true || leads to "Object possibly 'undefined'"

[yonilerner]

TypeScript Version: Nightly (as of date of issue creation)

Search Terms:

• "Object is possibly undefined" (and variations)
• "true ||"

Code

interface Foo {
    bar?: boolean
}
function test(x: Foo | undefined) {
    if (!x?.bar) {
        return
    }
    return true || x.bar
}

Expected behavior:
Compiles with no errors

Actual behavior:
"Object is 'undefined'" on x in the statement return true || x.bar
This is especially weird because if you remove the true || so you just have return x.bar, there is no error, and if you move the extra condition to the end so you have return x.bar || true there is also no error.

Playground Link: http://www.typescriptlang.org/play/index.html?ts=Nightly#code/JYOwLgpgTgZghgYwgAgGIHt3IN4FgBQyRyARnFAPwBcpmANhHCAQL4EwCuICYw6IySAGcwACgAeNDFgA+yLgBMIMUBAUBKHAWLJgMZKICE4igDoyUTXkI7iUCGA5RmNom1fJ7j54KgcUMnLi5uSsQA

[jack-williams]

I think this is duplicate of #26914.

[yonilerner]

Makes sense. Should I close this or wait for someone else to mark it duplicate?

[RyanCavanaugh]

Always OK to self-close here. Thanks for asking!