@s[type=...] is treated as @e[type=...]

The bug

When using type in an @s selector, it suddenly starts selecting all entities that meet the conditions rather than just the sender.

How to reproduce

1. Enter a world with any entities
2. /say @s
3. /say @s[type=!player]
   →  Every entity in the world is found

 

Notes

Does not affect any other selector options