Import async-trait 0.1.66upstream/0.1.66upstream

48 files changed, 4129 insertions, 0 deletions

diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..df0cdd6
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,6 @@
+{
+  "git": {
+    "sha1": "9a9b32228707aded43b07a50e8f69f92d15ca7a3"
+  },
+  "path_in_vcs": ""
+}
\ No newline at end of file
diff --git a/.clippy.toml b/.clippy.toml
new file mode 100644
index 0000000..21a08b0
--- /dev/null
+++ b/.clippy.toml
@@ -0,0 +1 @@
+msrv = "1.39.0"
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..51fdd49
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,84 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+  schedule: [cron: "40 1 * * *"]
+
+permissions:
+  contents: read
+
+env:
+  RUSTFLAGS: -Dwarnings
+
+jobs:
+  pre_ci:
+    uses: dtolnay/.github/.github/workflows/pre_ci.yml@master
+
+  test:
+    name: Rust ${{matrix.rust}}
+    needs: pre_ci
+    if: needs.pre_ci.outputs.continue
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        rust: [nightly, beta, stable, 1.56.0]
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{matrix.rust}}
+      - name: Enable type layout randomization
+        run: echo RUSTFLAGS=${RUSTFLAGS}\ -Zrandomize-layout >> $GITHUB_ENV
+        if: matrix.rust == 'nightly'
+      - name: Enable nightly-only tests
+        run: echo RUSTFLAGS=${RUSTFLAGS}\ --cfg=async_trait_nightly_testing >> $GITHUB_ENV
+        if: matrix.rust == 'nightly'
+      - run: cargo test
+
+  msrv:
+    name: Rust 1.39.0
+    needs: pre_ci
+    if: needs.pre_ci.outputs.continue
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@1.39.0
+      - run: cargo check
+
+  clippy:
+    name: Clippy
+    runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request'
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@clippy
+      - run: cargo clippy --tests -- -Dclippy::all -Dclippy::pedantic
+
+  miri:
+    name: Miri
+    needs: pre_ci
+    if: needs.pre_ci.outputs.continue
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@miri
+      - run: cargo miri test
+        env:
+          MIRIFLAGS: -Zmiri-strict-provenance
+
+  outdated:
+    name: Outdated
+    runs-on: ubuntu-latest
+    if: github.event_name != 'pull_request'
+    timeout-minutes: 45
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/install@cargo-outdated
+      - run: cargo outdated --workspace --exit-code 1
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/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..c29ebe2
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,62 @@
+# 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 are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+rust-version = "1.39"
+name = "async-trait"
+version = "0.1.66"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+description = "Type erasure for async trait methods"
+documentation = "https://docs.rs/async-trait"
+readme = "README.md"
+keywords = ["async"]
+categories = [
+    "asynchronous",
+    "no-std",
+]
+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 = "1.0.96"
+features = [
+    "full",
+    "visit-mut",
+]
+
+[dev-dependencies.futures]
+version = "0.3"
+
+[dev-dependencies.rustversion]
+version = "1.0"
+
+[dev-dependencies.tracing]
+version = "0.1.14"
+
+[dev-dependencies.tracing-attributes]
+version = "0.1.14"
+
+[dev-dependencies.trybuild]
+version = "1.0.49"
+features = ["diff"]
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..152ec78
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,30 @@
+[package]
+name = "async-trait"
+version = "0.1.66"
+authors = ["David Tolnay <dtolnay@gmail.com>"]
+categories = ["asynchronous", "no-std"]
+description = "Type erasure for async trait methods"
+documentation = "https://docs.rs/async-trait"
+edition = "2018"
+keywords = ["async"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/dtolnay/async-trait"
+rust-version = "1.39"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = { version = "1.0.96", features = ["full", "visit-mut"] }
+
+[dev-dependencies]
+futures = "0.3"
+rustversion = "1.0"
+tracing = "0.1.14"
+tracing-attributes = "0.1.14"
+trybuild = { version = "1.0.49", features = ["diff"] }
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..1b5ec8b
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,176 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
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+END OF TERMS AND CONDITIONS
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
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diff --git a/README.md b/README.md
new file mode 100644
index 0000000..39e368b
--- /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&logo=docs.rs" height="20">](https://docs.rs/async-trait)
+[<img alt="build status" src="https://img.shields.io/github/actions/workflow/status/dtolnay/async-trait/ci.yml?branch=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.
+
+- &#128077;&ensp;Self by value, by reference, by mut reference, or no self;
+- &#128077;&ensp;Any number of arguments, any return value;
+- &#128077;&ensp;Generic type parameters and lifetime parameters;
+- &#128077;&ensp;Associated types;
+- &#128077;&ensp;Having async and non-async functions in the same trait;
+- &#128077;&ensp;Default implementations provided by the trait;
+- &#128077;&ensp;Elided lifetimes;
+- &#128077;&ensp;Dyn-capable traits.
+
+<br>
+
+## Explanation
+
+Async fns get transformed into methods that return `Pin<Box<dyn Future + Send +
+'async_trait>>` 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_trait>(
+        &'async_trait self,
+    ) -> Pin<Box<dyn std::future::Future<Output = ()> + Send + 'async_trait>>
+    where
+        Self: Sync + 'async_trait,
+    {
+        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 implementations)
+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/build.rs b/build.rs
new file mode 100644
index 0000000..d7f6b15
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,31 @@
+use std::env;
+use std::process::Command;
+use std::str;
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+
+    let compiler = match rustc_minor_version() {
+        Some(compiler) => compiler,
+        None => return,
+    };
+
+    if compiler < 45 {
+        println!("cargo:rustc-cfg=no_span_mixed_site");
+    }
+
+    if compiler < 47 {
+        println!("cargo:rustc-cfg=self_span_hack");
+    }
+}
+
+fn rustc_minor_version() -> Option<u32> {
+    let rustc = env::var_os("RUSTC")?;
+    let output = Command::new(rustc).arg("--version").output().ok()?;
+    let version = str::from_utf8(&output.stdout).ok()?;
+    let mut pieces = version.split('.');
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+    pieces.next()?.parse().ok()
+}
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/bound.rs b/src/bound.rs
new file mode 100644
index 0000000..50182f6
--- /dev/null
+++ b/src/bound.rs
@@ -0,0 +1,48 @@
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::quote_spanned;
+use syn::punctuated::Punctuated;
+use syn::{Token, TypeParamBound};
+
+pub type Supertraits = Punctuated<TypeParamBound, Token![+]>;
+
+pub enum InferredBound {
+    Send,
+    Sync,
+}
+
+pub fn has_bound(supertraits: &Supertraits, bound: &InferredBound) -> bool {
+    for supertrait in supertraits {
+        if let TypeParamBound::Trait(supertrait) = supertrait {
+            if supertrait.path.is_ident(bound)
+                || supertrait.path.segments.len() == 3
+                    && (supertrait.path.segments[0].ident == "std"
+                        || supertrait.path.segments[0].ident == "core")
+                    && supertrait.path.segments[1].ident == "marker"
+                    && supertrait.path.segments[2].ident == *bound
+            {
+                return true;
+            }
+        }
+    }
+    false
+}
+
+impl InferredBound {
+    fn as_str(&self) -> &str {
+        match self {
+            InferredBound::Send => "Send",
+            InferredBound::Sync => "Sync",
+        }
+    }
+
+    pub fn spanned_path(&self, span: Span) -> TokenStream {
+        let ident = Ident::new(self.as_str(), span);
+        quote_spanned!(span=> ::core::marker::#ident)
+    }
+}
+
+impl PartialEq<InferredBound> for Ident {
+    fn eq(&self, bound: &InferredBound) -> bool {
+        self == bound.as_str()
+    }
+}
diff --git a/src/expand.rs b/src/expand.rs
new file mode 100644
index 0000000..2499177
--- /dev/null
+++ b/src/expand.rs
@@ -0,0 +1,495 @@
+use crate::bound::{has_bound, InferredBound, Supertraits};
+use crate::lifetime::{AddLifetimeToImplTrait, CollectLifetimes};
+use crate::parse::Item;
+use crate::receiver::{has_self_in_block, has_self_in_sig, mut_pat, ReplaceSelf};
+use proc_macro2::{Span, TokenStream};
+use quote::{format_ident, quote, quote_spanned, ToTokens};
+use std::collections::BTreeSet as Set;
+use std::mem;
+use syn::punctuated::Punctuated;
+use syn::visit_mut::{self, VisitMut};
+use syn::{
+    parse_quote, parse_quote_spanned, Attribute, Block, FnArg, GenericArgument, GenericParam,
+    Generics, Ident, ImplItem, Lifetime, LifetimeDef, Pat, PatIdent, PathArguments, Receiver,
+    ReturnType, Signature, Stmt, Token, TraitItem, Type, TypePath, 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 {
+        generics: &'a Generics,
+        supertraits: &'a Supertraits,
+    },
+    Impl {
+        impl_generics: &'a Generics,
+        associated_type_impl_traits: &'a Set<Ident>,
+    },
+}
+
+impl Context<'_> {
+    fn lifetimes<'a>(&'a self, used: &'a [Lifetime]) -> impl Iterator<Item = &'a LifetimeDef> {
+        let generics = match self {
+            Context::Trait { generics, .. } => generics,
+            Context::Impl { impl_generics, .. } => impl_generics,
+        };
+        generics.params.iter().filter_map(move |param| {
+            if let GenericParam::Lifetime(param) = param {
