Having this assignment "unwrapped" feels a little weird to me. The reason is that it will be evaluated when the `shared_examples` block is evaluated rather than within the scope of the example.

How about using an instance variable in the `before` hook? e.g.

```ruby
before { @subject_id_in_before = subject.object_id }

it 'should be memoized' do
  expect(subject_id_in_let).to eq(@subject_id_in_before)
end
```