Ensure that Parameters compare equal when they have the same hash (#1…

…1652)

Previously, only the `Parameter.uuid` was compared, so `Paramemter`
instances with different names could compare equal if they had been
constructed using a common value for the `uuid` parameter (which is
usually not passed explicitly).

qiskit/circuit/parameter.py

@@ -138,7 +138,7 @@ def __repr__(self):
 
     def __eq__(self, other):
         if isinstance(other, Parameter):
-            return self._uuid == other._uuid
+            return (self._uuid, self._name) == (other._uuid, other._name)
         elif isinstance(other, ParameterExpression):
             return super().__eq__(other)
         else:

releasenotes/notes/parameter-hash-eq-645f9de55aa78d02.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    :class:`.Parameter` was updated so that instances that compare equal always
+    have the same hash. Previously, only the :attr:`.Parameter.uuid` was
+    compared, so :class:`.Paramemter` instances with different names could
+    compare equal if they had been constructed using a common value for the
+    ``uuid`` parameter (which is usually not passed explicitly).

test/python/circuit/test_parameters.py

@@ -111,10 +111,14 @@ def test_equality(self):
         param = Parameter("a")
         param_copy = Parameter(param.name, uuid=param.uuid)
         param_different = Parameter("a")
+        param_same_uuid_diff_name = Parameter("b", uuid=param.uuid)
 
         self.assertEqual(param, param, "Parameter does not equal itself")
         self.assertEqual(param, param_copy, "Parameters with same data are not equal")
         self.assertNotEqual(param, param_different, "Different Parameters are treated as equal")
+        self.assertNotEqual(
+            param, param_same_uuid_diff_name, "Parameters with different names are treated as equal"
+        )
 
     def test_gate(self):
         """Test instantiating gate with variable parameters"""