object is possibly undefined even though check is done

TypeScript Version: 3.6.3

Search Terms: object is possibly undefined

Code

const foo = (bar: { baz?: { name: string } }) => {
    const isBarBazDefined = !!bar.baz;
    if(isBarBazDefined) console.log(bar.baz.name);
}

Expected behavior:
Typescript should not give an 'object is possibly undefined' error.

Actual behavior:
Typescript does give an 'object is possibly undefined' error.

Playground Link:
http://www.typescriptlang.org/play/?ssl=4&ssc=2&pln=1&pc=1#code/MYewdgzgLgBAZiEMC8MAUAjAhgJwFwwDeM2AXgPwHFhYC2ApgdDgJZgDmMAvtwJQoA+IgCgYYmKEiwWEAEK55pACL04begBMUMAIQ7sOAHRkA3KPEs4aGfJyKVasJv6SIIADb1D7kO0y5jLFJDGgZeMy4gA

Related Issues:
Couldn't find any.

I realise this is very simple case, but I haven't been able to find an existing issue or FAQ entry on the subject...

This is a duplicate of #12184 - narrowing results cannot be assigned to an identifier and reused.

Thanks. Is there any recommended workaround, besides again doing the check ?

Jonathan Loss (@barroudjo)

Jonathan Loss (@barroudjo) The quick and easy way is a ! assertion:

const foo = (bar: { baz?: { name: string } }) => {
    const isBarBazDefined = !!bar.baz;
    if(isBarBazDefined) console.log(bar.baz!.name);
}

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.

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