Here is an interesting test case that shows that fi we define
(define-syntax-rule (letec-m f) (let/ec c (f c)))
(define                    (letec-f f) (let/ec c (f c)))

we can get two different behaviors with letec-m compiles wrongly.
Obviously a bug!

This is important in casy you would like to make a loop macro effectively
with a continue directive.