From 006b94f5a24a794665788737fec8d54086284317 Mon Sep 17 00:00:00 2001
From: Luke Lau <luke_lau@icloud.com>
Date: Tue, 13 Aug 2019 11:21:41 +0100
Subject: [PATCH] Check for the right number of bindings in pattern matching

---
 ast.scm       | 39 ++++++++++++++++++++++++++++++++-------
 codegen.scm   |  4 +---
 tests.scm     | 43 +++++++++++++++++++++++++++++++++++++------
 typecheck.scm |  2 +-
 4 files changed, 71 insertions(+), 17 deletions(-)

diff --git a/ast.scm b/ast.scm
index 8a98617..b3f21bd 100644
--- a/ast.scm
+++ b/ast.scm
@@ -83,27 +83,47 @@
 					;   v
 					; (let ([a (foo~0 (foo 123 345)]
                                         ;       [b (foo~1 (foo 123 345)]) a)
-(define (expand-pattern-matches x)  
+(define (expand-pattern-matches program)
+  (define (go 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))])
+		   [destructor (lambda (i) (dtor-name sum-name i))]
+		   [products (cdr binding-name)]
+
+		   [data-layouts (program-data-layouts program)]
+
+		   [type (data-tor-type data-layouts sum-name)]
+
+		   [sum (assoc sum-name (cdr (assoc type data-layouts)))]
+		   
+		   [expected-number (length (cdr sum))])
+
+					; assert that there is the correct number of bindings
+	      (when (not (= (length products)
+			    expected-number))
+		(error #f (format "Got ~a bindings: expected ~a for ~a"
+			       (length products)
+			       expected-number
+			       binding)))
+	      
 	      (flat-map (lambda (y i)
 			  (pattern-match (list y `(,(destructor i) ,body))))
-		      (cdr binding-name)
-		      (range 0 (length (cdr binding-name))))))))
+			products
+			(range 0 (length products)))))))
     (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)]))
+	       ,@(map go (let-body x)))]
+      [else (ast-traverse go x)]))
+  (program-map-exprs go program))
 
 (define (lambda? x)
   (and (list? x) (eq? (car x) 'lambda)))
 
-
 (define (statement-type x)
   (cond
    [(and (list? x)
@@ -137,6 +157,11 @@
      ,@(filter (lambda (x) (eqv? (statement-type x) 'expr))
 	       program)))
 
+(define (data-tor-type data-layouts tor)
+  (let* ([tors (flat-map data-tors data-layouts)]
+	 [info (cadr (assoc tor tors))])
+    (car info)))
+
 					; a data tor is either a constructor or destructor for an ADT
 					; data-tors returns constructors and destructors for a data-layout
 					; (data A (foo Int Bool)
diff --git a/codegen.scm b/codegen.scm
index 8e3a7d5..dededbe 100644
--- a/codegen.scm
+++ b/codegen.scm
@@ -658,9 +658,7 @@
   (set! cur-lambda 0)
   (let* ([data-layouts (program-data-layouts program)]
 
-	 [pattern-matched (program-map-exprs
-			   expand-pattern-matches
-			   program)]
+	 [pattern-matched (expand-pattern-matches program)]
 	 [type-annotated (annotate-types pattern-matched)]
 	 [stack-annotated (annotate-stack-values data-layouts
 						 type-annotated)]
diff --git a/tests.scm b/tests.scm
index bcd878a..fa5b195 100644
--- a/tests.scm
+++ b/tests.scm
@@ -7,7 +7,13 @@
 	   (format "test failed:\nexpected: ~a\nactual:   ~a"
 		   expected actual))))
 
-(define (test . xs) (apply test-f (cons equal? xs)))
+(define-syntax test
+  (syntax-rules ()
+    ((_ a e)
+     (begin
+       (display (quote a))
+       (newline)
+       (test-f equal? a e)))))
 
 (define-syntax test-types
   (syntax-rules ()
@@ -30,7 +36,7 @@
   (display prog)
   (newline)
   (compile-to-binary prog "/tmp/test-prog" host-os)
-  (test (system "/tmp/test-prog") exit-code))
+  (test-f equal? (system "/tmp/test-prog") exit-code))
 
 (define (test-expr prog exit-code)
   (test-prog (list prog) exit-code))
@@ -41,7 +47,24 @@
   (compile-to-binary prog "/tmp/test-prog" host-os)
   (system "/tmp/test-prog > /tmp/test-output.txt")
   (let ((str (read-file "/tmp/test-output.txt")))
-    (test str output)))
+    (test-f equal? str output)))
+
+(define-syntax test-exception
+  (syntax-rules ()
+    ((_ f)
+     (begin
+       (display (quote f))
+       (newline)
+       (call/cc (lambda (k)
+		  (with-exception-handler
+		   (lambda (x)
+		     (when (eqv? 'no-exception x)
+		       (error #f "test failed: no exception thrown"))
+		     (k))
+		   (lambda ()
+		     (begin
+		       f
+		       (raise 'no-exception))))))))))
 
 (test (data-tors '(A . ((foo Int Bool)
 			(bar Bool))))
@@ -61,11 +84,19 @@
 	(bar . (abs Bool A))
 	(bar~0 . (abs A Bool))))
 
-(test (expand-pattern-matches '(let ([(foo x y) (foo 123 234)] [z (f 123)]) x))
-      '(let ([x (foo~0 (foo 123 234))]
+(test (expand-pattern-matches
+       '((data A (foo Int Int))
+	 (let ([(foo x y) (foo 123 234)] [z (f 123)]) x)))
+      '((data A (foo Int Int))
+	(let ([x (foo~0 (foo 123 234))]
 	      [y (foo~1 (foo 123 234))]
 	      [z (f 123)])
-	 x))
+	  x)))
+
+(test-exception
+ (expand-pattern-matches '((data A (foo Int Int))
+			   (let ([(foo x) (foo 123 234)])
+			     x))))
 
 (test-types (typecheck '((lambda (x) (+ ((lambda (y) (x y 3)) 5) 2))))
 	    '(abs (abs Int (abs Int Int)) Int))
diff --git a/typecheck.scm b/typecheck.scm
index a526620..d180e44 100644
--- a/typecheck.scm
+++ b/typecheck.scm
@@ -259,7 +259,7 @@
 
 					; we typecheck the lambda calculus only (only single arg lambdas)
 (define (typecheck prog)
-  (let ([expanded (program-map-exprs expand-pattern-matches prog)])
+  (let ([expanded (expand-pattern-matches prog)])
     (cadr (check (init-adts-env expanded) (normalize (program-body expanded))))))
 
 
-- 
2.30.2