Which @angular/* package(s) are the source of the bug?

core

Is this a regression?

No

Description

The new type of SimpleChange does not reflect the possible undefined value for the public previousValue property.

However, the previousValue might be undefined during runtime, e.g. for the first change.

Please provide a link to a minimal reproduction of the bug

No response

Please provide the exception or error you saw

Please provide the environment you discovered this bug in (run ng version)

Angular 21.x.x

Anything else?

No response