From: Luke Lau <luke_lau@icloud.com>
Date: Thu, 15 Aug 2019 00:12:31 +0000 (+0100)
Subject: WIP on typechecking case statements
X-Git-Url: http://git.lukelau.me/?p=scheme.git;a=commitdiff_plain;h=7bcc8cc8aa41849a6f6e0615a1309b7ac3b3956f

WIP on typechecking case statements
---

diff --git a/typecheck.scm b/typecheck.scm
index d180e44..6aca2c1 100644
--- a/typecheck.scm
+++ b/typecheck.scm
@@ -244,7 +244,40 @@
 		      annotated)))
 
 	  
-	  ('app (check-app env x)))))
+	  ('app (check-app env x))
+	  ['case
+	      (let* ([expr-type-res (check env (case-expr x))]
+		     [expr-type (cadr env)]
+		     [case-match-type-res (map (lambda (x) (check env x))
+					       (map car (case-cases x)))]
+		     [case-match-types (map cadr case-match-type-res)]
+		     
+		     [case-expr-type-res (map (lambda (x) (check env x))
+					      (map cadr (case-cases x)))]
+		     [case-expr-types (map cadr case-expr-types-res)]
+
+		     [case-match-equality-cs (fold-left constraint-merge '()
+							(map (lambda (t) (~ t expr-type)) case-match-types))]
+
+		     [case-expr-equality-cs (fold-left constraint-merge '()
+						       (map (lambda (t) (~ t (car case-expr-type-res)))
+							    (cdr case-expr-type-res)))]
+
+		     [resolved-type (substitute case-expr-eqaulity-cs (car case-expr-type-res))]
+
+		     [annotated `((case (,(case-expr x) : ,expr-type)
+				    ,(map (lambda (c e et)
+					    `(,c (,e : ,et)))
+					  (map car (case-cases x))
+					  (map cadr (case-cases x))
+					  case-expr-types)) : ,resolved-type)]
+		     
+		     [cs (fold-left constraint-merge '()
+				    (append case-match-equality-cs
+					    case-expr-equality-cs
+					    (cadr expr-type-res)))])
+		(list cs resolved-type annotated))])))
+		
     ;; (display "result of ")
     ;; (display x)
     ;; (display ":\n\t")