From 0db4aa6c791e5ed27bfd9c4461e7a5337ee699e1 Mon Sep 17 00:00:00 2001
From: Luke Lau <luke_lau@icloud.com>
Date: Thu, 15 Aug 2019 17:36:32 +0100
Subject: [PATCH] Start work on collecting all bindings when typechecking
 nested pattern match

---
 typecheck.scm | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/typecheck.scm b/typecheck.scm
index c6b90e7..b346675 100644
--- a/typecheck.scm
+++ b/typecheck.scm
@@ -191,6 +191,16 @@
 (define (check-case dls env x)
 
   (define (check-match switch-type x)
+    
+    (define (get-bindings product-types pattern)
+      (define (go product-type product)
+	     (case (ast-type x)
+	       ['var (list (cons product product-type))]
+					; an inner pattern match
+	       ['app (get-bindings product-type product)]))
+      (flat-map go product-types (cdr pattern)))
+
+    
     (let ([pattern (car x)]
 	  [expr (cadr x)])
       (case (ast-type pattern)
@@ -199,8 +209,8 @@
 	  (let ([sum (assoc (car pattern) (cdr (assoc switch-type dls)))])
 	    (unless sum (error #f "can't pattern match ~a with ~a" switch-type pattern))
 	    (let* ([names (cdr pattern)]
-		   [types (cdr sum)]
-		   [new-env (fold-left env-insert env names types)])
+		   [product-types (cdr sum)]
+		   [new-env (append (get-bindings product-types pattern) env)])
 	      (check dls new-env expr)))]
 					; pattern match with binding and no constructor
 	['var (check dls (env-insert env pattern switch-type) expr)]
-- 
2.30.2