Import async-trait crate.
Bug: 164106399
Bug: 158290206
Test: mm
Change-Id: I0c4a491b785134e4ac1d5572e5ff94b8699dc0bc
diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..c4c65e4
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,5 @@
+{
+ "git": {
+ "sha1": "89923af3d553c990336ec29a68e50e15efff1734"
+ }
+}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..1ee3325
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,34 @@
+name: CI
+
+on:
+ push:
+ pull_request:
+ schedule: [cron: "40 1 * * *"]
+
+jobs:
+ test:
+ name: Rust ${{matrix.rust}}
+ runs-on: ubuntu-latest
+ strategy:
+ fail-fast: false
+ matrix:
+ rust: [beta, stable, 1.39.0]
+ include:
+ - rust: nightly
+ rustflags: --cfg async_trait_nightly_testing
+ steps:
+ - uses: actions/checkout@v2
+ - uses: dtolnay/rust-toolchain@master
+ with:
+ toolchain: ${{matrix.rust}}
+ - run: cargo test
+ env:
+ RUSTFLAGS: ${{matrix.rustflags}}
+
+ clippy:
+ name: Clippy
+ runs-on: ubuntu-latest
+ steps:
+ - uses: actions/checkout@v2
+ - uses: dtolnay/rust-toolchain@clippy
+ - run: cargo clippy --tests -- -Dclippy::all
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6936990
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+/target
+**/*.rs.bk
+Cargo.lock
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..6e5e11d
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,19 @@
+// This file is generated by cargo2android.py --run --device --dependencies.
+
+rust_proc_macro {
+ name: "libasync_trait",
+ crate_name: "async_trait",
+ srcs: ["src/lib.rs"],
+ edition: "2018",
+ rustlibs: [
+ "libproc_macro2",
+ "libquote",
+ "libsyn",
+ ],
+}
+
+// dependent_library ["feature_list"]
+// proc-macro2-1.0.19 "default,proc-macro"
+// quote-1.0.7 "default,proc-macro"
+// syn-1.0.38 "clone-impls,default,derive,extra-traits,full,parsing,printing,proc-macro,quote,visit,visit-mut"
+// unicode-xid-0.2.1 "default"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..675035a
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,51 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies
+#
+# If you believe there's an error in this file please file an
+# issue against the rust-lang/cargo repository. If you're
+# editing this file be aware that the upstream Cargo.toml
+# will likely look very different (and much more reasonable)
+
+[package]
+edition = "2018"
+name = "async-trait"
+version = "0.1.36"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+description = "Type erasure for async trait methods"
+documentation = "https://docs.rs/async-trait"
+readme = "README.md"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/dtolnay/async-trait"
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[lib]
+proc-macro = true
+[dependencies.proc-macro2]
+version = "1.0"
+
+[dependencies.quote]
+version = "1.0"
+
+[dependencies.syn]
+version = "1.0"
+features = ["full", "visit-mut"]
+[dev-dependencies.rustversion]
+version = "1.0"
+
+[dev-dependencies.tracing]
+version = "0.1.14"
+
+[dev-dependencies.tracing-attributes]
+version = "0.1.8"
+
+[dev-dependencies.tracing-futures]
+version = "0.2"
+
+[dev-dependencies.trybuild]
+version = "1.0.19"
+features = ["diff"]
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..2921a5f
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,28 @@
+[package]
+name = "async-trait"
+version = "0.1.36"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+edition = "2018"
+license = "MIT OR Apache-2.0"
+description = "Type erasure for async trait methods"
+repository = "https://github.com/dtolnay/async-trait"
+documentation = "https://docs.rs/async-trait"
+readme = "README.md"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = { version = "1.0", features = ["full", "visit-mut"] }
+
+[dev-dependencies]
+rustversion = "1.0"
+tracing = "0.1.14"
+tracing-attributes = "0.1.8"
+tracing-futures = "0.2"
+trybuild = { version = "1.0.19", features = ["diff"] }
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
diff --git a/LICENSE b/LICENSE
new file mode 120000
index 0000000..6b579aa
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1 @@
+LICENSE-APACHE
\ No newline at end of file
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..16fe87b
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
+ Apache License
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+ http://www.apache.org/licenses/
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diff --git a/LICENSE-MIT b/LICENSE-MIT
new file mode 100644
index 0000000..31aa793
--- /dev/null
+++ b/LICENSE-MIT
@@ -0,0 +1,23 @@
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
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+The above copyright notice and this permission notice
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+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
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+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
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+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
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diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..889b98f
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,19 @@
+name: "async-trait"
+description: "Async trait methods."
+third_party {
+ url {
+ type: HOMEPAGE
+ value: "https://crates.io/crates/async-trait"
+ }
+ url {
+ type: GIT
+ value: "https://github.com/dtolnay/async-trait"
+ }
+ version: "0.1.36"
+ license_type: NOTICE
+ last_upgrade_date {
+ year: 2020
+ month: 8
+ day: 11
+ }
+}
diff --git a/MODULE_LICENSE_APACHE2 b/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_APACHE2
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..7d3e050
--- /dev/null
+++ b/README.md
@@ -0,0 +1,262 @@
+Async trait methods
+===================
+
+[<img alt="github" src="https://img.shields.io/badge/github-dtolnay/async--trait-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/async-trait)
+[<img alt="crates.io" src="https://img.shields.io/crates/v/async-trait.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/async-trait)
+[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-async--trait-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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" height="20">](https://docs.rs/async-trait)
+[<img alt="build status" src="https://img.shields.io/github/workflow/status/dtolnay/async-trait/CI/master?style=for-the-badge" height="20">](https://github.com/dtolnay/async-trait/actions?query=branch%3Amaster)
+
+The initial round of stabilizations for the async/await language feature in Rust
+1.39 did not include support for async fn in traits. Trying to include an async
+fn in a trait produces the following error:
+
+```rust
+trait MyTrait {
+ async fn f() {}
+}
+```
+
+```console
+error[E0706]: trait fns cannot be declared `async`
+ --> src/main.rs:4:5
+ |
+4 | async fn f() {}
+ | ^^^^^^^^^^^^^^^
+```
+
+This crate provides an attribute macro to make async fn in traits work.
+
+Please refer to [*why async fn in traits are hard*][hard] for a deeper analysis
+of how this implementation differs from what the compiler and language hope to
+deliver in the future.
+
+[hard]: https://smallcultfollowing.com/babysteps/blog/2019/10/26/async-fn-in-traits-are-hard/
+
+<br>
+
+## Example
+
+This example implements the core of a highly effective advertising platform
+using async fn in a trait.
+
+The only thing to notice here is that we write an `#[async_trait]` macro on top
+of traits and trait impls that contain async fn, and then they work.
+
+```rust
+use async_trait::async_trait;
+
+#[async_trait]
+trait Advertisement {
+ async fn run(&self);
+}
+
+struct Modal;
+
+#[async_trait]
+impl Advertisement for Modal {
+ async fn run(&self) {
+ self.render_fullscreen().await;
+ for _ in 0..4u16 {
+ remind_user_to_join_mailing_list().await;
+ }
+ self.hide_for_now().await;
+ }
+}
+
+struct AutoplayingVideo {
+ media_url: String,
+}
+
+#[async_trait]
+impl Advertisement for AutoplayingVideo {
+ async fn run(&self) {
+ let stream = connect(&self.media_url).await;
+ stream.play().await;
+
+ // Video probably persuaded user to join our mailing list!
+ Modal.run().await;
+ }
+}
+```
+
+<br>
+
+## Supported features
+
+It is the intention that all features of Rust traits should work nicely with
+\#\[async_trait\], but the edge cases are numerous. *Please file an issue if you
+see unexpected borrow checker errors, type errors, or warnings.* There is no use
+of `unsafe` in the expanded code, so rest assured that if your code compiles it
+can't be that badly broken.
+
+- 👍 Self by value, by reference, by mut reference, or no self;
+- 👍 Any number of arguments, any return value;
+- 👍 Generic type parameters and lifetime parameters;
+- 👍 Associated types;
+- 👍 Having async and non-async functions in the same trait;
+- 👍 Default implementations provided by the trait;
+- 👍 Elided lifetimes;
+- 👍 Dyn-capable traits.
+
+<br>
+
+## Explanation
+
+Async fns get transformed into methods that return `Pin<Box<dyn Future + Send +
+'async>>` and delegate to a private async freestanding function.
+
+For example the `impl Advertisement for AutoplayingVideo` above would be
+expanded as:
+
+```rust
+impl Advertisement for AutoplayingVideo {
+ fn run<'async>(
+ &'async self,
+ ) -> Pin<Box<dyn std::future::Future<Output = ()> + Send + 'async>>
+ where
+ Self: Sync + 'async,
+ {
+ async fn run(_self: &AutoplayingVideo) {
+ /* the original method body */
+ }
+
+ Box::pin(run(self))
+ }
+}
+```
+
+<br>
+
+## Non-threadsafe futures
+
+Not all async traits need futures that are `dyn Future + Send`. To avoid having
+Send and Sync bounds placed on the async trait methods, invoke the async trait
+macro as `#[async_trait(?Send)]` on both the trait and the impl blocks.
+
+<br>
+
+## Elided lifetimes
+
+Be aware that async fn syntax does not allow lifetime elision outside of `&` and
+`&mut` references. (This is true even when not using #\[async_trait\].)
+Lifetimes must be named or marked by the placeholder `'_`.
+
+Fortunately the compiler is able to diagnose missing lifetimes with a good error
+message.
+
+```rust
+type Elided<'a> = &'a usize;
+
+#[async_trait]
+trait Test {
+ async fn test(not_okay: Elided, okay: &usize) {}
+}
+```
+
+```console
+error[E0726]: implicit elided lifetime not allowed here
+ --> src/main.rs:9:29
+ |
+9 | async fn test(not_okay: Elided, okay: &usize) {}
+ | ^^^^^^- help: indicate the anonymous lifetime: `<'_>`
+```
+
+The fix is to name the lifetime or use `'_`.
+
+```rust
+#[async_trait]
+trait Test {
+ // either
+ async fn test<'e>(elided: Elided<'e>) {}
+ // or
+ async fn test(elided: Elided<'_>) {}
+}
+```
+
+<br>
+
+## Dyn traits
+
+Traits with async methods can be used as trait objects as long as they meet the
+usual requirements for dyn -- no methods with type parameters, no self by value,
+no associated types, etc.
+
+```rust
+#[async_trait]
+pub trait ObjectSafe {
+ async fn f(&self);
+ async fn g(&mut self);
+}
+
+impl ObjectSafe for MyType {...}
+
+let value: MyType = ...;
+let object = &value as &dyn ObjectSafe; // make trait object
+```
+
+The one wrinkle is in traits that provide default implementations of async
+methods. In order for the default implementation to produce a future that is
+Send, the async\_trait macro must emit a bound of `Self: Sync` on trait methods
+that take `&self` and a bound `Self: Send` on trait methods that take `&mut
+self`. An example of the former is visible in the expanded code in the
+explanation section above.
+
+If you make a trait with async methods that have default implementations,
+everything will work except that the trait cannot be used as a trait object.
