Not a language per se, but subsets of languages used for fantasy consoles usually do not implement import functionality. TIC-80, PICO-8, etc. etc. WIKI I wouldn't call that a feature, but it drives you to write less and more space-optimized code.
Now that I think about it, source code size could be a feature in itself, look at codeGolf-oriented esolangs:- Pyth
- CJam
- GolfScript
- Microscript/Microscript II
- Seriously
- Rotor
- Minkolang
- Gaia
- Jelly
- 05AB1E
- japt
- and more...
I’m not smart enough to know, but what kind of use case(s) do you imagine for this?
I know encapsulation is desirable in part because of security. I figured something similar could happen by removing the ability to import anything from another program. However, I struggled to think about other situations in which no imports were desirable, and so I wondered…
There are certainly situations where it would be valuable to be able to place limits on what can be imported, but I can't imagine trying to work with a language that was completely devoid of imports. Because that would mean 100% of your source would have to be in a single file, which sounds absolutely awful for anything but the most trivial applications.