How to use equality Operator on typescript Types

Question

I am trying to check the value with equality operator as below

<button type="button" class="btn btn-light {{ currentStep != 'collection' ? 'd-none' : '' }}"
            style="background-color: #BEDBBF;color: #007F00;margin-right: 5px;"
                (click)="back()">
    Back
</button>

In Component.ts file

currentStep: steps = 'collection';

&

export type steps = 'collection' | 'tagging' | 'summary';

Somehow not equal operator not working here.

Dont know why below error showing

error TS2367: This condition will always return 'true' since the types '"summary" | "tagging"' and '"collection"' have no overlap.