+                if used.contains(&param.lifetime) {
+                    return Some(param);
+                }
+            }
+            None
+        })
+    }
+}
+
+pub fn expand(input: &mut Item, is_local: bool) {
+    match input {
+        Item::Trait(input) => {
+            let context = Context::Trait {
+                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);
+                        method.attrs.push(parse_quote!(#[must_use]));
+                        if let Some(block) = block {
+                            has_self |= has_self_in_block(block);
+                            transform_block(context, sig, block);
+                            method.attrs.push(lint_suppress_with_body());
+                        } else {
+                            method.attrs.push(lint_suppress_without_body());
+                        }
+                        let has_default = method.default.is_some();
+                        transform_sig(context, sig, has_self, has_default, is_local);
+                    }
+                }
+            }
+        }
+        Item::Impl(input) => {
+            let mut associated_type_impl_traits = Set::new();
+            for inner in &input.items {
+                if let ImplItem::Type(assoc) = inner {
+                    if let Type::ImplTrait(_) = assoc.ty {
+                        associated_type_impl_traits.insert(assoc.ident.clone());
+                    }
+                }
+            }
+
+            let context = Context::Impl {
+                impl_generics: &input.generics,
+                associated_type_impl_traits: &associated_type_impl_traits,
+            };
+            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);
+                        transform_sig(context, sig, has_self, false, is_local);
+                        method.attrs.push(lint_suppress_with_body());
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn lint_suppress_with_body() -> Attribute {
+    parse_quote! {
+        #[allow(
+            clippy::async_yields_async,
+            clippy::let_unit_value,
+            clippy::no_effect_underscore_binding,
+            clippy::shadow_same,
+            clippy::type_complexity,
+            clippy::type_repetition_in_bounds,
+            clippy::used_underscore_binding
+        )]
+    }
+}
+
+fn lint_suppress_without_body() -> Attribute {
+    parse_quote! {
+        #[allow(
+            clippy::type_complexity,
+            clippy::type_repetition_in_bounds
+        )]
+    }
+}
+
+// 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,
+) {
+    let default_span = sig.asyncness.take().unwrap().span;
+    sig.fn_token.span = default_span;
+
+    let (ret_arrow, ret) = match &sig.output {
+        ReturnType::Default => (Token![->](default_span), quote_spanned!(default_span=> ())),
+        ReturnType::Type(arrow, ret) => (*arrow, quote!(#ret)),
+    };
+
+    let mut lifetimes = CollectLifetimes::new();
+    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),
+        }
+    }
+
+    for param in &mut sig.generics.params {
+        match param {
+            GenericParam::Type(param) => {
+                let param_name = &param.ident;
+                let span = match param.colon_token.take() {
+                    Some(colon_token) => colon_token.span,
+                    None => param_name.span(),
+                };
+                let bounds = mem::replace(&mut param.bounds, Punctuated::new());
+                where_clause_or_default(&mut sig.generics.where_clause)
+                    .predicates
+                    .push(parse_quote_spanned!(span=> #param_name: 'async_trait + #bounds));
+            }
+            GenericParam::Lifetime(param) => {
+                let param_name = &param.lifetime;
+                let span = match param.colon_token.take() {
+                    Some(colon_token) => colon_token.span,
+                    None => param_name.span(),
+                };
+                let bounds = mem::replace(&mut param.bounds, Punctuated::new());
+                where_clause_or_default(&mut sig.generics.where_clause)
+                    .predicates
+                    .push(parse_quote_spanned!(span=> #param: 'async_trait + #bounds));
+            }
+            GenericParam::Const(_) => {}
+        }
+    }
+
+    for param in context.lifetimes(&lifetimes.explicit) {
+        let param = &param.lifetime;
+        let span = param.span();
+        where_clause_or_default(&mut sig.generics.where_clause)
+            .predicates
+            .push(parse_quote_spanned!(span=> #param: 'async_trait));
+    }
+
+    if sig.generics.lt_token.is_none() {
+        sig.generics.lt_token = Some(Token![<](sig.ident.span()));
+    }
+    if sig.generics.gt_token.is_none() {
+        sig.generics.gt_token = Some(Token![>](sig.paren_token.span));
+    }
+
+    for elided in lifetimes.elided {
+        sig.generics.params.push(parse_quote!(#elided));
+        where_clause_or_default(&mut sig.generics.where_clause)
+            .predicates
+            .push(parse_quote_spanned!(elided.span()=> #elided: 'async_trait));
+    }
+
+    sig.generics
+        .params
+        .push(parse_quote_spanned!(default_span=> 'async_trait));
+
+    if has_self {
+        let bounds: &[InferredBound] = match sig.inputs.iter().next() {
+            Some(FnArg::Receiver(Receiver {
+                reference: Some(_),
+                mutability: None,
+                ..
+            })) => &[InferredBound::Sync],
+            Some(FnArg::Typed(arg))
+                if match arg.pat.as_ref() {
+                    Pat::Ident(pat) => pat.ident == "self",
+                    _ => false,
+                } =>
+            {
+                match arg.ty.as_ref() {
+                    // self: &Self
+                    Type::Reference(ty) if ty.mutability.is_none() => &[InferredBound::Sync],
+                    // self: Arc<Self>
+                    Type::Path(ty)
+                        if {
+                            let segment = ty.path.segments.last().unwrap();
+                            segment.ident == "Arc"
+                                && match &segment.arguments {
+                                    PathArguments::AngleBracketed(arguments) => {
+                                        arguments.args.len() == 1
+                                            && match &arguments.args[0] {
+                                                GenericArgument::Type(Type::Path(arg)) => {
+                                                    arg.path.is_ident("Self")
+                                                }
+                                                _ => false,
+                                            }
+                                    }
+                                    _ => false,
+                                }
+                        } =>
+                    {
+                        &[InferredBound::Sync, InferredBound::Send]
+                    }
+                    _ => &[InferredBound::Send],
+                }
+            }
+            _ => &[InferredBound::Send],
+        };
+
+        let bounds = bounds.iter().filter_map(|bound| {
+            let assume_bound = match context {
+                Context::Trait { supertraits, .. } => !has_default || has_bound(supertraits, bound),
+                Context::Impl { .. } => true,
+            };
+            if assume_bound || is_local {
+                None
+            } else {
+                Some(bound.spanned_path(default_span))
+            }
+        });
+
+        where_clause_or_default(&mut sig.generics.where_clause)
+            .predicates
+            .push(parse_quote_spanned! {default_span=>
+                Self: #(#bounds +)* '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) => {
+                let type_is_reference = match *arg.ty {
+                    Type::Reference(_) => true,
+                    _ => false,
+                };
+                if let Pat::Ident(pat) = &mut *arg.pat {
+                    if pat.ident == "self" || !type_is_reference {
+                        pat.by_ref = None;
+                        pat.mutability = None;
+                    }
+                } else if !type_is_reference {
+                    let positional = positional_arg(i, &arg.pat);
+                    let m = mut_pat(&mut arg.pat);
+                    arg.pat = parse_quote!(#m #positional);
+                }
+                AddLifetimeToImplTrait.visit_type_mut(&mut arg.ty);
+            }
+        }
+    }
+
+    let bounds = if is_local {
+        quote_spanned!(default_span=> 'async_trait)
+    } else {
+        quote_spanned!(default_span=> ::core::marker::Send + 'async_trait)
+    };
+    sig.output = parse_quote_spanned! {default_span=>
+        #ret_arrow ::core::pin::Pin<Box<
+            dyn ::core::future::Future<Output = #ret> + #bounds
+        >>
+    };
+}
+
+// Input:
+//     async fn f<T>(&self, x: &T, (a, b): (A, B)) -> Ret {
+//         self + x + a + b
+//     }
+//
+// Output:
+//     Box::pin(async move {
+//         let ___ret: Ret = {
+//             let __self = self;
+//             let x = x;
+//             let (a, b) = __arg1;
+//
+//             __self + x + a + b
+//         };
+//
+//         ___ret
+//     })
+fn transform_block(context: Context, sig: &mut Signature, block: &mut Block) {
+    if let Some(Stmt::Item(syn::Item::Verbatim(item))) = block.stmts.first() {
+        if block.stmts.len() == 1 && item.to_string() == ";" {
+            return;
+        }
+    }
+
+    let mut self_span = None;
+    let decls = sig
+        .inputs
+        .iter()
+        .enumerate()
+        .map(|(i, arg)| match arg {
+            FnArg::Receiver(Receiver {
+                self_token,
+                mutability,
+                ..
