WIP on typechecking case statements

[scheme.git] / ast.scm

diff --git a/ast.scm b/ast.scm
index b3f21bd07d6d07ba2b64017cff0a365cbf77abd4..86d522560a8012546e6a754499b1216052d8ce70 100644 (file)
--- a/ast.scm
+++ b/ast.scm
@@ -1,3 +1,5 @@
+(load "utils.scm")
+
 (define (ast-type x)
   (define (builtin? x)
     (case x
@@ -15,6 +17,7 @@
       ('if 'if)
       ('let 'let)
       ('lambda 'lambda)
+      ('case 'case)
       ('closure 'closure) ; only available in codegen
       ('static-string 'static-string) ; only available in codegen
       ('stack 'stack) ; only available in codegen (tag that value is passed via stack)
@@ -33,7 +36,11 @@
     ('app (map f x))
     ('lambda `(lambda ,(lambda-args x) ,(f (lambda-body x))))
     ('if `(if ,@(map f (cdr x))))
-    ('stack `(stack ,(cadr x) ,(map f (caddr x))))
+    ('case `(case ,(f (case-expr x))
+             ,@(map (lambda (x)
+                      (list (car x) (f (cadr x))))
+                    (case-cases x))))
+    ('stack `(stack ,(cadr x) ,(f (caddr x))))
     (else x)))
 
 (define (ast-collect f x)
@@ -48,6 +55,9 @@
                     (inner (lambda-body x)))]
     ['if (append (f x)
                 (flat-map inner (cdr x)))]
+    ['case (append (f x)
+                  (inner (case-expr x))
+                  (flat-map inner (map cadr (case-cases x))))]
     ['stack (append (f x)
                    (inner (caddr x)))]
     [else (f x)]))
@@ -78,6 +88,9 @@
 (define let-bindings cadr)
 (define let-body cddr)
 
+(define case-expr cadr)
+(define case-cases cddr)
+
                                        ; (let ([(foo a b) (foo 123 345)]) a)
                                        ;   |
                                        ;   v
@@ -99,10 +112,17 @@
 
                   [type (data-tor-type data-layouts sum-name)]
 
-                  [sum (assoc sum-name (cdr (assoc type data-layouts)))]
+                  [sums (cdr (assoc type data-layouts))]
+                  [sum (assoc sum-name sums)]
                   
                   [expected-number (length (cdr sum))])
 
+                                       ; assert that we only do a let pattern match on an ADT with exactly one sum
+             (when (not (= 1 (length sums)))
+               (error #f (format "Cannot pattern match a ~a in a let since it has ~a possible constructors"
+                                 type
+                                 (length sums))))
+
                                        ; assert that there is the correct number of bindings
              (when (not (= (length products)
                            expected-number))
@@ -169,10 +189,10 @@
                                        ;        |
                                        ;        v
                                        ; (foo   . ((A foo constructor) . (abs Int (abs Bool A))))
-                                       ; (foo~0 . ((A foo 0)           . (abs A Int)))
-                                       ; (foo~1 . ((A foo 1)           . (abs A Bool)))
+                                       ; (foo~0 . ((A foo 0 Int)       . (abs A Int)))
+                                       ; (foo~1 . ((A foo 1 Bool)      . (abs A Bool)))
                                        ; (bar   . ((A bar constructor) . (abs Bool A)))
-                                       ; (bar~0 . ((A bar 0)           . (abs A Bool)))
+                                       ; (bar~0 . ((A bar 0 Bool)      . (abs A Bool)))
                                        ;  ------+-------------------------------------
                                        ;  tor   | info                 | type
 
@@ -181,8 +201,9 @@
     (fold-right (lambda (x acc) `(abs ,x ,acc)) t products))
 
   (define (destructor ctor-name prod-type part-type index)
-    (let ([name (dtor-name ctor-name index)])
-      (cons name (cons (list prod-type ctor-name index) `(abs ,prod-type ,part-type)))))
+    (let* ([name (dtor-name ctor-name index)]
+          [info (list prod-type ctor-name index part-type)])
+      (cons name (cons info `(abs ,prod-type ,part-type)))))
   
   (let ([type-name (car data-layout)]
         [ctors (cdr data-layout)])
@@ -322,26 +343,3 @@
           (strong-connect v)))
        (car graph)))
     result))
-
-
-                                       ; utils
-
-(define (range s n)
-  (if (= 0 n) '()
-      (append (range s (- n 1))
-             (list (+ s (- n 1))))))
-
-(define (flat-map f . xs) (fold-left append '() (apply map (cons f xs))))
-(define (repeat x n) (if (<= n 0) '()
-                        (cons x (repeat x (- n 1)))))
-
-
-(define-syntax push!
-  (syntax-rules ()
-    ((_ s x) (set! s (cons x s)))))
-
-(define-syntax pop!
-  (syntax-rules ()
-    ((_ s) (let ([x (car s)])
-            (set! s (cdr s))
-            x))))