Personally, I think pass by-value with copy-on-write semantics like
arrays is the sweet spot. Mutability is fine if it is localized.
I think having a no-constructor construction syntax is also a good
idea. I've discussed it with a few people, but don't can't remember if
it's ever been brought up on-list. Basically, the idea is to use a
JSON-like syntax with the type-name in front, and I think it can be
fine to use on regular classes that don't have a constructor too:
struct Point2d {
float $x;
float $y;
}
$origin = Point2D { x: 0, y: 0 };
This syntax has no conflicts. We could also add an object literal
syntax for creating ad-hoc stdClass objects like so: $obj = { x: 1, y: 1}
. This has an ambiguity, but I believe I have solved the issue
without too much trouble once before.
I think structs, pass by-value with copy-on-write, and brace
construction would go really well together.