List pattern matching

[giacomocavalieri]

There's a strange pattern that I don't think should compile when pattern matching on a list:

case list {
  [first..rest] -> todo
//^^^^^^^^^^^^^ This compiles as [first, ..rest]
  _ -> todo
}

I think it should be a parse error instead

[zanddev]

@giacomocavalieri This is a duplicate of #3107, but this issue is written better than mine.

[lpil]

It would be a breaking change to make this an error, but we could emit a warning.

[giacomocavalieri]

Oh right that's unfortunate, I'll work on adding the warning then!

[lpil]

Thank you

[giacomocavalieri]

I was wondering, what would the warning say? Does it even make sense to have a warning to suggest a different way of writing it even if the formatter already takes care of it?

Something like this, maybe?

  [a..b]
  ^^^^^^

This is the same as writing `[a, ..b]`

[lpil]

Maybe we could say that the syntax is deprecated?