+            }) => {
+                let ident = Ident::new("__self", self_token.span);
+                self_span = Some(self_token.span);
+                quote!(let #mutability #ident = #self_token;)
+            }
+            FnArg::Typed(arg) => {
+                // If there is a #[cfg(...)] attribute that selectively enables
+                // the parameter, forward it to the variable.
+                //
+                // This is currently not applied to the `self` parameter.
+                let attrs = arg.attrs.iter().filter(|attr| attr.path.is_ident("cfg"));
+
+                if let Pat::Ident(PatIdent {
+                    ident, mutability, ..
+                }) = &*arg.pat
+                {
+                    if ident == "self" {
+                        self_span = Some(ident.span());
+                        let prefixed = Ident::new("__self", ident.span());
+                        quote!(let #mutability #prefixed = #ident;)
+                    } else if let Type::Reference(_) = *arg.ty {
+                        quote!()
+                    } else {
+                        quote! {
+                            #(#attrs)*
+                            let #mutability #ident = #ident;
+                        }
+                    }
+                } else if let Type::Reference(_) = *arg.ty {
+                    quote!()
+                } else {
+                    let pat = &arg.pat;
+                    let ident = positional_arg(i, pat);
+                    if let Pat::Wild(_) = **pat {
+                        quote! {
+                            #(#attrs)*
+                            let #ident = #ident;
+                        }
+                    } else {
+                        quote! {
+                            #(#attrs)*
+                            let #pat = {
+                                let #ident = #ident;
+                                #ident
+                            };
+                        }
+                    }
+                }
+            }
+        })
+        .collect::<Vec<_>>();
+
+    if let Some(span) = self_span {
+        let mut replace_self = ReplaceSelf(span);
+        replace_self.visit_block_mut(block);
+    }
+
+    let stmts = &block.stmts;
+    let let_ret = match &mut sig.output {
+        ReturnType::Default => quote_spanned! {block.brace_token.span=>
+            #(#decls)*
+            let _: () = { #(#stmts)* };
+        },
+        ReturnType::Type(_, ret) => {
+            if contains_associated_type_impl_trait(context, ret) {
+                if decls.is_empty() {
+                    quote!(#(#stmts)*)
+                } else {
+                    quote!(#(#decls)* { #(#stmts)* })
+                }
+            } else {
+                quote_spanned! {block.brace_token.span=>
+                    if let ::core::option::Option::Some(__ret) = ::core::option::Option::None::<#ret> {
+                        return __ret;
+                    }
+                    #(#decls)*
+                    let __ret: #ret = { #(#stmts)* };
+                    #[allow(unreachable_code)]
+                    __ret
+                }
+            }
+        }
+    };
+    let box_pin = quote_spanned!(block.brace_token.span=>
+        Box::pin(async move { #let_ret })
+    );
+    block.stmts = parse_quote!(#box_pin);
+}
+
+fn positional_arg(i: usize, pat: &Pat) -> Ident {
+    let span: Span = syn::spanned::Spanned::span(pat);
+    #[cfg(not(no_span_mixed_site))]
+    let span = span.resolved_at(Span::mixed_site());
+    format_ident!("__arg{}", i, span = span)
+}
+
+fn contains_associated_type_impl_trait(context: Context, ret: &mut Type) -> bool {
+    struct AssociatedTypeImplTraits<'a> {
+        set: &'a Set<Ident>,
+        contains: bool,
+    }
+
+    impl<'a> VisitMut for AssociatedTypeImplTraits<'a> {
+        fn visit_type_path_mut(&mut self, ty: &mut TypePath) {
+            if ty.qself.is_none()
+                && ty.path.segments.len() == 2
+                && ty.path.segments[0].ident == "Self"
+                && self.set.contains(&ty.path.segments[1].ident)
+            {
+                self.contains = true;
+            }
+            visit_mut::visit_type_path_mut(self, ty);
+        }
+    }
+
+    match context {
+        Context::Trait { .. } => false,
+        Context::Impl {
+            associated_type_impl_traits,
+            ..
+        } => {
+            let mut visit = AssociatedTypeImplTraits {
+                set: associated_type_impl_traits,
+                contains: false,
+            };
+            visit.visit_type_mut(ret);
+            visit.contains
+        }
+    }
+}
+
+fn where_clause_or_default(clause: &mut Option<WhereClause>) -> &mut WhereClause {
+    clause.get_or_insert_with(|| WhereClause {
+        where_token: Default::default(),
+        predicates: Punctuated::new(),
+    })
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..b973640
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,341 @@
+//! [![github]](https://github.com/dtolnay/async-trait)&ensp;[![crates-io]](https://crates.io/crates/async-trait)&ensp;[![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&logo=docs.rs
+//!
+//! <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.
+//!
+//! > &#9745;&emsp;Self by value, by reference, by mut reference, or no self;<br>
+//! > &#9745;&emsp;Any number of arguments, any return value;<br>
+//! > &#9745;&emsp;Generic type parameters and lifetime parameters;<br>
+//! > &#9745;&emsp;Associated types;<br>
+//! > &#9745;&emsp;Having async and non-async functions in the same trait;<br>
+//! > &#9745;&emsp;Default implementations provided by the trait;<br>
+//! > &#9745;&emsp;Elided lifetimes;<br>
+//! > &#9745;&emsp;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 implementations) 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;
+//! ```
+
+#![doc(html_root_url = "https://docs.rs/async-trait/0.1.66")]
+#![allow(
+    clippy::default_trait_access,
+    clippy::doc_markdown,
+    clippy::explicit_auto_deref,
+    clippy::if_not_else,
+    clippy::items_after_statements,
+    clippy::module_name_repetitions,
+    clippy::shadow_unrelated,
+    clippy::similar_names,
+    clippy::too_many_lines
+)]
+
+extern crate proc_macro;
+
+mod args;
+mod bound;
+mod expand;
+mod lifetime;
+mod parse;
+mod receiver;
+
+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..1e5a658
--- /dev/null
+++ b/src/lifetime.rs
@@ -0,0 +1,110 @@
+use proc_macro2::{Span, TokenStream};
+use std::mem;
+use syn::visit_mut::{self, VisitMut};
+use syn::{
+    parse_quote_spanned, token, Expr, GenericArgument, Lifetime, Receiver, ReturnType, Token, Type,
+    TypeBareFn, TypeImplTrait, TypeParen, TypePtr, TypeReference,
+};
+
+pub struct CollectLifetimes {
+    pub elided: Vec<Lifetime>,
+    pub explicit: Vec<Lifetime>,
+}
+
+impl CollectLifetimes {
+    pub fn new() -> Self {
+        CollectLifetimes {
+            elided: Vec::new(),
+            explicit: Vec::new(),
+        }
+    }
+
+    fn visit_opt_lifetime(&mut self, reference: Token![&], lifetime: &mut Option<Lifetime>) {
+        match lifetime {
+            None => *lifetime = Some(self.next_lifetime(reference.span)),
+            Some(lifetime) => self.visit_lifetime(lifetime),
+        }
+    }
+
+    fn visit_lifetime(&mut self, lifetime: &mut Lifetime) {
+        if lifetime.ident == "_" {
+            *lifetime = self.next_lifetime(lifetime.span());
+        } else {
+            self.explicit.push(lifetime.clone());
+        }
+    }
+
+    fn next_lifetime(&mut self, span: Span) -> Lifetime {
+        let name = format!("'life{}", self.elided.len());
+        let life = Lifetime::new(&name, span);
+        self.elided.push(life.clone());
+        life
+    }
+}
+
+impl VisitMut for CollectLifetimes {
+    fn visit_receiver_mut(&mut self, arg: &mut Receiver) {
+        if let Some((reference, lifetime)) = &mut arg.reference {
+            self.visit_opt_lifetime(*reference, lifetime);
+        }
+    }
+
+    fn visit_type_reference_mut(&mut self, ty: &mut TypeReference) {
+        self.visit_opt_lifetime(ty.and_token, &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);
+    }
+}
+
+pub struct AddLifetimeToImplTrait;
+
+impl VisitMut for AddLifetimeToImplTrait {
+    fn visit_type_impl_trait_mut(&mut self, ty: &mut TypeImplTrait) {
+        let span = ty.impl_token.span;
+        let lifetime = parse_quote_spanned!(span=> 'async_trait);
+        ty.bounds.insert(0, lifetime);
+        if let Some(punct) = ty.bounds.pairs_mut().next().unwrap().punct_mut() {
+            punct.span = span;
+        }
+        visit_mut::visit_type_impl_trait_mut(self, ty);
+    }
+
+    fn visit_type_reference_mut(&mut self, ty: &mut TypeReference) {
+        parenthesize_impl_trait(&mut ty.elem, ty.and_token.span);
+        visit_mut::visit_type_reference_mut(self, ty);
+    }
+
+    fn visit_type_ptr_mut(&mut self, ty: &mut TypePtr) {
+        parenthesize_impl_trait(&mut ty.elem, ty.star_token.span);
+        visit_mut::visit_type_ptr_mut(self, ty);
+    }
+
+    fn visit_type_bare_fn_mut(&mut self, ty: &mut TypeBareFn) {
+        if let ReturnType::Type(arrow, return_type) = &mut ty.output {
+            parenthesize_impl_trait(return_type, arrow.spans[0]);
+        }
+        visit_mut::visit_type_bare_fn_mut(self, ty);
+    }
+
+    fn visit_expr_mut(&mut self, _e: &mut Expr) {
+        // Do not recurse into impl Traits inside of an array length expression.
