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

Partner Rank: 3

Verification builds: 1.2, 1.9, 1.13.0.1, 1.13.0.4
Regression builds: Broken since 1.2.2001.0, can't test anything earlier (likely always broken)

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

Impact: Have to use time or space-inefficient workarounds, annoying and potentially dangerous.

Repro Steps:

1. Open any world with entities
2. /say @s
3. /say @s[type=!player]

Expected Results: Second command prints nothing, since you are a player.

Observed Results: Second command prints every entity in the world.

Screenshots/Videos attached: Yes

Notes: Tested all other selector arguments, only type seems to be affected. An upcoming project is affected by this bug. It can be worked around but at a decently high cost.