Not sure, maybe my wording isn't clear enough. What I intended to say is that arguments can be named, not that they have to. In any case, the order of arguments must match the order of parameters, named or not.

But you’re also missing one use of the impl keyword: fn func() -> impl Trait.

That removal could actually happen, so I didn't list it. (Rust started requiring dyn and disallowed naked trait returns with edition 2018. So dropping the impl in that position might not be completely impossible like the other uses of impl.)

Are you suggesting using keywords/methods [for array and slice syntax] instead?

Yes, just methods.

I can understand someone preferring the PartialEq/PartialOrd behavior

You can have both – that's what's being made possible by them not being in a hierarchy.

I think if-let makes sense, but don’t expand it.

It's a bit late for that, isn't it? ;-)

Why? What value does -> () provide? Why not elide that?

What value is provided by keeping it? Why a syntactic special-case for exactly that type and not any other random type?

languages w/o them feel awkward since you’re generally limited to one statement per line

Then fixing that might make sense. :-)