From 28ad5f98833e3bc6ea3de5a74dea548d075d3da5 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 6 Mar 2021 21:01:44 -0800
Subject: [PATCH 1/3] Add regression test for issue 149

---
 tests/test.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tests/test.rs b/tests/test.rs
index a97af36..06c0918 100644
--- a/tests/test.rs
+++ b/tests/test.rs
@@ -1258,3 +1258,23 @@ pub mod issue147 {
         }
     }
 }
+
+// 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;
+        }
+    }
+}

From c8b4dc52e72a46cd9fd12a276ec432748afd5cbb Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 6 Mar 2021 21:05:39 -0800
Subject: [PATCH 2/3] Prepend early return to force unsize coercion

---
 src/expand.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/expand.rs b/src/expand.rs
index b0ebb4c..2b000ab 100644
--- a/src/expand.rs
+++ b/src/expand.rs
@@ -345,6 +345,10 @@ fn transform_block(sig: &mut Signature, block: &mut Block) {
     }
 
     let stmts = &block.stmts;
+    let ret = match &sig.output {
+        ReturnType::Default => quote!(()),
+        ReturnType::Type(_, ret) => quote!(#ret),
+    };
     let let_ret = match &sig.output {
         ReturnType::Default => quote_spanned! {block.brace_token.span=>
             let _: () = { #(#decls)* #(#stmts)* };
@@ -356,7 +360,12 @@ fn transform_block(sig: &mut Signature, block: &mut Block) {
         },
     };
     let box_pin = quote_spanned!(block.brace_token.span=>
-        Box::pin(async move { #let_ret })
+        Box::pin(async move {
+            if let ::core::option::Option::Some(__ret) = ::core::option::Option::None::<#ret> {
+                return __ret;
+            }
+            #let_ret
+        })
     );
     block.stmts = parse_quote!(#box_pin);
 }

From 3596fe77343155543e3baab4e2ff6ef7e3b2d19c Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sat, 6 Mar 2021 21:09:32 -0800
Subject: [PATCH 3/3] Remove unneeded early return from unit case

---
 src/expand.rs | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/src/expand.rs b/src/expand.rs
index 2b000ab..06c4ba3 100644
--- a/src/expand.rs
+++ b/src/expand.rs
@@ -345,27 +345,21 @@ fn transform_block(sig: &mut Signature, block: &mut Block) {
     }
 
     let stmts = &block.stmts;
-    let ret = match &sig.output {
-        ReturnType::Default => quote!(()),
-        ReturnType::Type(_, ret) => quote!(#ret),
-    };
     let let_ret = match &sig.output {
         ReturnType::Default => quote_spanned! {block.brace_token.span=>
             let _: () = { #(#decls)* #(#stmts)* };
         },
         ReturnType::Type(_, ret) => quote_spanned! {block.brace_token.span=>
+            if let ::core::option::Option::Some(__ret) = ::core::option::Option::None::<#ret> {
+                return __ret;
+            }
             let __ret: #ret = { #(#decls)* #(#stmts)* };
             #[allow(unreachable_code)]
             __ret
         },
     };
     let box_pin = quote_spanned!(block.brace_token.span=>
-        Box::pin(async move {
-            if let ::core::option::Option::Some(__ret) = ::core::option::Option::None::<#ret> {
-                return __ret;
-            }
-            #let_ret
-        })
+        Box::pin(async move { #let_ret })
     );
     block.stmts = parse_quote!(#box_pin);
 }