[SR-2921] Some implicitly coerced from <x> to Any warnings missing a source location

[swift-ci]

Previous ID	SR-2921
Radar	rdar://problem/28722908
Original Reporter	benasher44 (JIRA User)
Type	Bug
Status	Closed
Resolution	Done

Attachment: Download

Environment

macOS Sierra
Swift 3.0.1
Xcode 8.1b3

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, TypeChecker
Assignee	benasher44 (JIRA)
Priority	Medium

md5: 83cc0bca9622db0226c0caa1153a1c2b

relates to:

• SR-2928 Collection casts from collections of optionals to collections of Any need custom handling

Issue Description:

The result from compiling a few different files in our project is warnings emitted in Xcode that look like this:

<unknown>:0: warning: expression implicitly coerced from 'String?' to Any
<unknown>:0: note: provide a default value to avoid this warning
<unknown>:0: note: force-unwrap the value to avoid this warning
<unknown>:0: note: explicitly cast to Any with 'as Any' to silence this warning
<unknown>:0: warning: expression implicitly coerced from 'String?' to Any
<unknown>:0: note: provide a default value to avoid this warning
<unknown>:0: note: force-unwrap the value to avoid this warning
<unknown>:0: note: explicitly cast to Any with 'as Any' to silence this warning
<unknown>:0: warning: expression implicitly coerced from 'String?' to Any
<unknown>:0: note: provide a default value to avoid this warning
<unknown>:0: note: force-unwrap the value to avoid this warning
<unknown>:0: note: explicitly cast to Any with 'as Any' to silence this warning

I've gone through and explicitly unwrapped as many String!/? s as I can identify, but I can't seem to get these to go away. I've tried coming up with a small repro case, since I can't attach the files in question, but so far I haven't figured out what triggers this. We have about 13 of them like this.

[swift-ci]

Comment by Ben A (JIRA)

Call sites that I can pick out easily that might trigger this seem to be:

• dictionary literals where values are being coerced

• dictionary subscripts where the values are being coerced

But as I said, I've tried explicitly unwrapping values in these cases to no avail.

[belkadan]

@rudkx, CodaFi (JIRA User), can you think of where this would happen?

[rudkx]

I saw a report of this yesterday, and in that case the issue was a dictionary [ String : UIColor? ] that was being passed to a function expecting [ String : Any ].

I'm not sure why the source location is wrong in that case.

[swift-ci]

Comment by Ben A (JIRA)

If any headway is made here, I'm happy to try out a snapshot or build a toolchain locally to try it out in Xcode to verify the fix. And of course I'll update here if I can come up with an isolated repro case.

[rudkx]

I just figured out what the issue is (at least with the test case I mentioned) and will submit a patch soon.

[rudkx]

PR that fixes the source locations: #5259

I opened SR-2928 to track fixing the warning messages and fixits.

[rudkx]

Merged: 623a163

[rudkx]

The source locations should now appear. Please re-open, or open a new ticket, if you find that it's not happening once you pick up a build that has the fix.

[swift-ci]

Comment by Ben A (JIRA)

@rudkx thanks!

[swift-ci]

Comment by Ben A (JIRA)

Tested with swift-DEVELOPMENT-SNAPSHOT-2016-10-13-a, and this is fixed now. Thanks!

[dmcgloin]

Not fixed for me using swift-DEVELOPMENT-SNAPSHOT-2016-11-01 (a)

[rudkx]

@dmcgloin Do you have a test case that demonstrates the issue you're seeing?

[dmcgloin]

I will try to extract a simple example as soon as possible

[swift-ci]

Comment by Mitchell Clay (JIRA)

Noticed this error in XCode 8.1 release, sample code:

func nullToNil(value : Any?) -> Any? {
        if value is NSNull {
            return nil
        }
        return value
}

func parse(json: [String: Any]) {
    let childObject = json["child"] as! [String: Any?]
    let desc = nullToNil(childObject["description"]) as? String
}

I will get "Expression implicitly coerced from Any? to Any" on the "let desc" line

EDIT:

I have realized that this may not be a bug with current version more that it was a bug with previous version that is now fixed. The correct code is:

func nullToNil(value : Any?) -> Any? {
        if value is NSNull {
            return nil
        }
        return value
}

func parse(json: [String: Any]) {
    let childObject = json["child"] as! [String: *Any*]
    let desc = nullToNil(childObject["description"]) as? String
}

Because childObject["description"] is automatically considering the fact that the key may be wrong so a nil value could be returned, but for parsing JSON it will be a value or NSNull.

[dmcgloin]

Here's a snippet that produces a warning without source location.

This occurs with Xcode 8 version 8.1 (8B62) with default Swift 3.
It also occurs with Xcode 8 version 8.1 (8B62) with swift-DEVELOPMENT-SNAPSHOT-2016-10-13-a toolchain.

Please disregard the two warnings about using let instead of var.

    func doTest()
    {
        var color: String? = "Blue"
        var flavor: String? = "Vanilla"
        
        let additionalProperties = ["Color": color, "Flavor": flavor]
        self.logEvent("Something happened", additionalProperties: additionalProperties)
    }

    func logEvent(_ eventName: String, additionalProperties: [String: Any]? = nil)
    {
    }