add regression tests for add_missing_impl_members

src/tools/rust-analyzer/crates/ide-assists/src/handlers/add_missing_impl_members.rs

@@ -2500,6 +2500,40 @@ fn foo(&self, my_macro: usize) {
         ${0:todo!()}
     }
 }
+"#,
+        );
+    }
+
+    #[test]
+    fn regression_test_for_when_impl_for_unit() {
+        check_assist(
+            add_missing_impl_members,
+            r#"
+trait Test {
+    fn f<B>()
+    where
+        B: IntoIterator,
+        <B as IntoIterator>::Item: Copy;
+}
+impl Test for () {
+    $0
+}
+"#,
+            r#"
+trait Test {
+    fn f<B>()
+    where
+        B: IntoIterator,
+        <B as IntoIterator>::Item: Copy;
+}
+impl Test for () {
+    fn f<B>()
+    where
+        B: IntoIterator,
+        <B as IntoIterator>::Item: Copy {
+        ${0:todo!()}
+    }
+}
 "#,
         );
     }