+        //
+        //    fn outer(arg: [u8; { fn inner(_: impl Trait) {}; 0 }]);
+    }
+}
+
+fn parenthesize_impl_trait(elem: &mut Type, paren_span: Span) {
+    if let Type::ImplTrait(_) = *elem {
+        let placeholder = Type::Verbatim(TokenStream::new());
+        *elem = Type::Paren(TypeParen {
+            paren_token: token::Paren(paren_span),
+            elem: Box::new(mem::replace(elem, placeholder)),
+        });
+    }
+}
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..2230db6
--- /dev/null
+++ b/src/receiver.rs
@@ -0,0 +1,179 @@
+use proc_macro2::{Group, Span, TokenStream, TokenTree};
+use std::iter::FromIterator;
+use syn::visit_mut::{self, VisitMut};
+use syn::{
+    Block, ExprPath, Ident, Item, Macro, Pat, PatIdent, PatPath, Path, Receiver, Signature, Token,
+    TypePath,
+};
+
+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_block(block: &mut Block) -> bool {
+    let mut visitor = HasSelf(false);
+    visitor.visit_block_mut(block);
+    visitor.0
+}
+
+fn has_self_in_token_stream(tokens: TokenStream) -> bool {
+    tokens.into_iter().any(|tt| match tt {
+        TokenTree::Ident(ident) => ident == "Self",
+        TokenTree::Group(group) => has_self_in_token_stream(group.stream()),
+        _ => false,
+    })
+}
+
+pub fn mut_pat(pat: &mut Pat) -> Option<Token![mut]> {
+    let mut visitor = HasMutPat(None);
+    visitor.visit_pat_mut(pat);
+    visitor.0
+}
+
+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,
+    })
+}
+
+struct HasMutPat(Option<Token![mut]>);
+
+impl VisitMut for HasMutPat {
+    fn visit_pat_ident_mut(&mut self, i: &mut PatIdent) {
+        if let Some(m) = i.mutability {
+            self.0 = Some(m);
+        } else {
+            visit_mut::visit_pat_ident_mut(self, i);
+        }
+    }
+}
+
+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.
+    }
+
+    fn visit_macro_mut(&mut self, mac: &mut Macro) {
+        if !contains_fn(mac.tokens.clone()) {
+            self.0 |= has_self_in_token_stream(mac.tokens.clone());
+        }
+    }
+}
+
+pub struct ReplaceSelf(pub Span);
+
+impl ReplaceSelf {
+    #[cfg_attr(not(self_span_hack), allow(clippy::unused_self))]
+    fn prepend_underscore_to_self(&self, ident: &mut Ident) -> bool {
+        let modified = ident == "self";
+        if modified {
+            *ident = Ident::new("__self", ident.span());
+            #[cfg(self_span_hack)]
+            ident.set_span(self.0);
+        }
+        modified
+    }
+
+    fn visit_token_stream(&mut self, tokens: &mut TokenStream) -> bool {
+        let mut out = Vec::new();
+        let mut modified = false;
+        visit_token_stream_impl(self, tokens.clone(), &mut modified, &mut out);
+        if modified {
+            *tokens = TokenStream::from_iter(out);
+        }
+        return modified;
+
+        fn visit_token_stream_impl(
+            visitor: &mut ReplaceSelf,
+            tokens: TokenStream,
+            modified: &mut bool,
+            out: &mut Vec<TokenTree>,
+        ) {
+            for tt in tokens {
+                match tt {
+                    TokenTree::Ident(mut ident) => {
+                        *modified |= visitor.prepend_underscore_to_self(&mut ident);
+                        out.push(TokenTree::Ident(ident));
+                    }
+                    TokenTree::Group(group) => {
+                        let mut content = group.stream();
+                        *modified |= visitor.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),
+                }
+            }
+        }
+    }
+}
+
+impl VisitMut for ReplaceSelf {
+    fn visit_ident_mut(&mut self, i: &mut Ident) {
+        self.prepend_underscore_to_self(i);
+    }
+
+    fn visit_path_mut(&mut self, p: &mut Path) {
+        if p.segments.len() == 1 {
+            // Replace `self`, but not `self::function`.
+            self.visit_ident_mut(&mut p.segments[0].ident);
+        }
+        for segment in &mut p.segments {
+            self.visit_path_arguments_mut(&mut segment.arguments);
+        }
+    }
+
+    fn visit_item_mut(&mut self, i: &mut Item) {
+        // Visit `macro_rules!` because locally defined macros can refer to
+        // `self`.
+        //
+        // Visit `futures::select` and similar select macros, which commonly
+        // appear syntactically like an item despite expanding to an expression.
+        //
+        // Otherwise, do not recurse into nested items.
+        if let Item::Macro(i) = i {
+            if i.mac.path.is_ident("macro_rules")
+                || i.mac.path.segments.last().unwrap().ident == "select"
+            {
+                self.visit_macro_mut(&mut i.mac);
+            }
+        }
+    }
+
+    fn visit_macro_mut(&mut self, mac: &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(mac.tokens.clone()) {
+            self.visit_token_stream(&mut mac.tokens);
+        }
+    }
+}
diff --git a/tests/compiletest.rs b/tests/compiletest.rs
new file mode 100644
index 0000000..7974a62
--- /dev/null
+++ b/tests/compiletest.rs
@@ -0,0 +1,7 @@
+#[rustversion::attr(not(nightly), ignore)]
+#[cfg_attr(miri, 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..912fb79
--- /dev/null
+++ b/tests/executor/mod.rs
@@ -0,0 +1,36 @@
+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).
