),
+        });
+
+        id
+    }
+
+    fn gen_cat(&mut self, name: Option<Name>, span: Option<Span>, cat: Cat) -> Self::Id {
+        let span = span.unwrap_or_else(Span::call_site);
+        let (_, name_spans, ids) = self.recurse_exprs(cat);
+
+        if let Some(&id) = self.cat_map.get(&ids) {
+            return id;
         }
+
+        let (id, name) = self.new_type_name("Cat", name, span);
+        let ty_names: Vec<_> = self.ty_names(ids.iter().copied()).collect();
+        let named = name_spans.iter().any(|(name, _)| name.is_some());
+        let (indexes, number_parts): (Vec<_>, Vec<_>) =
+            Self::indexes("part", name_spans.iter().cloned().map(|(_, span)| span)).unzip();
+        let name_parts: Vec<_> = Self::name_parts_snake("part", name_spans).collect();
+        let rest = if named {
+            quote_spanned! {span=>
+                #[derive(Clone, Debug, Eq, Hash, PartialEq)]
+                pub struct #name {
+                    #(pub #name_parts: #ty_names),*
+                }
+
+                impl ::std::fmt::Display for #name {
+                    fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                        #(self.#name_parts.fmt(f)?;)*
+                        Ok(())
+                    }
+                }
+
+                impl Parse for #name {
+                    fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
+                        #(let #number_parts = input.take()?;)*
+                        Ok(Self {#(#name_parts: #number_parts),*})
+                    }
+                }
+            }
+        } else {
+            quote_spanned! {span=>
+                #[derive(Clone, Debug, Eq, Hash, PartialEq)]
+                pub struct #name(#(pub #ty_names),*);
+
+                impl ::std::fmt::Display for #name {
+                    fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                        #(self.#indexes.fmt(f)?;)*
+                        Ok(())
+                    }
+                }
+
+                impl Parse for #name {
+                    fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
+                        #(let #number_parts = input.take()?;)*
+                        Ok(Self(#(#number_parts),*))
+                    }
+                }
+            }
+        };
+
+        self.cat_map.insert(ids.clone(), id);
+        self.data.push(Ty {
+            name: TokenTree::from(name).into(),
+            rest,
+            deps: ids.into_iter().collect(),
+        });
+        id
+    }
+
+    fn gen_alt(&mut self, name: Option<Name>, span: Option<Span>, alt: Alt) -> Self::Id {
+        let span = span.unwrap_or_else(Span::call_site);
+        let (tys, name_spans, ids) = self.recurse_exprs(alt);
+
+        if let Some(&id) = self.alt_map.get(&ids) {
+            return id;
+        }
+
+        let (id, name) = self.new_type_name("Alt", name, span);
+        let ty_names: Vec<_> = self.ty_names(ids.iter().copied()).collect();
+        let name_parts: Vec<_> = Self::name_parts_camel("Branch", name_spans).collect();
+
+        let nullable = tys
+            .iter()
+            .enumerate()
+            .find(|(_, ty)| ty.nullable())
+            .map(|(idx, _)| name_parts[idx].clone());
+        let (first_alts, firsts): (Vec<_>, Vec<_>) = tys
+            .iter()
+            .map(|ty| ty.first_set())
+            .cloned()
+            .enumerate()
+            .filter(|(_, fs)| !fs.is_empty())
+            .map(|(idx, fs)| {
+                let fs = fs.into_iter();
+                (name_parts[idx].clone(), quote! {#(Some(#fs))|*})
+            })
+            .unzip();
+        let all_firsts = tys
+            .iter()
+            .map(|ty| ty.first_set())
+            .cloned()
+            .flat_map(FirstSet::into_iter);
+
+        let mut rest = quote_spanned! {span=>
+            #[derive(Clone, Debug, Eq, Hash, PartialEq)]
+            pub enum #name {
+                #(#name_parts(#ty_names)),*
+            }
+
+            impl ::std::fmt::Display for #name {
+                fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                    match self {
+                        #(Self::#name_parts(inner) => inner.fmt(f)),*
+                    }
+                }
+            }
+        };
+
+        rest.extend(if let Some(nullable) = nullable {
+                quote_spanned! {span=>
+                    impl Parse for #name {
+                        fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
+                            match input.peek() {
+                                #(#firsts => Ok(Self::#first_alts(input.take()?)),)*
+                                _ => Ok(Self::#nullable(input.take()?))