+Creating a value of type `&dyn Trait` will produce an error that looks like
+this:
+
+```console
+error: the trait `Test` cannot be made into an object
+ --> src/main.rs:8:5
+ |
+8 | async fn cannot_dyn(&self) {}
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+```
+
+For traits that need to be object safe and need to have default implementations
+for some async methods, there are two resolutions. Either you can add Send
+and/or Sync as supertraits (Send if there are `&mut self` methods with default
+implementations, Sync if there are `&self` methods with default implementions)
+to constrain all implementors of the trait such that the default implementations
+are applicable to them:
+
+```rust
+#[async_trait]
+pub trait ObjectSafe: Sync { // added supertrait
+ async fn can_dyn(&self) {}
+}
+
+let object = &value as &dyn ObjectSafe;
+```
+
+or you can strike the problematic methods from your trait object by bounding
+them with `Self: Sized`:
+
+```rust
+#[async_trait]
+pub trait ObjectSafe {
+ async fn cannot_dyn(&self) where Self: Sized {}
+
+ // presumably other methods
+}
+
+let object = &value as &dyn ObjectSafe;
+```
+
+<br>
+
+#### License
+
+<sup>
+Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
+2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
+</sup>
+
+<br>
+
+<sub>
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
+be dual licensed as above, without any additional terms or conditions.
+</sub>
diff --git a/src/args.rs b/src/args.rs
new file mode 100644
index 0000000..72d97e9
--- /dev/null
+++ b/src/args.rs
@@ -0,0 +1,36 @@
+use proc_macro2::Span;
+use syn::parse::{Error, Parse, ParseStream, Result};
+use syn::Token;
+
+#[derive(Copy, Clone)]
+pub struct Args {
+ pub local: bool,
+}
+
+mod kw {
+ syn::custom_keyword!(Send);
+}
+
+impl Parse for Args {
+ fn parse(input: ParseStream) -> Result<Self> {
+ match try_parse(input) {
+ Ok(args) if input.is_empty() => Ok(args),
+ _ => Err(error()),
+ }
+ }
+}
+
+fn try_parse(input: ParseStream) -> Result<Args> {
+ if input.peek(Token![?]) {
+ input.parse::<Token![?]>()?;
+ input.parse::<kw::Send>()?;
+ Ok(Args { local: true })
+ } else {
+ Ok(Args { local: false })
+ }
+}
+
+fn error() -> Error {
+ let msg = "expected #[async_trait] or #[async_trait(?Send)]";
+ Error::new(Span::call_site(), msg)
+}
diff --git a/src/expand.rs b/src/expand.rs
new file mode 100644
index 0000000..7d0cec2
--- /dev/null
+++ b/src/expand.rs
@@ -0,0 +1,475 @@
+use crate::lifetime::{has_async_lifetime, CollectLifetimes};
+use crate::parse::Item;
+use crate::receiver::{
+ has_self_in_block, has_self_in_sig, has_self_in_where_predicate, ReplaceReceiver,
+};
+use proc_macro2::{Span, TokenStream};
+use quote::{format_ident, quote, quote_spanned, ToTokens};
+use std::mem;
+use syn::punctuated::Punctuated;
+use syn::visit_mut::VisitMut;
+use syn::{
+ parse_quote, Block, FnArg, GenericParam, Generics, Ident, ImplItem, Lifetime, Pat, PatIdent,
+ Path, Receiver, ReturnType, Signature, Stmt, Token, TraitItem, Type, TypeParam, TypeParamBound,
+ WhereClause,
+};
+
+impl ToTokens for Item {
+ fn to_tokens(&self, tokens: &mut TokenStream) {
+ match self {
+ Item::Trait(item) => item.to_tokens(tokens),
+ Item::Impl(item) => item.to_tokens(tokens),
+ }
+ }
+}
+
+#[derive(Clone, Copy)]
+enum Context<'a> {
+ Trait {
+ name: &'a Ident,
+ generics: &'a Generics,
+ supertraits: &'a Supertraits,
+ },
+ Impl {
+ impl_generics: &'a Generics,
+ receiver: &'a Type,
+ as_trait: &'a Path,
+ },
+}
+
+impl Context<'_> {
+ fn lifetimes<'a>(&'a self, used: &'a [Lifetime]) -> impl Iterator<Item = &'a GenericParam> {
+ let generics = match self {
+ Context::Trait { generics, .. } => generics,
+ Context::Impl { impl_generics, .. } => impl_generics,
+ };
+ generics.params.iter().filter(move |param| {
+ if let GenericParam::Lifetime(param) = param {
+ used.contains(¶m.lifetime)
+ } else {
+ false
+ }
+ })
+ }
+}
+
+type Supertraits = Punctuated<TypeParamBound, Token![+]>;
+
+pub fn expand(input: &mut Item, is_local: bool) {
+ match input {
+ Item::Trait(input) => {
+ let context = Context::Trait {
+ name: &input.ident,
+ generics: &input.generics,
+ supertraits: &input.supertraits,
+ };
+ for inner in &mut input.items {
+ if let TraitItem::Method(method) = inner {
+ let sig = &mut method.sig;
+ if sig.asyncness.is_some() {
+ let block = &mut method.default;
+ let mut has_self = has_self_in_sig(sig);
+ if let Some(block) = block {
+ has_self |= has_self_in_block(block);
+ transform_block(context, sig, block, has_self, is_local);
+ }
+ let has_default = method.default.is_some();
+ transform_sig(context, sig, has_self, has_default, is_local);
+ method.attrs.push(parse_quote!(#[must_use]));
+ }
+ }
+ }
+ }
+ Item::Impl(input) => {
+ let mut lifetimes = CollectLifetimes::new("'impl");
+ lifetimes.visit_type_mut(&mut *input.self_ty);
+ lifetimes.visit_path_mut(&mut input.trait_.as_mut().unwrap().1);
+ let params = &input.generics.params;
+ let elided = lifetimes.elided;
+ input.generics.params = parse_quote!(#(#elided,)* #params);
+
+ let context = Context::Impl {
+ impl_generics: &input.generics,
+ receiver: &input.self_ty,
+ as_trait: &input.trait_.as_ref().unwrap().1,
+ };
+ for inner in &mut input.items {
+ if let ImplItem::Method(method) = inner {
+ let sig = &mut method.sig;
+ if sig.asyncness.is_some() {
+ let block = &mut method.block;
+ let has_self = has_self_in_sig(sig) || has_self_in_block(block);
+ transform_block(context, sig, block, has_self, is_local);
+ transform_sig(context, sig, has_self, false, is_local);
+ }
+ }
+ }
+ }
+ }
+}
+
+// Input:
+// async fn f<T>(&self, x: &T) -> Ret;
+//
+// Output:
+// fn f<'life0, 'life1, 'async_trait, T>(
+// &'life0 self,
+// x: &'life1 T,
+// ) -> Pin<Box<dyn Future<Output = Ret> + Send + 'async_trait>>
+// where
+// 'life0: 'async_trait,
+// 'life1: 'async_trait,
+// T: 'async_trait,
+// Self: Sync + 'async_trait;
+fn transform_sig(
+ context: Context,
+ sig: &mut Signature,
+ has_self: bool,
+ has_default: bool,
+ is_local: bool,
+) {
+ sig.fn_token.span = sig.asyncness.take().unwrap().span;
+
+ let ret = match &sig.output {
+ ReturnType::Default => quote!(()),
+ ReturnType::Type(_, ret) => quote!(#ret),
+ };
+
+ let mut lifetimes = CollectLifetimes::new("'life");
+ for arg in sig.inputs.iter_mut() {
+ match arg {
+ FnArg::Receiver(arg) => lifetimes.visit_receiver_mut(arg),
+ FnArg::Typed(arg) => lifetimes.visit_type_mut(&mut arg.ty),
+ }
+ }
+
+ let where_clause = sig
+ .generics
+ .where_clause
+ .get_or_insert_with(|| WhereClause {
+ where_token: Default::default(),
+ predicates: Punctuated::new(),
+ });
+ for param in sig
+ .generics
+ .params
+ .iter()
+ .chain(context.lifetimes(&lifetimes.explicit))
+ {
+ match param {
+ GenericParam::Type(param) => {
+ let param = ¶m.ident;
+ where_clause
+ .predicates
+ .push(parse_quote!(#param: 'async_trait));
+ }
+ GenericParam::Lifetime(param) => {
+ let param = ¶m.lifetime;
+ where_clause
+ .predicates
+ .push(parse_quote!(#param: 'async_trait));
+ }
+ GenericParam::Const(_) => {}
+ }
+ }
+ for elided in lifetimes.elided {
+ sig.generics.params.push(parse_quote!(#elided));
+ where_clause
+ .predicates
+ .push(parse_quote!(#elided: 'async_trait));
+ }
+ sig.generics.params.push(parse_quote!('async_trait));
+ if has_self {
+ let bound: Ident = match sig.inputs.iter().next() {
+ Some(FnArg::Receiver(Receiver {
+ reference: Some(_),
+ mutability: None,
+ ..
+ })) => parse_quote!(Sync),
+ Some(FnArg::Typed(arg))
+ if match (arg.pat.as_ref(), arg.ty.as_ref()) {
+ (Pat::Ident(pat), Type::Reference(ty)) => {
+ pat.ident == "self" && ty.mutability.is_none()
+ }
+ _ => false,
+ } =>
+ {
+ parse_quote!(Sync)
+ }
+ _ => parse_quote!(Send),
+ };
+ let assume_bound = match context {
+ Context::Trait { supertraits, .. } => !has_default || has_bound(supertraits, &bound),
+ Context::Impl { .. } => true,
+ };
+ where_clause.predicates.push(if assume_bound || is_local {
+ parse_quote!(Self: 'async_trait)
+ } else {
+ parse_quote!(Self: ::core::marker::#bound + 'async_trait)
+ });
+ }
+
+ for (i, arg) in sig.inputs.iter_mut().enumerate() {
+ match arg {
+ FnArg::Receiver(Receiver {
+ reference: Some(_), ..
