https://errorvault.dev/tags/await/ Recent content in Await on ErrorVault — Developer Error Code Dictionary Hugo en-us Mon, 15 Jun 2026 10:20:04 +0800 https://errorvault.dev/rust/rust-e0770-async-fn-return-type-impl-trait/ Mon, 15 Jun 2026 10:20:04 +0800 https://errorvault.dev/rust/rust-e0770-async-fn-return-type-impl-trait/ <h1 id="fix-e0770-async-fn-return-type-cannot-contain-impl-trait">Fix E0770: Async Fn Return Type Cannot Contain <code>impl Trait</code></h1> <p>Rust&rsquo;s <code>async fn</code> syntax provides a convenient way to write asynchronous code, but it comes with strict limitations on what return types are allowed. Error E0770 is a compile-time error that occurs when developers attempt to use <code>impl Trait</code> in the return type of an <code>async fn</code>. Understanding why this restriction exists and how to work around it is essential for writing idiomatic async Rust code.</p>