diff -r 93e0a19c805a -r 0206df35882c jitcraft/SemanticAnalysis.cpp
--- a/jitcraft/SemanticAnalysis.cpp	Tue Jul 17 03:59:52 2012 -0700
+++ b/jitcraft/SemanticAnalysis.cpp	Tue Jul 17 21:40:44 2012 -0700
@@ -207,7 +207,13 @@
         }
     }
 
-    if (token >= TOK_EQUALS && token <= TOK_OR) {
+    if (token == TOK_OR || token == TOK_AND) {
+        if (!canTest(node, left) || !canTest(node, right))
+            return NULL;
+        return zone_->types()->getPrimitive(PrimitiveType_Int32);
+    }
+
+    if (token >= TOK_EQUALS && token <= TOK_GE) {
         if ((left->isFloat() || (left->isInt32() && !left->tag())) &&
             (right->isFloat() || (right->isInt32() && !right->tag())))
         {
@@ -230,7 +236,7 @@
 bool
 SemanticAnalysis::canTest(AstNode *node, Handle<Type> type)
 {
-    if (type->isArray()) {
+    if (type->isArray() || (type->isInt32() && type->tag())) {
         cc_.reportError(node->pos(), Message_ArrayIsNotBoolean);
         return false;
     }
@@ -340,13 +346,21 @@
 
     switch (node->token())
     {
+      case TOK_NOT:
+        if (!canTest(node->expression(), type))
+            return;
+        type = zone_->types()->getPrimitive(PrimitiveType_Int32);
+        if (!type)
+            return;
+        node->setType(type);
+        break;
+
       default:
         assert(node->token() == TOK_TILDE);
         if (!type->isInt32() || type->tag()) {
             unaryTypeError(node, node->token(), type);
             return;
         }
-        
         node->setType(type);
         break;
     }