+#[allow(clippy::missing_panics_doc)]
+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..4fc46f0
--- /dev/null
+++ b/tests/test.rs
@@ -0,0 +1,1606 @@
+#![cfg_attr(
+    async_trait_nightly_testing,
+    feature(min_specialization, type_alias_impl_trait)
+)]
+#![deny(rust_2021_compatibility)]
+#![allow(
+    clippy::let_underscore_untyped,
+    clippy::let_unit_value,
+    clippy::missing_panics_doc,
+    clippy::missing_safety_doc,
+    clippy::needless_return,
+    clippy::trivially_copy_pass_by_ref,
+    clippy::unused_async
+)]
+
+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 {}
+
+pub async fn test_can_destruct() {
+    #[async_trait]
+    trait CanDestruct {
+        async fn f(&self, foos: (u8, u8, u8, u8));
+    }
+
+    #[async_trait]
+    impl CanDestruct for Struct {
+        async fn f(&self, (a, ref mut b, ref c, d): (u8, u8, u8, u8)) {
+            let _a: u8 = a;
+            let _b: &mut u8 = b;
+            let _c: &u8 = c;
+            let _d: u8 = d;
+        }
+    }
+}
+
+pub async fn test_self_in_macro() {
+    #[async_trait]
+    trait Trait {
+        async fn a(self);
+        async fn b(&mut self);
+        async fn c(&self);
+    }
+
+    #[async_trait]
+    impl Trait for String {
+        async fn a(self) {
+            println!("{}", self);
+        }
+        async fn b(&mut self) {
+            println!("{}", self);
+        }
+        async fn c(&self) {
+            println!("{}", self);
+        }
+    }
+}
+
+pub async fn test_inference() {
+    #[async_trait]
+    pub trait Trait {
+        async fn f() -> Box<dyn Iterator<Item = ()>> {
+            Box::new(std::iter::empty())
+        }
+    }
+}
+
+pub async fn test_internal_items() {
+    #[async_trait]
+    #[allow(dead_code, clippy::items_after_statements)]
+    pub trait Trait: Sized {
+        async fn f(self) {
+            struct Struct;
+
+            impl Struct {
+                fn f(self) {
+                    let _ = self;
+                }
+            }
+        }
+    }
+}
+
+pub async fn test_unimplemented() {
+    #[async_trait]
+    pub trait Trait {
+        async fn f() {
+            unimplemented!()
+        }
+    }
+}
+
+// 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]
+    #[cfg_attr(miri, ignore)] // https://github.com/matklad/once_cell/pull/185
+    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 {
+    #![allow(clippy::needless_arbitrary_self_type)]
+
+    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::let_underscore_future, 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::let_underscore_future, 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/92#issuecomment-683370136
+pub mod issue92_2 {
+    use async_trait::async_trait;
+
+    macro_rules! mac {
+        ($($tt:tt)*) => {
+            $($tt)*
+        };
+    }
+
+    pub trait Trait1 {
+        fn func1();
+    }
+
+    #[async_trait]
+    pub trait Trait2: Trait1 {
+        async fn func2() {
+            mac!(Self::func1());
+
+            macro_rules! mac2 {
+                ($($tt:tt)*) => {
+                    Self::func1();
+                };
+            }
+            mac2!();
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/104
+pub 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
+pub 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> ProcessPool for &P
+    where
+        P: ?Sized + 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
+pub mod issue110 {
+    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) {}
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/120
+pub mod issue120 {
+    #![deny(clippy::trivially_copy_pass_by_ref)]
+
+    use async_trait::async_trait;
+
+    #[async_trait]
+    trait Trait {
+        async fn f(&self);
+    }
+
+    #[async_trait]
+    impl Trait for () {
+        async fn f(&self) {}
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/123
+pub mod issue123 {
+    use async_trait::async_trait;
+
+    #[async_trait]
+    trait Trait<T = ()> {
+        async fn f(&self) -> &str
+        where
+            T: 'async_trait,
+        {
+            "default"
+        }
+    }
+
+    #[async_trait]
+    impl<T> Trait<T> for () {}
+}
+
+// https://github.com/dtolnay/async-trait/issues/129
+pub mod issue129 {
+    use async_trait::async_trait;
+
+    #[async_trait]
+    pub trait TestTrait {
+        async fn a(_b: u8, c: u8) -> u8 {
+            c
+        }
+    }
+
+    pub struct TestStruct;
+
+    #[async_trait]
+    impl TestTrait for TestStruct {
+        async fn a(_b: u8, c: u8) -> u8 {
+            c
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/134
+#[cfg(async_trait_nightly_testing)]
+pub mod issue134 {
+    use async_trait::async_trait;
+
+    #[async_trait]
+    trait TestTrait {
+        async fn run<const DUMMY: bool>(self)
+        where
+            Self: Sized,
+        {
+        }
+    }
+
+    pub struct TestStruct;
+
+    #[async_trait]
+    impl TestTrait for TestStruct {
+        async fn run<const DUMMY: bool>(self)
+        where
+            Self: Sized,
+        {
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/pull/125#pullrequestreview-491880881
+pub mod drop_order {
+    use crate::executor;
+    use async_trait::async_trait;
+    use std::sync::atomic::{AtomicBool, Ordering};
+
+    struct Flagger<'a>(&'a AtomicBool);
+
+    impl Drop for Flagger<'_> {
+        fn drop(&mut self) {
+            self.0.fetch_xor(true, Ordering::AcqRel);
+        }
+    }
+
+    #[async_trait]
+    trait Trait {
+        async fn async_trait(_: Flagger<'_>, flag: &AtomicBool);
+    }
+
+    struct Struct;
+
+    #[async_trait]
+    impl Trait for Struct {
+        async fn async_trait(_: Flagger<'_>, flag: &AtomicBool) {
+            flag.fetch_or(true, Ordering::AcqRel);
+        }
+    }
+
+    async fn standalone(_: Flagger<'_>, flag: &AtomicBool) {
+        flag.fetch_or(true, Ordering::AcqRel);
+    }
+
+    #[async_trait]
+    trait SelfTrait {
+        async fn async_trait(self, flag: &AtomicBool);
+    }
+
+    #[async_trait]
+    impl SelfTrait for Flagger<'_> {
+        async fn async_trait(self, flag: &AtomicBool) {
+            flag.fetch_or(true, Ordering::AcqRel);
+        }
+    }
+
+    #[test]
+    fn test_drop_order() {
+        // 0 : 0 ^ 1 = 1 | 1 = 1 (if flagger then block)
+        // 0 : 0 | 1 = 1 ^ 1 = 0 (if block then flagger)
+
+        let flag = AtomicBool::new(false);
+        executor::block_on_simple(standalone(Flagger(&flag), &flag));
+        assert!(!flag.load(Ordering::Acquire));
+
+        executor::block_on_simple(Struct::async_trait(Flagger(&flag), &flag));
+        assert!(!flag.load(Ordering::Acquire));
+
+        executor::block_on_simple(Flagger(&flag).async_trait(&flag));
+        assert!(!flag.load(Ordering::Acquire));
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/145
+pub mod issue145 {
+    #![deny(clippy::type_complexity)]
+
+    use async_trait::async_trait;
+
+    #[async_trait]
+    pub trait ManageConnection: Sized + Send + Sync + 'static {
+        type Connection: Send + 'static;
+        type Error: Send + 'static;
+
+        async fn connect(&self) -> Result<Self::Connection, Self::Error>;
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/147
+pub mod issue147 {
+    #![deny(clippy::let_unit_value)]
+
+    use async_trait::async_trait;
+
+    pub struct MyType;
+
+    #[async_trait]
+    pub trait MyTrait {
+        async fn x();
+        async fn y() -> ();
+        async fn z();
+    }
+
+    #[async_trait]
+    impl MyTrait for MyType {
+        async fn x() {}
+        async fn y() -> () {}
+        async fn z() {
+            unimplemented!()
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/149
+pub mod issue149 {
+    use async_trait::async_trait;
+
+    pub struct Thing;
+    pub trait Ret {}
+    impl Ret for Thing {}
+
+    pub async fn ok() -> &'static dyn Ret {
+        return &Thing;
+    }
+
+    #[async_trait]
+    pub trait Trait {
+        async fn fail() -> &'static dyn Ret {
+            return &Thing;
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/152
+#[cfg(async_trait_nightly_testing)]
+pub mod issue152 {
+    use async_trait::async_trait;
+
+    #[async_trait]
+    trait Trait {
+        type Assoc;
+
+        async fn f(&self) -> Self::Assoc;
+    }
+
+    struct Struct;
+
+    #[async_trait]
+    impl Trait for Struct {
+        type Assoc = impl Sized;
+
+        async fn f(&self) -> Self::Assoc {}
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/154
+pub mod issue154 {
+    #![deny(clippy::items_after_statements)]
