Trying to delete an issue type with an issue of that issue type in the trash causes confusion

Trying to delete an issue type requires not having any issue with that issue type first, whether deleting the issues or changing the issue type.

If a project is moved to the Trash, the issues in it can still block deleting an issue type, and even though the message will indicate that there are X number of issues pending, trying to see which issues are those will not show them in the issue search, as the issues in the trash are not shown in the search.

The suggestion is to improve the visibility of issues in the trash or to include mentions in the messages that indicate this behavior.

Including full error message to improve searchability:

Note: This issue type cannot be deleted - there are currently 1 matching issues with no suitable alternative issue types (only issues you have permission to see will be displayed, which may be different from the total count shown on this page).

In order for an issue type to be deleted, it needs to be associated with one workflow, field configuration and field screen scheme across all projects. If this is not the case, Jira can not provide a list of valid replacement issue types.