Make get_scalar_constant_value() support Shape_i()(Constant)

theano/tensor/basic.py

@@ -566,6 +566,9 @@ def get_scalar_constant_value(v):
         if isinstance(v.owner.op, scal.Second):
             x, y = v.owner.inputs
             return get_scalar_constant_value(y)
+        if (isinstance(v.owner.op, theano.compile.ops.Shape_i) and
+            isinstance(v.owner.inputs[0], Constant)):
+            return v.owner.inputs[0].data.shape[v.owner.op.i]
         # Don't act as the constant_folding optimization here as this
         # fct is used too early in the optimization phase.  This would
         # mess with the stabilization optimization.

theano/tensor/tests/test_basic.py

@@ -5921,6 +5921,13 @@ class T_get_scalar_constant_value(unittest.TestCase):
             get_scalar_constant_value,
             mv[t()])
 
+    def test_shape_i(self):
+        c = theano.tensor.constant(numpy.random.rand(3, 4))
+        s = opt.Shape_i(0)(c)
+        assert get_scalar_constant_value(s) == 3
+        s = opt.Shape_i(1)(c)
+        assert get_scalar_constant_value(s) == 4
+
 
 class T_as_tensor_variable(unittest.TestCase):
     """