Added a test case for the situation of an Op has no input

theano/gof/tests/test_op.py

-
 from copy import copy
+
+import theano
+
 from theano.gof.op import *
 from theano.gof.type import Type, Generic
 from theano.gof.graph import Apply, Variable
@@ -23,6 +25,11 @@ class MyType(Type):
     def __repr__(self):
         return str(self.thingy)
 
+    def filter(self, x, strict=True, allow_downcast=None):
+        # Dummy filter: we want this type to represent strings that
+        # start with `self.thingy`.
+        assert isinstance(x, str) and x.startswith(self.thingy)
+        return x
 
 class MyOp(Op):
 
@@ -37,6 +44,23 @@ class MyOp(Op):
 MyOp = MyOp()
 
 
+class NoInputOp(Op):
+
+    """An Op to test the corner-case of an Op with no input."""
+
+    def __eq__(self, other):
+        return type(self) == type(other)
+
+    def __hash__(self):
+        return hash(type(self))
+
+    def make_node(self):
+        return Apply(self, [], [MyType('test')()])
+
+    def perform(self, node, inputs, output_storage):
+        output_storage[0][0] = 'test Op no input'
+
+
 class TestOp:
 
     # Sanity tests
@@ -56,6 +80,11 @@ class TestOp:
             if str(e) != "Error 1":
                 raise
 
+    def test_op_no_input(self):
+        x = NoInputOp()()
+        f = theano.function([], x)
+        rval = f()
+        assert rval == 'test Op no input'
 
 
 if __name__ == '__main__':