Type guard/Equality narrowing doesn't work on "any"

[kkmuffme]

Bug Report

🔎 Search Terms

type guard equality narrowing strict equal equality

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I found earlier issues (Number, enum, and boolean literal types #9407 and the PR that added this feature Number, enum, and boolean literal types #9407)

⏯ Playground Link

https://www.typescriptlang.org/play?#code/FAMwrgdgxgLglgewgAgEYEMBOAKZWDmAXHhAJ7ICUyA3sMvcnCMrgcgLyfIRgA2vlGnQYjMAUxhhMKAgG5h9AL7AFjZq0z4OXEOl4BnMYNojREqTM3yRy5SqA

💻 Code

function bar( arg: any ) {
    if ( arg === null ) {
        return arg;
    }

    if ( arg === false ) {
        return arg;
    }
}

🙁 Actual behavior

arg should be null/false inside the if conditions

🙂 Expected behavior

arg is any

The docs say this should work https://www.typescriptlang.org/docs/handbook/2/narrowing.html
When using unknown instead of any it works perfectly fine. I think adjusting this, so it works for any too, isn't too far fetched.

[jcalz]

References:

• Equality narrowing for unknown: requested in Equality operator with unknown does not narrow the type of the unknown #25172 and implemented in Fix #25172: Add narrowing for unknown with triple equals #26941.
• General narrowing for any: requested in allow narrowing from any #9999 and implemented for "most situations" in Narrow from 'any' in most situations #10334, but apparently not equality narrowing

[RyanCavanaugh]

I don't know why you wouldn't just write false or null in those cases instead of writing the argument name again, but I guess it would be more correct to do this for primitives at least.