Separate out the fold codegen
diff --git a/codegen/src/fold.rs b/codegen/src/fold.rs
new file mode 100644
index 0000000..3122473
--- /dev/null
+++ b/codegen/src/fold.rs
@@ -0,0 +1,402 @@
+use crate::file;
+use quote::quote;
+use syn_codegen as types;
+
+const FOLD_SRC: &str = "../src/gen/fold.rs";
+
+mod codegen {
+ use inflections::Inflect;
+ use proc_macro2::{Span, TokenStream};
+ use quote::{quote, TokenStreamExt};
+ use syn::*;
+ use syn_codegen as types;
+
+ #[derive(Default)]
+ pub struct State {
+ pub fold_trait: TokenStream,
+ pub fold_impl: TokenStream,
+ }
+
+ fn under_name(name: &str) -> Ident {
+ Ident::new(&name.to_snake_case(), Span::call_site())
+ }
+
+ fn simple_visit(item: &str, name: &TokenStream) -> TokenStream {
+ let ident = under_name(item);
+
+ let method = Ident::new(&format!("fold_{}", ident), Span::call_site());
+ quote! {
+ _visitor.#method(#name)
+ }
+ }
+
+ fn box_visit(
+ elem: &types::Type,
+ features: &types::Features,
+ defs: &types::Definitions,
+ name: &TokenStream,
+ ) -> Option<TokenStream> {
+ let res = visit(elem, features, defs, "e!(*#name))?;
+ Some(quote! {
+ Box::new(#res)
+ })
+ }
+
+ fn vec_visit(
+ elem: &types::Type,
+ features: &types::Features,
+ defs: &types::Definitions,
+ name: &TokenStream,
+ ) -> Option<TokenStream> {
+ let operand = quote!(it);
+ let val = visit(elem, features, defs, &operand)?;
+ Some(quote! {
+ FoldHelper::lift(#name, |it| { #val })
+ })
+ }
+
+ fn punctuated_visit(
+ elem: &types::Type,
+ features: &types::Features,
+ defs: &types::Definitions,
+ name: &TokenStream,
+ ) -> Option<TokenStream> {
+ let operand = quote!(it);
+ let val = visit(elem, features, defs, &operand)?;
+ Some(quote! {
+ FoldHelper::lift(#name, |it| { #val })
+ })
+ }
+
+ fn option_visit(
+ elem: &types::Type,
+ features: &types::Features,
+ defs: &types::Definitions,
+ name: &TokenStream,
+ ) -> Option<TokenStream> {
+ let it = quote!(it);
+ let val = visit(elem, features, defs, &it)?;
+ Some(quote! {
+ (#name).map(|it| { #val })
+ })
+ }
+
+ fn tuple_visit(
+ elems: &[types::Type],
+ features: &types::Features,
+ defs: &types::Definitions,
+ name: &TokenStream,
+ ) -> Option<TokenStream> {
+ if elems.is_empty() {
+ return None;
+ }
+
+ let mut code = TokenStream::new();
+ for (i, elem) in elems.iter().enumerate() {
+ let i = Index::from(i);
+ let it = quote!((#name).#i);
+ let val = visit(elem, features, defs, &it).unwrap_or(it);
+ code.append_all(val);
+ code.append_all(quote!(,));
+ }
+ Some(quote! {
+ (#code)
+ })
+ }
+
+ fn token_punct_visit(repr: &str, name: &TokenStream) -> TokenStream {
+ let ty: TokenStream = syn::parse_str(&format!("Token![{}]", repr)).unwrap();
+ quote! {
+ #ty(tokens_helper(_visitor, &#name.spans))
+ }
+ }
+
+ fn token_keyword_visit(repr: &str, name: &TokenStream) -> TokenStream {
+ let ty: TokenStream = syn::parse_str(&format!("Token![{}]", repr)).unwrap();
+ quote! {
+ #ty(tokens_helper(_visitor, &#name.span))
+ }
+ }
+
+ fn token_group_visit(ty: &str, name: &TokenStream) -> TokenStream {
+ let ty = Ident::new(ty, Span::call_site());
+ quote! {
+ #ty(tokens_helper(_visitor, &#name.span))
+ }
+ }
+
+ fn visit(
+ ty: &types::Type,
+ features: &types::Features,
+ defs: &types::Definitions,
+ name: &TokenStream,
