1 // compile-flags: --emit=link
4 #![crate_type = "proc-macro"]
5 #![feature(repr128, proc_macro_hygiene, proc_macro_quote, box_patterns)]
6 #![allow(clippy::useless_conversion)]
8 extern crate proc_macro;
12 use proc_macro::TokenStream;
13 use quote::{quote, quote_spanned};
14 use syn::parse_macro_input;
15 use syn::spanned::Spanned;
18 parse_quote, FnArg, ImplItem, ItemImpl, ItemTrait, Lifetime, Pat, PatIdent, PatType, Signature, TraitItem, Type,
21 #[proc_macro_attribute]
22 pub fn fake_async_trait(_args: TokenStream, input: TokenStream) -> TokenStream {
23 let mut item = parse_macro_input!(input as ItemTrait);
24 for inner in &mut item.items {
25 if let TraitItem::Method(method) = inner {
26 let sig = &method.sig;
27 let block = &mut method.default;
28 if let Some(block) = block {
29 let brace = block.brace_token;
31 let my_block = quote_spanned!( brace.span => {
32 // Should not trigger `empty_line_after_outer_attr`
37 *block = parse_quote!(#my_block);
41 TokenStream::from(quote!(#item))
44 #[proc_macro_attribute]
45 pub fn rename_my_lifetimes(_args: TokenStream, input: TokenStream) -> TokenStream {
46 fn make_name(count: usize) -> String {
47 format!("'life{}", count)
50 fn mut_receiver_of(sig: &mut Signature) -> Option<&mut FnArg> {
51 let arg = sig.inputs.first_mut()?;
52 if let FnArg::Typed(PatType { pat, .. }) = arg {
53 if let Pat::Ident(PatIdent { ident, .. }) = &**pat {
63 let mut item = parse_macro_input!(input as ItemImpl);
65 // Look for methods having arbitrary self type taken by &mut ref
66 for inner in &mut item.items {
67 if let ImplItem::Method(method) = inner {
68 if let Some(FnArg::Typed(pat_type)) = mut_receiver_of(&mut method.sig) {
69 if let box Type::Reference(reference) = &mut pat_type.ty {
70 // Target only unnamed lifetimes
71 let name = match &reference.lifetime {
72 Some(lt) if lt.ident == "_" => make_name(elided),
73 None => make_name(elided),
78 // HACK: Syn uses `Span` from the proc_macro2 crate, and does not seem to reexport it.
79 // In order to avoid adding the dependency, get a default span from a non-existent token.
80 // A default span is needed to mark the code as coming from expansion.
81 let span = Star::default().span();
83 // Replace old lifetime with the named one
84 let lifetime = Lifetime::new(&name, span);
85 reference.lifetime = Some(parse_quote!(#lifetime));
87 // Add lifetime to the generics of the method
88 method.sig.generics.params.push(parse_quote!(#lifetime));
94 TokenStream::from(quote!(#item))