+
+    use async_trait::async_trait;
+
+    #[async_trait]
+    pub trait MyTrait {
+        async fn f(&self);
+    }
+
+    pub struct Struct;
+
+    #[async_trait]
+    impl MyTrait for Struct {
+        async fn f(&self) {
+            const MAX: u16 = 128;
+            println!("{}", MAX);
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/158
+pub mod issue158 {
+    use async_trait::async_trait;
+
+    fn f() {}
+
+    #[async_trait]
+    pub trait Trait {
+        async fn f(&self) {
+            self::f();
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/161
+#[allow(clippy::mut_mut)]
+pub mod issue161 {
+    use async_trait::async_trait;
+    use futures::future::FutureExt;
+    use std::sync::Arc;
+
+    #[async_trait]
+    pub trait Trait {
+        async fn f(self: Arc<Self>);
+    }
+
+    pub struct MyStruct(bool);
+
+    #[async_trait]
+    impl Trait for MyStruct {
+        async fn f(self: Arc<Self>) {
+            futures::select! {
+                _ = async {
+                    println!("{}", self.0);
+                }.fuse() => {}
+            }
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/169
+#[deny(where_clauses_object_safety)]
+pub mod issue169 {
+    use async_trait::async_trait;
+
+    #[async_trait]
+    pub trait Trait: ::core::marker::Sync {
+        async fn f(&self) {}
+    }
+
+    pub fn test(_t: &dyn Trait) {}
+}
+
+// https://github.com/dtolnay/async-trait/issues/177
+pub mod issue177 {
+    use async_trait::async_trait;
+
+    #[async_trait]
+    pub trait Trait {
+        async fn foo(&self, _callback: impl FnMut(&str) + Send) {}
+    }
+
+    pub struct Struct;
+
+    #[async_trait]
+    impl Trait for Struct {
+        async fn foo(&self, _callback: impl FnMut(&str) + Send) {}
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/183
+pub mod issue183 {
+    #![deny(clippy::shadow_same)]
+
+    use async_trait::async_trait;
+
+    #[async_trait]
+    trait Foo {
+        async fn foo(_n: i32) {}
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/199
+pub mod issue199 {
+    use async_trait::async_trait;
+    use std::cell::Cell;
+
+    struct IncrementOnDrop<'a>(&'a Cell<usize>);
+
+    impl<'a> Drop for IncrementOnDrop<'a> {
+        fn drop(&mut self) {
+            self.0.set(self.0.get() + 1);
+        }
+    }
+
+    #[async_trait(?Send)]
+    trait Trait {
+        async fn f(counter: &Cell<usize>, arg: IncrementOnDrop<'_>);
+    }
+
+    struct Struct;
+
+    #[async_trait(?Send)]
+    impl Trait for Struct {
+        async fn f(counter: &Cell<usize>, _: IncrementOnDrop<'_>) {
+            assert_eq!(counter.get(), 0); // second arg not dropped yet
+        }
+    }
+
+    #[test]
+    fn test() {
+        let counter = Cell::new(0);
+        let future = Struct::f(&counter, IncrementOnDrop(&counter));
+        assert_eq!(counter.get(), 0);
+        drop(future);
+        assert_eq!(counter.get(), 1);
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/204
+pub mod issue204 {
+    use async_trait::async_trait;
+
+    #[async_trait]
+    pub trait Trait {
+        async fn f(arg: &impl Trait);
+        async fn g(arg: *const impl Trait);
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/210
+pub mod issue210 {
+    use async_trait::async_trait;
+    use std::sync::Arc;
+
+    #[async_trait]
+    pub trait Trait {
+        async fn f(self: Arc<Self>) {}
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/226
+pub mod issue226 {
+    use async_trait::async_trait;
+
+    #[async_trait]
+    pub trait Trait {
+        async fn cfg_param(&self, param: u8);
+        async fn cfg_param_wildcard(&self, _: u8);
+        async fn cfg_param_tuple(&self, (left, right): (u8, u8));
+    }
+
+    struct Struct;
+
+    #[async_trait]
+    impl Trait for Struct {
+        async fn cfg_param(&self, #[cfg(any())] param: u8, #[cfg(all())] _unused: u8) {}
+
+        async fn cfg_param_wildcard(&self, #[cfg(any())] _: u8, #[cfg(all())] _: u8) {}
+
+        async fn cfg_param_tuple(
+            &self,
+            #[cfg(any())] (left, right): (u8, u8),
+            #[cfg(all())] (_left, _right): (u8, u8),
+        ) {
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/232
+pub mod issue232 {
+    use async_trait::async_trait;
+
+    #[async_trait]
+    pub trait Generic<T> {
+        async fn take_ref(&self, thing: &T);
+    }
+
+    pub struct One;
+
+    #[async_trait]
+    impl<T> Generic<T> for One {
+        async fn take_ref(&self, _: &T) {}
+    }
+
+    pub struct Two;
+
+    #[async_trait]
+    impl<T: Sync> Generic<(T, T)> for Two {
+        async fn take_ref(&self, (a, b): &(T, T)) {
+            let _ = a;
+            let _ = b;
+        }
+    }
+
+    pub struct Three;
+
+    #[async_trait]
+    impl<T> Generic<(T, T, T)> for Three {
+        async fn take_ref(&self, (_a, _b, _c): &(T, T, T)) {}
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/234
+pub mod issue234 {
+    use async_trait::async_trait;
+
+    pub struct Droppable;
+
+    impl Drop for Droppable {
+        fn drop(&mut self) {}
+    }
+
+    pub struct Tuple<T, U>(T, U);
+
+    #[async_trait]
+    pub trait Trait {
+        async fn f(arg: Tuple<Droppable, i32>);
+    }
+
+    pub struct UnderscorePattern;
+
+    #[async_trait]
+    impl Trait for UnderscorePattern {
+        async fn f(Tuple(_, _int): Tuple<Droppable, i32>) {}
+    }
+
+    pub struct DotDotPattern;
+
+    #[async_trait]
+    impl Trait for DotDotPattern {
+        async fn f(Tuple { 1: _int, .. }: Tuple<Droppable, i32>) {}
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/236
+pub mod issue236 {
+    #![deny(clippy::async_yields_async)]
+    #![allow(clippy::manual_async_fn)]
+
+    use async_trait::async_trait;
+    use std::future::{self, Future, Ready};
+
+    // Does not trigger the lint.
+    pub async fn async_fn() -> Ready<()> {
+        future::ready(())
+    }
+
+    #[allow(clippy::async_yields_async)]
+    pub fn impl_future_fn() -> impl Future<Output = Ready<()>> {
+        async { future::ready(()) }
+    }
+
+    // The async_trait attribute turns the former into the latter, so we make it
+    // put its own allow(async_yeilds_async) to remain consistent with async fn.
+    #[async_trait]
+    pub trait Trait {
+        async fn f() -> Ready<()> {
+            future::ready(())
+        }
+    }
+}
+
+// https://github.com/dtolnay/async-trait/issues/238
+pub mod issue238 {
+    #![deny(single_use_lifetimes)]
+
+    use async_trait::async_trait;
+
+    #[async_trait]
+    pub trait Trait {
+        async fn f();
+    }
+
+    pub struct Struct;
+
+    #[async_trait]
+    impl Trait for &Struct {
+        async fn f() {}
+    }
+}
diff --git a/tests/ui/arg-implementation-detail.rs b/tests/ui/arg-implementation-detail.rs
new file mode 100644
index 0000000..b83aa72
--- /dev/null
+++ b/tests/ui/arg-implementation-detail.rs
@@ -0,0 +1,22 @@
+use async_trait::async_trait;
+
+pub struct Struct;
+
+#[async_trait]
+pub trait Trait {
+    async fn f((_a, _b): (Struct, Struct)) {
+        // Expands to something like:
+        //
+        //    fn f(__arg0: (Struct, Struct)) -> … {
+        //        Box::pin(async move {
+        //            let (_a, _b) = __arg0;
+        //            …
+        //        })
+        //    }
+        //
+        // but user's code must not be allowed to name that temporary argument:
+        let _ = __arg0;
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/arg-implementation-detail.stderr b/tests/ui/arg-implementation-detail.stderr
new file mode 100644
index 0000000..e742688
--- /dev/null
+++ b/tests/ui/arg-implementation-detail.stderr
@@ -0,0 +1,5 @@
+error[E0425]: cannot find value `__arg0` in this scope
+  --> tests/ui/arg-implementation-detail.rs:18:17
+   |
+18 |         let _ = __arg0;
+   |                 ^^^^^^ not found in this scope
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..50b2048
--- /dev/null
+++ b/tests/ui/bare-trait-object.stderr
@@ -0,0 +1,21 @@
+error: trait objects without an explicit `dyn` are deprecated
+  --> tests/ui/bare-trait-object.rs:11:16
+   |
+11 | impl Trait for Send + Sync {
+   |                ^^^^^^^^^^^
+   |
+   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
+note: the lint level is defined here
+  --> tests/ui/bare-trait-object.rs:1:9
+   |
+1  | #![deny(bare_trait_objects)]
+   |         ^^^^^^^^^^^^^^^^^^
+help: use `dyn`
+   |
+11 | impl Trait for dyn Send + Sync {
+   |                +++
+help: alternatively use a blanket implementation to implement `Trait` for all types that also implement `Send + Sync`
+   |
