Issue with: Property cannot be accessed on possibly null value

[dugokontov]

I have modified your example 03_Null/nulls.js:

/* @flow */
var x = null;
function length() {
    if (x === null) {
        return 0;
    }
    return x.length;
}

var total = length("Hello") + length();

When I run flow on this file I get following error:

nulls.js:7:16,23: property length
Property cannot be accessed on possibly null value
nulls.js:2:13,16: null

But, if I move line var x = null; inside function length, everything will work as expected. It looks like flow doesn't work well with variables outside it's scope.

[vjeux]

function length() { ... }
length("Hello")

Flow should warn that you're calling a function that takes 0 arguments with 1 argument no?

[dugokontov]

It is a valid point, but issue still exist with updated example:

/* @flow */
var x = null;
function length() {
    if (x === null || x === undefined) {
        return 0;
    }
    return x.length;
}

var total = length();

[avikchaudhuri]

Please use x == null as a workaround. (Known issue about Flow not understanding === undefined.)

[avikchaudhuri]

Merging with #21

[dugokontov]

It looks like this is something else, since this doesn't work even with with x == null

/* @flow */
var x = null;
function length() {
    if (x == null) {
        return 0;
    }
    return x.length;
}

var total = length();

I still get

nulls.js:7:16,23: property length
Property cannot be accessed on possibly null value
nulls.js:2:13,16: null

As I said before, I don't get this error when var x = null; is inside function length

[arb]

@dugokontov did you ever find a solution to this? I'm noticing this issue now with early returns and nullable input arguments.

[dugokontov]

@arb no ):
For some reason @avikchaudhuri closed this issue a long time ago...

[linuxonrails]

I have the same problem :-(