Add recursion

[khatchad]

• Change TODOs to notes.
• Add recursive function test.
• Change function name.
• Format.
• Add recursive test.
• Add transitive recursive test.
• We want it to have an error.
• Add hybrid recursive test.
• Also assert refactoring kind.
• Change if to assertion.
• Add test.
• Add assertions.
• Fix message.
• Add transitive test.
• Add retracing case.
• Progress.
• Progress.
• Remove unused import.
• Progress.
• Add comments.
• Add precondition failures for recursion.
• Add warning for recursion.
• Add assertion.
• Progress.
• Test to exercise infinite recursion.
• Simplify side-effects algorithm.
• Avoid infinite loops.
• Fix test code.
• Fix assertions.