additional fix and test for ticket #650

Cython/Compiler/Nodes.py

@@ -4145,7 +4145,9 @@ class RaiseStatNode(StatNode):
         if self.exc_type and not self.exc_value and not self.exc_tb:
             exc = self.exc_type
             import ExprNodes
-            if isinstance(exc, ExprNodes.SimpleCallNode) and not exc.args:
+            if (isinstance(exc, ExprNodes.SimpleCallNode) and 
+                not (exc.args or (exc.arg_tuple is not None and 
+                                  exc.arg_tuple.args))):
                 exc = exc.function # extract the exception type
             if exc.is_name and exc.entry.is_builtin:
                 self.builtin_exc_name = exc.name

tests/run/raise_memory_error_T650.pyx

@@ -23,3 +23,12 @@ def raise_me_instance():
     ... else: print('NOT RAISED!')
     """
     raise MemoryError()
+
+def raise_me_instance_value():
+    """
+    >>> raise_me_instance_value()
+    Traceback (most recent call last):
+        ...
+    MemoryError: oom
+    """
+    raise MemoryError("oom")