+                            }
+                        }
+                    }
+                }
+            } else {
+                quote_spanned! {span=>
+                    impl Parse for #name {
+                        fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
+                            match input.peek() {
+                                #(#firsts => Ok(Self::#first_alts(input.take()?)),)*
+                                Some(c) => Err(TakeError::BadBranch(input.pos(), c, &[#(#all_firsts),*])),
+                                None => Err(TakeError::EndOfStream(input.pos()))
+                            }
+                        }
+                    }
+                }
+            });
+
+        if ids.iter().all(|id| self.can_char.contains(id)) {
+            self.can_char.insert(id);
+            rest.extend(quote_spanned! {span=>
+                impl From<#name> for char {
+                    fn from(alt: #name) -> Self {
+                        match alt {
+                            #(#name::#name_parts(inner) => inner.into()),*
+                        }
+                    }
+                 }
+            })
+        }
+
+        self.alt_map.insert(ids.clone(), id);
+        self.data.push(Ty {
+            name: TokenTree::from(name).into(),
+            rest,
+            deps: ids.into_iter().collect(),
+        });
+        id
+    }
+
+    fn gen_fix(&mut self, name: Option<Name>, span: Option<Span>, fix: Fix) -> Self::Id {
+        let span = span.unwrap_or_else(Span::call_site);
+        let inner = fix.unwrap();
+
+        if let Some(&id) = self.fix_map.get(&inner) {
+            return id;
+        }
+
+        let (id, name) = self.new_type_name("Fix", name, span);
+        self.fix_map.insert(inner.clone(), id);
+
+        self.data.push(Ty {
+            name: TokenTree::from(name.clone()).into(),
+            rest: TokenStream::new(),
+            deps: BTreeSet::new(),
+        });
+
+        self.context.push(id);
+        let inner = inner.gen(self);
+        self.context.pop();
+
+        let inner_ty = self.data[inner].name.clone();
+        let rest = quote_spanned! {span=>
+            #[derive(Clone, Debug, Eq, Hash, PartialEq)]
+            pub struct #name(pub #inner_ty);
+
+            impl ::std::fmt::Display for #name {
+                fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+                    self.0.fmt(f)
+                }
+            }
+
+            impl Parse for #name {
+                fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
+                    input.take().map(Self)
+                }
+            }
+        };
+        self.data[id].rest = rest;
+        self.data[id].deps = [inner].iter().cloned().collect();
+        id
+    }
+
+    fn gen_variable(&mut self, name: Option<Name>, span: Option<Span>, var: Variable) -> Self::Id {
+        let span = span.unwrap_or_else(Span::call_site);
+        let fix_id = self.context[self.context.len() - var.index() - 1];
+
+        if let Some(&id) = self.var_map.get(&fix_id) {
+            return id;
+        }
+
+        let id = self.data.len();
+        let fix_ty = self.data[fix_id].name.clone();
+        let name = quote! {Box<#fix_ty>};
+        self.var_map.insert(fix_id, id);
+        self.data.push(Ty {
+            name,
+            rest: TokenStream::new(),
+            deps: BTreeSet::new(),
+        });
+
+        id
+    }
+
+    fn emit_code(self, name: Option<Name>, span: Option<Span>, id: Self::Id) -> Self::Code {
+        let span = span.unwrap_or_else(Span::call_site);
+
+        let mut tokens = quote_spanned! {span=>
+            use ::chewed::*;
+        };
+
+        let mut todo = [id].iter().copied().collect::<BTreeSet<_>>();
+        let mut completed = BTreeSet::new();
+
+        while !todo.is_empty() {
+            let next = todo.clone();
+            completed.append(&mut todo);
+
+            for ty in next {
+                let ty = self.data[ty].clone();
+                tokens.extend(ty.rest);
+                todo.extend(ty.deps.into_iter().filter(|id| !completed.contains(id)));
+            }
+        }
+
+        let root_name = self.data[id].name.clone();
+
+        tokens.extend(if let Some(name) = name {
+            let name = name.into_ident(span);
+            let count = self.name_map.get(&name).copied().unwrap_or_default() + 1;
+            let name = format_ident!("{}{}", name, count);
+            quote_spanned! {span=>
+                pub type #name = #root_name;
+            }
+        } else {
+            quote_spanned! {span=>
+                pub type Ast = #root_name;
+            }
