X-Git-Url: https://ruin.nu/git/index.pl?a=blobdiff_plain;f=Typecheck.hs;h=ec40b1f0bc7dc8e249e6e95b738ac3a85bbb2077;hb=0a07bb2f351aa3315fde0768db723650f23c31b6;hp=6e845ba2cb56b9625570676c65e6354da53eb4ba;hpb=597c13d7ed33501aa73e49ae42653e169cea33f4;p=proglang.git

diff --git a/Typecheck.hs b/Typecheck.hs
index 6e845ba..ec40b1f 100644
--- a/Typecheck.hs
+++ b/Typecheck.hs
@@ -70,7 +70,9 @@ typeCheckStm (SDecl t i e) = do
 	t2 <- typeCheckExp e
 	if t == t2 || t2 == NoType then do
 		m <- get
-		put (insert i t m)
+		case insertLookupWithKey (\k a1 a2 -> a1) i t m of 
+			(Nothing,m') -> put m'
+			_ -> fail $ "Duplicate variable declaration: "++show i
 		return NoType
 		else fail $ "Illegal to assign an expression of type "++show t2++" to variable "++show i++" of type "++show t
 typeCheckStm (SPrint e) = do