98 lines
3.4 KiB
Rust
98 lines
3.4 KiB
Rust
#![feature(repr128, proc_macro_hygiene, proc_macro_quote, box_patterns)]
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#![allow(incomplete_features)]
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#![allow(clippy::useless_conversion, clippy::uninlined_format_args)]
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extern crate proc_macro;
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extern crate quote;
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extern crate syn;
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use proc_macro::TokenStream;
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use quote::{quote, quote_spanned};
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use syn::spanned::Spanned;
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use syn::token::Star;
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use syn::{
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parse_macro_input, parse_quote, FnArg, ImplItem, ItemImpl, ItemTrait, Lifetime, Pat, PatIdent, PatType, Signature,
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TraitItem, Type,
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};
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#[proc_macro_attribute]
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pub fn dummy(_args: TokenStream, input: TokenStream) -> TokenStream {
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input
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}
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#[proc_macro_attribute]
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pub fn fake_async_trait(_args: TokenStream, input: TokenStream) -> TokenStream {
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let mut item = parse_macro_input!(input as ItemTrait);
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for inner in &mut item.items {
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if let TraitItem::Fn(method) = inner {
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let sig = &method.sig;
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let block = &mut method.default;
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if let Some(block) = block {
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let brace = block.brace_token;
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let my_block = quote_spanned!( brace.span => {
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// Should not trigger `empty_line_after_outer_attr`
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#[crate_type = "lib"]
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#sig #block
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Vec::new()
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});
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*block = parse_quote!(#my_block);
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}
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}
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}
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TokenStream::from(quote!(#item))
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}
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#[proc_macro_attribute]
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pub fn rename_my_lifetimes(_args: TokenStream, input: TokenStream) -> TokenStream {
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fn make_name(count: usize) -> String {
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format!("'life{}", count)
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}
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fn mut_receiver_of(sig: &mut Signature) -> Option<&mut FnArg> {
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let arg = sig.inputs.first_mut()?;
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if let FnArg::Typed(PatType { pat, .. }) = arg {
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if let Pat::Ident(PatIdent { ident, .. }) = &**pat {
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if ident == "self" {
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return Some(arg);
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}
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}
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}
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None
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}
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let mut elided = 0;
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let mut item = parse_macro_input!(input as ItemImpl);
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// Look for methods having arbitrary self type taken by &mut ref
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for inner in &mut item.items {
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if let ImplItem::Fn(method) = inner {
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if let Some(FnArg::Typed(pat_type)) = mut_receiver_of(&mut method.sig) {
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if let box Type::Reference(reference) = &mut pat_type.ty {
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// Target only unnamed lifetimes
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let name = match &reference.lifetime {
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Some(lt) if lt.ident == "_" => make_name(elided),
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None => make_name(elided),
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_ => continue,
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};
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elided += 1;
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// HACK: Syn uses `Span` from the proc_macro2 crate, and does not seem to reexport it.
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// In order to avoid adding the dependency, get a default span from a nonexistent token.
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// A default span is needed to mark the code as coming from expansion.
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let span = Star::default().span();
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// Replace old lifetime with the named one
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let lifetime = Lifetime::new(&name, span);
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reference.lifetime = Some(parse_quote!(#lifetime));
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// Add lifetime to the generics of the method
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method.sig.generics.params.push(parse_quote!(#lifetime));
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}
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}
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}
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}
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TokenStream::from(quote!(#item))
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}
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