+ }) => {}
+ FnArg::Receiver(arg) => arg.mutability = None,
+ FnArg::Typed(arg) => {
+ if let Pat::Ident(ident) = &mut *arg.pat {
+ ident.by_ref = None;
+ ident.mutability = None;
+ } else {
+ let positional = positional_arg(i);
+ *arg.pat = parse_quote!(#positional);
+ }
+ }
+ }
+ }
+
+ let bounds = if is_local {
+ quote!('async_trait)
+ } else {
+ quote!(::core::marker::Send + 'async_trait)
+ };
+
+ sig.output = parse_quote! {
+ -> ::core::pin::Pin<Box<
+ dyn ::core::future::Future<Output = #ret> + #bounds
+ >>
+ };
+}
+
+// Input:
+// async fn f<T>(&self, x: &T) -> Ret {
+// self + x
+// }
+//
+// Output:
+// async fn f<T, AsyncTrait>(_self: &AsyncTrait, x: &T) -> Ret {
+// _self + x
+// }
+// Box::pin(async_trait_method::<T, Self>(self, x))
+fn transform_block(
+ context: Context,
+ sig: &mut Signature,
+ block: &mut Block,
+ has_self: bool,
+ is_local: bool,
+) {
+ if let Some(Stmt::Item(syn::Item::Verbatim(item))) = block.stmts.first() {
+ if block.stmts.len() == 1 && item.to_string() == ";" {
+ return;
+ }
+ }
+
+ let inner = format_ident!("__{}", sig.ident);
+ let args = sig.inputs.iter().enumerate().map(|(i, arg)| match arg {
+ FnArg::Receiver(Receiver { self_token, .. }) => quote!(#self_token),
+ FnArg::Typed(arg) => {
+ if let Pat::Ident(PatIdent { ident, .. }) = &*arg.pat {
+ quote!(#ident)
+ } else {
+ positional_arg(i).into_token_stream()
+ }
+ }
+ });
+
+ let mut standalone = sig.clone();
+ standalone.ident = inner.clone();
+
+ let generics = match context {
+ Context::Trait { generics, .. } => generics,
+ Context::Impl { impl_generics, .. } => impl_generics,
+ };
+
+ let mut outer_generics = generics.clone();
+ if !has_self {
+ if let Some(mut where_clause) = outer_generics.where_clause {
+ where_clause.predicates = where_clause
+ .predicates
+ .into_iter()
+ .filter_map(|mut pred| {
+ if has_self_in_where_predicate(&mut pred) {
+ None
+ } else {
+ Some(pred)
+ }
+ })
+ .collect();
+ outer_generics.where_clause = Some(where_clause);
+ }
+ }
+
+ let fn_generics = mem::replace(&mut standalone.generics, outer_generics);
+ standalone.generics.params.extend(fn_generics.params);
+ if let Some(where_clause) = fn_generics.where_clause {
+ standalone
+ .generics
+ .make_where_clause()
+ .predicates
+ .extend(where_clause.predicates);
+ }
+
+ if has_async_lifetime(&mut standalone, block) {
+ standalone.generics.params.push(parse_quote!('async_trait));
+ }
+
+ let mut types = standalone
+ .generics
+ .type_params()
+ .map(|param| param.ident.clone())
+ .collect::<Vec<_>>();
+
+ let mut self_bound = None::<TypeParamBound>;
+ match standalone.inputs.iter_mut().next() {
+ Some(
+ arg @ FnArg::Receiver(Receiver {
+ reference: Some(_), ..
+ }),
+ ) => {
+ let (lifetime, mutability, self_token) = match arg {
+ FnArg::Receiver(Receiver {
+ reference: Some((_, lifetime)),
+ mutability,
+ self_token,
+ ..
+ }) => (lifetime, mutability, self_token),
+ _ => unreachable!(),
+ };
+ let under_self = Ident::new("_self", self_token.span);
+ match context {
+ Context::Trait { .. } => {
+ self_bound = Some(match mutability {
+ Some(_) => parse_quote!(::core::marker::Send),
+ None => parse_quote!(::core::marker::Sync),
+ });
+ *arg = parse_quote! {
+ #under_self: &#lifetime #mutability AsyncTrait
+ };
+ }
+ Context::Impl { receiver, .. } => {
+ let mut ty = quote!(#receiver);
+ if let Type::TraitObject(trait_object) = receiver {
+ if trait_object.dyn_token.is_none() {
+ ty = quote!(dyn #ty);
+ }
+ if trait_object.bounds.len() > 1 {
+ ty = quote!((#ty));
+ }
+ }
+ *arg = parse_quote! {
+ #under_self: &#lifetime #mutability #ty
+ };
+ }
+ }
+ }
+ Some(arg @ FnArg::Receiver(_)) => {
+ let (self_token, mutability) = match arg {
+ FnArg::Receiver(Receiver {
+ self_token,
+ mutability,
+ ..
+ }) => (self_token, mutability),
+ _ => unreachable!(),
+ };
+ let under_self = Ident::new("_self", self_token.span);
+ match context {
+ Context::Trait { .. } => {
+ self_bound = Some(parse_quote!(::core::marker::Send));
+ *arg = parse_quote! {
+ #mutability #under_self: AsyncTrait
+ };
+ }
+ Context::Impl { receiver, .. } => {
+ *arg = parse_quote! {
+ #mutability #under_self: #receiver
+ };
+ }
+ }
+ }
+ Some(FnArg::Typed(arg)) => {
+ if let Pat::Ident(arg) = &mut *arg.pat {
+ if arg.ident == "self" {
+ arg.ident = Ident::new("_self", arg.ident.span());
+ }
+ }
+ }
+ _ => {}
+ }
+
+ if let Context::Trait { name, generics, .. } = context {
+ if has_self {
+ let (_, generics, _) = generics.split_for_impl();
+ let mut self_param: TypeParam = parse_quote!(AsyncTrait: ?Sized + #name #generics);
+ if !is_local {
+ self_param.bounds.extend(self_bound);
+ }
+ standalone
+ .generics
+ .params
+ .push(GenericParam::Type(self_param));
+ types.push(Ident::new("Self", Span::call_site()));
+ }
+ }
+
+ if let Some(where_clause) = &mut standalone.generics.where_clause {
+ // Work around an input bound like `where Self::Output: Send` expanding
+ // to `where <AsyncTrait>::Output: Send` which is illegal syntax because
+ // `where<T>` is reserved for future use... :(
+ where_clause.predicates.insert(0, parse_quote!((): Sized));
+ }
+
+ let mut replace = match context {
+ Context::Trait { .. } => ReplaceReceiver::with(parse_quote!(AsyncTrait)),
+ Context::Impl {
+ receiver, as_trait, ..
+ } => ReplaceReceiver::with_as_trait(receiver.clone(), as_trait.clone()),
+ };
+ replace.visit_signature_mut(&mut standalone);
+ replace.visit_block_mut(block);
+
+ let mut generics = types;
+ let consts = standalone
+ .generics
+ .const_params()
+ .map(|param| param.ident.clone());
+ generics.extend(consts);
+
+ let allow_non_snake_case = if sig.ident != sig.ident.to_string().to_lowercase() {
+ Some(quote!(non_snake_case,))
+ } else {
+ None
+ };
+
+ let brace = block.brace_token;
+ let box_pin = quote_spanned!(brace.span=> {
+ #[allow(
+ #allow_non_snake_case
+ clippy::missing_docs_in_private_items,
+ clippy::needless_lifetimes,
+ clippy::ptr_arg,
+ clippy::type_repetition_in_bounds,
+ clippy::used_underscore_binding,
+ )]
+ #standalone #block
+ Box::pin(#inner::<#(#generics),*>(#(#args),*))
+ });
+ *block = parse_quote!(#box_pin);
+ block.brace_token = brace;
+}
+
+fn positional_arg(i: usize) -> Ident {
+ format_ident!("__arg{}", i)
+}
+
+fn has_bound(supertraits: &Supertraits, marker: &Ident) -> bool {
+ for bound in supertraits {
+ if let TypeParamBound::Trait(bound) = bound {
+ if bound.path.is_ident(marker) {
+ return true;
+ }
+ }
+ }
+ false
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..f0102d8
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,328 @@
+//! [![github]](https://github.com/dtolnay/async-trait) [![crates-io]](https://crates.io/crates/async-trait) [![docs-rs]](https://docs.rs/async-trait)
+//!
+//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
+//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
+//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logoColor=white&logo=data:image/svg+xml;base64,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
+//!
+//! <br>
+//!
+//! <h5>Type erasure for async trait methods</h5>
+//!
+//! The initial round of stabilizations for the async/await language feature in
+//! Rust 1.39 did not include support for async fn in traits. Trying to include
+//! an async fn in a trait produces the following error:
+//!
+//! ```compile_fail
+//! trait MyTrait {
+//! async fn f() {}
+//! }
+//! ```
+//!
+//! ```text
+//! error[E0706]: trait fns cannot be declared `async`
+//! --> src/main.rs:4:5
+//! |
+//! 4 | async fn f() {}
+//! | ^^^^^^^^^^^^^^^
+//! ```
+//!
+//! This crate provides an attribute macro to make async fn in traits work.
+//!
+//! Please refer to [*why async fn in traits are hard*][hard] for a deeper
+//! analysis of how this implementation differs from what the compiler and
+//! language hope to deliver in the future.
+//!
+//! [hard]: https://smallcultfollowing.com/babysteps/blog/2019/10/26/async-fn-in-traits-are-hard/
+//!
+//! <br>
+//!
+//! # Example
+//!
+//! This example implements the core of a highly effective advertising platform
+//! using async fn in a trait.
+//!
+//! The only thing to notice here is that we write an `#[async_trait]` macro on
+//! top of traits and trait impls that contain async fn, and then they work.
+//!
+//! ```
+//! use async_trait::async_trait;
+//!
+//! #[async_trait]
+//! trait Advertisement {
+//! async fn run(&self);
+//! }
+//!
+//! struct Modal;
+//!
+//! #[async_trait]
+//! impl Advertisement for Modal {
+//! async fn run(&self) {
+//! self.render_fullscreen().await;
+//! for _ in 0..4u16 {
+//! remind_user_to_join_mailing_list().await;
+//! }
+//! self.hide_for_now().await;
+//! }
+//! }
+//!
+//! struct AutoplayingVideo {
+//! media_url: String,
+//! }
+//!
+//! #[async_trait]
+//! impl Advertisement for AutoplayingVideo {
+//! async fn run(&self) {
+//! let stream = connect(&self.media_url).await;
+//! stream.play().await;
+//!
+//! // Video probably persuaded user to join our mailing list!
+//! Modal.run().await;
+//! }
+//! }
+//! #
+//! # impl Modal {
+//! # async fn render_fullscreen(&self) {}
+//! # async fn hide_for_now(&self) {}
+//! # }
+//! #
+//! # async fn remind_user_to_join_mailing_list() {}
+//! #
+//! # struct Stream;
+//! # async fn connect(_media_url: &str) -> Stream { Stream }
+//! # impl Stream {
+//! # async fn play(&self) {}
+//! # }
+//! ```
+//!
+//! <br><br>
+//!
+//! # Supported features
+//!
+//! It is the intention that all features of Rust traits should work nicely with
+//! #\[async_trait\], but the edge cases are numerous. Please file an issue if
+//! you see unexpected borrow checker errors, type errors, or warnings. There is
+//! no use of `unsafe` in the expanded code, so rest assured that if your code
+//! compiles it can't be that badly broken.
+//!
+//! > ☑ Self by value, by reference, by mut reference, or no self;<br>
+//! > ☑ Any number of arguments, any return value;<br>
+//! > ☑ Generic type parameters and lifetime parameters;<br>
+//! > ☑ Associated types;<br>
+//! > ☑ Having async and non-async functions in the same trait;<br>
+//! > ☑ Default implementations provided by the trait;<br>
+//! > ☑ Elided lifetimes;<br>
+//! > ☑ Dyn-capable traits.<br>
+//!
+//! <br>
+//!
+//! # Explanation
+//!
+//! Async fns get transformed into methods that return `Pin<Box<dyn Future +
+//! Send + 'async>>` and delegate to a private async freestanding function.
+//!
+//! For example the `impl Advertisement for AutoplayingVideo` above would be
+//! expanded as:
+//!
+//! ```
+//! # const IGNORE: &str = stringify! {
+//! impl Advertisement for AutoplayingVideo {
+//! fn run<'async>(
+//! &'async self,
+//! ) -> Pin<Box<dyn core::future::Future<Output = ()> + Send + 'async>>
+//! where
+//! Self: Sync + 'async,
+//! {
+//! async fn run(_self: &AutoplayingVideo) {
+//! /* the original method body */
+//! }
+//!
+//! Box::pin(run(self))
+//! }
+//! }
+//! # };
+//! ```
+//!
+//! <br><br>
+//!
+//! # Non-threadsafe futures
+//!
