Add additional tests for static AFIT

src/test/ui/async-await/in-trait/async-recursive-generic.rs

@@ -0,0 +1,21 @@
+// edition: 2021
+
+#![feature(async_fn_in_trait)]
+#![allow(incomplete_features)]
+
+trait MyTrait<T> {
+    async fn foo_recursive(&self, n: usize) -> T;
+}
+
+impl<T> MyTrait<T> for T where T: Copy {
+    async fn foo_recursive(&self, n: usize) -> T {
+        //~^ ERROR recursion in an `async fn` requires boxing
+        if n > 0 {
+            self.foo_recursive(n - 1).await
+        } else {
+            *self
+        }
+    }
+}
+
+fn main() {}