5 files changed, 103 insertions, 0 deletions
diff --git a/tests/ui/issues/auxiliary/issue-111011.rs b/tests/ui/issues/auxiliary/issue-111011.rs
new file mode 100644
index 00000000000..927134a588c
--- /dev/null
+++ b/tests/ui/issues/auxiliary/issue-111011.rs
@@ -0,0 +1,12 @@
+#![feature(async_closure)]
+
+// edition:2021
+
+fn foo<X>(x: impl FnOnce() -> Box<X>) {}
+// just to make sure async closures can still be suggested for boxing.
+fn bar<X>(x: Box<dyn FnOnce() -> X>) {}
+
+fn main() {
+    foo(async move || {}); //~ ERROR mismatched types
+    bar(async move || {}); //~ ERROR mismatched types
+}
diff --git a/tests/ui/issues/auxiliary/issue-111011.stderr b/tests/ui/issues/auxiliary/issue-111011.stderr
new file mode 100644
index 00000000000..082f0f035ad
--- /dev/null
+++ b/tests/ui/issues/auxiliary/issue-111011.stderr
@@ -0,0 +1,34 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-111011.rs:10:23
+   |
+LL |     foo(async move || {});
+   |                       ^^ expected `Box<_>`, found `async` closure body
+   |
+   = note:            expected struct `Box<_>`
+           found `async` closure body `[async closure body@$DIR/issue-111011.rs:10:23: 10:25]`
+   = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
+
+error[E0308]: mismatched types
+  --> $DIR/issue-111011.rs:11:9
+   |
+LL |     bar(async move || {});
+   |     --- ^^^^^^^^^^^^^^^^ expected `Box<dyn FnOnce() -> _>`, found closure
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected struct `Box<(dyn FnOnce() -> _ + 'static)>`
+             found closure `[closure@$DIR/issue-111011.rs:11:9: 11:22]`
+   = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
+note: function defined here
+  --> $DIR/issue-111011.rs:7:4
+   |
+LL | fn bar<X>(x: Box<dyn FnOnce() -> X>) {}
+   |    ^^^    -------------------------
+help: store this in the heap by calling `Box::new`
+   |
+LL |     bar(Box::new(async move || {}));
+   |         +++++++++                +
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/suggestions/suggest-boxed-empty-block.fixed b/tests/ui/suggestions/suggest-boxed-empty-block.fixed
new file mode 100644
index 00000000000..46683aa0953
--- /dev/null
+++ b/tests/ui/suggestions/suggest-boxed-empty-block.fixed
@@ -0,0 +1,12 @@
+#![feature(async_closure)]
+
+// edition:2021
+// run-rustfix
+
+fn foo<T>(_: Box<T>) {}
+fn bar<T>(_: impl Fn() -> Box<T>) {}
+
+fn main() {
+    foo(Box::new(())); //~ ERROR mismatched types
+    bar(|| Box::new(())); //~ ERROR mismatched types
+}
diff --git a/tests/ui/suggestions/suggest-boxed-empty-block.rs b/tests/ui/suggestions/suggest-boxed-empty-block.rs
new file mode 100644
index 00000000000..e19670a5018
--- /dev/null
+++ b/tests/ui/suggestions/suggest-boxed-empty-block.rs
@@ -0,0 +1,12 @@
+#![feature(async_closure)]
+
+// edition:2021
+// run-rustfix
+
+fn foo<T>(_: Box<T>) {}
+fn bar<T>(_: impl Fn() -> Box<T>) {}
+
+fn main() {
+    foo({}); //~ ERROR mismatched types
+    bar(|| {}); //~ ERROR mismatched types
+}
diff --git a/tests/ui/suggestions/suggest-boxed-empty-block.stderr b/tests/ui/suggestions/suggest-boxed-empty-block.stderr
new file mode 100644
index 00000000000..474a37b888f
--- /dev/null
+++ b/tests/ui/suggestions/suggest-boxed-empty-block.stderr
@@ -0,0 +1,33 @@
+error[E0308]: mismatched types
+  --> $DIR/suggest-boxed-empty-block.rs:10:9
+   |
+LL |     foo({});
+   |         ^^ expected `Box<_>`, found `()`
+   |
+   = note: expected struct `Box<_>`
+           found unit type `()`
+   = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
+help: store this in the heap by calling `Box::new`
+   |
+LL -     foo({});
+LL +     foo(Box::new(()));
+   |
+
+error[E0308]: mismatched types
+  --> $DIR/suggest-boxed-empty-block.rs:11:12
+   |
+LL |     bar(|| {});
+   |            ^^ expected `Box<_>`, found `()`
+   |
+   = note: expected struct `Box<_>`
+           found unit type `()`
+   = note: for more on the distinction between the stack and the heap, read https://doc.rust-lang.org/book/ch15-01-box.html, https://doc.rust-lang.org/rust-by-example/std/box.html, and https://doc.rust-lang.org/std/boxed/index.html
+help: store this in the heap by calling `Box::new`
+   |
+LL -     bar(|| {});
+LL +     bar(|| Box::new(()));
+   |
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.