Add test for async/await combined with const-generics.

src/test/ui/const-generics/issue-74906.rs

@@ -0,0 +1,25 @@
+// edition:2018
+// check-pass
+// revisions: full min
+#![cfg_attr(full, feature(const_generics))]
+#![cfg_attr(full, allow(incomplete_features))]
+#![cfg_attr(min, feature(min_const_generics))]
+
+const SIZE: usize = 16;
+
+struct Bar<const H: usize> {}
+
+struct Foo<const H: usize> {}
+
+impl<const H: usize> Foo<H> {
+    async fn biz(_: &[[u8; SIZE]]) -> Vec<()> {
+        vec![]
+    }
+
+    pub async fn baz(&self) -> Bar<H> {
+        Self::biz(&vec![]).await;
+        Bar {}
+    }
+}
+
+fn main() { }