Ah, that is right. I apologize, I think I've learned that three times now, but for some reason my brain refuses to accept it.

I like that previous editions get new features when possible, unlike say C++, but I wish they'd gone with semantic versioning for the language version, like python did when both 2 and 3 were active. Oh well, I just need to remember that the edition is like the major version, and compiler version is sort of like minor version, and both are needed to specify forwards compatibility.

I'm not sure semver would really do it here, because then you could have say:

  2.17
  1.17

What would you call the compiler binary that could compile both language v1 and language v2, with (shared) minor-version .17?

The issue is that semantic versions are a hierarchy, whereas Rust edition x compiler version are a matrix

It might make more sense to think of editions as optional changes to the surface syntax, and nothing more. They are not nearly as important as the name makes them sound.

They are often small, but it's a mistake to say they're surface-level. Changes to syntax or semantics only get made when absolutely necessary to allow for essential features or fixes.