Added test for impl member assist when impl def is missing braces

crates/assists/src/handlers/add_missing_impl_members.rs

@@ -313,6 +313,25 @@ impl Foo for S {
         );
     }
 
+    #[test]
+    fn test_impl_def_without_braces() {
+        check_assist(
+            add_missing_impl_members,
+            r#"
+trait Foo { fn foo(&self); }
+struct S;
+impl Foo for S<|>"#,
+            r#"
+trait Foo { fn foo(&self); }
+struct S;
+impl Foo for S {
+    fn foo(&self) {
+        ${0:todo!()}
+    }
+}"#,
+        );
+    }
+
     #[test]
     fn fill_in_type_params_1() {
         check_assist(