+//! Not all async traits need futures that are `dyn Future + Send`. To avoid
+//! having Send and Sync bounds placed on the async trait methods, invoke the
+//! async trait macro as `#[async_trait(?Send)]` on both the trait and the impl
+//! blocks.
+//!
+//! <br>
+//!
+//! # Elided lifetimes
+//!
+//! Be aware that async fn syntax does not allow lifetime elision outside of `&`
+//! and `&mut` references. (This is true even when not using #\[async_trait\].)
+//! Lifetimes must be named or marked by the placeholder `'_`.
+//!
+//! Fortunately the compiler is able to diagnose missing lifetimes with a good
+//! error message.
+//!
+//! ```compile_fail
+//! # use async_trait::async_trait;
+//! #
+//! type Elided<'a> = &'a usize;
+//!
+//! #[async_trait]
+//! trait Test {
+//! async fn test(not_okay: Elided, okay: &usize) {}
+//! }
+//! ```
+//!
+//! ```text
+//! error[E0726]: implicit elided lifetime not allowed here
+//! --> src/main.rs:9:29
+//! |
+//! 9 | async fn test(not_okay: Elided, okay: &usize) {}
+//! | ^^^^^^- help: indicate the anonymous lifetime: `<'_>`
+//! ```
+//!
+//! The fix is to name the lifetime or use `'_`.
+//!
+//! ```
+//! # use async_trait::async_trait;
+//! #
+//! # type Elided<'a> = &'a usize;
+//! #
+//! #[async_trait]
+//! trait Test {
+//! // either
+//! async fn test<'e>(elided: Elided<'e>) {}
+//! # }
+//! # #[async_trait]
+//! # trait Test2 {
+//! // or
+//! async fn test(elided: Elided<'_>) {}
+//! }
+//! ```
+//!
+//! <br><br>
+//!
+//! # Dyn traits
+//!
+//! Traits with async methods can be used as trait objects as long as they meet
+//! the usual requirements for dyn -- no methods with type parameters, no self
+//! by value, no associated types, etc.
+//!
+//! ```
+//! # use async_trait::async_trait;
+//! #
+//! #[async_trait]
+//! pub trait ObjectSafe {
+//! async fn f(&self);
+//! async fn g(&mut self);
+//! }
+//!
+//! # const IGNORE: &str = stringify! {
+//! impl ObjectSafe for MyType {...}
+//!
+//! let value: MyType = ...;
+//! # };
+//! #
+//! # struct MyType;
+//! #
+//! # #[async_trait]
+//! # impl ObjectSafe for MyType {
+//! # async fn f(&self) {}
+//! # async fn g(&mut self) {}
+//! # }
+//! #
+//! # let value: MyType = MyType;
+//! let object = &value as &dyn ObjectSafe; // make trait object
+//! ```
+//!
+//! The one wrinkle is in traits that provide default implementations of async
+//! methods. In order for the default implementation to produce a future that is
+//! Send, the async_trait macro must emit a bound of `Self: Sync` on trait
+//! methods that take `&self` and a bound `Self: Send` on trait methods that
+//! take `&mut self`. An example of the former is visible in the expanded code
+//! in the explanation section above.
+//!
+//! If you make a trait with async methods that have default implementations,
+//! everything will work except that the trait cannot be used as a trait object.
+//! Creating a value of type `&dyn Trait` will produce an error that looks like
+//! this:
+//!
+//! ```text
+//! error: the trait `Test` cannot be made into an object
+//! --> src/main.rs:8:5
+//! |
+//! 8 | async fn cannot_dyn(&self) {}
+//! | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+//! ```
+//!
+//! For traits that need to be object safe and need to have default
+//! implementations for some async methods, there are two resolutions. Either
+//! you can add Send and/or Sync as supertraits (Send if there are `&mut self`
+//! methods with default implementations, Sync if there are `&self` methods with
+//! default implementions) to constrain all implementors of the trait such that
+//! the default implementations are applicable to them:
+//!
+//! ```
+//! # use async_trait::async_trait;
+//! #
+//! #[async_trait]
+//! pub trait ObjectSafe: Sync { // added supertrait
+//! async fn can_dyn(&self) {}
+//! }
+//! #
+//! # struct MyType;
+//! #
+//! # #[async_trait]
+//! # impl ObjectSafe for MyType {}
+//! #
+//! # let value = MyType;
+//!
+//! let object = &value as &dyn ObjectSafe;
+//! ```
+//!
+//! or you can strike the problematic methods from your trait object by
+//! bounding them with `Self: Sized`:
+//!
+//! ```
+//! # use async_trait::async_trait;
+//! #
+//! #[async_trait]
+//! pub trait ObjectSafe {
+//! async fn cannot_dyn(&self) where Self: Sized {}
+//!
+//! // presumably other methods
+//! }
+//! #
+//! # struct MyType;
+//! #
+//! # #[async_trait]
+//! # impl ObjectSafe for MyType {}
+//! #
+//! # let value = MyType;
+//!
+//! let object = &value as &dyn ObjectSafe;
+//! ```
+
+extern crate proc_macro;
+
+mod args;
+mod expand;
+mod lifetime;
+mod parse;
+mod receiver;
+mod respan;
+
+use crate::args::Args;
+use crate::expand::expand;
+use crate::parse::Item;
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::parse_macro_input;
+
+#[proc_macro_attribute]
+pub fn async_trait(args: TokenStream, input: TokenStream) -> TokenStream {
+ let args = parse_macro_input!(args as Args);
+ let mut item = parse_macro_input!(input as Item);
+ expand(&mut item, args.local);
+ TokenStream::from(quote!(#item))
+}
diff --git a/src/lifetime.rs b/src/lifetime.rs
new file mode 100644
index 0000000..9d2066b
--- /dev/null
+++ b/src/lifetime.rs
@@ -0,0 +1,80 @@
+use proc_macro2::Span;
+use syn::visit_mut::{self, VisitMut};
+use syn::{Block, GenericArgument, Item, Lifetime, Receiver, Signature, TypeReference};
+
+pub fn has_async_lifetime(sig: &mut Signature, block: &mut Block) -> bool {
+ let mut visitor = HasAsyncLifetime(false);
+ visitor.visit_signature_mut(sig);
+ visitor.visit_block_mut(block);
+ visitor.0
+}
+
+struct HasAsyncLifetime(bool);
+
+impl VisitMut for HasAsyncLifetime {
+ fn visit_lifetime_mut(&mut self, life: &mut Lifetime) {
+ self.0 |= life.to_string() == "'async_trait";
+ }
+
+ fn visit_item_mut(&mut self, _: &mut Item) {
+ // Do not recurse into nested items.
+ }
+}
+
+pub struct CollectLifetimes {
+ pub elided: Vec<Lifetime>,
+ pub explicit: Vec<Lifetime>,
+ pub name: &'static str,
+}
+
+impl CollectLifetimes {
+ pub fn new(name: &'static str) -> Self {
+ CollectLifetimes {
+ elided: Vec::new(),
+ explicit: Vec::new(),
+ name,
+ }
+ }
+
+ fn visit_opt_lifetime(&mut self, lifetime: &mut Option<Lifetime>) {
+ match lifetime {
+ None => *lifetime = Some(self.next_lifetime()),
+ Some(lifetime) => self.visit_lifetime(lifetime),
+ }
+ }
+
+ fn visit_lifetime(&mut self, lifetime: &mut Lifetime) {
+ if lifetime.ident == "_" {
+ *lifetime = self.next_lifetime();
+ } else {
+ self.explicit.push(lifetime.clone());
+ }
+ }
+
+ fn next_lifetime(&mut self) -> Lifetime {
+ let name = format!("{}{}", self.name, self.elided.len());
+ let life = Lifetime::new(&name, Span::call_site());
+ self.elided.push(life.clone());
+ life
+ }
+}
+
+impl VisitMut for CollectLifetimes {
+ fn visit_receiver_mut(&mut self, arg: &mut Receiver) {
+ if let Some((_, lifetime)) = &mut arg.reference {
+ self.visit_opt_lifetime(lifetime);
+ }
+ }
+
+ fn visit_type_reference_mut(&mut self, ty: &mut TypeReference) {
+ self.visit_opt_lifetime(&mut ty.lifetime);
+ visit_mut::visit_type_reference_mut(self, ty);
+ }
+
+ fn visit_generic_argument_mut(&mut self, gen: &mut GenericArgument) {
+ if let GenericArgument::Lifetime(lifetime) = gen {
+ self.visit_lifetime(lifetime);
+ }
+ visit_mut::visit_generic_argument_mut(self, gen);
+ }
+}
diff --git a/src/parse.rs b/src/parse.rs
new file mode 100644
index 0000000..ebd2535
--- /dev/null
+++ b/src/parse.rs
@@ -0,0 +1,34 @@
+use proc_macro2::Span;
+use syn::parse::{Error, Parse, ParseStream, Result};
+use syn::{Attribute, ItemImpl, ItemTrait, Token};
+
+pub enum Item {
+ Trait(ItemTrait),
+ Impl(ItemImpl),
+}
+
+impl Parse for Item {
+ fn parse(input: ParseStream) -> Result<Self> {
+ let attrs = input.call(Attribute::parse_outer)?;
+ let mut lookahead = input.lookahead1();
+ if lookahead.peek(Token![unsafe]) {
+ let ahead = input.fork();
+ ahead.parse::<Token![unsafe]>()?;
+ lookahead = ahead.lookahead1();
+ }
+ if lookahead.peek(Token![pub]) || lookahead.peek(Token![trait]) {
+ let mut item: ItemTrait = input.parse()?;
+ item.attrs = attrs;
+ Ok(Item::Trait(item))
+ } else if lookahead.peek(Token![impl]) {
+ let mut item: ItemImpl = input.parse()?;
+ if item.trait_.is_none() {
+ return Err(Error::new(Span::call_site(), "expected a trait impl"));
+ }
+ item.attrs = attrs;
+ Ok(Item::Impl(item))
+ } else {
+ Err(lookahead.error())
+ }
+ }
+}
diff --git a/src/receiver.rs b/src/receiver.rs
new file mode 100644
index 0000000..1e9e397
--- /dev/null
+++ b/src/receiver.rs
@@ -0,0 +1,307 @@
+use crate::respan::respan;
+use proc_macro2::{Group, Spacing, Span, TokenStream, TokenTree};
+use quote::{quote, quote_spanned};
+use std::iter::FromIterator;
+use std::mem;
+use syn::punctuated::Punctuated;
+use syn::visit_mut::{self, VisitMut};
+use syn::{
+ parse_quote, Block, Error, ExprPath, ExprStruct, Ident, Item, Macro, PatPath, PatStruct,
+ PatTupleStruct, Path, PathArguments, QSelf, Receiver, Signature, Token, Type, TypePath,
+ WherePredicate,
+};
+
+pub fn has_self_in_sig(sig: &mut Signature) -> bool {
+ let mut visitor = HasSelf(false);
+ visitor.visit_signature_mut(sig);
+ visitor.0
+}
+
+pub fn has_self_in_where_predicate(where_predicate: &mut WherePredicate) -> bool {
+ let mut visitor = HasSelf(false);
+ visitor.visit_where_predicate_mut(where_predicate);
+ visitor.0
+}
+
+pub fn has_self_in_block(block: &mut Block) -> bool {
+ let mut visitor = HasSelf(false);
+ visitor.visit_block_mut(block);
+ visitor.0
+}
+
+struct HasSelf(bool);
+
+impl VisitMut for HasSelf {
+ fn visit_expr_path_mut(&mut self, expr: &mut ExprPath) {
+ self.0 |= expr.path.segments[0].ident == "Self";
+ visit_mut::visit_expr_path_mut(self, expr);
+ }
+
+ fn visit_pat_path_mut(&mut self, pat: &mut PatPath) {
+ self.0 |= pat.path.segments[0].ident == "Self";
+ visit_mut::visit_pat_path_mut(self, pat);
+ }
+
+ fn visit_type_path_mut(&mut self, ty: &mut TypePath) {
+ self.0 |= ty.path.segments[0].ident == "Self";
+ visit_mut::visit_type_path_mut(self, ty);
+ }
+
+ fn visit_receiver_mut(&mut self, _arg: &mut Receiver) {
+ self.0 = true;
+ }
+
+ fn visit_item_mut(&mut self, _: &mut Item) {
+ // Do not recurse into nested items.
