rust-analyzer

diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 7cda75b347..5aa1ca7e0b 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs

@@ -1364,6 +1364,23 @@ impl Function {

Type::new_with_resolver_inner(db, &resolver, ty)

}

+ pub fn async_ret_type(self, db: &dyn HirDatabase) -> Option<Type> {

+ if !self.is_async(db) {

+ return None;

+ }

+ let resolver = self.id.resolver(db.upcast());

+ let substs = TyBuilder::placeholder_subst(db, self.id);

+ let callable_sig = db.callable_item_signature(self.id.into()).substitute(Interner, &substs);

+ let ret_ty = callable_sig.ret().clone();

+ for pred in ret_ty.impl_trait_bounds(db).into_iter().flatten() {

+ if let WhereClause::AliasEq(output_eq) = pred.into_value_and_skipped_binders().0 {

+ return Type::new_with_resolver_inner(db, &resolver, output_eq.ty).into();

+ }

+ never!("Async fn ret_type should be impl Future");

+ None

+ }

pub fn self_param(self, db: &dyn HirDatabase) -> Option<SelfParam> {

if !db.function_data(self.id).has_self_param() {

return None;

diff --git a/crates/ide_completion/src/render/function.rs b/crates/ide_completion/src/render/function.rs
index 38520e1832..cbaecd208d 100644
--- a/crates/ide_completion/src/render/function.rs
+++ b/crates/ide_completion/src/render/function.rs

@@ -228,7 +228,7 @@ fn should_add_parens(ctx: &CompletionContext) -> bool {

}

fn detail(db: &dyn HirDatabase, func: hir::Function) -> String {

- let ret_ty = func.ret_type(db);

+ let ret_ty = func.async_ret_type(db).unwrap_or_else(|| func.ret_type(db));

let mut detail = String::new();

if func.is_const(db) {

diff --git a/crates/ide_completion/src/tests/expression.rs b/crates/ide_completion/src/tests/expression.rs
index f25e14e0fc..77296d9099 100644
--- a/crates/ide_completion/src/tests/expression.rs
+++ b/crates/ide_completion/src/tests/expression.rs

@@ -624,12 +624,12 @@ fn main() {

#[test]

fn detail_async_fn() {

- // FIXME: #11438

check_empty(

r#"

//- minicore: future, sized

trait Trait<T> {}

async fn foo() -> u8 {}

+async fn bar<U>() -> impl Trait<U> {}

fn main() {

self::$0

}

@@ -637,7 +637,8 @@ fn main() {

expect![[r"

tt Trait

fn main() fn()

- fn foo() async fn() -> impl Future<Output = u8>

+ fn bar() async fn() -> impl Trait<U>

+ fn foo() async fn() -> u8

"]],

);

}