Loosen type annotation to allow NotImplemented.

src/runtime/objmodel.cpp

@@ -4157,6 +4157,11 @@ Box* callCLFunc(FunctionMetadata* md, CallRewriteArgs* rewrite_args, int num_out
     if (!r) {
         assert(S == CAPI);
     } else {
+        // If this assertion is triggered because the type isn't what we expected,
+        // but something that should be allowed (e.g. NotImplementedType), it is
+        // possible that the program has a bad type annotation. For example, an
+        // attribute that we added in C++ should have return type UNKNOWN instead
+        // of BOXED_SOMETHING.
         ASSERT(chosen_cf->spec->rtn_type->isFitBy(r->cls), "%s (%p) was supposed to return %s, but gave a %s",
                g.func_addr_registry.getFuncNameAtAddress(chosen_cf->code, true, NULL).c_str(), chosen_cf->code,
                chosen_cf->spec->rtn_type->debugName().c_str(), r->cls->tp_name);

src/runtime/tuple.cpp

@@ -687,7 +687,9 @@ void setupTuple() {
 
     tuple_cls->giveAttr("__len__", new BoxedFunction(FunctionMetadata::create((void*)tupleLen, BOXED_INT, 1)));
     tuple_cls->giveAttr("__repr__", new BoxedFunction(FunctionMetadata::create((void*)tupleRepr, STR, 1)));
-    tuple_cls->giveAttr("__add__", new BoxedFunction(FunctionMetadata::create((void*)tupleAdd, BOXED_TUPLE, 2)));
+
+    // Return type is UNKNOWN as it could be NotImplemented.
+    tuple_cls->giveAttr("__add__", new BoxedFunction(FunctionMetadata::create((void*)tupleAdd, UNKNOWN, 2)));
     tuple_cls->giveAttr("__mul__", new BoxedFunction(FunctionMetadata::create((void*)tupleMul, BOXED_TUPLE, 2)));
     tuple_cls->giveAttr("__rmul__", new BoxedFunction(FunctionMetadata::create((void*)tupleMul, BOXED_TUPLE, 2)));
 

test/tests/tuples.py

@@ -95,6 +95,11 @@ print (1, 2, 3) + ()
 print () + (1, 2, 3)
 print (1, 2) + (2, 3)
 
+try:
+    (1, 2) + "a"
+except TypeError as e:
+    print "adding failed"
+
 ## __new__
 print tuple()
 print tuple((1,3,7,42))