Address #336 case 3

Fix error condition for bad abstract types - don't return NULL, panic.

src/core/marsh.c

@@ -1098,7 +1098,7 @@ static const uint8_t *unmarshal_one_abstract(UnmarshalState *st, const uint8_t *
     Janet key;
     data = unmarshal_one(st, data, &key, flags + 1);
     const JanetAbstractType *at = janet_get_abstract_type(key);
-    if (at == NULL) return NULL;
+    if (at == NULL) goto oops;
     if (at->unmarshal) {
         JanetMarshalContext context = {NULL, st, flags, data, at};
         *out = janet_wrap_abstract(at->unmarshal(&context));
@@ -1107,7 +1107,8 @@ static const uint8_t *unmarshal_one_abstract(UnmarshalState *st, const uint8_t *
         }
         return context.data;
     }
-    return NULL;
+oops:
+    janet_panic("invalid abstract type");
 }
 
 static const uint8_t *unmarshal_one(

test/suite8.janet

@@ -212,5 +212,6 @@
 
 (assert-error "unmarshal errors 1" (unmarshal @"\xd6\xb9\xb9"))
 (assert-error "unmarshal errors 2" (unmarshal @"\xd7bc"))
+(assert-error "unmarshal errors 3" (unmarshal "\xd3\x01\xd9\x01\x62\xcf\x03\x78\x79\x7a" load-image-dict))
 
 (end-suite)

tools/afl/generate_unmarshal_testcases.janet

@@ -8,15 +8,15 @@
 
 (def cases [
   nil
-  
+
   "abc"
-  
+
   :def
-  
+
   'hij
-  
+
   123
-  
+
   (int/s64 123)
 
   "7"
@@ -28,12 +28,12 @@
   {:a 123}
 
   @{:b 'xyz}
-  
+
   (peg/compile
     '{:a (* "a" :b "a")
       :b (* "b" (+ :a 0) "b")
       :main (* "(" :b ")")})
-  
+
   (fn f [a] (fn [] {:ab a}))
 
   (fn f [a] (print "hello world!"))