| use crate::error::Result; |
| use crate::{file, full, gen}; |
| use proc_macro2::{Ident, Span, TokenStream}; |
| use quote::quote; |
| use syn::Index; |
| use syn_codegen::{Data, Definitions, Features, Node, Type}; |
| |
| const FOLD_SRC: &str = "../src/gen/fold.rs"; |
| |
| fn simple_visit(item: &str, name: &TokenStream) -> TokenStream { |
| let ident = gen::under_name(item); |
| let method = Ident::new(&format!("fold_{}", ident), Span::call_site()); |
| quote! { |
| _visitor.#method(#name) |
| } |
| } |
| |
| fn visit( |
| ty: &Type, |
| features: &Features, |
| defs: &Definitions, |
| name: &TokenStream, |
| ) -> Option<TokenStream> { |
| match ty { |
| Type::Box(t) => { |
| let res = visit(t, features, defs, "e!(*#name))?; |
| Some(quote! { |
| Box::new(#res) |
| }) |
| } |
| Type::Vec(t) => { |
| let operand = quote!(it); |
| let val = visit(t, features, defs, &operand)?; |
| Some(quote! { |
| FoldHelper::lift(#name, |it| { #val }) |
| }) |
| } |
| Type::Punctuated(p) => { |
| let operand = quote!(it); |
| let val = visit(&p.element, features, defs, &operand)?; |
| Some(quote! { |
| FoldHelper::lift(#name, |it| { #val }) |
| }) |
| } |
| Type::Option(t) => { |
| let it = quote!(it); |
| let val = visit(t, features, defs, &it)?; |
| Some(quote! { |
| (#name).map(|it| { #val }) |
| }) |
| } |
| Type::Tuple(t) => { |
| let mut code = TokenStream::new(); |
| for (i, elem) in t.iter().enumerate() { |
| let i = Index::from(i); |
| let it = quote!((#name).#i); |
| let val = visit(elem, features, defs, &it).unwrap_or(it); |
| code.extend(val); |
| code.extend(quote!(,)); |
| } |
| Some(quote! { |
| (#code) |
| }) |
| } |
| Type::Token(t) => { |
| let repr = &defs.tokens[t]; |
| let is_keyword = repr.chars().next().unwrap().is_alphabetic(); |
| let spans = if is_keyword { |
| quote!(span) |
| } else { |
| quote!(spans) |
| }; |
| let ty: TokenStream = syn::parse_str(&format!("Token![{}]", repr)).unwrap(); |
| Some(quote! { |
| #ty(tokens_helper(_visitor, &#name.#spans)) |
| }) |
| } |
| Type::Group(t) => { |
| let ty = Ident::new(t, Span::call_site()); |
| Some(quote! { |
| #ty(tokens_helper(_visitor, &#name.span)) |
| }) |
| } |
| Type::Syn(t) => { |
| fn requires_full(features: &Features) -> bool { |
| features.any.contains("full") && features.any.len() == 1 |
| } |
| let mut res = simple_visit(t, name); |
| let target = defs.types.iter().find(|ty| ty.ident == *t).unwrap(); |
| if requires_full(&target.features) && !requires_full(features) { |
| res = quote!(full!(#res)); |
| } |
| Some(res) |
| } |
| Type::Ext(t) if gen::TERMINAL_TYPES.contains(&&t[..]) => Some(simple_visit(t, name)), |
| Type::Ext(_) | Type::Std(_) => None, |
| } |
| } |
| |
| fn node(traits: &mut TokenStream, impls: &mut TokenStream, s: &Node, defs: &Definitions) { |
| let under_name = gen::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 { |
| 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.extend(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.extend(quote! { |
| #binding, |
| }); |
| |
| let owned_binding = quote!(#binding); |
| |
| fold_fields.extend( |
| visit(ty, &s.features, defs, &owned_binding).unwrap_or(owned_binding), |
| ); |
| |
| fold_fields.extend(quote!(,)); |
| } |
| |
| fold_variants.extend(quote! { |
| #ty::#variant_ident(#bind_fold_fields) => { |
| #ty::#variant_ident( |
| #fold_fields |
| ) |
| } |
| }); |
| } |
| } |
| |
| fold_impl.extend(quote! { |
| match _i { |
| #fold_variants |
| } |
| }); |
| } |
| 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.extend(quote! { |
| #id: #fold, |
| }); |
| } |
| |
| if !fields.is_empty() { |
| fold_impl.extend(quote! { |
| #ty { |
| #fold_fields |
| } |
| }) |
| } else { |
| if ty == "Ident" { |
| fold_impl.extend(quote! { |
| let mut _i = _i; |
| let span = _visitor.fold_span(_i.span()); |
| _i.set_span(span); |
| }); |
| } |
| fold_impl.extend(quote! { |
| _i |
| }); |
| } |
| } |
| Data::Private => { |
| if ty == "Ident" { |
| fold_impl.extend(quote! { |
| let mut _i = _i; |
| let span = _visitor.fold_span(_i.span()); |
| _i.set_span(span); |
| }); |
| } |
| fold_impl.extend(quote! { |
| _i |
| }); |
| } |
| } |
| |
| let fold_span_only = |
| s.data == Data::Private && !gen::TERMINAL_TYPES.contains(&s.ident.as_str()); |
| if fold_span_only { |
| fold_impl = quote! { |
| let span = _visitor.fold_span(_i.span()); |
| let mut _i = _i; |
| _i.set_span(span); |
| _i |
| }; |
| } |
| |
| traits.extend(quote! { |
| fn #fold_fn(&mut self, i: #ty) -> #ty { |
| #fold_fn(self, i) |
| } |
| }); |
| |
| impls.extend(quote! { |
| pub fn #fold_fn<V: Fold + ?Sized>( |
| _visitor: &mut V, _i: #ty |
| ) -> #ty { |
| #fold_impl |
| } |
| }); |
| } |
| |
| pub fn generate(defs: &Definitions) -> Result<()> { |
| let (traits, impls) = gen::traverse(defs, node); |
| let full_macro = full::get_macro(); |
| 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]: self |
| /// |
| /// *This trait is available if Syn is built with the `"fold"` feature.* |
| pub trait Fold { |
| #traits |
| } |
| |
| #impls |
| }, |
| )?; |
| Ok(()) |
| } |