chalk: add known-bug test that was previously ICEing.

src/test/ui/chalkify/bugs/async.rs

@@ -0,0 +1,9 @@
+// check-fail
+// known-bug
+// compile-flags: -Z chalk --edition=2021
+
+fn main() -> () {}
+
+async fn foo(x: u32) -> u32 {
+    x
+}

src/test/ui/chalkify/bugs/async.stderr

@@ -0,0 +1,39 @@
+error[E0277]: the trait bound `[static generator@$DIR/async.rs:7:29: 9:2]: Generator<ResumeTy>` is not satisfied
+  --> $DIR/async.rs:7:29
+   |
+LL |   async fn foo(x: u32) -> u32 {
+   |  _____________________________^
+LL | |     x
+LL | | }
+   | |_^ the trait `Generator<ResumeTy>` is not implemented for `[static generator@$DIR/async.rs:7:29: 9:2]`
+   |
+note: required by a bound in `from_generator`
+  --> $SRC_DIR/core/src/future/mod.rs:LL:COL
+   |
+LL |     T: Generator<ResumeTy, Yield = ()>,
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `from_generator`
+
+error[E0280]: the requirement `<[static generator@$DIR/async.rs:7:29: 9:2] as Generator<ResumeTy>>::Yield == ()` is not satisfied
+  --> $DIR/async.rs:7:29
+   |
+LL |   async fn foo(x: u32) -> u32 {
+   |  _____________________________^
+LL | |     x
+LL | | }
+   | |_^
+   |
+note: required by a bound in `from_generator`
+  --> $SRC_DIR/core/src/future/mod.rs:LL:COL
+   |
+LL |     T: Generator<ResumeTy, Yield = ()>,
+   |                            ^^^^^^^^^^ required by this bound in `from_generator`
+
+error[E0280]: the requirement `<impl Future<Output = [async output]> as Future>::Output == u32` is not satisfied
+  --> $DIR/async.rs:7:25
+   |
+LL | async fn foo(x: u32) -> u32 {
+   |                         ^^^
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0277`.

src/tools/tidy/src/error_codes_check.rs

@@ -10,8 +10,8 @@
 
 // A few of those error codes can't be tested but all the others can and *should* be tested!
 const EXEMPTED_FROM_TEST: &[&str] = &[
-    "E0279", "E0280", "E0313", "E0377", "E0461", "E0462", "E0465", "E0476", "E0514", "E0519",
+    "E0279", "E0313", "E0377", "E0461", "E0462", "E0465", "E0476", "E0514", "E0519", "E0523",
-    "E0523", "E0554", "E0640", "E0717", "E0729",
+    "E0554", "E0640", "E0717", "E0729",
 ];
 
 // Some error codes don't have any tests apparently...