Background
This request would fulfill any query that is running reports against closed sprints. This allows for easy extension of Sprint reporting via dashboards and gadgets on JIRA dashboards as well as Confluence dashboards.

Use-case
These types of queries are completely analogous to the specific JQL function latestReleasedVersion() available against Fix Version/s, Affects Version/s fields and custom fields extending that type. This obviously would return the most recently completed sprint's issues.

Example
I should be able to write a query such as:

project = ExDevelopment AND Sprint in lastSprint()