+11 | impl<T: Send + Sync> Trait for T {
+   |     ++++++++++++++++           ~
diff --git a/tests/ui/consider-restricting.rs b/tests/ui/consider-restricting.rs
new file mode 100644
index 0000000..e23c8b1
--- /dev/null
+++ b/tests/ui/consider-restricting.rs
@@ -0,0 +1,26 @@
+// https://github.com/rust-lang/rust/issues/93828
+
+use async_trait::async_trait;
+
+pub trait IntoUrl {}
+
+#[async_trait]
+pub trait ClientExt {
+    async fn publish<T: IntoUrl>(&self, url: T);
+}
+
+struct Client;
+
+#[async_trait]
+impl ClientExt for Client {
+    async fn publish<T: IntoUrl>(&self, url: T) {}
+}
+
+struct Client2;
+
+#[async_trait]
+impl ClientExt for Client2 {
+    async fn publish<T>(&self, url: T) {}
+}
+
+fn main() {}
diff --git a/tests/ui/consider-restricting.stderr b/tests/ui/consider-restricting.stderr
new file mode 100644
index 0000000..62ff894
--- /dev/null
+++ b/tests/ui/consider-restricting.stderr
@@ -0,0 +1,33 @@
+error: future cannot be sent between threads safely
+  --> tests/ui/consider-restricting.rs:16:49
+   |
+16 |     async fn publish<T: IntoUrl>(&self, url: T) {}
+   |                                                 ^^ future created by async block is not `Send`
+   |
+note: captured value is not `Send`
+  --> tests/ui/consider-restricting.rs:16:41
+   |
+16 |     async fn publish<T: IntoUrl>(&self, url: T) {}
+   |                                         ^^^ has type `T` which is not `Send`
+   = note: required for the cast from `[async block@$DIR/tests/ui/consider-restricting.rs:16:49: 16:51]` to the object type `dyn Future<Output = ()> + Send`
+help: consider further restricting this bound
+   |
+16 |     async fn publish<T: IntoUrl + std::marker::Send>(&self, url: T) {}
+   |                                 +++++++++++++++++++
+
+error: future cannot be sent between threads safely
+  --> tests/ui/consider-restricting.rs:23:40
+   |
+23 |     async fn publish<T>(&self, url: T) {}
+   |                                        ^^ future created by async block is not `Send`
+   |
+note: captured value is not `Send`
+  --> tests/ui/consider-restricting.rs:23:32
+   |
+23 |     async fn publish<T>(&self, url: T) {}
+   |                                ^^^ has type `T` which is not `Send`
+   = note: required for the cast from `[async block@$DIR/tests/ui/consider-restricting.rs:23:40: 23:42]` to the object type `dyn Future<Output = ()> + Send`
+help: consider further restricting this bound
+   |
+23 |     async fn publish<T + std::marker::Send>(&self, url: T) {}
+   |                        +++++++++++++++++++
diff --git a/tests/ui/delimiter-span.rs b/tests/ui/delimiter-span.rs
new file mode 100644
index 0000000..51a44a2
--- /dev/null
+++ b/tests/ui/delimiter-span.rs
@@ -0,0 +1,24 @@
+#![allow(unused_macro_rules)]
+
+use async_trait::async_trait;
+
+macro_rules! picky {
+    ($(t:tt)*) => {};
+}
+
+#[async_trait]
+trait Trait {
+    async fn method();
+}
+
+struct Struct;
+
+#[async_trait]
+impl Trait for Struct {
+    async fn method() {
+        picky!({ 123, self });
+        picky!({ 123 });
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/delimiter-span.stderr b/tests/ui/delimiter-span.stderr
new file mode 100644
index 0000000..f03da4c
--- /dev/null
+++ b/tests/ui/delimiter-span.stderr
@@ -0,0 +1,21 @@
+error: no rules expected the token `{`
+  --> tests/ui/delimiter-span.rs:19:16
+   |
+5  | macro_rules! picky {
+   | ------------------ when calling this macro
+...
+19 |         picky!({ 123, self });
+   |                ^ no rules expected this token in macro call
+   |
+   = note: while trying to match sequence start
+
+error: no rules expected the token `{`
+  --> tests/ui/delimiter-span.rs:20:16
+   |
+5  | macro_rules! picky {
+   | ------------------ when calling this macro
+...
+20 |         picky!({ 123 });
+   |                ^ no rules expected this token in macro call
+   |
+   = note: while trying to match sequence start
diff --git a/tests/ui/lifetime-defined-here.rs b/tests/ui/lifetime-defined-here.rs
new file mode 100644
index 0000000..237cf66
--- /dev/null
+++ b/tests/ui/lifetime-defined-here.rs
@@ -0,0 +1,23 @@
+use async_trait::async_trait;
+
+#[async_trait]
+trait Foo {
+    async fn bar(&self, x: &str, y: &'_ str) -> &'static str;
+}
+
+struct S(String);
+
+#[async_trait]
+impl Foo for S {
+    async fn bar(&self, x: &str, y: &'_ str) -> &'static str {
+        if false {
+            &self.0
+        } else if false {
+            x
+        } else {
+            y
+        }
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/lifetime-defined-here.stderr b/tests/ui/lifetime-defined-here.stderr
new file mode 100644
index 0000000..9ffef5b
--- /dev/null
+++ b/tests/ui/lifetime-defined-here.stderr
@@ -0,0 +1,29 @@
+error: lifetime may not live long enough
+  --> tests/ui/lifetime-defined-here.rs:12:49
+   |
+12 |     async fn bar(&self, x: &str, y: &'_ str) -> &'static str {
+   |                  -                              ^^^^^^^^^^^^ type annotation requires that `'life0` must outlive `'static`
+   |                  |
+   |                  lifetime `'life0` defined here
+
+error: lifetime may not live long enough
+  --> tests/ui/lifetime-defined-here.rs:12:49
+   |
+12 |     async fn bar(&self, x: &str, y: &'_ str) -> &'static str {
+   |                            -                    ^^^^^^^^^^^^ type annotation requires that `'life1` must outlive `'static`
+   |                            |
+   |                            lifetime `'life1` defined here
+
+error: lifetime may not live long enough
+  --> tests/ui/lifetime-defined-here.rs:12:49
+   |
+12 |     async fn bar(&self, x: &str, y: &'_ str) -> &'static str {
+   |                                      --         ^^^^^^^^^^^^ type annotation requires that `'life2` must outlive `'static`
+   |                                      |
+   |                                      lifetime `'life2` defined here
+
+help: the following changes may resolve your lifetime errors
+  |
+  = help: replace `'life0` with `'static`
+  = help: replace `'life1` with `'static`
+  = help: replace `'life2` with `'static`
diff --git a/tests/ui/lifetime-span.rs b/tests/ui/lifetime-span.rs
new file mode 100644
index 0000000..01981e6
--- /dev/null
+++ b/tests/ui/lifetime-span.rs
@@ -0,0 +1,36 @@
+use async_trait::async_trait;
+
+struct A;
+struct B;
+
+#[async_trait]
+pub trait Trait<'r> {
+    async fn method(&'r self);
+}
+
+#[async_trait]
+impl Trait for A {
+    async fn method(&self) {}
+}
+
+#[async_trait]
+impl<'r> Trait<'r> for B {
+    async fn method(&self) {}
+}
+
+#[async_trait]
+pub trait Trait2 {
+    async fn method<'r>(&'r self);
+}
+
+#[async_trait]
+impl Trait2 for A {
+    async fn method(&self) {}
+}
+
+#[async_trait]
+impl<'r> Trait2<'r> for B {
+    async fn method(&'r self) {}
+}
+
+fn main() {}
diff --git a/tests/ui/lifetime-span.stderr b/tests/ui/lifetime-span.stderr
new file mode 100644
index 0000000..fa16ac7
--- /dev/null
+++ b/tests/ui/lifetime-span.stderr
@@ -0,0 +1,24 @@
+error[E0726]: implicit elided lifetime not allowed here
+  --> tests/ui/lifetime-span.rs:12:6
+   |
+12 | impl Trait for A {
+   |      ^^^^^ expected lifetime parameter
+   |
+help: indicate the anonymous lifetime
+   |
+12 | impl Trait<'_> for A {
+   |           ++++
+
+error[E0107]: trait takes 0 lifetime arguments but 1 lifetime argument was supplied
+  --> tests/ui/lifetime-span.rs:32:10
+   |
+32 | impl<'r> Trait2<'r> for B {
+   |          ^^^^^^---- help: remove these generics
+   |          |
+   |          expected 0 lifetime arguments
+   |
+note: trait defined here, with 0 lifetime parameters
+  --> tests/ui/lifetime-span.rs:22:11
+   |
+22 | pub trait Trait2 {
+   |           ^^^^^^
diff --git a/tests/ui/missing-async-in-impl.rs b/tests/ui/missing-async-in-impl.rs
new file mode 100644
index 0000000..3a5f58c
--- /dev/null
+++ b/tests/ui/missing-async-in-impl.rs
@@ -0,0 +1,15 @@
+use async_trait::async_trait;
+
+#[async_trait]
+pub trait Trait {
+    async fn method();
+}
+
+pub struct Struct;
+
+#[async_trait]
+impl Trait for Struct {
+    fn method() {}
+}
+
+fn main() {}
diff --git a/tests/ui/missing-async-in-impl.stderr b/tests/ui/missing-async-in-impl.stderr
new file mode 100644
index 0000000..e461c85
--- /dev/null
+++ b/tests/ui/missing-async-in-impl.stderr
@@ -0,0 +1,8 @@
+error[E0195]: lifetime parameters or bounds on method `method` do not match the trait declaration
+  --> tests/ui/missing-async-in-impl.rs:12:14
+   |
+5  |     async fn method();
+   |              -------- lifetimes in impl do not match this method in trait
+...