+ }
+}
+
+pub struct ReplaceReceiver {
+ pub with: Type,
+ pub as_trait: Option<Path>,
+}
+
+impl ReplaceReceiver {
+ pub fn with(ty: Type) -> Self {
+ ReplaceReceiver {
+ with: ty,
+ as_trait: None,
+ }
+ }
+
+ pub fn with_as_trait(ty: Type, as_trait: Path) -> Self {
+ ReplaceReceiver {
+ with: ty,
+ as_trait: Some(as_trait),
+ }
+ }
+
+ fn self_ty(&self, span: Span) -> Type {
+ respan(&self.with, span)
+ }
+
+ fn self_to_qself_type(&self, qself: &mut Option<QSelf>, path: &mut Path) {
+ let include_as_trait = true;
+ self.self_to_qself(qself, path, include_as_trait);
+ }
+
+ fn self_to_qself_expr(&self, qself: &mut Option<QSelf>, path: &mut Path) {
+ let include_as_trait = false;
+ self.self_to_qself(qself, path, include_as_trait);
+ }
+
+ fn self_to_qself(&self, qself: &mut Option<QSelf>, path: &mut Path, include_as_trait: bool) {
+ if path.leading_colon.is_some() {
+ return;
+ }
+
+ let first = &path.segments[0];
+ if first.ident != "Self" || !first.arguments.is_empty() {
+ return;
+ }
+
+ if path.segments.len() == 1 {
+ self.self_to_expr_path(path);
+ return;
+ }
+
+ let span = first.ident.span();
+ *qself = Some(QSelf {
+ lt_token: Token,
+ ty: Box::new(self.self_ty(span)),
+ position: 0,
+ as_token: None,
+ gt_token: Token,
+ });
+
+ if include_as_trait && self.as_trait.is_some() {
+ let as_trait = self.as_trait.as_ref().unwrap().clone();
+ path.leading_colon = as_trait.leading_colon;
+ qself.as_mut().unwrap().position = as_trait.segments.len();
+
+ let segments = mem::replace(&mut path.segments, as_trait.segments);
+ path.segments.push_punct(Default::default());
+ path.segments.extend(segments.into_pairs().skip(1));
+ } else {
+ path.leading_colon = Some(**path.segments.pairs().next().unwrap().punct().unwrap());
+
+ let segments = mem::replace(&mut path.segments, Punctuated::new());
+ path.segments = segments.into_pairs().skip(1).collect();
+ }
+ }
+
+ fn self_to_expr_path(&self, path: &mut Path) {
+ if path.leading_colon.is_some() {
+ return;
+ }
+
+ let first = &path.segments[0];
+ if first.ident != "Self" || !first.arguments.is_empty() {
+ return;
+ }
+
+ if let Type::Path(self_ty) = self.self_ty(first.ident.span()) {
+ let variant = mem::replace(path, self_ty.path);
+ for segment in &mut path.segments {
+ if let PathArguments::AngleBracketed(bracketed) = &mut segment.arguments {
+ if bracketed.colon2_token.is_none() && !bracketed.args.is_empty() {
+ bracketed.colon2_token = Some(Default::default());
+ }
+ }
+ }
+ if variant.segments.len() > 1 {
+ path.segments.push_punct(Default::default());
+ path.segments.extend(variant.segments.into_pairs().skip(1));
+ }
+ } else {
+ let span = path.segments[0].ident.span();
+ let msg = "Self type of this impl is unsupported in expression position";
+ let error = Error::new(span, msg).to_compile_error();
+ *path = parse_quote!(::core::marker::PhantomData::<#error>);
+ }
+ }
+
+ fn visit_token_stream(&self, tokens: &mut TokenStream) -> bool {
+ let mut out = Vec::new();
+ let mut modified = false;
+ let mut iter = tokens.clone().into_iter().peekable();
+ while let Some(tt) = iter.next() {
+ match tt {
+ TokenTree::Ident(mut ident) => {
+ modified |= prepend_underscore_to_self(&mut ident);
+ if ident == "Self" {
+ modified = true;
+ if self.as_trait.is_none() {
+ let ident = Ident::new("AsyncTrait", ident.span());
+ out.push(TokenTree::Ident(ident));
+ } else {
+ let self_ty = self.self_ty(ident.span());
+ match iter.peek() {
+ Some(TokenTree::Punct(p))
+ if p.as_char() == ':' && p.spacing() == Spacing::Joint =>
+ {
+ let next = iter.next().unwrap();
+ match iter.peek() {
+ Some(TokenTree::Punct(p)) if p.as_char() == ':' => {
+ let span = ident.span();
+ out.extend(quote_spanned!(span=> <#self_ty>));
+ }
+ _ => out.extend(quote!(#self_ty)),
+ }
+ out.push(next);
+ }
+ _ => out.extend(quote!(#self_ty)),
+ }
+ }
+ } else {
+ out.push(TokenTree::Ident(ident));
+ }
+ }
+ TokenTree::Group(group) => {
+ let mut content = group.stream();
+ modified |= self.visit_token_stream(&mut content);
+ let mut new = Group::new(group.delimiter(), content);
+ new.set_span(group.span());
+ out.push(TokenTree::Group(new));
+ }
+ other => out.push(other),
+ }
+ }
+ if modified {
+ *tokens = TokenStream::from_iter(out);
+ }
+ modified
+ }
+}
+
+impl VisitMut for ReplaceReceiver {
+ // `Self` -> `Receiver`
+ fn visit_type_mut(&mut self, ty: &mut Type) {
+ if let Type::Path(node) = ty {
+ if node.qself.is_none() && node.path.is_ident("Self") {
+ *ty = self.self_ty(node.path.segments[0].ident.span());
+ } else {
+ self.visit_type_path_mut(node);
+ }
+ } else {
+ visit_mut::visit_type_mut(self, ty);
+ }
+ }
+
+ // `Self::Assoc` -> `<Receiver>::Assoc`
+ fn visit_type_path_mut(&mut self, ty: &mut TypePath) {
+ if ty.qself.is_none() {
+ self.self_to_qself_type(&mut ty.qself, &mut ty.path);
+ }
+ visit_mut::visit_type_path_mut(self, ty);
+ }
+
+ // `Self::method` -> `<Receiver>::method`
+ fn visit_expr_path_mut(&mut self, expr: &mut ExprPath) {
+ if expr.qself.is_none() {
+ prepend_underscore_to_self(&mut expr.path.segments[0].ident);
+ self.self_to_qself_expr(&mut expr.qself, &mut expr.path);
+ }
+ visit_mut::visit_expr_path_mut(self, expr);
+ }
+
+ fn visit_expr_struct_mut(&mut self, expr: &mut ExprStruct) {
+ self.self_to_expr_path(&mut expr.path);
+ visit_mut::visit_expr_struct_mut(self, expr);
+ }
+
+ fn visit_pat_path_mut(&mut self, pat: &mut PatPath) {
+ if pat.qself.is_none() {
+ self.self_to_qself_expr(&mut pat.qself, &mut pat.path);
+ }
+ visit_mut::visit_pat_path_mut(self, pat);
+ }
+
+ fn visit_pat_struct_mut(&mut self, pat: &mut PatStruct) {
+ self.self_to_expr_path(&mut pat.path);
+ visit_mut::visit_pat_struct_mut(self, pat);
+ }
+
+ fn visit_pat_tuple_struct_mut(&mut self, pat: &mut PatTupleStruct) {
+ self.self_to_expr_path(&mut pat.path);
+ visit_mut::visit_pat_tuple_struct_mut(self, pat);
+ }
+
+ fn visit_item_mut(&mut self, i: &mut Item) {
+ match i {
+ // Visit `macro_rules!` because locally defined macros can refer to `self`.
+ Item::Macro(i) if i.mac.path.is_ident("macro_rules") => {
+ self.visit_macro_mut(&mut i.mac)
+ }
+ // Otherwise, do not recurse into nested items.
+ _ => {}
+ }
+ }
+
+ fn visit_macro_mut(&mut self, i: &mut Macro) {
+ // We can't tell in general whether `self` inside a macro invocation
+ // refers to the self in the argument list or a different self
+ // introduced within the macro. Heuristic: if the macro input contains
+ // `fn`, then `self` is more likely to refer to something other than the
+ // outer function's self argument.
+ if !contains_fn(i.tokens.clone()) {
+ self.visit_token_stream(&mut i.tokens);
+ }
+ }
+}
+
+fn contains_fn(tokens: TokenStream) -> bool {
+ tokens.into_iter().any(|tt| match tt {
+ TokenTree::Ident(ident) => ident == "fn",
+ TokenTree::Group(group) => contains_fn(group.stream()),
+ _ => false,
+ })
+}
+
+fn prepend_underscore_to_self(ident: &mut Ident) -> bool {
+ let modified = ident == "self";
+ if modified {
+ *ident = Ident::new("_self", ident.span());
+ }
+ modified
+}
diff --git a/src/respan.rs b/src/respan.rs
new file mode 100644
index 0000000..38f6612
--- /dev/null
+++ b/src/respan.rs
@@ -0,0 +1,22 @@
+use proc_macro2::{Span, TokenStream};
+use quote::ToTokens;
+use syn::parse::Parse;
+
+pub(crate) fn respan<T>(node: &T, span: Span) -> T
+where
+ T: ToTokens + Parse,
+{
+ let tokens = node.to_token_stream();
+ let respanned = respan_tokens(tokens, span);
+ syn::parse2(respanned).unwrap()
+}
+
+fn respan_tokens(tokens: TokenStream, span: Span) -> TokenStream {
+ tokens
+ .into_iter()
+ .map(|mut token| {
+ token.set_span(span);
+ token
+ })
+ .collect()
+}
diff --git a/tests/compiletest.rs b/tests/compiletest.rs
new file mode 100644
index 0000000..f9aea23
--- /dev/null
+++ b/tests/compiletest.rs
@@ -0,0 +1,6 @@
+#[rustversion::attr(not(nightly), ignore)]
+#[test]
+fn ui() {
+ let t = trybuild::TestCases::new();
+ t.compile_fail("tests/ui/*.rs");
+}
diff --git a/tests/executor/mod.rs b/tests/executor/mod.rs
new file mode 100644
index 0000000..f48b348
--- /dev/null
+++ b/tests/executor/mod.rs
@@ -0,0 +1,35 @@
+use std::future::Future;
+use std::pin::Pin;
+use std::ptr;
+use std::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
+
+// Executor for a future that resolves immediately (test only).
