Broken rounded corners for "input-group-prepend" with class "invalid-feedback"

[pranuel]

Hi,

I want report a bug for the class "input-group-prepend" in combination with a div for displaying the "invalid-feedback".

Actual behaviour: If you implement this like documented by bootstrap the input's corners to the right are not rounded.
Expected behaviour: The corners to the right should be rounded, too.

How to reproduce this behaviour:

• go to the bootstrap docs for form validation: https://getbootstrap.com/docs/4.0/components/forms/#custom-styles
• Have a look at the "Username" input group: The top right and the bottom right corners are not rounded

I think this results from the :last-child selector which is used by bootstrap to decide whether or not to use rounded corners for the input.

[rafalp]

Duplicate of #25110