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#![recursion_limit = "128"] extern crate proc_macro; extern crate proc_macro2; extern crate quote; extern crate syn; use proc_macro2::{Span, TokenStream}; use quote::quote; use syn::parse_macro_input; use syn::visit::Visit; use syn::{ArgCaptured, Block, FnArg, Ident, Pat, TraitItemMethod, Type, TypeReference}; #[derive(Default)] struct VisitorImpls { tokens: TokenStream, count: usize, } impl VisitorImpls { fn generate_visit( &mut self, method_name: &Ident, arg_pat: &Pat, ty: &Type, walk: &Block, ) { self.tokens.extend(quote! { impl MutVisit for #ty { fn visit<F: MutVisitor>(&mut self, f: &mut F) { f.#method_name(self) } } }); let folder_name = format!("Folder{}", self.count); let folder_ident = Ident::new(&folder_name, Span::call_site()); if !walk.stmts.is_empty() { let noop_fn_name = format!("noop_{}", method_name); let noop_fn = Ident::new(&noop_fn_name, Span::call_site()); self.tokens.extend(quote! { impl WalkAst for #ty { fn walk<T: MutVisitor>(&mut self, v: &mut T) { syntax::mut_visit::#noop_fn(self, v); } } }); } self.tokens.extend(quote! { struct #folder_ident<F> where F: FnMut(&mut #ty) { callback: F, } impl<F> MutVisitor for #folder_ident<F> where F: FnMut(&mut #ty) { fn #method_name(&mut self, #arg_pat: &mut #ty) { #walk (self.callback)(#arg_pat) } } impl MutVisitNodes for #ty { fn visit<T, F>(target: &mut T, callback: F) where T: MutVisit, F: FnMut(&mut Self) { let mut f = #folder_ident { callback }; target.visit(&mut f) } } }); self.count += 1; } fn generate_flat_map( &mut self, method_name: &Ident, arg_pat: &Pat, ty: &Type, walk: &Block, ) { self.tokens.extend(quote! { impl MutVisit for #ty { fn visit<F: MutVisitor>(&mut self, f: &mut F) { let new = f.#method_name(self.clone()); *self = new.lone(); } fn flat_map<F: MutVisitor>(self, f: &mut F) -> SmallVec<[#ty; 1]> { f.#method_name(self) } } }); let folder_name = format!("Folder{}", self.count); let folder_ident = Ident::new(&folder_name, Span::call_site()); if !walk.stmts.is_empty() { let noop_fn_name = format!("noop_{}", method_name); let noop_fn = Ident::new(&noop_fn_name, Span::call_site()); self.tokens.extend(quote! { impl WalkAst for #ty { fn walk<T: MutVisitor>(&mut self, v: &mut T) { *self = syntax::mut_visit::#noop_fn(self.clone(), v).lone(); } } }) } self.tokens.extend(quote! { struct #folder_ident<F> where F: FnMut(#ty) -> SmallVec<[#ty; 1]> { callback: F, } impl<F> MutVisitor for #folder_ident<F> where F: FnMut(#ty) -> SmallVec<[#ty; 1]> { fn #method_name(&mut self, #arg_pat: #ty) -> SmallVec<[#ty; 1]> { let mut v = #walk; v.flat_map_in_place(|x| (self.callback)(x)); v } } impl FlatMapNodes for #ty { fn visit<T, F>(target: &mut T, callback: F) where T: MutVisit, F: FnMut(#ty) -> SmallVec<[#ty; 1]> { let mut f = #folder_ident { callback }; target.visit(&mut f) } fn flat_map<T, F>(target: T, callback: F) -> SmallVec<[T; 1]> where T: MutVisit, F: FnMut(#ty) -> SmallVec<[#ty; 1]> { let mut f = #folder_ident { callback }; target.flat_map(&mut f) } } }); self.count += 1; } } impl<'ast> Visit<'ast> for VisitorImpls { fn visit_trait_item_method(&mut self, m: &TraitItemMethod) { let method_name = &m.sig.ident; let method_noop = m.default.as_ref().unwrap(); match &m.sig.decl.inputs[1] { FnArg::Captured(ArgCaptured { pat, ty, .. }) => match ty { Type::Reference(TypeReference { mutability: Some(_), elem, .. }) => self.generate_visit(method_name, &pat, &elem, method_noop), _ => self.generate_flat_map(method_name, &pat, &ty, method_noop), }, _ => {} } } } #[proc_macro] pub fn gen_visitor_impls(tokens: proc_macro::TokenStream) -> proc_macro::TokenStream { let visitor_trait: syn::ItemTrait = parse_macro_input!(tokens); let mut visitor = VisitorImpls::default(); visitor.visit_item_trait(&visitor_trait); visitor.tokens.into() }