+ ) -> Option<TokenStream> {
+ match ty {
+ types::Type::Box(t) => box_visit(&*t, features, defs, name),
+ types::Type::Vec(t) => vec_visit(&*t, features, defs, name),
+ types::Type::Punctuated(p) => punctuated_visit(&p.element, features, defs, name),
+ types::Type::Option(t) => option_visit(&*t, features, defs, name),
+ types::Type::Tuple(t) => tuple_visit(t, features, defs, name),
+ types::Type::Token(t) => {
+ let repr = &defs.tokens[t];
+ let is_keyword = repr.chars().next().unwrap().is_alphabetic();
+ if is_keyword {
+ Some(token_keyword_visit(repr, name))
+ } else {
+ Some(token_punct_visit(repr, name))
+ }
+ }
+ types::Type::Group(t) => Some(token_group_visit(&t[..], name)),
+ types::Type::Syn(t) => {
+ fn requires_full(features: &types::Features) -> bool {
+ features.any.contains("full") && features.any.len() == 1
+ }
+
+ let res = simple_visit(t, name);
+
+ let target = defs.types.iter().find(|ty| ty.ident == *t).unwrap();
+
+ Some(
+ if requires_full(&target.features) && !requires_full(features) {
+ quote! {
+ full!(#res)
+ }
+ } else {
+ res
+ },
+ )
+ }
+ types::Type::Ext(t) if super::TERMINAL_TYPES.contains(&&t[..]) => {
+ Some(simple_visit(t, name))
+ }
+ types::Type::Ext(_) | types::Type::Std(_) => None,
+ }
+ }
+
+ fn visit_features(features: &types::Features) -> TokenStream {
+ let features = &features.any;
+ match features.len() {
+ 0 => quote!(),
+ 1 => quote!(#[cfg(feature = #(#features)*)]),
+ _ => quote!(#[cfg(any(#(feature = #features),*))]),
+ }
+ }
+
+ pub fn generate(state: &mut State, s: &types::Node, defs: &types::Definitions) {
+ let features = visit_features(&s.features);
+ let under_name = under_name(&s.ident);
+ let ty = Ident::new(&s.ident, Span::call_site());
+ let fold_fn = Ident::new(&format!("fold_{}", under_name), Span::call_site());
+
+ let mut fold_impl = TokenStream::new();
+
+ match &s.data {
+ types::Data::Enum(variants) => {
+ let mut fold_variants = TokenStream::new();
+
+ for (variant, fields) in variants {
+ let variant_ident = Ident::new(variant, Span::call_site());
+
+ if fields.is_empty() {
+ fold_variants.append_all(quote! {
+ #ty::#variant_ident => {
+ #ty::#variant_ident
+ }
+ });
+ } else {
+ let mut bind_fold_fields = TokenStream::new();
+ let mut fold_fields = TokenStream::new();
+
+ for (idx, ty) in fields.iter().enumerate() {
+ let name = format!("_binding_{}", idx);
+ let binding = Ident::new(&name, Span::call_site());
+
+ bind_fold_fields.append_all(quote! {
+ #binding,
+ });
+
+ let owned_binding = quote!(#binding);
+
+ fold_fields.append_all(
+ visit(ty, &s.features, defs, &owned_binding)
+ .unwrap_or(owned_binding),
+ );
+
+ fold_fields.append_all(quote!(,));
+ }
+
+ fold_variants.append_all(quote! {
+ #ty::#variant_ident(#bind_fold_fields) => {
+ #ty::#variant_ident(
+ #fold_fields
+ )
+ }
+ });
+ }
+ }
+
+ fold_impl.append_all(quote! {
+ match _i {
+ #fold_variants
+ }
+ });
+ }
+ types::Data::Struct(fields) => {
+ let mut fold_fields = TokenStream::new();
+
+ for (field, ty) in fields {
+ let id = Ident::new(&field, Span::call_site());
+ let ref_toks = quote!(_i.#id);
+ let fold = visit(&ty, &s.features, defs, &ref_toks).unwrap_or(ref_toks);
+
+ fold_fields.append_all(quote! {
+ #id: #fold,
+ });
+ }
+
+ if !fields.is_empty() {
