R1:c1a8b83bd7ea

Correct PHPDoc or add default return for numerous methods

Summary:
Correct PHPDoc when none of the method calls try to handle a return value.
Add missing fallback `return` statements (which may never be reached if previous condition checks were always true).

This reduces the amount of errors reported by static code analysis tools.

Test Plan: Carefully read the code and check all places in which a function gets called whether a return value is expected.

Reviewers: O1 Blessed Committers, valerio.bozzolan…