Modifying state during view update

[v-oleksandr]

Hi all!
I'm quite new to TCA and SwiftUI.
When I'm trying to show ProgressView in my project, Xcode shows strange warning:
Modifying state during view update, this will cause undefined behavior.

I'm also noticed this is happens in the example project (TicTacToe). Just after login.
When loginButtonTapped action fires: state.isLoginRequestInFlight = true in loginReducer.

Is this some known issue? Or what exactly causing this? Obviously I don't understand why the view updating during this action