diff options
Diffstat (limited to 'syn/codegen/src/fold.rs')
-rw-r--r-- | syn/codegen/src/fold.rs | 284 |
1 files changed, 284 insertions, 0 deletions
diff --git a/syn/codegen/src/fold.rs b/syn/codegen/src/fold.rs new file mode 100644 index 0000000..6914d76 --- /dev/null +++ b/syn/codegen/src/fold.rs @@ -0,0 +1,284 @@ +use crate::{file, full, gen}; +use anyhow::Result; +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! { + f.#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 = if repr == "await" { + quote!(crate::token::Await) + } else { + syn::parse_str(&format!("Token![{}]", repr)).unwrap() + }; + Some(quote! { + #ty(tokens_helper(f, &#name.#spans)) + }) + } + Type::Group(t) => { + let ty = Ident::new(t, Span::call_site()); + Some(quote! { + #ty(tokens_helper(f, &#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 + ) + } + }); + } + } + + let nonexhaustive = if s.exhaustive { + None + } else { + Some(quote!(_ => unreachable!())) + }; + + fold_impl.extend(quote! { + match node { + #fold_variants + #nonexhaustive + } + }); + } + 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!(node.#id); + + if let Type::Syn(ty) = ty { + if ty == "Reserved" { + fold_fields.extend(quote! { + #id: #ref_toks, + }); + continue; + } + } + + 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 node = node; + let span = f.fold_span(node.span()); + node.set_span(span); + }); + } + fold_impl.extend(quote! { + node + }); + } + } + Data::Private => { + if ty == "Ident" { + fold_impl.extend(quote! { + let mut node = node; + let span = f.fold_span(node.span()); + node.set_span(span); + }); + } + fold_impl.extend(quote! { + node + }); + } + } + + 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 = f.fold_span(node.span()); + let mut node = node; + node.set_span(span); + node + }; + } + + traits.extend(quote! { + fn #fold_fn(&mut self, i: #ty) -> #ty { + #fold_fn(self, i) + } + }); + + impls.extend(quote! { + pub fn #fold_fn<F>(f: &mut F, node: #ty) -> #ty + where + F: Fold + ?Sized, + { + #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, unused_variables)] + + use crate::*; + #[cfg(any(feature = "full", feature = "derive"))] + use crate::token::{Brace, Bracket, Paren, Group}; + use proc_macro2::Span; + #[cfg(any(feature = "full", feature = "derive"))] + use crate::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(()) +} |