+ fold_impl.append_all(quote! {
+ #ty {
+ #fold_fields
+ }
+ })
+ } else {
+ if ty == "Ident" {
+ fold_impl.append_all(quote! {
+ let mut _i = _i;
+ let span = _visitor.fold_span(_i.span());
+ _i.set_span(span);
+ });
+ }
+ fold_impl.append_all(quote! {
+ _i
+ });
+ }
+ }
+ types::Data::Private => {
+ if ty == "Ident" {
+ fold_impl.append_all(quote! {
+ let mut _i = _i;
+ let span = _visitor.fold_span(_i.span());
+ _i.set_span(span);
+ });
+ }
+ fold_impl.append_all(quote! {
+ _i
+ });
+ }
+ }
+
+ let include_fold_impl = match &s.data {
+ types::Data::Private => super::TERMINAL_TYPES.contains(&s.ident.as_str()),
+ types::Data::Struct(_) | types::Data::Enum(_) => true,
+ };
+
+ state.fold_trait.append_all(quote! {
+ #features
+ fn #fold_fn(&mut self, i: #ty) -> #ty {
+ #fold_fn(self, i)
+ }
+ });
+
+ if include_fold_impl {
+ state.fold_impl.append_all(quote! {
+ #features
+ pub fn #fold_fn<V: Fold + ?Sized>(
+ _visitor: &mut V, _i: #ty
+ ) -> #ty {
+ #fold_impl
+ }
+ });
+ }
+ }
+}
+
+const TERMINAL_TYPES: &[&str] = &["Span", "Ident"];
+
+pub fn generate(defs: &types::Definitions) {
+ let mut state = codegen::State::default();
+ for s in &defs.types {
+ codegen::generate(&mut state, s, defs);
+ }
+ for tt in TERMINAL_TYPES {
+ let s = types::Node {
+ ident: tt.to_string(),
+ features: types::Features::default(),
+ data: types::Data::Private,
+ };
+ codegen::generate(&mut state, &s, defs);
+ }
+
+ let full_macro = quote! {
+ #[cfg(feature = "full")]
+ macro_rules! full {
+ ($e:expr) => {
+ $e
+ };
+ }
+
+ #[cfg(all(feature = "derive", not(feature = "full")))]
+ macro_rules! full {
+ ($e:expr) => {
+ unreachable!()
+ };
+ }
+ };
+
+ let fold_trait = state.fold_trait;
+ let fold_impl = state.fold_impl;
+ file::write(
+ FOLD_SRC,
+ quote! {
+ // Unreachable code is generated sometimes without the full feature.
+ #![allow(unreachable_code)]
+
+ use *;
+ #[cfg(any(feature = "full", feature = "derive"))]
+ use token::{Brace, Bracket, Paren, Group};
+ use proc_macro2::Span;
+ #[cfg(any(feature = "full", feature = "derive"))]
+ use gen::helper::fold::*;
+
+ #full_macro
+
+ /// Syntax tree traversal to transform the nodes of an owned syntax tree.
+ ///
+ /// See the [module documentation] for details.
+ ///
+ /// [module documentation]: index.html
+ ///
+ /// *This trait is available if Syn is built with the `"fold"` feature.*
+ pub trait Fold {
+ #fold_trait
+ }
+
+ #[cfg(any(feature = "full", feature = "derive"))]
+ macro_rules! fold_span_only {
+ ($f:ident : $t:ident) => {
+ pub fn $f<V: Fold + ?Sized>(_visitor: &mut V, mut _i: $t) -> $t {
+ let span = _visitor.fold_span(_i.span());
+ _i.set_span(span);
+ _i
+ }
+ }
+ }
+
+ #[cfg(any(feature = "full", feature = "derive"))]
+ fold_span_only!(fold_lit_byte: LitByte);
+ #[cfg(any(feature = "full", feature = "derive"))]
+ fold_span_only!(fold_lit_byte_str: LitByteStr);
+ #[cfg(any(feature = "full", feature = "derive"))]
+ fold_span_only!(fold_lit_char: LitChar);
+ #[cfg(any(feature = "full", feature = "derive"))]
+ fold_span_only!(fold_lit_float: LitFloat);
+ #[cfg(any(feature = "full", feature = "derive"))]
+ fold_span_only!(fold_lit_int: LitInt);
+ #[cfg(any(feature = "full", feature = "derive"))]
+ fold_span_only!(fold_lit_str: LitStr);
+
+ #fold_impl
+ },
+ );
+}