+ ; (let ([(foo a b) (foo 123 345)]) a)
+ ; |
+ ; v
+ ; (let ([a (foo~0 (foo 123 345)]
+ ; [b (foo~1 (foo 123 345)]) a)
+(define (expand-pattern-matches x)
+ (define (pattern-match binding)
+ (let ([binding-name (car binding)]
+ [body (cadr binding)])
+ (if (eqv? (ast-type binding-name) 'var)
+ (list (list binding-name body))
+ (let* ([sum-name (car binding-name)]
+ [destructor (lambda (i) (dtor-name sum-name i))])
+ (flat-map (lambda (y i)
+ (pattern-match (list y `(,(destructor i) ,body))))
+ (cdr binding-name)
+ (range 0 (length (cdr binding-name))))))))
+ (case (ast-type x)
+ ['let `(let ,(flat-map pattern-match (let-bindings x))
+ ,@(map expand-pattern-matches (let-body x)))]
+ [else (ast-traverse expand-pattern-matches x)]))
+