Avoid Moment typechecks when (un)freezing circuits (#7150)

Author: maffoo

cirq-core/cirq/circuits/circuit.py

@@ -1867,7 +1867,7 @@ def freeze(self) -> 'cirq.FrozenCircuit':
         from cirq.circuits.frozen_circuit import FrozenCircuit
 
         if self._frozen is None:
-            self._frozen = FrozenCircuit.from_moments(*self._moments)
+            self._frozen = FrozenCircuit._from_moments(self._moments)
         return self._frozen
 
     def unfreeze(self, copy: bool = True) -> 'cirq.Circuit':

cirq-core/cirq/circuits/frozen_circuit.py

@@ -84,7 +84,7 @@ def freeze(self) -> 'cirq.FrozenCircuit':
         return self
 
     def unfreeze(self, copy: bool = True) -> 'cirq.Circuit':
-        return Circuit.from_moments(*self)
+        return Circuit._from_moments(self._moments)
 
     @property
     def tags(self) -> Tuple[Hashable, ...]: