Fix mypy errors attributed to pytorch_lightning.utilities.distributed (#13678)

Co-authored-by: Carlos Mocholí <carlossmocholi@gmail.com>

Author: krishnakalyan3

pyproject.toml

@@ -84,7 +84,6 @@ module = [
     "pytorch_lightning.tuner.batch_size_scaling",
     "pytorch_lightning.utilities.auto_restart",
     "pytorch_lightning.utilities.data",
-    "pytorch_lightning.utilities.distributed",
     "pytorch_lightning.utilities.meta",
 ]
 ignore_errors = "True"

src/pytorch_lightning/utilities/distributed.py

@@ -145,6 +145,7 @@ def sync_ddp(result: Tensor, group: Optional[Any] = None, reduce_op: Optional[Un
     if group is None:
         group = torch.distributed.group.WORLD
 
+    op: Optional[ReduceOp]
     if isinstance(reduce_op, str):
         if reduce_op.lower() in ("avg", "mean"):
             op = ReduceOp.SUM
@@ -174,7 +175,7 @@ def sync_ddp(result: Tensor, group: Optional[Any] = None, reduce_op: Optional[Un
 
 class AllGatherGrad(torch.autograd.Function):
     @staticmethod
-    def forward(
+    def forward(  # type: ignore[override]
         ctx: Any,
         tensor: Tensor,
         group: Optional["torch.distributed.ProcessGroup"] = group.WORLD,
@@ -317,7 +318,7 @@ def register_ddp_comm_hook(
         ddp_comm_hook = ddp_comm_wrapper(ddp_comm_hook)
 
     new_rank_zero_debug(f"Registering DDP comm hook: {ddp_comm_hook.__qualname__}.")
-    model.register_comm_hook(state=ddp_comm_state, hook=ddp_comm_hook)
+    model.register_comm_hook(state=ddp_comm_state, hook=ddp_comm_hook)  # type: ignore[operator]
 
 
 def tpu_distributed() -> bool: