Flag boolean in comparison operator operands as errors

From #15444 (comment)

var x: boolean, y: boolean;
if (x > y) {  // suspicious!
}

Well, that is the most concise way of writing:

let x: boolean, y: boolean;
if (x && !y) {
}

Accepting PRs: Disallow non-any/number/string operands on either side of <, >, etc.. Should be an easy change

Should {} also be comparable?

At least I have used it in the past to indicate a "comparable" that was not any (i.e. couldn't do anything with it other than compare; using any would allow property access and other shenanigans).

Should {} also be comparable?

Could you elaborate on the scenario? What was the run-time value supposed to be?

In this specific case, it was a function that received a function that produces an ordered list of sorting keys; where the value of the sorting keys are anything comparable. As the function doesn't need the keys to be anything in particular (besides comparable), they were typed as {} (instead of any). At the time that included both numbers and Date objects.

Speaking of which, are Date objects comparable because of spec magic, or because of Symbol.toPrimitive 🤔

Speaking of which, are Date objects comparable because of spec magic

Extreme spec magic; see #2361 (comment)

I've just taken a stab at this issue. The conformance tests for comparison operators work as expected. However, a few tests still fail, such as:

// asyncFunctionDeclaration5_es5.ts

    async function foo(await): Promise<void> {
                       ~~~~~
!!! error TS1138: Parameter declaration expected.
                       ~~~~~
!!! error TS2304: Cannot find name 'await'.
                            ~
!!! error TS1005: ';' expected.
                             ~
!!! error TS1128: Declaration or statement expected.
                               ~~~~~~~~~~~~~~~
                                       ~~~~
!!! error TS2532: Object is possibly 'undefined'.
                                           ~
!!! error TS1109: Expression expected.
    }
    ~
!!! error TS2365: Operator '>' cannot be applied to types 'boolean' and '{}'.

... or ...

// parserTypeAssertionInObjectCreationExpression1.ts

    new <T>Foo()
    ~~~~~~~~~~~~
!!! error TS2365: Operator '>' cannot be applied to types 'boolean' and 'any'.
        ~
!!! error TS1109: Expression expected.
         ~
!!! error TS2304: Cannot find name 'T'.
           ~~~
!!! error TS2304: Cannot find name 'Foo'.

Am I right to assume that this is an issue with (graceful) parsing? If so, should I deal with this in a new issue?

I've not opened a PR yet, BTW. Can do though if you prefer to. Any guidance is much appreciated 🙂

Am I right to assume that this is an issue with (graceful) parsing? If so, should I deal with this in a new issue?

yes.

Maybe late to the party, but I think Date should be comparable as well. It's true that the arithmetic operators yield strange results, but AFAIK the relational ones do not and are frequently used in JS sources.

Marin Marinov (@gcnew)

Marin Marinov (@gcnew) Came here from issue #17119

As the comments stand now, I don't think this issue is a clear duplicate, and if we're keeping addressing that issue in this thread, then at least I want to make it clear. As the reporter Moved to @ad-si (@adius) said, it would be nice if typescript produced a warning for below (d1, d2 are Dates)

d1 === d2
d1 == d2

As Marin Marinov (@gcnew) pointed out <, >, <=, >= work fine

Flag non-any/number/string operands on either side of comparison as e…

Working on this, I’ll follow up with a PR via Bloomberg in the by Monday

I would love to work on this if no one hasn't already or working on it now with a bit a of help!!

Working on this, I’ll follow up with a PR via Bloomberg in the by Monday

I want to work with on it, can I ?

Stella (@LeonxLJX)

I'd like to take this one (Flag boolean in comparison operator operands as errors). I'll look into the root cause and follow up with a PR. (claiming via Stella (@LeonxLJX))

Stella (@LeonxLJX)

I'd like to take this one (Flag boolean in comparison operator operands as errors). I'll dig into the root cause and follow up with a PR shortly. (claiming via Stella (@LeonxLJX))

Stella (@LeonxLJX)

I'd like to take this one (Flag boolean in comparison operator operands as errors). I'll look into the root cause and follow up with a PR. (claiming via Stella (@LeonxLJX))

Navigation Menu

Repository navigation

Flag boolean in comparison operator operands as errors #15506

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Flag boolean in comparison operator operands as errors #15506

Description

Activity

dmichon-msft commented on May 2, 2017

RyanCavanaugh commented on May 8, 2017

Jessidhia commented on May 10, 2017

DanielRosenwasser commented on May 10, 2017

Jessidhia commented on May 10, 2017

RyanCavanaugh commented on May 10, 2017

FabianLauer commented on Jun 12, 2017

mhegazy commented on Jun 12, 2017

gcnew commented on Jun 14, 2017

staeke commented on Feb 16, 2018

Richard-Lynch commented on Sep 27, 2019

HersiYussuf commented on Jun 1, 2024

HersiYussuf commented on Jun 1, 2024

LeonxLJX commented on Sep 1, 2026

LeonxLJX commented on Sep 1, 2026

LeonxLJX commented on Sep 1, 2026

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions