Possibly undefined but it's not

[mbayou]

Hi,

I have an issue about the strictNullChecks, indeed I am using it right now and it says "Object is possibly 'undefined'." on an object cannot be undefined.

TypeScript Version: 2.5.3

Code

Failling code

// Retrieve circle with identifier
const circle: Circle | undefined = await this.circleDao.findById(command.getId());
// Check if localAuthority is found in database
Utils.checkArgument(circle !== undefined, "Circle with id '" + command.getId() + "' cannot be found");

// Compiler fail on this line with message "Object is possibly 'undefined'."
circle.setDefaultCircle(command.isDefaultCircle());

Utils.ts method

public static checkArgument(expression: boolean, message?: string) {
        if (!expression) {
            throw new IllegalArgumentError(message);
        }
}

Expected behavior:

When I check if an object is undefined in an external method the compiler can see it and don't throw error : "Object is possibly 'undefined'."

Actual behavior:

When I check if an object is undefined in an external method the compiler throw error : "Object is possibly 'undefined'."

[Ghabriel]

See #9998 .

[mhegazy]

also see #16546 and #9655

[mhegazy]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.