(ec2): Subnet and ISubnet variable naming causes Pylance type error

Describe the bug

The L2 construct Subnet doesn’t use the same method parameter names as ISubnet in associate_network_acl. This makes Pylance believe that Subnet does not implement the interface ISubnet, causing it to raise warnings.

Expected Behavior

Pylance would understand that “Subnet” implements “ISubnet” and not raise errors.

Current Behavior

(variable) subnet: Subnet
Argument of type "list[Subnet]" cannot be assigned to parameter "subnets" of type "Sequence[ISubnet] | None" in function "__init__"
  Type "list[Subnet]" cannot be assigned to type "Sequence[ISubnet] | None"
    TypeVar "_T_co@Sequence" is covariant
      "Subnet" is incompatible with protocol "ISubnet"
        "associate_network_acl" is an incompatible type
          Type "(id: str, network_acl: INetworkAcl) -> None" cannot be assigned to type "(id: str, acl: INetworkAcl) -> None"

Reproduction Steps

In VS Code with the “Pylance” language server extension enabled, add this stack to a CDK project and look for the red squiggly lines in the SubnetSelection constructor.

from aws_cdk import (
    # Duration,
    Stack,
    aws_ec2 as ec2,
)
from constructs import Construct


class ReproStack(Stack):
    def __init__(self, scope: Construct, construct_id: str, **kwargs) -> None:
        super().__init__(scope, construct_id, **kwargs)

        vpc = ec2.Vpc(self, "vpc")
        subnet = ec2.Subnet(
            self,
            "subnet",
            availability_zone="us-east-1a",
            vpc_id=vpc.vpc_id,
            cidr_block="10.0.0.0/16",
        )

        subnet_filter = ec2.SubnetSelection(subnets=[subnet])

Possible Solution

Change the parameter name for the INetworkAcl type to be consistent across Subnet and ISubnet.

https://github.com/aws/aws-cdk/blob/f199faddc0b8e565aa413e480e51d25fed5321bf/packages/%40aws-cdk/aws-ec2/lib/vpc.ts#L61

https://github.com/aws/aws-cdk/blob/f199faddc0b8e565aa413e480e51d25fed5321bf/packages/%40aws-cdk/aws-ec2/lib/vpc.ts#L1757

Additional Information/Context

No response

CDK CLI Version

2.22.0 (build 1db4b16)

Framework Version

Pylance v2022.4.3

Node.js Version

v16.14.2

OS

Ubuntu 20.04.4 LTS (WSL 2)

Language

Python

Language Version

3.10.4

Other information

No response

[gshpychka]

This happens in a lot of constructs and is being tracked here: https://github.com/aws/aws-cdk/issues/15584 and https://github.com/aws/jsii/issues/2927

[gshpychka]

Are there any workarounds available? Like muting pyright warnings etc. The issues from previous comment are more than one year old 😃 Just wondering how people work with python CDK.

yes, the current workaround is to use typing.cast to satisfy the type checker.