Comment by OptionOfT

> Even modern languages like Rust did a crappy job of enforcing it: https://doc.rust-lang.org/std/primitive.char.html#method.to_... .

What were they supposed to do?

According to Wikipedia:

> Traditionally, ⟨ß⟩ did not have a capital form, and was capitalized as ⟨SS⟩. Some type designers introduced capitalized variants. In 2017, the Council for German Orthography officially adopted a capital form ⟨ẞ⟩ as an acceptable variant, ending a long debate.[4] Since 2024 the capital has been preferred over ⟨SS⟩.[5]

Source: https://en.wikipedia.org/wiki/%C3%9F#:~:text=Traditionally%2...

So this has been adopted since 2017. And Rust follows the unicode standard. It's not up to Rust, it's up to Unicode. And if that was what the mapping was in 2017, that's on Unicode, not Rust.

But I'm unsure if we can change the existing Unicode mapping without breaking backwards compatibility? I did learn that ẞ (the uppercase variant) is the same as SS (copy the SS and you'll see the ẞ highlighted, both upper and lowercase).