Custom Post Type Slug Conflicts With Page Slug

[pressuser79]

1. Create a page called "test. It will be visible at ​http://site.com/test
2. Create a new Custom Post Type (CPT), say "Examples".
3. Inside the editor for the CPT, add a new post. Give it a name of "test".

Ideally the CPT SHOULD be visible at ​http://site.com/examples/test, but Wordpress will prefer it to exist at a slug that does not conflict with the page slug - probably something like ​http://site.com/examples/test-2.

This constraint makes Wordpress almost unusable for some sites.

[SergeyBiryukov]

Duplicate of #18962.