+        });
+
+        tokens
     }
 }
diff --git a/src/lower/rust.rs b/src/lower/rust.rs
deleted file mode 100644
index 7931306..0000000
--- a/src/lower/rust.rs
+++ /dev/null
@@ -1,273 +0,0 @@
-use std::collections::{BTreeSet, HashMap};
-
-use proc_macro2::{Span, TokenStream, TokenTree};
-use quote::{format_ident, quote};
-
-use crate::chomp::{
-    ast,
-    typed::{Alt, Cat, Epsilon, Fix, Literal, Typed, TypedExpression, Variable},
-};
-
-use super::{Backend, GenerateCode};
-
-#[derive(Debug)]
-pub struct RustBackend {
-    // Indexed by ID, stores type, impl and dependencies
-    data: Vec<(TokenStream, TokenStream, BTreeSet<usize>)>,
-    eps_id: Option<usize>,
-    lit_map: HashMap<String, usize>,
-    cat_map: HashMap<(usize, usize), usize>,
-    alt_map: HashMap<(usize, usize), usize>,
-    fix_map: HashMap<Box<TypedExpression>, usize>,
-    var_map: HashMap<usize, usize>, // Key is fix point ID
-    context: Vec<usize>,
-}
-
-impl Default for RustBackend {
-    fn default() -> Self {
-        Self {
-            data: Vec::new(),
-            eps_id: None,
-            lit_map: HashMap::new(),
-            cat_map: HashMap::new(),
-            alt_map: HashMap::new(),
-            fix_map: HashMap::new(),
-            var_map: HashMap::new(),
-            context: Vec::new(),
-        }
-    }
-}
-
-impl Backend for RustBackend {
-    type Id = usize;
-
-    type Code = TokenStream;
-
-    fn gen_epsilon(&mut self, _eps: Epsilon) -> Self::Id {
-        match self.eps_id {
-            Some(id) => id,
-            None => {
-                let id = self.data.len();
-                let ty = quote! { () };
-                let tokens = TokenStream::new();
-                self.data.push((ty, tokens, BTreeSet::new()));
-                id
-            }
-        }
-    }
-
-    fn gen_literal(&mut self, lit: Literal) -> Self::Id {
-        let lit: ast::Literal = lit.into();
-        if let Some(&id) = self.lit_map.get(&lit.value()) {
-            id
-        } else {
-            let id = self.data.len();
-            let name = format_ident!("Lit{}", id);
-            let doc_name = format!(
-                r#"The literal string `"{}"`."#,
-                lit.value().escape_debug().collect::<String>()
-            );
-            let lit = lit.as_litstr(Span::call_site());
-            let tokens = quote! {
-                #[doc=#doc_name]
-                #[derive(Clone, Debug, Eq, Hash, PartialEq)]
-                pub struct #name;
-
-                impl Parse for #name {
-                    fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
-                        input.consume_str(#lit).map(|()| #name)
-                    }
-                }
-            };
-
-            self.data
-                .push((TokenTree::from(name).into(), tokens, BTreeSet::new()));
-            self.lit_map.insert(lit.value(), id);
-
-            id
-        }
-    }
-
-    fn gen_cat(&mut self, cat: Cat) -> Self::Id {
-        let (fst, _punct, snd) = cat.unwrap();
-        let fst = fst.gen(self);
-        let snd = snd.gen(self);
-
-        if let Some(&id) = self.cat_map.get(&(fst, snd)) {
-            id
-        } else {
-            let id = self.data.len();
-            let fst_ty = self.data[fst].0.clone();
-            let snd_ty = self.data[snd].0.clone();
-            self.data.push((
-                quote! {(#fst_ty, #snd_ty)},
-                TokenStream::new(),
-                [fst, snd].iter().cloned().collect(),
-            ));
-            self.cat_map.insert((fst, snd), id);
-            id
-        }
-    }
-
-    fn gen_alt(&mut self, alt: Alt) -> Self::Id {
-        let iter_first = alt.get_type().first_set().clone().into_iter();
-
-        let (left, _punct, right) = alt.unwrap();
-        let left_ty = left.get_type();
-        let right_ty = right.get_type();
-
-        let left_null = left_ty.nullable();
-        let left_first = left_ty.first_set().clone();
-
-        let right_null = right_ty.nullable();
-        let right_first = right_ty.first_set().clone();
-
-        let left = left.gen(self);
-        let right = right.gen(self);
-
-        if let Some(&id) = self.alt_map.get(&(left, right)) {
-            id
-        } else {
-            let id = self.data.len();
-            let left_ty = self.data[left].0.clone();
-            let right_ty = self.data[right].0.clone();
-            let name = format_ident!("Alt{}", id);
-            let mut tokens = quote! {
-                #[derive(Clone, Debug, Eq, Hash, PartialEq)]
-                pub enum #name {
-                    Left(#left_ty),
-                    Right(#right_ty),
