For me honestly it's one of the (many) things I dislike the most about Ruby.
Sure, I understand the "elegant" aspect, two symbols are shortened to one (although I'd argue that's not that important when it comes to clarity and legibility).
But every time I read "unless" in code it's quite jarring. I have to consciously translate it to "if not", and even then seeing the "unless" keeps tripping me off, perhaps because it's awkward in English to start a sentence out of the blue with "unless".
It's a matter of taste, but I tend to agree that the more features or constructs a language has, no matter how terse or convenient, the more unnecessary complexity is generated by using that language.
The `unless` keyword makes the interpreter slightly more complicated and is another piece of language the human brain needs to recognize. It may seem inconsequential, but grains of sand make a hill, as they say.
My ideal language would leave out pretty much anything that can be achieved with more basic constructs. It would of course have if-else, and leave out `unless`, but there would also be no switch statements or ternaries. Branching must be done with if-else or by looking up a value in a hash. No `for` or `while` loops because a simple `loop` construct with `continue` and `break` statements can do everything that `for` and `while` could do in other languages. No classes or inheritance because they're magical and they can be effectively simulated by the end developer if that's what they really want.
What I think would be really cool is to have a language with a syntax like Ruby but with only the most basic of programming language constructs.
I've thought about that, but that's closer to the metal than I prefer and I think it's not beneficial for less experienced programmers.
Structured programming is, I believe, a good idea for the vast majority of use cases. Though one can technically use structured programming while using goto, encouraging goto can therefore allow programmers to go down a path that is counterproductive. It's basically the opposite end of the spectrum from OOP where encouragement of rampant objectiveness and inheritance makes programmers write code that is way too complicated.
There's absolutely a place for goto. I once made a "language" (actually YAML) specifically for developing for the Amazon Alexa platform, and it used something similar to goto called "go to scene" and "go to random". For that sort of thing, goto can be much more practical and even easier to reason about than "better" constructs in general purpose high-level programming languages. It's just not something I would consider appropriate for the kind of language I am proposing, though I still ponder on it.
Many language implementations internally translate source into a simplified de-sugared dialect as you describe as an early compilation step. I believe both ghc and rustc currently do this.
Though, I think it's rare to expand a pattern match/switch into an if-else tree, and much more common to expand an if-else into a 2-way pattern match/switch.
If you're really keen on such a language, you could fairly easily implement such a language as a pre-commit hook source code re-formatter so that all of the source in your repository is in your favorite language subset.
Sure, I understand the "elegant" aspect, two symbols are shortened to one (although I'd argue that's not that important when it comes to clarity and legibility).
But every time I read "unless" in code it's quite jarring. I have to consciously translate it to "if not", and even then seeing the "unless" keeps tripping me off, perhaps because it's awkward in English to start a sentence out of the blue with "unless".