!2430 fix bug of type cast

Merge pull request !2430 from liangzelang/dev

mindspore/nn/optim/adam.py

@@ -72,9 +72,9 @@ def _update_run_op(beta1, beta2, eps, lr, weight_decay_tensor, param, m, v, grad
     update_with_lr = op_mul(lr, update)
     next_param = param_fp32 - op_reshape(update_with_lr, op_shape(param_fp32))
 
-    next_v = F.depend(next_v, F.assign(param, op_cast(next_param, mstype.float16)))
-    next_v = F.depend(next_v, F.assign(m, op_cast(next_m, mstype.float16)))
-    next_v = F.depend(next_v, F.assign(v, op_cast(next_v, mstype.float16)))
+    next_v = F.depend(next_v, F.assign(param, op_cast(next_param, F.dtype(param))))
+    next_v = F.depend(next_v, F.assign(m, op_cast(next_m, F.dtype(m))))
+    next_v = F.depend(next_v, F.assign(v, op_cast(next_v, F.dtype(v))))
     return next_v