+pub fn block_on_simple<F: Future>(mut fut: F) -> F::Output {
+ unsafe fn clone(_null: *const ()) -> RawWaker {
+ unimplemented!()
+ }
+
+ unsafe fn wake(_null: *const ()) {
+ unimplemented!()
+ }
+
+ unsafe fn wake_by_ref(_null: *const ()) {
+ unimplemented!()
+ }
+
+ unsafe fn drop(_null: *const ()) {}
+
+ let data = ptr::null();
+ let vtable = &RawWakerVTable::new(clone, wake, wake_by_ref, drop);
+ let raw_waker = RawWaker::new(data, vtable);
+ let waker = unsafe { Waker::from_raw(raw_waker) };
+ let mut cx = Context::from_waker(&waker);
+
+ // fut does not move until it gets dropped.
+ let fut = unsafe { Pin::new_unchecked(&mut fut) };
+
+ match fut.poll(&mut cx) {
+ Poll::Ready(output) => output,
+ Poll::Pending => panic!("future did not resolve immediately"),
+ }
+}
diff --git a/tests/test.rs b/tests/test.rs
new file mode 100644
index 0000000..3ea2d15
--- /dev/null
+++ b/tests/test.rs
@@ -0,0 +1,961 @@
+#![cfg_attr(async_trait_nightly_testing, feature(specialization, const_generics))]
+
+use async_trait::async_trait;
+
+pub mod executor;
+
+// Dummy module to check that the expansion refer to rust's core crate
+mod core {}
+
+#[async_trait]
+trait Trait {
+ type Assoc;
+
+ async fn selfvalue(self)
+ where
+ Self: Sized,
+ {
+ }
+
+ async fn selfref(&self) {}
+
+ async fn selfmut(&mut self) {}
+
+ async fn required() -> Self::Assoc;
+
+ async fn elided_lifetime(_x: &str) {}
+
+ async fn explicit_lifetime<'a>(_x: &'a str) {}
+
+ async fn generic_type_param<T: Send>(x: Box<T>) -> T {
+ *x
+ }
+
+ async fn calls(&self) {
+ self.selfref().await;
+ Self::elided_lifetime("").await;
+ <Self>::elided_lifetime("").await;
+ }
+
+ async fn calls_mut(&mut self) {
+ self.selfmut().await;
+ }
+}
+
+struct Struct;
+
+#[async_trait]
+impl Trait for Struct {
+ type Assoc = ();
+
+ async fn selfvalue(self) {}
+
+ async fn selfref(&self) {}
+
+ async fn selfmut(&mut self) {}
+
+ async fn required() -> Self::Assoc {}
+
+ async fn elided_lifetime(_x: &str) {}
+
+ async fn explicit_lifetime<'a>(_x: &'a str) {}
+
+ async fn generic_type_param<T: Send>(x: Box<T>) -> T {
+ *x
+ }
+
+ async fn calls(&self) {
+ self.selfref().await;
+ Self::elided_lifetime("").await;
+ <Self>::elided_lifetime("").await;
+ }
+
+ async fn calls_mut(&mut self) {
+ self.selfmut().await;
+ }
+}
+
+pub async fn test() {
+ let mut s = Struct;
+ s.selfref().await;
+ s.selfmut().await;
+ s.selfvalue().await;
+
+ Struct::required().await;
+ Struct::elided_lifetime("").await;
+ Struct::explicit_lifetime("").await;
+ Struct::generic_type_param(Box::new("")).await;
+
+ let mut s = Struct;
+ s.calls().await;
+ s.calls_mut().await;
+}
+
+pub async fn test_object_safe_without_default() {
+ #[async_trait]
+ trait ObjectSafe {
+ async fn f(&self);
+ }
+
+ #[async_trait]
+ impl ObjectSafe for Struct {
+ async fn f(&self) {}
+ }
+
+ let object = &Struct as &dyn ObjectSafe;
+ object.f().await;
+}
+
+pub async fn test_object_safe_with_default() {
+ #[async_trait]
+ trait ObjectSafe: Sync {
+ async fn f(&self) {}
+ }
+
+ #[async_trait]
+ impl ObjectSafe for Struct {
+ async fn f(&self) {}
+ }
+
+ let object = &Struct as &dyn ObjectSafe;
+ object.f().await;
+}
+
+pub async fn test_object_no_send() {
+ #[async_trait(?Send)]
+ trait ObjectSafe: Sync {
+ async fn f(&self) {}
+ }
+
+ #[async_trait(?Send)]
+ impl ObjectSafe for Struct {
+ async fn f(&self) {}
+ }
+
+ let object = &Struct as &dyn ObjectSafe;
+ object.f().await;
+}
+
+#[async_trait]
+pub unsafe trait UnsafeTrait {}
+
+#[async_trait]
+unsafe impl UnsafeTrait for () {}
+
+#[async_trait]
+pub(crate) unsafe trait UnsafeTraitPubCrate {}
+
+#[async_trait]
+unsafe trait UnsafeTraitPrivate {}
+
+// https://github.com/dtolnay/async-trait/issues/1
+pub mod issue1 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ trait Issue1 {
+ async fn f<U>(&self);
+ }
+
+ #[async_trait]
+ impl<T: Sync> Issue1 for Vec<T> {
+ async fn f<U>(&self) {}
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/2
+pub mod issue2 {
+ use async_trait::async_trait;
+ use std::future::Future;
+
+ #[async_trait]
+ pub trait Issue2: Future {
+ async fn flatten(self) -> <Self::Output as Future>::Output
+ where
+ Self::Output: Future + Send,
+ Self: Sized,
+ {
+ let nested_future = self.await;
+ nested_future.await
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/9
+pub mod issue9 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ pub trait Issue9: Sized + Send {
+ async fn f(_x: Self) {}
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/11
+pub mod issue11 {
+ use async_trait::async_trait;
+ use std::sync::Arc;
+
+ #[async_trait]
+ trait Issue11 {
+ async fn example(self: Arc<Self>);
+ }
+
+ struct Struct;
+
+ #[async_trait]
+ impl Issue11 for Struct {
+ async fn example(self: Arc<Self>) {}
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/15
+pub mod issue15 {
+ use async_trait::async_trait;
+ use std::marker::PhantomData;
+
+ trait Trait {}
+
+ #[async_trait]
+ trait Issue15 {
+ async fn myfn(&self, _: PhantomData<dyn Trait + Send>) {}
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/17
+pub mod issue17 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ trait Issue17 {
+ async fn f(&self);
+ }
+
+ struct Struct {
+ string: String,
+ }
+
+ #[async_trait]
+ impl Issue17 for Struct {
+ async fn f(&self) {
+ println!("{}", self.string);
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/23
+pub mod issue23 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ pub trait Issue23 {
+ async fn f(self);
+
+ async fn g(mut self)
+ where
+ Self: Sized,
+ {
+ do_something(&mut self);
+ }
+ }
+
+ struct S {}
+
+ #[async_trait]
+ impl Issue23 for S {
+ async fn f(mut self) {
+ do_something(&mut self);
+ }
+ }
+
+ fn do_something<T>(_: &mut T) {}
+}
+
+// https://github.com/dtolnay/async-trait/issues/25
+#[cfg(async_trait_nightly_testing)]
+pub mod issue25 {
+ use crate::executor;
+ use async_trait::async_trait;
+ use std::fmt::{Display, Write};
+
+ #[async_trait]
+ trait AsyncToString {
+ async fn async_to_string(&self) -> String;
+ }
+
+ #[async_trait]
+ impl AsyncToString for String {
+ async fn async_to_string(&self) -> String {
+ "special".to_owned()
+ }
+ }
+
+ macro_rules! hide_from_stable_parser {
+ ($($tt:tt)*) => {
+ $($tt)*
+ };
+ }
+
+ hide_from_stable_parser! {
+ #[async_trait]
+ impl<T: ?Sized + Display + Sync> AsyncToString for T {
+ default async fn async_to_string(&self) -> String {
+ let mut buf = String::new();
+ buf.write_fmt(format_args!("{}", self)).unwrap();
+ buf
+ }
+ }
+ }
+
+ #[test]
+ fn test() {
+ let fut = true.async_to_string();
+ assert_eq!(executor::block_on_simple(fut), "true");
+
+ let string = String::new();
+ let fut = string.async_to_string();
+ assert_eq!(executor::block_on_simple(fut), "special");
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/28
+pub mod issue28 {
+ use async_trait::async_trait;
+
+ struct Str<'a>(&'a str);
+
+ #[async_trait]
+ trait Trait1<'a> {
+ async fn f(x: Str<'a>) -> &'a str;
+ async fn g(x: Str<'a>) -> &'a str {
+ x.0
+ }
+ }
+
+ #[async_trait]
+ impl<'a> Trait1<'a> for str {
+ async fn f(x: Str<'a>) -> &'a str {
+ x.0
+ }
+ }
+
+ #[async_trait]
+ trait Trait2 {
+ async fn f();
+ }
+
+ #[async_trait]
+ impl<'a> Trait2 for &'a () {
+ async fn f() {}
+ }
+
+ #[async_trait]
+ trait Trait3<'a, 'b> {
+ async fn f(_: &'a &'b ()); // chain 'a and 'b
+ async fn g(_: &'b ()); // chain 'b only
+ async fn h(); // do not chain
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/31
+pub mod issue31 {
+ use async_trait::async_trait;
+
+ pub struct Struct<'a> {
+ pub name: &'a str,
+ }
+
+ #[async_trait]
+ pub trait Trait<'a> {
+ async fn hello(thing: Struct<'a>) -> String;
+ async fn hello_twice(one: Struct<'a>, two: Struct<'a>) -> String {
+ let str1 = Self::hello(one).await;
+ let str2 = Self::hello(two).await;
+ str1 + &str2
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/42
+pub mod issue42 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ pub trait Context: Sized {
+ async fn from_parts() -> Self;
+ }
+
+ pub struct TokenContext;
+
+ #[async_trait]
+ impl Context for TokenContext {
+ async fn from_parts() -> TokenContext {
+ TokenContext
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/44
+pub mod issue44 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ pub trait StaticWithWhereSelf
+ where
+ Box<Self>: Sized,
+ Self: Sized + Send,
+ {
+ async fn get_one() -> u8 {
+ 1
+ }
+ }
+
+ pub struct Struct;
+
+ #[async_trait]
+ impl StaticWithWhereSelf for Struct {}
+}
+
+// https://github.com/dtolnay/async-trait/issues/45
+pub mod issue45 {
+ use crate::executor;
+ use async_trait::async_trait;
+ use std::fmt::Debug;
+ use std::sync::atomic::{AtomicU64, Ordering};
+ use std::sync::{Arc, Mutex};
+ use tracing::event::Event;
+ use tracing::field::{Field, Visit};
+ use tracing::span::{Attributes, Id, Record};
+ use tracing::{info, instrument, subscriber, Metadata, Subscriber};
+
+ #[async_trait]
+ pub trait Parent {
+ async fn foo(&mut self, v: usize);
+ }
+
+ #[async_trait]
+ pub trait Child {
+ async fn bar(&self);
+ }
+
+ #[derive(Debug)]
+ struct Impl(usize);
+
+ #[async_trait]
+ impl Parent for Impl {
+ #[instrument]
+ async fn foo(&mut self, v: usize) {
+ self.0 = v;
+ self.bar().await;
+ }
+ }
+
+ #[async_trait]
+ impl Child for Impl {
+ // Let's check that tracing detects the renaming of the `self` variable
+ // too, as tracing::instrument is not going to be able to skip the
+ // `self` argument if it can't find it in the function signature.
