Rollup merge of #69175 - estebank:shall-not-ice, r=petrochenkov

Do not ICE when encountering `yield` inside `async` block

Fix #67158.

src/test/ui/generator/async-generator-issue-67158.rs

@@ -0,0 +1,6 @@
+#![feature(generators)]
+// edition:2018
+// Regression test for #67158.
+fn main() {
+    async { yield print!(":C") }; //~ ERROR `async` generators are not yet supported
+}

src/test/ui/generator/async-generator-issue-67158.stderr

@@ -0,0 +1,9 @@
+error[E0727]: `async` generators are not yet supported
+  --> $DIR/async-generator-issue-67158.rs:5:13
+   |
+LL |     async { yield print!(":C") };
+   |             ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0727`.