Hi there. Designer of this feature :D
> is non-intuitive and unnecessary.
intuitive is definitely in the eye of the beholder. When people saw:
`HashSet<string> people = [with(StringComparer.CaseInsensitiveComparer), .. group1, group2]`
they found it understandable. And this was also much nicer than what they'd have to write today (which would bring them out of the nice declarative collection-expression space).
Does that make it 'necessary'? Ultimately that's up to the individual. We felt like it was. Not being able to do simple things like this felt like a 'bitter pill'. Customization of collection construction is common (looking in codebases, it shows up about 7% of the time). So having to 'fall out' from the uniform collection-expr system into the much more verbose and clunky forms just for this common enough case felt 'necessary' to us.
>But I feel that there has to be a direction, things have to work together to make a language feel coherent.
I feel like this is conflicting feedback. Collection expressions made the language more coherent. Instead of 7 different ways of doing things (some of which were genuinely not efficient), we gave one uniform way of doing it. That makes things more coherent. Making it so you don't have to drop out of that for something as simple as configuring the collection makes things more coherent.
Practically speaking, I've found that Claude never uses collection expressions, so the feature has disappeared from my code. Before AI, the feature was looked at with skepticism by my coworkers. We like writing "var" for all variable declarations. You have to write the type on the left side if you want to declare a variable with a collection expression, and we would never do that otherwise. Can't do `foreach (var x in [1, 2, 3])`. Too often, you have to make specific accommodations in your code to allow the collection expression to be valid.
Collection expressions today are more the sort of thing that a code poet or golfer can do to prettify their code than something a newbie can count on using. It's tough to explain "you can only use this when the collection type is implied in that spot" to a newbie. The value of the base feature is still unproven for me. I'm not sure I agree, without some convincing, that collection expressions made the language more coherent rather than doing https://xkcd.com/927.