+12 |     fn method() {}
+   |              ^ lifetimes do not match method in trait
diff --git a/tests/ui/missing-async-in-trait.rs b/tests/ui/missing-async-in-trait.rs
new file mode 100644
index 0000000..56fea7a
--- /dev/null
+++ b/tests/ui/missing-async-in-trait.rs
@@ -0,0 +1,15 @@
+use async_trait::async_trait;
+
+#[async_trait]
+pub trait Trait {
+    fn method();
+}
+
+pub struct Struct;
+
+#[async_trait]
+impl Trait for Struct {
+    async fn method() {}
+}
+
+fn main() {}
diff --git a/tests/ui/missing-async-in-trait.stderr b/tests/ui/missing-async-in-trait.stderr
new file mode 100644
index 0000000..c92c38d
--- /dev/null
+++ b/tests/ui/missing-async-in-trait.stderr
@@ -0,0 +1,8 @@
+error[E0195]: lifetime parameters or bounds on method `method` do not match the trait declaration
+  --> tests/ui/missing-async-in-trait.rs:12:14
+   |
+5  |     fn method();
+   |              - lifetimes in impl do not match this method in trait
+...
+12 |     async fn method() {}
+   |              ^^^^^^^^ lifetimes do not match method in trait
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..e6ddb42
--- /dev/null
+++ b/tests/ui/missing-body.stderr
@@ -0,0 +1,7 @@
+error: associated function in `impl` without body
+  --> tests/ui/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..fd6fc31
--- /dev/null
+++ b/tests/ui/must-use.stderr
@@ -0,0 +1,11 @@
+error: unused return value of `Interface::f` that must be used
+  --> tests/ui/must-use.rs:18:5
+   |
+18 |     Thing.f();
+   |     ^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> tests/ui/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..04493f8
--- /dev/null
+++ b/tests/ui/self-span.stderr
@@ -0,0 +1,27 @@
+error[E0308]: mismatched types
+  --> tests/ui/self-span.rs:17:21
+   |
+17 |         let _: () = self;
+   |                --   ^^^^ expected `()`, found `S`
+   |                |
+   |                expected due to this
+
+error: the `Self` constructor can only be used with tuple or unit structs
+  --> tests/ui/self-span.rs:18:23
+   |
+18 |         let _: Self = Self;
+   |                       ^^^^ help: use curly brackets: `Self { /* fields */ }`
+
+error[E0308]: mismatched types
+  --> tests/ui/self-span.rs:25:21
+   |
+25 |         let _: () = self;
+   |                --   ^^^^ expected `()`, found `E`
+   |                |
+   |                expected due to this
+
+error[E0533]: expected value, found struct variant `Self::V`
+  --> tests/ui/self-span.rs:26:23
+   |
+26 |         let _: Self = Self::V;
+   |                       ^^^^^^^ not a value
diff --git a/tests/ui/send-not-implemented.rs b/tests/ui/send-not-implemented.rs
new file mode 100644
index 0000000..d8883fb
--- /dev/null
+++ b/tests/ui/send-not-implemented.rs
@@ -0,0 +1,22 @@
+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;
+    }
+
+    async fn test_ret(&self) -> bool {
+        let mutex = Mutex::new(());
+        let _guard = mutex.lock().unwrap();
+        f().await;
+        true
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/send-not-implemented.stderr b/tests/ui/send-not-implemented.stderr
new file mode 100644
index 0000000..d68fc43
--- /dev/null
+++ b/tests/ui/send-not-implemented.stderr
@@ -0,0 +1,47 @@
+error: future cannot be sent between threads safely
+  --> tests/ui/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 created by async block is not `Send`
+   |
+   = help: within `[async block@$DIR/tests/ui/send-not-implemented.rs:8:26: 12:6]`, the trait `Send` is not implemented for `MutexGuard<'_, ()>`
+note: future is not `Send` as this value is used across an await
+  --> tests/ui/send-not-implemented.rs:11:12
+   |
+10 |         let _guard = mutex.lock().unwrap();
+   |             ------ has type `MutexGuard<'_, ()>` which is not `Send`
+11 |         f().await;
+   |            ^^^^^^ await occurs here, with `_guard` maybe used later
+12 |     }
+   |     - `_guard` is later dropped here
+   = note: required for the cast from `[async block@$DIR/tests/ui/send-not-implemented.rs:8:26: 12:6]` to the object type `dyn Future<Output = ()> + Send`
+
+error: future cannot be sent between threads safely
+  --> tests/ui/send-not-implemented.rs:14:38
+   |
+14 |       async fn test_ret(&self) -> bool {
+   |  ______________________________________^
+15 | |         let mutex = Mutex::new(());
+16 | |         let _guard = mutex.lock().unwrap();
+17 | |         f().await;
+18 | |         true
+19 | |     }
+   | |_____^ future created by async block is not `Send`
+   |
+   = help: within `[async block@$DIR/tests/ui/send-not-implemented.rs:14:38: 19:6]`, the trait `Send` is not implemented for `MutexGuard<'_, ()>`
+note: future is not `Send` as this value is used across an await
+  --> tests/ui/send-not-implemented.rs:17:12
+   |
+16 |         let _guard = mutex.lock().unwrap();
+   |             ------ has type `MutexGuard<'_, ()>` which is not `Send`
+17 |         f().await;
+   |            ^^^^^^ await occurs here, with `_guard` maybe used later
+18 |         true
+19 |     }
+   |     - `_guard` is later dropped here
+   = note: required for the cast from `[async block@$DIR/tests/ui/send-not-implemented.rs:14:38: 19:6]` to the object type `dyn Future<Output = bool> + Send`
diff --git a/tests/ui/unreachable.rs b/tests/ui/unreachable.rs
new file mode 100644
index 0000000..cac2826
--- /dev/null
+++ b/tests/ui/unreachable.rs
@@ -0,0 +1,20 @@
+#![deny(warnings)]
+
+use async_trait::async_trait;
+
+#[async_trait]
+pub trait Trait {
+    async fn f() {
+        unimplemented!()
+    }
+}
+
+#[async_trait]
+pub trait TraitFoo {
+    async fn f() {
+        let _y = unimplemented!();
+        let _z = _y;
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/unreachable.stderr b/tests/ui/unreachable.stderr
new file mode 100644
index 0000000..08595e5
--- /dev/null
+++ b/tests/ui/unreachable.stderr
@@ -0,0 +1,14 @@
+error: unreachable statement
+  --> tests/ui/unreachable.rs:16:9
+   |
+15 |         let _y = unimplemented!();
+   |                  ---------------- any code following this expression is unreachable
+16 |         let _z = _y;
+   |         ^^^^^^^^^^^^ unreachable statement
+   |
+note: the lint level is defined here
+  --> tests/ui/unreachable.rs:1:9
+   |
+1  | #![deny(warnings)]
+   |         ^^^^^^^^
+   = note: `#[deny(unreachable_code)]` implied by `#[deny(warnings)]`
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..1493945
--- /dev/null
+++ b/tests/ui/unsupported-self.stderr
@@ -0,0 +1,5 @@
+error: the `Self` constructor can only be used with tuple or unit structs
+  --> tests/ui/unsupported-self.rs:11:17
+   |
+11 |         let _ = Self;
+   |                 ^^^^