+ #[instrument(skip(self))]
+ async fn bar(&self) {
+ info!(val = self.0);
+ }
+ }
+
+ // A simple subscriber implementation to test the behavior of async-trait
+ // with tokio-rs/tracing. This implementation is not robust against race
+ // conditions, but it's not an issue here as we are only polling on a single
+ // future at a time.
+ #[derive(Debug)]
+ struct SubscriberInner {
+ current_depth: AtomicU64,
+ // We assert that nested functions work. If the fix were to break, we
+ // would see two top-level functions instead of `bar` nested in `foo`.
+ max_depth: AtomicU64,
+ max_span_id: AtomicU64,
+ // Name of the variable / value / depth when the event was recorded.
+ value: Mutex<Option<(&'static str, u64, u64)>>,
+ }
+
+ #[derive(Debug, Clone)]
+ struct TestSubscriber {
+ inner: Arc<SubscriberInner>,
+ }
+
+ impl TestSubscriber {
+ fn new() -> Self {
+ TestSubscriber {
+ inner: Arc::new(SubscriberInner {
+ current_depth: AtomicU64::new(0),
+ max_depth: AtomicU64::new(0),
+ max_span_id: AtomicU64::new(1),
+ value: Mutex::new(None),
+ }),
+ }
+ }
+ }
+
+ struct U64Visitor(Option<(&'static str, u64)>);
+
+ impl Visit for U64Visitor {
+ fn record_debug(&mut self, _field: &Field, _value: &dyn Debug) {}
+
+ fn record_u64(&mut self, field: &Field, value: u64) {
+ self.0 = Some((field.name(), value));
+ }
+ }
+
+ impl Subscriber for TestSubscriber {
+ fn enabled(&self, _metadata: &Metadata) -> bool {
+ true
+ }
+ fn new_span(&self, _span: &Attributes) -> Id {
+ Id::from_u64(self.inner.max_span_id.fetch_add(1, Ordering::AcqRel))
+ }
+ fn record(&self, _span: &Id, _values: &Record) {}
+ fn record_follows_from(&self, _span: &Id, _follows: &Id) {}
+ fn event(&self, event: &Event) {
+ let mut visitor = U64Visitor(None);
+ event.record(&mut visitor);
+ if let Some((s, v)) = visitor.0 {
+ let current_depth = self.inner.current_depth.load(Ordering::Acquire);
+ *self.inner.value.lock().unwrap() = Some((s, v, current_depth));
+ }
+ }
+ fn enter(&self, _span: &Id) {
+ let old_depth = self.inner.current_depth.fetch_add(1, Ordering::AcqRel);
+ if old_depth + 1 > self.inner.max_depth.load(Ordering::Acquire) {
+ self.inner.max_depth.fetch_add(1, Ordering::AcqRel);
+ }
+ }
+ fn exit(&self, _span: &Id) {
+ self.inner.current_depth.fetch_sub(1, Ordering::AcqRel);
+ }
+ }
+
+ #[test]
+ fn tracing() {
+ // Create the future outside of the subscriber, as no call to tracing
+ // should be made until the future is polled.
+ let mut struct_impl = Impl(0);
+ let fut = struct_impl.foo(5);
+ let subscriber = TestSubscriber::new();
+ subscriber::with_default(subscriber.clone(), || executor::block_on_simple(fut));
+ // Did we enter bar inside of foo?
+ assert_eq!(subscriber.inner.max_depth.load(Ordering::Acquire), 2);
+ // Have we exited all spans?
+ assert_eq!(subscriber.inner.current_depth.load(Ordering::Acquire), 0);
+ // Did we create only two spans? Note: spans start at 1, hence the -1.
+ assert_eq!(subscriber.inner.max_span_id.load(Ordering::Acquire) - 1, 2);
+ // Was the value recorded at the right depth i.e. in the right function?
+ // If so, was it the expected value?
+ assert_eq!(*subscriber.inner.value.lock().unwrap(), Some(("val", 5, 2)));
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/46
+pub mod issue46 {
+ use async_trait::async_trait;
+
+ macro_rules! implement_commands_workaround {
+ ($tyargs:tt : $ty:tt) => {
+ #[async_trait]
+ pub trait AsyncCommands1: Sized {
+ async fn f<$tyargs: $ty>(&mut self, x: $tyargs) {
+ self.f(x).await
+ }
+ }
+ };
+ }
+
+ implement_commands_workaround!(K: Send);
+
+ macro_rules! implement_commands {
+ ($tyargs:ident : $ty:ident) => {
+ #[async_trait]
+ pub trait AsyncCommands2: Sized {
+ async fn f<$tyargs: $ty>(&mut self, x: $tyargs) {
+ self.f(x).await
+ }
+ }
+ };
+ }
+
+ implement_commands!(K: Send);
+}
+
+// https://github.com/dtolnay/async-trait/issues/53
+pub mod issue53 {
+ use async_trait::async_trait;
+
+ pub struct Unit;
+ pub struct Tuple(u8);
+ pub struct Struct {
+ pub x: u8,
+ }
+
+ #[async_trait]
+ pub trait Trait {
+ async fn method();
+ }
+
+ #[async_trait]
+ impl Trait for Unit {
+ async fn method() {
+ let _ = Self;
+ }
+ }
+
+ #[async_trait]
+ impl Trait for Tuple {
+ async fn method() {
+ let _ = Self(0);
+ }
+ }
+
+ #[async_trait]
+ impl Trait for Struct {
+ async fn method() {
+ let _ = Self { x: 0 };
+ }
+ }
+
+ #[async_trait]
+ impl Trait for std::marker::PhantomData<Struct> {
+ async fn method() {
+ let _ = Self;
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/57
+#[cfg(async_trait_nightly_testing)]
+pub mod issue57 {
+ use crate::executor;
+ use async_trait::async_trait;
+
+ #[async_trait]
+ trait Trait {
+ async fn const_generic<T: Send, const C: usize>(_: [T; C]) {}
+ }
+
+ struct Struct;
+
+ #[async_trait]
+ impl Trait for Struct {
+ async fn const_generic<T: Send, const C: usize>(_: [T; C]) {}
+ }
+
+ #[test]
+ fn test() {
+ let fut = Struct::const_generic([0; 10]);
+ executor::block_on_simple(fut);
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/68
+pub mod issue68 {
+ #[rustversion::since(1.40)] // procedural macros cannot expand to macro definitions in 1.39.
+ #[async_trait::async_trait]
+ pub trait Example {
+ async fn method(&self) {
+ macro_rules! t {
+ () => {{
+ let _: &Self = self;
+ }};
+ }
+ t!();
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/73
+pub mod issue73 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ pub trait Example {
+ const ASSOCIATED: &'static str;
+
+ async fn associated(&self) {
+ println!("Associated:{}", Self::ASSOCIATED);
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/81
+pub mod issue81 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ pub trait Trait {
+ async fn handle(&self);
+ }
+
+ pub enum Enum {
+ Variant,
+ }
+
+ #[async_trait]
+ impl Trait for Enum {
+ async fn handle(&self) {
+ let Enum::Variant = self;
+ let Self::Variant = self;
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/83
+pub mod issue83 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ pub trait Trait {
+ async fn f(&self) {}
+ async fn g(self: &Self) {}
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/85
+pub mod issue85 {
+ #![deny(non_snake_case)]
+
+ use async_trait::async_trait;
+
+ #[async_trait]
+ pub trait Trait {
+ #[allow(non_snake_case)]
+ async fn camelCase();
+ }
+
+ pub struct Struct;
+
+ #[async_trait]
+ impl Trait for Struct {
+ async fn camelCase() {}
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/87
+pub mod issue87 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ pub trait Trait {
+ async fn f(&self);
+ }
+
+ pub enum Tuple {
+ V(),
+ }
+
+ pub enum Struct {
+ V {},
+ }
+
+ #[async_trait]
+ impl Trait for Tuple {
+ async fn f(&self) {
+ let Tuple::V() = self;
+ let Self::V() = self;
+ let _ = Self::V;
+ let _ = Self::V();
+ }
+ }
+
+ #[async_trait]
+ impl Trait for Struct {
+ async fn f(&self) {
+ let Struct::V {} = self;
+ let Self::V {} = self;
+ let _ = Self::V {};
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/89
+pub mod issue89 {
+ #![allow(bare_trait_objects)]
+
+ use async_trait::async_trait;
+
+ #[async_trait]
+ trait Trait {
+ async fn f(&self);
+ }
+
+ #[async_trait]
+ impl Trait for Send + Sync {
+ async fn f(&self) {}
+ }
+
+ #[async_trait]
+ impl Trait for dyn Fn(i8) + Send + Sync {
+ async fn f(&self) {}
+ }
+
+ #[async_trait]
+ impl Trait for (dyn Fn(u8) + Send + Sync) {
+ async fn f(&self) {}
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/92
+pub mod issue92 {
+ use async_trait::async_trait;
+
+ macro_rules! mac {
+ ($($tt:tt)*) => {
+ $($tt)*
+ };
+ }
+
+ pub struct Struct<T> {
+ _x: T,
+ }
+
+ impl<T> Struct<T> {
+ const ASSOCIATED1: &'static str = "1";
+ async fn associated1() {}
+ }
+
+ #[async_trait]
+ pub trait Trait
+ where
+ mac!(Self): Send,
+ {
+ const ASSOCIATED2: &'static str;
+ type Associated2;
+
+ #[allow(path_statements, clippy::no_effect)]
+ async fn associated2(&self) {
+ // trait items
+ mac!(let _: Self::Associated2;);
+ mac!(let _: <Self>::Associated2;);
+ mac!(let _: <Self as Trait>::Associated2;);
+ mac!(Self::ASSOCIATED2;);
+ mac!(<Self>::ASSOCIATED2;);
+ mac!(<Self as Trait>::ASSOCIATED2;);
+ mac!(let _ = Self::associated2(self););
+ mac!(let _ = <Self>::associated2(self););
+ mac!(let _ = <Self as Trait>::associated2(self););
+ }
+ }
+
+ #[async_trait]
+ impl<T: Send + Sync> Trait for Struct<T>
+ where
+ mac!(Self): Send,
+ {
+ const ASSOCIATED2: &'static str = "2";
+ type Associated2 = ();
+
+ #[allow(path_statements, clippy::no_effect)]
+ async fn associated2(&self) {
+ // inherent items
+ mac!(Self::ASSOCIATED1;);
+ mac!(<Self>::ASSOCIATED1;);
+ mac!(let _ = Self::associated1(););
+ mac!(let _ = <Self>::associated1(););
+
+ // trait items
+ mac!(let _: <Self as Trait>::Associated2;);
+ mac!(Self::ASSOCIATED2;);
+ mac!(<Self>::ASSOCIATED2;);
+ mac!(<Self as Trait>::ASSOCIATED2;);