-                }
-            };
-
-            let other = if left_null {
-                let iter = right_first.into_iter();
-
-                quote! {
-                    impl Parse for #name {
-                        fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
-                            match input.peek() {
-                                #(Some(#iter))|* => input.take().map(Self::Right),
-                                _ => input.take().map(Self::Left),
-                            }
-                        }
-                    }
-                }
-            } else if right_null {
-                let iter = left_first.into_iter();
-
-                quote! {
-                    impl Parse for #name {
-                        fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
-                            match input.peek() {
-                                #(Some(#iter))|* => input.take().map(Self::Left),
-                                _ => input.take().map(Self::Right),
-                            }
-                        }
-                    }
-                }
-            } else {
-                let iter_left = left_first.into_iter();
-                let iter_right = right_first.into_iter();
-
-                quote! {
-                    impl Parse for #name {
-                        fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
-                            match input.peek().ok_or_else(|| TakeError::EndOfStream(input.pos()))? {
-                                #(#iter_left)|* => input.take().map(Self::Left),
-                                #(#iter_right)|* => input.take().map(Self::Right),
-                                c => Err(TakeError::BadBranch(input.pos(), c, &[#(#iter_first),*]))
-                            }
-                        }
-                    }
-                }
-            };
-
-            tokens.extend(other);
-            self.data.push((
-                TokenTree::from(name).into(),
-                tokens,
-                [left, right].iter().cloned().collect(),
-            ));
-            self.alt_map.insert((left, right), id);
-            id
-        }
-    }
-
-    fn gen_fix(&mut self, fix: Fix) -> Self::Id {
-        let (_arg, inner, _span) = fix.unwrap();
-        if let Some(&id) = self.fix_map.get(&inner) {
-            id
-        } else {
-            let id = self.data.len();
-            let name = format_ident!("Fix{}", id);
-            self.data.push((
-                TokenTree::from(name.clone()).into(),
-                TokenStream::new(),
-                BTreeSet::new(),
-            ));
-
-            self.context.push(id);
-            let inner = inner.gen(self);
-            self.context.pop();
-
-            let inner_ty = self.data[inner].0.clone();
-            let tokens = quote! {
-                #[derive(Clone, Debug, Eq, Hash, PartialEq)]
-                pub struct #name(#inner_ty);
-
-                impl Parse for #name {
-                    fn take<P: Parser + ?Sized>(input: &mut P) -> Result<Self, TakeError> {
-                        input.take().map(Self)
-                    }
-                }
-            };
-            self.data[id].1 = tokens;
-            self.data[id].2 = [inner].iter().cloned().collect();
-            id
-        }
-    }
-
-    fn gen_variable(&mut self, var: Variable) -> Self::Id {
-        let fix_id = self.context[self.context.len() - var.index() - 1];
-        if let Some(&id) = self.var_map.get(&fix_id) {
-            id
-        } else {
-            let id = self.data.len();
-            let fix_ty = self.data[fix_id].0.clone();
-            let name = quote! {Box<#fix_ty>};
-            self.data.push((name, TokenStream::new(), BTreeSet::new()));
-            self.var_map.insert(fix_id, id);
-            id
-        }
-    }
-
-    fn emit_code(self, id: Self::Id) -> Self::Code {
-        let mut tokens = quote! {
-            use ::chewed::*;
-        };
-
-        let (root_ty, root_impl, mut todo) = self.data[id].clone();
-        tokens.extend(root_impl);
-        let mut completed = [id].iter().cloned().collect::<BTreeSet<_>>();
-
-        while !todo.is_empty() {
-            let mut next = BTreeSet::new();
-            completed.extend(todo.clone());
-
-            for ty in todo {
-                let ty = self.data[ty].clone();
-                tokens.extend(ty.1);
-                next.extend(ty.2.into_iter().filter(|id| !completed.contains(id)));
-            }
-
-            todo = next;
-        }
-
-        tokens.extend(quote! {
-            pub type Ast = #root_ty;
-        });
-
-        tokens
-    }
-}