Make sure Discretization.complex_dtype is actually a dtype

meshmode/discretization/__init__.py

@@ -203,10 +203,10 @@ class Discretization(object):
             self.nnodes += ng.nnodes
 
         self.real_dtype = np.dtype(real_dtype)
-        self.complex_dtype = {
+        self.complex_dtype = np.dtype({
                 np.float32: np.complex64,
                 np.float64: np.complex128
-                }[self.real_dtype.type]
+                }[self.real_dtype.type])
 
     @property
     def dim(self):