+ mac!(let _ = Self::associated2(self););
+ mac!(let _ = <Self>::associated2(self););
+ mac!(let _ = <Self as Trait>::associated2(self););
+ }
+ }
+
+ pub struct Unit;
+
+ #[async_trait]
+ impl Trait for Unit {
+ const ASSOCIATED2: &'static str = "2";
+ type Associated2 = ();
+
+ async fn associated2(&self) {
+ mac!(let Self: Self = *self;);
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/104
+mod issue104 {
+ use async_trait::async_trait;
+
+ #[async_trait]
+ trait T1 {
+ async fn id(&self) -> i32;
+ }
+
+ macro_rules! impl_t1 {
+ ($ty:ty, $id:expr) => {
+ #[async_trait]
+ impl T1 for $ty {
+ async fn id(&self) -> i32 {
+ $id
+ }
+ }
+ };
+ }
+
+ struct Foo;
+
+ impl_t1!(Foo, 1);
+}
+
+// https://github.com/dtolnay/async-trait/issues/106
+mod issue106 {
+ use async_trait::async_trait;
+ use std::future::Future;
+
+ #[async_trait]
+ pub trait ProcessPool: Send + Sync {
+ type ThreadPool;
+
+ async fn spawn<F, Fut, T>(&self, work: F) -> T
+ where
+ F: FnOnce(&Self::ThreadPool) -> Fut + Send,
+ Fut: Future<Output = T> + 'static;
+ }
+
+ #[async_trait]
+ impl<P: ?Sized> ProcessPool for &P
+ where
+ P: ProcessPool,
+ {
+ type ThreadPool = P::ThreadPool;
+
+ async fn spawn<F, Fut, T>(&self, work: F) -> T
+ where
+ F: FnOnce(&Self::ThreadPool) -> Fut + Send,
+ Fut: Future<Output = T> + 'static,
+ {
+ (**self).spawn(work).await
+ }
+ }
+}
+
+// https://github.com/dtolnay/async-trait/issues/110
+mod issue110 {
+ #![deny(clippy::all)]
+
+ use async_trait::async_trait;
+ use std::marker::PhantomData;
+
+ #[async_trait]
+ pub trait Loader {
+ async fn load(&self, key: &str);
+ }
+
+ pub struct AwsEc2MetadataLoader<'a> {
+ marker: PhantomData<&'a ()>,
+ }
+
+ #[async_trait]
+ impl Loader for AwsEc2MetadataLoader<'_> {
+ async fn load(&self, _key: &str) {}
+ }
+}
diff --git a/tests/ui/bare-trait-object.rs b/tests/ui/bare-trait-object.rs
new file mode 100644
index 0000000..afcd6b4
--- /dev/null
+++ b/tests/ui/bare-trait-object.rs
@@ -0,0 +1,15 @@
+#![deny(bare_trait_objects)]
+
+use async_trait::async_trait;
+
+#[async_trait]
+trait Trait {
+ async fn f(&self);
+}
+
+#[async_trait]
+impl Trait for Send + Sync {
+ async fn f(&self) {}
+}
+
+fn main() {}
diff --git a/tests/ui/bare-trait-object.stderr b/tests/ui/bare-trait-object.stderr
new file mode 100644
index 0000000..98cf679
--- /dev/null
+++ b/tests/ui/bare-trait-object.stderr
@@ -0,0 +1,11 @@
+error: trait objects without an explicit `dyn` are deprecated
+ --> $DIR/bare-trait-object.rs:11:16
+ |
+11 | impl Trait for Send + Sync {
+ | ^^^^^^^^^^^ help: use `dyn`: `dyn Send + Sync`
+ |
+note: the lint level is defined here
+ --> $DIR/bare-trait-object.rs:1:9
+ |
+1 | #![deny(bare_trait_objects)]
+ | ^^^^^^^^^^^^^^^^^^
diff --git a/tests/ui/delimiter-span.rs b/tests/ui/delimiter-span.rs
new file mode 100644
index 0000000..68456fa
--- /dev/null
+++ b/tests/ui/delimiter-span.rs
@@ -0,0 +1,21 @@
+use async_trait::async_trait;
+
+macro_rules! picky {
+ (ident) => {};
+}
+
+#[async_trait]
+trait Trait {
+ async fn method();
+}
+
+struct Struct;
+
+#[async_trait]
+impl Trait for Struct {
+ async fn method() {
+ picky!({ 123 });
+ }
+}
+
+fn main() {}
diff --git a/tests/ui/delimiter-span.stderr b/tests/ui/delimiter-span.stderr
new file mode 100644
index 0000000..e080445
--- /dev/null
+++ b/tests/ui/delimiter-span.stderr
@@ -0,0 +1,8 @@
+error: no rules expected the token `{`
+ --> $DIR/delimiter-span.rs:17:16
+ |
+3 | macro_rules! picky {
+ | ------------------ when calling this macro
+...
+17 | picky!({ 123 });
+ | ^ no rules expected this token in macro call
diff --git a/tests/ui/missing-body.rs b/tests/ui/missing-body.rs
new file mode 100644
index 0000000..f3e1126
--- /dev/null
+++ b/tests/ui/missing-body.rs
@@ -0,0 +1,15 @@
+use async_trait::async_trait;
+
+#[async_trait]
+trait Trait {
+ async fn f(&self);
+}
+
+struct Thing;
+
+#[async_trait]
+impl Trait for Thing {
+ async fn f(&self);
+}
+
+fn main() {}
diff --git a/tests/ui/missing-body.stderr b/tests/ui/missing-body.stderr
new file mode 100644
index 0000000..2d9b09c
--- /dev/null
+++ b/tests/ui/missing-body.stderr
@@ -0,0 +1,7 @@
+error: associated function in `impl` without body
+ --> $DIR/missing-body.rs:12:5
+ |
+12 | async fn f(&self);
+ | ^^^^^^^^^^^^^^^^^-
+ | |
+ | help: provide a definition for the function: `{ <body> }`
diff --git a/tests/ui/must-use.rs b/tests/ui/must-use.rs
new file mode 100644
index 0000000..7ad0d9b
--- /dev/null
+++ b/tests/ui/must-use.rs
@@ -0,0 +1,21 @@
+#![deny(unused_must_use)]
+
+use async_trait::async_trait;
+
+#[async_trait]
+trait Interface {
+ async fn f(&self);
+}
+
+struct Thing;
+
+#[async_trait]
+impl Interface for Thing {
+ async fn f(&self) {}
+}
+
+pub async fn f() {
+ Thing.f();
+}
+
+fn main() {}
diff --git a/tests/ui/must-use.stderr b/tests/ui/must-use.stderr
new file mode 100644
index 0000000..c09a51e
--- /dev/null
+++ b/tests/ui/must-use.stderr
@@ -0,0 +1,11 @@
+error: unused return value of `Interface::f` that must be used
+ --> $DIR/must-use.rs:18:5
+ |
+18 | Thing.f();
+ | ^^^^^^^^^^
+ |
+note: the lint level is defined here
+ --> $DIR/must-use.rs:1:9
+ |
+1 | #![deny(unused_must_use)]
+ | ^^^^^^^^^^^^^^^
diff --git a/tests/ui/self-span.rs b/tests/ui/self-span.rs
new file mode 100644
index 0000000..b01f247
--- /dev/null
+++ b/tests/ui/self-span.rs
@@ -0,0 +1,30 @@
+use async_trait::async_trait;
+
+pub struct S {}
+
+pub enum E {
+ V {},
+}
+
+#[async_trait]
+pub trait Trait {
+ async fn method(self);
+}
+
+#[async_trait]
+impl Trait for S {
+ async fn method(self) {
+ let _: () = self;
+ let _: Self = Self;
+ }
+}
+
+#[async_trait]
+impl Trait for E {
+ async fn method(self) {
+ let _: () = self;
+ let _: Self = Self::V;
+ }
+}
+
+fn main() {}
diff --git a/tests/ui/self-span.stderr b/tests/ui/self-span.stderr
new file mode 100644
index 0000000..f897c01
--- /dev/null
+++ b/tests/ui/self-span.stderr
@@ -0,0 +1,30 @@
+error[E0423]: expected value, found struct `S`
+ --> $DIR/self-span.rs:18:23
+ |
+3 | pub struct S {}
+ | --------------- `S` defined here
+...
+18 | let _: Self = Self;
+ | ^^^^ did you mean `S { /* fields */ }`?
+
+error[E0308]: mismatched types
+ --> $DIR/self-span.rs:17:21
+ |
+17 | let _: () = self;
+ | -- ^^^^ expected `()`, found struct `S`
+ | |
+ | expected due to this
+
+error[E0308]: mismatched types
+ --> $DIR/self-span.rs:25:21
+ |
+25 | let _: () = self;
+ | -- ^^^^ expected `()`, found enum `E`
+ | |
+ | expected due to this
+
+error[E0533]: expected unit struct, unit variant or constant, found struct variant `Self::V`
+ --> $DIR/self-span.rs:26:23
+ |
+26 | let _: Self = Self::V;
+ | ^^^^^^^
diff --git a/tests/ui/send-not-implemented.rs b/tests/ui/send-not-implemented.rs
new file mode 100644
index 0000000..a3e3856
--- /dev/null
+++ b/tests/ui/send-not-implemented.rs
@@ -0,0 +1,15 @@
+use async_trait::async_trait;
+use std::sync::Mutex;
+
+async fn f() {}
+
+#[async_trait]
+trait Test {
+ async fn test(&self) {
+ let mutex = Mutex::new(());
+ let _guard = mutex.lock().unwrap();
+ f().await;
+ }
+}
+
+fn main() {}
diff --git a/tests/ui/send-not-implemented.stderr b/tests/ui/send-not-implemented.stderr
new file mode 100644
index 0000000..2f288f5
--- /dev/null
+++ b/tests/ui/send-not-implemented.stderr
@@ -0,0 +1,22 @@
+error: future cannot be sent between threads safely
+ --> $DIR/send-not-implemented.rs:8:26
+ |
+8 | async fn test(&self) {
+ | __________________________^
+9 | | let mutex = Mutex::new(());
+10 | | let _guard = mutex.lock().unwrap();
+11 | | f().await;
+12 | | }
+ | |_____^ future returned by `__test` is not `Send`
+ |
+ = help: within `impl std::future::Future`, the trait `std::marker::Send` is not implemented for `std::sync::MutexGuard<'_, ()>`
+note: future is not `Send` as this value is used across an await
+ --> $DIR/send-not-implemented.rs:11:9
+ |
+10 | let _guard = mutex.lock().unwrap();
+ | ------ has type `std::sync::MutexGuard<'_, ()>` which is not `Send`
+11 | f().await;
+ | ^^^^^^^^^ await occurs here, with `_guard` maybe used later
+12 | }
+ | - `_guard` is later dropped here
+ = note: required for the cast to the object type `dyn std::future::Future<Output = ()> + std::marker::Send`
diff --git a/tests/ui/unsupported-self.rs b/tests/ui/unsupported-self.rs
new file mode 100644
index 0000000..5868c61
--- /dev/null
+++ b/tests/ui/unsupported-self.rs
@@ -0,0 +1,15 @@
+use async_trait::async_trait;
+
+#[async_trait]
+pub trait Trait {
+ async fn method();
+}
+
+#[async_trait]
+impl Trait for &'static str {
+ async fn method() {
+ let _ = Self;
+ }
+}
+
+fn main() {}
diff --git a/tests/ui/unsupported-self.stderr b/tests/ui/unsupported-self.stderr
new file mode 100644
index 0000000..c1ea955
--- /dev/null
+++ b/tests/ui/unsupported-self.stderr
@@ -0,0 +1,5 @@
+error: Self type of this impl is unsupported in expression position
+ --> $DIR/unsupported-self.rs:11:17
+ |
+11 | let _ = Self;
+ | ^^^^
