added some sanity checks in Result constructor

compile.py

@@ -91,6 +91,9 @@ class FunctionFactory:
     def __init__(self, inputs, outputs, linker = 'py', optimizer = std_opt, borrow_outputs = False):
         if len(inputs) != len(set(inputs)):
             print >>sys.stderr, "Warning: duplicate inputs"
+        for r in list(inputs) + list(outputs):
+            if not isinstance(r, gof.Result):
+                raise TypeError("All inputs and outputs to FunctionFactory should be Result instances. Received:", type(r), r)
         env = std_env(inputs, outputs)
         if None is not optimizer:
             optimizer(env)

gof/graph.py

@@ -89,8 +89,14 @@ class Result(object2):
     #__slots__ = ['type', 'owner', 'index', 'name']
     def __init__(self, type, owner = None, index = None, name = None):
         self.type = type
+        if owner is not None and not isinstance(owner, Apply):
+            raise TypeError("owner must be an Apply instance", owner)
         self.owner = owner
+        if index is not None and not isinstance(index, int):
+            raise TypeError("index must be an int", index)
         self.index = index
+        if name is not None and not isinstance(name, str):
+            raise TypeError("name must be a string", name)
         self.name = name
     def __str__(self):
         if self.name is not None: