From f81548d92652cb477d8dabde87f7310412675aac Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Fri, 3 Mar 2023 21:30:54 -0800
Subject: [PATCH 1/2] Add regression test for issue 238

Currently fails:

    error: lifetime parameter `'impl0` only used once
        --> tests/test.rs:1603:20
         |
    1603 |     impl Trait for &Struct {
         |                    ^
         |                    |
         |                    this lifetime...
         |                    ...is used only here
         |
    note: the lint level is defined here
        --> tests/test.rs:1591:13
         |
    1591 |     #![deny(single_use_lifetimes)]
         |             ^^^^^^^^^^^^^^^^^^^^
    help: elide the single-use lifetime
         |
    1602 ~
    1603 ~     impl Trait for Struct {
         |
---
 tests/test.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/tests/test.rs b/tests/test.rs
index 102f97e..4fc46f0 100644
--- a/tests/test.rs
+++ b/tests/test.rs
@@ -1585,3 +1585,22 @@ pub mod issue236 {
         }
     }
 }
+
+// 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() {}
+    }
+}

From 5883ac897efdc706cc5a256a0fa4aa3b108f1dd9 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Fri, 3 Mar 2023 22:49:19 -0800
Subject: [PATCH 2/2] Delete replacement of elided lifetimes in impl heading

---
 src/expand.rs   | 9 +--------
 src/lifetime.rs | 6 ++----
 2 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/src/expand.rs b/src/expand.rs
index 88338db..2499177 100644
--- a/src/expand.rs
+++ b/src/expand.rs
@@ -80,13 +80,6 @@ pub fn expand(input: &mut Item, is_local: bool) {
             }
         }
         Item::Impl(input) => {
-            let mut lifetimes = CollectLifetimes::new("'impl");
-            lifetimes.visit_type_mut(&mut *input.self_ty);
-            lifetimes.visit_path_mut(&mut input.trait_.as_mut().unwrap().1);
-            let params = &input.generics.params;
-            let elided = lifetimes.elided;
-            input.generics.params = parse_quote!(#(#elided,)* #params);
-
             let mut associated_type_impl_traits = Set::new();
             for inner in &input.items {
                 if let ImplItem::Type(assoc) = inner {
@@ -167,7 +160,7 @@ fn transform_sig(
         ReturnType::Type(arrow, ret) => (*arrow, quote!(#ret)),
     };
 
-    let mut lifetimes = CollectLifetimes::new("'life");
+    let mut lifetimes = CollectLifetimes::new();
     for arg in sig.inputs.iter_mut() {
         match arg {
             FnArg::Receiver(arg) => lifetimes.visit_receiver_mut(arg),
diff --git a/src/lifetime.rs b/src/lifetime.rs
index 86eac24..1e5a658 100644
--- a/src/lifetime.rs
+++ b/src/lifetime.rs
@@ -9,15 +9,13 @@ use syn::{
 pub struct CollectLifetimes {
     pub elided: Vec<Lifetime>,
     pub explicit: Vec<Lifetime>,
-    pub name: &'static str,
 }
 
 impl CollectLifetimes {
-    pub fn new(name: &'static str) -> Self {
+    pub fn new() -> Self {
         CollectLifetimes {
             elided: Vec::new(),
             explicit: Vec::new(),
-            name,
         }
     }
 
@@ -37,7 +35,7 @@ impl CollectLifetimes {
     }
 
     fn next_lifetime(&mut self, span: Span) -> Lifetime {
-        let name = format!("{}{}", self.name, self.elided.len());
+        let name = format!("'life{}", self.elided.len());
         let life = Lifetime::new(&name, span);
         self.elided.push(life.clone());
         life