From: Luke Lau <luke_lau@icloud.com>
Date: Thu, 15 Aug 2019 12:45:53 +0000 (+0100)
Subject: Handle pattern matching entire expressions
X-Git-Url: https://git.lukelau.me/?p=scheme.git;a=commitdiff_plain;h=e66dabdbc34b1bf5d59cf2596ced19525661a378

Handle pattern matching entire expressions
---

diff --git a/ast.scm b/ast.scm
index 109ce91..d2328cc 100644
--- a/ast.scm
+++ b/ast.scm
@@ -82,6 +82,9 @@
     ['lambda (either (p x)
 		     (inner (lambda-body x)))]
     ['if (either (p x) (any inner (cdr x)))]
+    ['case (either (p x)
+		   (any inner (map cadr (case-cases x)))
+		   (inner (case-switch x)))]
     ['stack (either (p x) (inner (caddr x)))]
     [else (p x)]))
 
diff --git a/tests.scm b/tests.scm
index 49fc2c4..7185032 100644
--- a/tests.scm
+++ b/tests.scm
@@ -169,6 +169,19 @@
       y)))
  'Int)
 
+					; case statements
+(test-types
+ (typecheck '((data A (foo B))
+	      (data B (bar Int))
+	      (case (foo (bar 32))
+		[(foo x) x])))
+ 'B)
+
+(test-types
+ (typecheck '((case 42
+		[23 (= 1 2)]
+		[x (= x 1)])))
+ 'Bool)
 
 					; type annotations
 
@@ -282,8 +295,8 @@
 (test-prog '((data Foo [a] [b] [c])
 	     (let ([x b])
 	       (case x
-		 [a 1]
-		 [b 2]
-		 [c 3])))
+		 [a b]
+		 [b a]
+		 [c x])))
 	   2)
 
diff --git a/typecheck.scm b/typecheck.scm
index ebfd816..064f65f 100644
--- a/typecheck.scm
+++ b/typecheck.scm
@@ -193,16 +193,19 @@
   (define (check-match switch-type x)
     (let ([pattern (car x)]
 	  [expr (cadr x)])
-      (if (eqv? (ast-type pattern) 'app)
+      (case (ast-type pattern)
+	['app
 					; a pattern match with bindings
 	  (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)])
-	      (check dls new-env expr)))
+	      (check dls new-env expr)))]
+					; pattern match with binding and no constructor
+	['var (check dls (env-insert env pattern switch-type) expr)]
 					; a pattern match without bindings
-	  (check dls env expr))))
+	[else (check dls env expr)])))
   
   (let* ([switch-type-res (check dls env (case-switch x))]
 	 [switch-type (cadr switch-type-res)]
@@ -216,9 +219,9 @@
 
 	 [resolved-type (substitute case-expr-equality-cs (car case-expr-types))]
 
-	 [annotated `((case (,(case-expr x) : ,switch-type)
-			,(map (lambda (c e et)
-				`(,c (,e : ,et)))
+	 [annotated `((case (,(case-switch x) : ,switch-type)
+			,@(map (lambda (c e et)
+				 `(,c ((,e : ,et))))
 			       (map car (case-cases x))
 			       (map cadr (case-cases x))
 			       case-expr-types)) : ,resolved-type)]
@@ -345,11 +348,15 @@
 	`((let ,(map (lambda (o n) (list (car o) (denormalize (cadr o) (cadr n))))
 		     (let-bindings orig)
 		     (let-bindings (ann-expr normed)))
-	    ,@(map (lambda (o n) (denormalize o n))
+	    ,@(map denormalize
 		   (let-body orig)
 		   (let-body (ann-expr normed)))) : ,(ann-type normed))]
     ['if `((if ,@(map denormalize (cdr orig) (cdr (ann-expr normed))))
-	   : (ann-type normed))]
+	   : ,(ann-type normed))]
+    ['case `((case ,(denormalize (case-switch orig) (case-switch (ann-expr normed)))
+	       ,@(map (lambda (o n) (cons (car o) (denormalize (cadr o) (cadr n))))
+		      (case-cases orig) (case-cases (ann-expr normed))))
+	     : ,(ann-type normed))]
     [else normed]))
 
 (define ann-expr car)
@@ -359,7 +366,9 @@
 (define (annotate-types prog)
   (denormalize
    (program-body prog)
-   (caddr (check (init-adts-env prog) (normalize (program-body prog))))))
+   (caddr (check (program-data-layouts prog)
+		 (init-adts-env prog)
+		 (normalize (program-body prog))))))
 
   
 					; returns a list of constraints